One of the challenges of working with ancient DNA samples is that damage accumulates over time, breaking up the structure of the double helix into ever smaller fragments. In the samples we've worked with, these fragments scatter and mix with contaminants, making reconstructing a genome a large technical challenge.

But a dramatic paper released on Thursday shows that this isn't always true. Damage does create progressively smaller fragments of DNA over time. But, if they're trapped in the right sort of material, they'll stay right where they are, essentially preserving some key features of ancient chromosomes. Researchers have now used that to detail the chromosome structure of mammoths, with some implications for how these mammals regulated some key genes.

DNA meets Hi-C

The backbone of DNA's double helix consists of alternating sugars and phosphates, chemically linked together (the bases of DNA are chemically linked to these sugars). Damage from things like radiation can break these chemical linkages, with fragmentation increasing over time. When samples reach the age of something like a Neanderthal, very few fragments are longer than 100 base pairs. Since chromosomes are millions of base pairs long, it was thought that this would inevitably destroy their structure, as many of the fragments would simply diffuse away.

But that will only be true if the medium they're in allows diffusion. And some scientists suspected that permafrost, which preserves the tissue of some now-extinct Arctic animals, might block that diffusion. So, they set out to test this using mammoth tissues, obtained from a sample termed YakInf that's roughly 50,000 years old.

The challenge is that the molecular techniques we use to probe chromosomes take place in liquid solutions, where fragments would just drift away from each other in any case. So, the team focused on an approach termed Hi-C, which specifically preserves information about which bits of DNA were close to each other. It does this by exposing chromosomes to a chemical that will link any pieces of DNA that are close physical proximity. So, even if those pieces are fragments, they'll be stuck to each other by the time they end up in a liquid solution.

A few enzymes are then used to convert these linked molecules to a single piece of DNA, which is then sequenced. This data, which will contain sequence information from two different parts of the genome, then tells us that those parts were once close to each other inside a cell.

Interpreting Hi-C

On its own, a single bit of data like this isn't especially interesting; two bits of genome might end up next to each other at random. But when you have millions of bits of data like this, you can start to construct a map of how the genome is structured.

There are two basic rules governing the pattern of interactions we'd expect to see. The first is that interactions within a chromosome are going to be more common than interactions between two chromosomes. And, within a chromosome, parts that are physically closer to each other on the molecule are more likely to interact than those that are farther apart.

So, if you are looking at a specific segment of, say, chromosome 12, most of the locations Hi-C will find it interacting with will also be on chromosome 12. And the frequency of interactions will go up as you move to sequences that are ever closer to the one you're interested in.

On its own, you can use Hi-C to help reconstruct a chromosome even if you start with nothing but fragments. But the exceptions to the expected pattern also tell us things about biology. For example, genes that are active tend to be on loops of DNA, with the two ends of the loop held together by proteins; the same is true for inactive genes. Interactions within these loops tend to be more frequent than interactions between them, subtly altering the frequency with which two fragments end up linked together during Hi-C.

Mammoth challenges

That's how Hi-C works in theory. Putting it into practice on a mammoth posed a number of pretty significant challenges. To start with, it's far easier to interpret Hi-C data if you already know what the genome should look like. Unfortunately, we only had a limited idea in the case of mammoths. The mammoth genome itself was highly fragmented due to its origin in ancient DNA. But even the genomes of its living relatives, the African and Asian elephants, are highly fragmented, since they were done a few years back using a quicker and inexpensive approach. So, as a first step, the researchers generated a high-quality genome for both the living species, including generating Hi-C data from them.

Hi-C data was generated from the mammoth by repeating the procedure 26 times, producing 4.4 billion sequence fragments from linked pieces of DNA. As is often the case with ancient DNA, most of these were contaminants—in this case, 97 percent were. After getting rid of data from neighboring fragments that had been linked back together, a total of 4.6 million fragments were useful for Hi-C analysis. That's only 0.1 percent of the original data; when Hi-C was done with Asian elephant cells, the corresponding figure was 43 percent, illustrating the scale of the challenge when working with ancient DNA.

That said, this sequence appeared to be the real deal. Changes in the base sequence that occur due to damage were elevated, and individual base differences were almost always the same as those seen in mammoths. There wasn't enough mammoth data to do the full Hi-C analysis from scratch, so the researchers focused on identifying differences between mammoth and elephant data. If there wasn't an indication of differences, the mammoth's chromosomes were assumed to look like an elephant's.

Critically, the results showed that the frequency of contact vs. distance along the chromosome relationship for the mammoth DNA was the same as that seen in Asian elephants. This indicates that the basic chromosome structure had been preserved over 50,000 years in ice, even as the underlying chromosome had decayed into ever-smaller fragments.

The resulting mammoth genome had the same total number of chromosomes as modern elephants, and large-scale rearrangements, like duplicated or flipped sequences, were infrequent. The data was also sufficient to pick out some of the loops that occur around active and inactive genes. The mammoth sample had come from skin tissue, and the pattern of looping was similar to that seen in elephant skin. In fact, data from elephant skin was more similar to mammoth skin than it was to any other elephant tissue tested.

There were a few differences, however, including a couple of genes that are known to be involved in hair production in other mammals. It's worth noting, however, that not all of these changes in gene activity were what you'd expect to be needed to produce more hair in the mammoth, suggesting that its shaggy coat was the result of a more complicated evolutionary path than "turn the hair genes on." That's consistent with the fact that there were over 800 differences in gene regulation identified in total.

Data from the X chromosome also had indications that one of the animal's two Xes was inactivated, indicating that it was a female.

Skin-deep

Based on the size of DNA fragments typically found in the mammoth genome, the researchers estimate that chromosome features down to roughly 50 nanometers had been preserved and that it was likely that many even smaller than that were still present in this sample. They suspect that the extremely cold, dry air of its habitat had essentially freeze-dried the chromosomes in place, something that might occur in other samples preserved in the Arctic or in dry environments with more moderate temperatures. (They tested the latter using beef.)

While the findings are impressive, it's important to highlight that this isn't a revolution in our understanding of the mammoth. Due to its close relationship with existing elephants, we'd have expected its genome to look and operate fairly similarly. And this has only told us about gene activity in skin cells; while those have some distinct adaptations in the mammoth, they're only one of a long list of tissues that would have needed to change to adapt to its very different diet and habitat.

That little dose of perspective, however, should not stop you from being amazed that we are able to obtain this sort of information from an animal that has been dead for 50,000 years.

Cell, 2024. DOI: 10.1016/j.cell.2024.06.002  (About DOIs).

Advances in artificial intelligence are making it increasingly difficult to distinguish between uniquely human behaviors and those that can be replicated by machines. Should artificial general intelligence (AGI) arrive in full force—artificial intelligence that surpasses human intelligence—the boundary between human and computer capabilities will diminish entirely.

In recent months, a significant swath of journalistic bandwidth has been devoted to this potentially dystopian topic. If AGI machines develop the ability to consciously experience life, the moral and legal considerations we’ll need to give them will rapidly become unwieldy. They will have feelings to consider, thoughts to share, intrinsic desires, and perhaps fundamental rights as newly minted beings. On the other hand, if AI does not develop consciousness—and instead simply the capacity to out-think us in every conceivable situation—we might find ourselves subservient to a vastly superior yet sociopathic entity.

Neither potential future feels all that cozy, and both require an answer to exceptionally mind-bending questions: What exactly is consciousness? And will it remain a biological trait, or could it ultimately be shared by the AGI devices we’ve created?

Consciousness in Von Neumann computers

For a computer to experience the vast repertoire of internal states accessible to human beings, its hardware presumably needs to function somewhat like a human brain. Human brains are extremely energy-efficient analog “devices” capable of high-levels of parallel processing.

Modern computers, based on Von Neumann architecture, are not any of these things—they are energy-intensive digital machines composed primarily of series circuitry.

Von Neumann computer chips physically separate memory from processing, requiring information to be retrieved from memory before calculations can be performed. “Classical Von Neumann computers have a separation between memory and processing. The instructions and the data are off in the memory, and the processor pulls them in, as much as it can in parallel, and then crunches the numbers and puts the data back in memory,” explains Stephen Deiss, a retired neuromorphic engineer from UC San Diego.

This restriction on how much information can be transferred within a specific time frame—and the limit it places on processing speed—is referred to as the Von Neumann bottleneck. The Von Neumann bottleneck prevents our current computers from matching—or even approaching—the processing capacity of a human brain. Because of it, many experts think that consciousness in modern-day computers is highly unlikely.

Consciousness in neuromorphic computers

Computer scientists are actively developing neuromorphic computer chips that evade the processing restrictions of Von Neumann computers by approximating the architecture of neurons. Some of these combine memory storage and processing units on a single chip. Others use specialized, low-powered processing elements such as memristors, a type of transistor that “remembers” past voltage states, to increase efficiency. Neuromorphic chips mimic the brain’s parallel wiring and low power requirements.

“A compute-in-memory device, which includes things like neuromorphic computers, uses the actual physics of the hardware to do the computation,” Deiss explains, referring to memristors. “The processing elements are the memory elements.”

If neuromorphic technology can be developed to the level needed to reproduce neuronal activity, neuromorphic computers might have a greater potential to experience life consciously rather than just compute intelligently. “If we ever achieve the level of processing complexity a human brain can do, then we’ll be able to point at [neuromorphic computers] and say, ‘This is working just like a brain—maybe it feels things just like we feel things,’” Deiss says.

Still, even in a future brimming with brain-like computer hardware and the stage set for artificial consciousness, there remains a big question: How will we know whether or not our AGI systems are experiencing sadness, hope, and the exquisite feeling of falling in love or if they just look like they are experiencing these things?

How will we ever know what's going on inside the mind of a machine?

A cornucopia of consciousness theories

There's only one way we can know: by empirically identifying how consciousness works in organic lifeforms and developing a method by which we can consistently recognize it. We need to understand consciousness in ourselves before we have any hope of recognizing its presence in artificial systems. So before we dive deep into the complex consequences of sentient silicon and envision a future filled with conscious computers, we must resolve an ancient question: What is consciousness, and who has it?

In recent decades, neuroscientists have wrenched this millennia-old question from the grip of philosophers, recognizing that the connection between neuronal activity and conscious experience is incontestable. Dozens of neuroscientific theories of consciousness (ToCs) exist—so many, in fact, that a concerted effort is underway to whittle down the list to a manageable few. We'll discuss just three of them here: Integrated Information Theory, Global Neuronal Workspace Theory, and Attention Schema Theory.

According to Integrated Information Theory (IIT), a ToC developed by Giulio Toloni, director of the Wisconsin Institute of Sleep and Consciousness at UW Madison, the key to consciousness lies in a system’s quantity of integrated information—how elaborately its components communicate with one another via networks of neurons or transistors. A system with a high level of integrated information is conscious; a system with low integrated information is not.

Christof Koch, a meritorious investigator at the Allen Institute for Brain Science in Seattle, Washington, and a proponent of IIT, explains that human brains have a high level of integrated information due to the extensive parallel wiring of their neuronal networks. Information can travel through multiple neuronal pathways simultaneously, which increases the brain’s processing capacity. Modern-day computers, subject to the Von Neumann bottleneck, are primarily composed of series circuits, so a comparable level of information processing is unobtainable.

Attention Schema Theory (AST), developed by Michael Graziano, professor of Psychology and Neuroscience at Princeton, posits a different view: Our brain makes a model of what we are paying attention to, called an “attention schema.” This model, like a model airplane, is a representation. A model airplane does not include a fully equipped cabin or a functional cockpit. Similarly, the attention schema of our own consciousness is an approximation: a mental model of what our mind is paying attention to and how we are experiencing it.

AST proposes that, despite its limitations, our attention schema is so convincing that we have a tendency to incorrectly deduce that consciousness is something mystical, something “more than” matter. In reality, we are only allowed access to this representation of our mind—not our mind itself—so we cannot directly understand how our mind works, much like how a model airplane cannot replicate the experience of flying.

Global Neuronal Workspace Theory (GNWT), founded by Bernard Baars, affiliated fellow in theoretical neurobiology at the Neurosciences Institute of UC San Diego, proposes that information our brain determines is sufficiently important is selectively and temporarily placed in a central workspace within our brain (analogous to a movie theater) so that we can pay attention to it. Information we do not need to consciously attend to is stored away in connected but separate areas (analogous to backstage).

“The basic idea [of GNWT] is fairly straightforward. At any given moment, only a subset of unconscious information is selected by attentional networks, and this selection serves to connect unconscious processing modules to a ‘global workspace.’ Whatever contents are in the workspace are consciously experienced at that moment,” says Michael Pitts, a psychology professor at Reed College in Oregon.

Despite disparate approaches, IIT, GNWT, and AST share a common goal of empirically unraveling the complex relationship between brain tissue and the experience of life. Once neuroscientists get a handle on how neuronal networks produce consciousness, this knowledge can be used to understand conscious experiences—or the lack thereof—in inorganic networks.

Is computer consciousness no more than a futuristic daydream?

According to IIT, consciousness in our current computers is flat-out impossible. The hype surrounding artificial consciousness is for naught. Hardware is hardware. No matter how brilliant a machine is at playing chess, Go, Texas hold’em, or Scotland Yard, at the end of the day, it does not know that it won a game, nor has it felt the emotional rollercoaster of competition. In Koch’s words, “It has experienced exactly nothing.”

“It is not enough to look at an AI system from the outside and ask if it is conscious based on how it is behaving,” Koch says. “You need to look under the hood. A Turing machine that appears to be thinking is not conscious.”

According to IIT, the inability of a machine to “be something” that experiences itself relating to the external world lies squarely in its limited causal power. Causal power is defined as the ability of a system to use its past state to influence its present state and to use its present state to influence its future state. The more a system can influence itself, the more causal power it has. Neuroscientists use the variable “phi” to represent the amount of causal power within a system, and it is measured by analyzing the self-influencing connections between circuit components.

Modern-day computer processors simply do not have the requisite number of self-influencing internal connections to hit the threshold value of integrated information required for experience to arise. Unlike a human brain, which contains approximately 86 billion neurons with 100 trillion connections between them, a computer contains far fewer looped, or self-influencing, connections. A computer might behave with extraordinary intelligence—even intelligence that exceeds that of humans—but this does not equate to an ability to exert an effect on itself: to be conscious.

“A popular way to summarize IIT is that it proposes that a system is conscious when the whole (the integration of information) is more than the sum of its parts,” Pitts says. “IIT focuses more on how a system is arranged and how it affects itself than on what it does. According to IIT, two systems can have the same input-output behavior, but depending on how the system is organized, one could be conscious while the other is not.”

Unlike the vast majority of ToCs, which are computational functionalist theories that assume consciousness can be reduced to the physical components that produce it, “IIT starts with consciousness and works backward to the physical substrate of consciousness. IIT does not start with a physical system, like a brain or machine, and assume that it can be reduced far enough to lead us to the source of consciousness,” Koch says.

Because of this premise, IIT does not fall neatly into any of the traditional philosophical theories of mind, such as materialism, dualism, idealism, or panpsychism. “This is the challenge when you encounter two thousand years of ‘isms.’ They are taught in all of the philosophy schools and in all of the books, and they are very well-established—but they are all philosophy. IIT doesn’t fit into any one [philosophy of mind],” Koch says.

Despite IIT’s compelling theoretical framework, some neuroscientists question the theory’s structure. IIT is founded on five axioms that are considered by theory supporters to be infallibly true. Pitts explains: “Some people have a problem with how IIT starts because it is an aspirational theory that makes bold claims. Instead of taking data and building up a theory, it starts from first principles. It outlines five axioms that have to be true of any conscious experience. Then it uses those axioms to derive postulates that can lead to predictions.

“One critique some researchers have of IIT,” Pitts adds, “is that you can never get an experimental result that is going to challenge the core of the theory because the axioms are set up to be a universally true starting point. It’s too flexible; it’s not falsifiable, some people would say.”

While IIT predicts that artificially intelligent computers do not possess the extra “something” required for consciousness (namely causal power), it does not dismiss the prospect of rapidly approaching highly intelligent machines—AGI systems that will surpass humans in their computational abilities. This is a crucial distinction we must remember to make, Koch cautions, as we evaluate how best to usher in a future brimming with AGI bots: “There is a difference between intelligence and consciousness.”

Is computer consciousness an inevitable reality?

On the other side of the neuroscientific consciousness coin are computational functionalist theories, such as Attention Schema Theory and Global Neuronal Workspace Theory. Both ToCs view artificial consciousness as inevitable. In fact, AST suggests that we ourselves are effectively machines that mistakenly believe we are conscious. Consciousness is simply the result of computations; the source of these computations (brain or machine) is irrelevant so long as they occur in a specified way.

Machine consciousness seems inevitable enough to some researchers that they decided to check if it’s already here. In August 2023, Patrick Butlin, a research fellow at the University of Oxford, and Robert Long, a research associate at the Center of AI Safety in San Francisco, posted a preprint paper on arXiv.org entitled “Consciousness in Artificial Intelligence: Insights from the Science of Consciousness.” Butlin, Long, and 18 collaborators evaluated six of the most prominent computational functionalist theories of consciousness and came up with a list of consciousness indicator properties—properties that are necessary for consciousness to arise in humans. They then looked for evidence of these indicator properties in AI systems.

Butlin, Long, and their collaborators came to the following conclusion: “Our analysis suggests that no current AI systems are conscious but also suggests that there are no obvious technical barriers to building AI systems which satisfy these indicators.”

Advocates of both AST and GNWT are comfortable with Butlin and Long’s conclusion. Graziano explains that “AST is built on the assumption that people are biological machines. Everything that a brain knows about itself is necessarily derived from information inside that brain. We think we have consciousness—we’re certain of it—because the brain builds self-models, or bundles of information, that describe itself in that manner. If the brain didn’t build those models, we wouldn’t know anything about consciousness. Build an artificial system with the same information structures inside itself, and it will have the same beliefs and certainties. It should be possible (and many are working on it) to build AI that also thinks it is conscious and thinks that other people are conscious.”

Graziano’s confidence in the eventuality of AI consciousness originates from the two foundational principles of AST. First, “Information that comes out of a brain must have been in that brain,” and second, “The brain’s models are never accurate.” Using these two principles as a starting point, Graziano writes that there is no “wiggle room”—the only logical, methodical explanation for consciousness is that it originates in the brain and is, like everything else that originates in the brain, an approximation of reality.

Koch disagrees. According to IIT, the subjective experience of tasting an apple cannot be replicated by a computer due to its limited ability to exert an influence over itself—the “effect” of consciousness cannot arise. “Just because something is a perfect replica of a human brain does not mean consciousness will arise out of it,” Koch explains. “There is a difference between a simulation of a thing and the thing itself.” Even if computers of the future become as complex as brains (in terms of self-influencing internal circuitry) consciousness will not automatically be produced. The level of integrated information in a simulated brain will not necessarily match the integrated information in a real brain.

AST counters this argument by saying that the subjective experience referred to by IIT (and other theories of consciousness) is nothing more than a mental schema—a convincing illusion. We do not actually experience anything subjectively when we eat an apple; our brain convinces us that we do. In the same way, artificial intelligence will soon be able to convince itself, through an internal representation of apple eating, that it has tasted a crunchy, juicy, bright red Honeycrisp.

“Consciousness is a property that we attribute to other people and to ourselves, and we do so because it serves as a useful way to predict behavior,” says Graziano. “AST proposes that the brain builds a model, or a simplified representation, of an attentional state. We make sense of that state of attention by attributing consciousness to it. As a result, we gain a better ability to predict ourselves or other people.”

Because AST and GNWT say there is nothing “special” about consciousness—it’s just the end result of a sequence of computations—both hold that computers are just as likely to experience life as we are.
Butlin echoes this view, saying, “I think it’s likely that AI systems will soon be built with many of the indicator properties and that these systems will be much more serious candidates for consciousness than any that currently exist. These systems probably still won’t be conscious, but they will make hard questions about consciousness very pressing.”

Is it possible to unify consciousness theories?

An overabundance of ToCs exists within the neuroscience community. Until this unwieldly group of disparate theories is cohesively unified or reduced to a single theory that matches experimental results, we will not have a precise way to identify machine consciousness. To start the reduction process, the Templeton World Charity Foundation (TWCF) is funding a series of adversarial collaborations intended to increase communication between consciousness researchers and reduce gaps between ToCs. This work is imperative, and urgent, if we want to understand human consciousness before computers are complex enough to potentially acquire it themselves.

Michael Pitts recalls the media attention surrounding the Association for the Scientific Study of Consciousness Conference in New York City in June 2023. Pitts and his colleagues, Liad Mudrik of Tel Aviv University and Lucia Melloni of the Max Planck Institute, presented the initial results of the first adversarial collaboration they designed to rigorously test two prominent neuroscientific theories of consciousness: Integrated Information Theory and Global Neuronal Workspace Theory.

“We presented our initial results at a conference in New York City last summer, and the press got the wrong impression. Their idea was ‘this is one theory against the other,’ or ‘one’s going to win and one’s going to lose,’ but that’s not how it works,” Pitts said. Media focus on the adversarial nature of the collaborations fuels the perception that consciousness research is disjointed and incoherent.

Pitts and his colleagues are in the early stages of brainstorming a concept called Selective Unification, with the hope that disparate consciousness theories can ultimately be combined into one empirically sound ToC: “The idea of Selective Unification is that we can carefully select certain aspects of theories that are supported by data and unify them into one theory,” Pitts says.

Using the results from current and future adversarial collaborations, he hopes to eliminate portions of ToCs that don’t match experimental data. Specific elements of theories that survive the chopping block, he theorizes, can then be combined into a new ToC with predictions that align with experimental evidence. Pitts says, “We don’t want to combine theories in a Frankenstein way but in a way where we retain consistent pieces and drop parts that are experimentally challenged.”

Koch, though equally committed to testing ToCs, does not believe it’s possible to combine select elements of multiple theories of consciousness. He says, “They are just fundamentally different animals. You can’t squash them together. They could both be wrong, but they cannot both be right.”

Preparing for AGI, conscious or not

Debates over the nature of consciousness and whether or not AGI will ultimately experience life as we do are not likely to be resolved soon. Yet technological advances are propelling us at warp speed into a future filled with machines that will, for all extents and purposes, behave as we do. How do we prepare for this?

Koch proposes that we make an effort to increase human intelligence to offset the impending discrepancy between organic and artificial brains. Conscious or unconscious, future AIs will be much smarter than us. Why not direct some technological resources toward increasing human intelligence alongside artificial intelligence?

Graziano suggests we prepare for conscious AI by preemptively considering AI sociopathy. With widespread AGI will come increased computer influence and power. If AI develops extreme intelligence without concurrently learning to navigate the complexities of human social norms, we might have sociopathic machines on-hand that chose to kill us instead of work with us.

“Most people concentrate on consciousness as a private, internal matter. But it also plays a central role in human social interaction,” Graziano says. “We recognize each other as conscious beings, and it allows us to treat each other in a certain way. When that ability begins to weaken, antisocial behavior emerges. That’s when people start to kill each other.”

“If we want AI to be prosocial, we might want to give it the mechanisms that make people prosocial,” Graziano suggests.

Koch offers one last suggestion: Rather than scramble to deal with the inevitable superiority of AGI and the resulting ambiguities of potential computer consciousness, he advises that we regulate AI right now. “We should put some guardrails on AI as they are in the EU—that’s the only thing we can do. AGI will get here very soon. We will see how we muddle through, for better or for worse.”

Lindsey Laughlin is a science writer and freelance journalist who lives in Portland, Oregon, with her husband and four children. She earned her BS from UC Davis with majors in physics, neuroscience, and philosophy.

Supermassive black holes appear to reside at the center of every galaxy and to have done so since galaxies formed early in the history of the Universe. Currently, however, we can't entirely explain their existence, since it's difficult to understand how they could grow quickly enough to reach the cutoff for supermassive as quickly as they did.

A possible bit of evidence was recently found by using about 20 years of data from the Hubble Space Telescope. The data comes from a globular cluster of stars that's thought to be the remains of a dwarf galaxy and shows that a group of stars near the cluster's core are moving so fast that they should have been ejected from it entirely. That implies that something massive is keeping them there, which the researchers argue is a rare intermediate-mass black hole, weighing in at over 8,000 times the mass of the Sun.

Moving fast

The fast-moving stars reside in Omega Centauri, the largest globular cluster in the Milky Way. With an estimated 10 million stars, it's a crowded environment, but observations are aided by its relative proximity, at "only" 17,000 light-years away. Those observations have been hinting that there might be a central black hole within the globular cluster, but the evidence has not been decisive.

The new work, done by a large international team, used over 500 images of Omega Centauri, taken by the Hubble Space Telescope over the course of 20 years. This allowed them to track the motion of stars within the cluster, allowing an estimate of their speed relative to the cluster's center of mass. While this has been done previously, the most recent data allowed an update that reduced the uncertainty in the stars' velocity.

Within the update data, a number of stars near the cluster's center stood out for their extreme velocities: seven of them were moving fast enough that the gravitational pull of the cluster isn't enough to keep them there. All seven should have been lost from the cluster within 1,000 years, although the uncertainties remained large for two of them. Based on the size of the cluster, there shouldn't even be a single foreground star between the Hubble and the Omega Cluster, so these really seem to be within the cluster despite their velocity.

The simplest explanation for that is that there's an additional mass holding them in place. That could potentially be several massive objects, but the close proximity of all these stars to the center of the cluster favor a single, compact object. Which means a black hole.

Based on the velocities, the researchers estimate that the object has a mass of at least 8,200 times that of the Sun. A couple of stars appear to be accelerating; if that holds up based on further observations, it would indicate that the black hole is over 20,000 solar masses. That places it firmly within black hole territory, though smaller than supermassive black holes, which are viewed as those with roughly a million solar masses or more. And it's considerably larger than you'd expect from black holes formed through the death of a star, which aren't expected to be much larger than 100 times the Sun's mass.

This places it in the category of intermediate-mass black holes, of which there are only a handful of potential sightings, none of them universally accepted. So, this is a significant finding if for no other reason than it may be the least controversial spotting of an intermediate-mass black hole yet.

What’s this telling us?

For now, there are still considerable uncertainties in some of the details here—but prospects for improving the situation exist. Observations with the Webb Space Telescope could potentially pick up the faint emissions from gas that's falling into the black hole. And it can track the seven stars identified here. Its spectrographs could also potentially pick up the red and blue shifts in light caused by the star's motion. Its location at a considerable distance from Hubble could also provide a more detailed three-dimensional picture of Omega Centauri's central structure.

Figuring this out could potentially tell us more about how black holes grow to supermassive scales. Earlier potential sightings of intermediate-mass black holes have also come in globular clusters, which may suggest that they're a general feature of large gatherings of stars.

But Omega Centauri differs from many other globular clusters, which often contain large populations of stars that all formed at roughly the same time, suggesting the clusters formed from a single giant cloud of materials. Omega Centauri has stars with a broad range of ages, which is one of the reasons why people think it's the remains of a dwarf galaxy that was sucked into the Milky Way.

If that's the case, then its central black hole is an analog of the supermassive black holes found in actual dwarf galaxies—which raises the question of why it's only intermediate-mass. Did something about its interactions with the Milky Way interfere with the black hole's growth?

And, in the end, none of this sheds light on how any black hole grows to be so much more massive than any star it could conceivably have formed from. Getting a better sense of this black hole's history could provide more perspective on some questions that are currently vexing astronomers.

Nature, 2024. DOI: 10.1038/s41586-024-07511-z  (About DOIs).

The inspiration for the titular device in last year's blockbuster, Indiana Jones and the Dial of Destiny, was an actual archaeological artifact: the Antikythera mechanism, a 2,200-year-old bronze mechanical computer. It doesn't have any mystical time-traveling powers, but the device has been the subject of fierce scientific scrutiny for many decades and is believed to have been used to predict eclipses and calculate the positions of the planets.

A new paper published in The Horological Journal found evidence, based on statistical techniques drawn from physics, particularly the study of gravitational waves, that the mechanism's calendar ring was designed to track the lunar calendar. This contradicts a century-long assumption among scholars of the mechanism that the calendar ring had 365 holes, thus tracking with a solar calendar, but is in keeping with the conclusions of a 2020 analysis.

“It’s a neat symmetry that we’ve adapted techniques we use to study the universe today to understand more about a mechanism that helped people keep track of the heavens nearly two millennia ago," said co-author Graham Woan, an astrophysicist at the University of Glasgow. “We hope that our findings about the Antikythera mechanism, although less supernaturally spectacular than those made by Indiana Jones, will help deepen our understanding of how this remarkable device was made and used by the Greeks.”

As previously reported, a Greek sponge diver named Elias Stadiatis discovered the wreck of an ancient cargo ship in 1900 off the coast of Antikythera Island in Greece. He and other divers recovered all kinds of artifacts from the ship. A year later, an archaeologist named Valerios Stais was studying what he thought was a piece of rock recovered from the shipwreck when he noticed that there was a gear wheel embedded in it. It turned out to be an ancient mechanical device. The Antikythera mechanism is now housed in the National Archaeological Museum of Athens.

In 1951, a British science historian named Derek J. de Solla Price began investigating the theoretical workings of the device. Based on X-ray and gamma-ray photographs of the fragments, Price and physicist Charalambos Karakalos published a 70-page paper in 1959 in the Transactions of the American Philosophical Society. Based on those images, they hypothesized that the mechanism had been used to calculate the motions of stars and planets—making it the first known analog computer.

Michael Wright, then curator of mechanical engineering at the Science Museum in London, made headlines back in 2002 with new, more detailed X-ray images of the device taken via linear tomography. Wright's closer analysis revealed a fixed central gear in the mechanism's main wheel, around which other moving gears could rotate. He concluded that the device was specifically designed to model "epicyclic" motion, keeping with the ancient Greek notion that celestial bodies moved in circular patterns called epicycles. (This was pre-Copernicus, so the fixed point around which they moved was believed to be the Earth.)

In 2021, an interdisciplinary team at University College London (UCL) led by mechanical engineer Tony Freeth, an honorary professor at University College London, introduced a new computational model, revealing a dazzling display of the ancient Greek cosmos. The team's efforts built on Wright's work as part of the ongoing Antikythera Mechanism Research Project, which undertook more advanced 3D X-ray imaging with the help of X-Tek Systems in the UK and Hewlett-Packard, among others. Those images revealed much more of the original Greek transcription, confirming it was an astronomical computer used to predict the positions of heavenly bodies in the sky. It's likely that the Antikythera mechanism once had 37 gears, of which 30 survive, and its front face had graduations showing the solar cycle and the zodiac, along with pointers to indicate the positions of the Sun and Moon.

Ring cycle

Freeth's team is currently building a replica mechanism, moving gears and all, using modern machinery. This latest paper relates to the work of a machinist named Chris Budiselic, who has been cataloging his yearslong efforts to re-create the device using tools from that age on his YouTube channel. In 2020, he and several collaborators published a paper on their analysis of X-ray imaging of the device—especially of the regularly spaced holes just beneath the calendar ring. It has long been unclear how many holes the mechanism might have had originally.

Budiselic et al. thought it was probably between 347 and 367 holes and favored the lower count, which would be in keeping with a lunar calendar as opposed to the 365-day Egyptian civil calendar. But the authors noted that their conclusion was still conjecture and that despite their access to high-resolution projections, the image quality was not ideal. For instance, some of the holes were filled with debris, requiring multiple measurements of some holes to reduce noise in the data.

Woan discovered Budiselic's data and attempted to create a replica of the calendar ring late last year after a colleague mentioned it to him. Intrigued, he spent a good part of the Christmas holiday thinking about what statistical techniques might be able to answer the question of how many holes the ring had likely contained. He decided to apply Bayesian analysis to calculate the number based on the positions of the surviving holes and the placement of the surviving fragments of the ring. That method suggested the ring contained either 354 or 355 holes.

Meanwhile, Woan's colleague, co-author Joseph Bayley, decided to apply a different statistical approach to the problem. A member of the university's Institute for Gravitational Research, he adapted the group's techniques for analyzing LIGO signals picked up by gravitational wave detectors, specifically Markov chain Monte Carlo and nested sampling methods. Bayley arrived at the same conclusion as Woan: either 354 or 355 holes.

The skeptics weigh in

“Previous studies had suggested that the calendar ring was likely to have tracked the lunar calendar, but the dual techniques we’ve applied in this piece of work greatly increase the likelihood that this was the case," said Bayley. “It’s given me a new appreciation for the Antikythera mechanism and the work and care that Greek craftspeople put into making it—the precision of the holes’ positioning would have required highly accurate measurement techniques and an incredibly steady hand to punch them."

But some Antikythera experts aren't buying it, including Freeth. “It’s just wrong,” Freeth told The New York Times, noting that the machinery already has an embedded lunar calendar based on the 19-year Metonic cycle that is much more precise. “Why put a second lunar calendar on the mechanism when you’ve already taken a lot of trouble to construct a lunar calendar of great accuracy and sophistication?”

Retired astrophysicist Mike Edwards, chair of the Antikythera Mechanism Research Project, was also unconvinced but thought there was no particular reason to doubt Woan et al.'s statistical findings. “The suggestion that 354 represents a lunar calendar does not seem to have any other support from within the mechanism—it is not at all clear how it would work and how it would relate to the markings on the front of the calendar ring,” he told The New York Times. “But the establishment of the count may perhaps tell us something about the level of precision in construction judged necessary and used by the mechanism’s builders.”

For patients with Type 2 diabetes, taking one of the new GLP-1 drugs, such as Ozempic, is associated with lower risks of developing 10 out of 13 obesity-associated cancers as compared with taking insulin, according to a recent study published in JAMA Network Open.

The study was retrospective, capturing data from over 1.6 million patients with Type 2 diabetes but no history of obesity-associated cancers prior to the study period. Using electronic health records, researchers had follow-up data for up to 15 years after the patients started taking either a GLP-1 drug, insulin, or metformin between 2008 and 2015.

This type of study can't prove that the GLP-1 drugs caused the lower associated risks, but the results fit with some earlier findings. That includes results from one trial that found a 32 percent overall lower risk of obesity-associated cancers following bariatric surgery for weight loss.

In the new study, led by researchers at Case Western Reserve University School of Medicine, some of the GLP-1-associated risk reductions were quite substantial. Compared with patients taking insulin, patients taking a GLP-1 drug had a 65 percent lower associated risk of gall bladder cancer, a 63 percent lower associated risk of meningioma (a type of brain tumor), a 59 percent lower associated risk for pancreatic cancer, and a 53 percent lower associated risk of hepatocellular carcinoma (liver cancer). The researchers also found lower associated risks for esophageal cancer, colorectal cancer, kidney cancer, ovarian cancer, endometrial cancer, and multiple myeloma.

Compared with insulin, the researchers saw no lowered associated risk for thyroid and breast cancers. There was a lower risk of stomach cancer calculated, but the finding was not statistically significant.

Gaps and goals

The GLP-1 drugs did not show such promising results against metformin in the study. Compared with patients taking metformin, patients on GLP-1 drugs saw lower associated risks of colorectal cancer, gall bladder cancer, and meningioma, but those calculations were not statistically significant. The results also unexpectedly indicated a higher risk of kidney cancer for those taking GLP-1 drugs, but the cause of that potentially higher risk (which was not seen in the comparison with insulins) is unclear. The researchers called for more research to investigate that possible association.

Overall, the researchers call for far more studies to try to confirm a link between GLP-1 drugs and lower cancer risks, as well as studies to try to understand the mechanisms behind those potential risk reductions. It's unclear if the lower risks may be driven simply by weight loss, or if insulin resistance, blood sugar levels, or some other mechanisms are at play.

The current study had several limitations given its retrospective, records-based design. Perhaps the biggest one is that the data didn't allow the researchers to track individual patients' weights throughout the study period. As such, researchers couldn't examine associated cancer risk reductions with actual weight loss. It's one more aspect that warrants further research.

Still, the study provides another promising result for the blockbuster, albeit pricy, drugs. The researchers suggest extending their work to assess whether GLP-1 drugs could be used to improve outcomes in patients with Type 2 diabetes or obesity who are already diagnosed with cancer, in addition to understanding if the drugs can help prevent the cancer.

Death was everywhere. Animal corpses littered the landscape and were mired in the local waterhole as ash swept around everything in its path. For some, death happened quickly; for others, it was slow and painful.

This was the scene in the aftermath of a supervolcanic eruption in Idaho, approximately 1,600 kilometers (900 miles) away. It was an eruption so powerful that it obliterated the volcano itself, leaving a crater 80 kilometers (50 miles) wide and spewing clouds of ash that the wind carried over long distances, killing almost everything that inhaled it. This was particularly true here, in this location in Nebraska, where animals large and small succumbed to the eruption’s deadly emissions.

Eventually, all traces of this horrific event were buried; life continued, evolved, and changed. That's why, millions of years later in the summer of 1971, Michael Voorhies was able to enjoy another delightful day of exploring.

Finding rhinos

He was, as he had been each summer between academic years, creating a geologic map of his hometown in Nebraska. This meant going from farm to farm and asking if he could walk through the property to survey the rocks and look for fossils. “I’m basically just a kid at heart, and being a paleontologist in the summer was my idea of heaven,” Voorhies, now retired from the University of Georgia, told Ars.

What caught his eye on one particular farm was a layer of volcanic ash—something treasured by geologists and paleontologists, who use it to get the age of deposits. But as he got closer, he also noticed exposed bone. “Finding what was obviously a lower jaw which was still attached to the skull, now that was really quite interesting!” he said. “Mostly what you find are isolated bones and teeth.”

That skull belonged to a juvenile rhino. Voorhies and some of his students returned to the site to dig further, uncovering the rest of the rhino’s completely articulated remains (meaning the bones of its skeleton were connected as they would be in life). More digging produced the intact skeletons of another five or six rhinos. That was enough to get National Geographic funding for a massive excavation that took place between 1978 and 1979. Crews amassed, among numerous other animals, the remarkable total of 70 complete rhino skeletons.

To put this into perspective, most fossil sites—even spectacular locations preserving multiple animals—are composed primarily of disarticulated skeletons, puzzle pieces that paleontologists painstakingly put back together. Here, however, was something no other site had ever before produced: vast numbers of complete skeletons preserved where they died.

Realizing there was still more yet to uncover, Voorhies and others appealed to the larger Nebraska community to help preserve the area. Thanks to hard work and substantial local donations, the Ashfall Fossil Beds park opened to the public in 1991, staffed by two full-time employees.

Fossils discovered are now left in situ, meaning they remain exposed exactly where they are found, protected by a massive structure called the Hubbard Rhino Barn. Excavations are conducted within the barn at a much slower and steadier pace than those in the '70s due in large part to the small, rotating number of seasonal employees—mostly college students—who excavate further each summer.

A full ecosystem

Almost 50 years of excavation and research have unveiled the story of a catastrophic event and its aftermath, which took place in a Nebraska that nobody would recognize—one where species like rhinoceros, camels, and saber-toothed deer were a common sight.

But to understand that story, we have to set the stage. The area we know today as Ashfall Fossil Beds was actually a waterhole during the Miocene, one frequented by a diversity of animals. We know this because there are fossils of those animals in a layer of sand at the very bottom of the waterhole, a layer that was not impacted by the supervolcanic eruption.

Rick Otto was one of the students who excavated fossils in 1978. He became Ashfall’s superintendent in 1991 and retired in late 2023. “There were animals dying a natural death around the Ashfall waterhole before the volcanic ash storm took place,” Otto told Ars, which explains the fossils found in that sand. After being scavenged, their bodies may have been trampled by some of the megafauna visiting the waterhole, which would have “worked those bones into the sand.”

This includes the fossils of gomphotheres—elephant-like animals that sometimes had four tusks and, at others, had flattened lower tusks resembling shovels. To date, no gomphothere fossils have been found in the ash bed; they have only been found in the sand below the ash.

Voorhies also noted the profuse “evidence of aquatic life in the sand layer just underneath the ash.” That includes ancient lizards, frogs, and turtles. Fossilized ripple marks offer further evidence of water.

“We know that this area had been used as a watering hole by dozens and dozens of species of animals, probably for centuries,” Voorhies continued, “because we find the scattered remains of pretty much the same kinds of animals that you find in the ash bed [in that bottom layer of sand].”

A paucity of bony fish fossils coupled with evidence of water level fluctuation further indicate a seasonal waterhole. The one at Ashfall, noted Sandy Mosel, a Museum Associate, is similar to waterholes in African countries today: a large “bowl-shaped depression in the landscape that would fill up with water during the rainy season, and then it would dry out almost completely during the dry season.” (Mosel started working at Ashfall the same year the park opened and has remained there ever since.)

That waterhole is the key to why so many fossils have been preserved and to understanding what happened to the animals within it. And what we know about the “sequence of deposition” of the site, Otto explained, came out of the excavations in the late '70s, when they “literally dissected the site.”

Massive excavation

In an expanse “about half the size of a basketball court,” the team worked in two separate shifts: one during the morning and the other through around 10 pm, Otto said. The process involved digging until finding remains, wrapping them in a field jacket—the plaster coating that protects and binds fossils so that they can be safely transported—and removing it from the area. The teams could then dig further.

Like a layer cake, distinct sets of animals were found grouped in sections of ash. The top layer contained the biggest animals—the rhinos—followed by a layer with horses and camels, then a layer of smaller animals such as saber-toothed deer. The final layer contained the tiniest of creatures, such as rodents and birds. Under all of the ash, they came upon the aforementioned waterhole sand, with an entirely different set of fossils representing over 60 species of vertebrates, none of which were fully articulated or even complete. These were the remains of animals that died long before the eruption.

These excavations uncovered the sequence of events in reverse. “That’s what helped put together the story, the evidence of what happened to the animals at that time,” Otto explained. The top layer exposed the animals that survived the longest; the final layer of sand would have been the bottom of the waterhole millions of years ago.

The animals found in the ash bed include, among many others, the rhinos (Teleoceras major)—bulky, stubby-legged tanks often referred to as “barrel-bodied.” There were also four species of camel, the biggest of which, according to Otto, “were not much bigger than a llama.” Five varieties of horses co-existed at this time, the largest of them “not much bigger than a white-tailed deer.” Twelve million years ago, this area also included a species of musk deer (Longirostromeryx wellsi), also known as saber-toothed deer for the two fangs that protruded from their mouths.

Largely flattened and broken fossils of birds, turtles, snakes, and rodents are found within the very bottom layer of ash, offering evidence of the first chapter in the sequence of devastating events.

Killed by Yellowstone

This was the work of a supervolcano—a name denoting its extra gigantic size—from the Yellowstone Hotspot. The initial eruption is thought to have covered the Great Plains 1,600 kilometers (about 900 miles) away from the volcano with perhaps a foot of ash—material that is essentially tiny glass shards. Wind then lofted that ash into clouds and continued to spread it over many weeks or months.

Breathing the ash was a death sentence, but it was immediate only for the tiniest animals with equally tiny lungs. They would have died soon after the ash began to fall, becoming quickly covered by it. Within days or weeks, saber-toothed deer visiting the waterhole succumbed and were also covered by ash. They were followed by the various species of camel and horses. Last to die were the rhinos. Having survived perhaps four to six weeks, they lay at the very top of the accumulated layers of ash before being buried as well, which is why their bodies were excavated first.

The distinct sets of animals in subsequent layers of ash provided evidence that their deaths were staggered.

Mosel described the scene as animals visiting the waterhole, perhaps to cool off. “They’d lay down; they wouldn’t get back up. That’s where they died.” That ash continued to fall, “drifting in [and] around them and over the top of them.” The deeper parts of the waterhole contain the most skeletons, she said, and “that is probably because there was enough water there that they could find comfort in it, yet keep their noses out of it when they laid down.”

Jon Smith is an associate scientist with the Kansas Geological Survey and has been researching, among other things, the ichnofossils at Ashfall. “Some of the layers have dog footprints on them,” Smith said. “I think at Ashfall you can definitely make a strong case that [these] dogs were digging down through the ash and eating really rotten meat.” Tellingly, they left coprolites—fossilized feces—and regurgitates—fossilized vomit. “It was coming out of one end,” he quipped, “maybe both.”

All of this, he added, provides evidence that bone-crushing dogs existed there, despite the lack of body fossils. Smith refers to these trace fossils, or ichnofossils, as the “hidden biodiversity” of the site. Other ichnofossils point to tinier members of the ecosystem: small mammal and arthropod burrows, and, surprisingly, the extensive underground homes of ancient ants, discovered thanks to Smith, who recognized what they were.

“All of these add up to a once-in-a-lifetime deposit,” Tucker said, explaining that other sites tend to be an “accumulation of bones over hundreds or thousands of years.” At Ashfall, it is “an instantaneous capture of what the landscape looked like.”

At least the landscape in the waterhole. The number of animals uncovered in the ash bed so far is phenomenal, but Otto pondered the potential number of animals that didn’t survive fossilization. Consider, he said, what happened when the waterhole was almost completely full of ash. “If an animal lay down and died at that time, its bones would have been close enough to the surface that the bones would have [eventually] deteriorated instead of having been preserved. So there probably were thousands and thousands of rhinos and horses and camels that died out in the open landscape away from the waterhole.”

Given the size of the eruption and the sheer amount and distance the ash fell, one might wonder why another similar site hasn’t been found anywhere else. Otto said that scientists have asked this very question. “This very same thing must have happened across the upper Great Plains—South Dakota, Nebraska, Kansas,” he noted. Volcanic ash has been found in at least a dozen other locations throughout Nebraska, but all of them are only a foot thick. The layer of ash would need to be at least 8 feet or so to indicate the former presence of a waterhole.

Otto feels it’s only a matter of time until we find similar sites, especially “as erosion continues to wear away at the local sedimentary rock. Some day, a thick exposure of ash is going to erode out,” revealing another remarkable fossil site.

Decades of influence

The wealth of information this site provides can’t be overstated, nor can its impact on those who have studied it. Otto went from excavating the site as a student in the '70s to becoming the park’s superintendent for over 30 years. Tucker’s passion for Ashfall sparked a career in paleontology. Mosel, who reluctantly answered an ad for a “Clerk/Typist” at Ashfall 33 years ago, said, “I have loved every minute of it. It has been the best job.” The culture within Ashfall encouraged informal learning, Mosel said, a setting in which she thrived.

Rachel Short, who interned at Ashfall during the summers of 2009 and 2010, said it helped shape her career. Prior to college, she didn’t realize paleontology could be a profession—now she’s an assistant professor in the Department of Natural Resource Management at South Dakota State University. At Ashfall, she not only learned a great deal about fossil excavation but also about interacting with the public and effective science communication.

“I spent a lot of years being asked, ‘Why? Why do we care? Why are you doing this?’” she recalled. These types of questions are one of the reasons she says she works so hard to articulate the meaning of her research. “I think as paleontologists or scientists, we have a responsibility to tell people why we care and what we’re getting out of it.”

Approximately a decade after her work at Ashfall, she discovered another rhino species at the Gray Fossil Site in Tennessee. “I really struggled with ‘how do we make the rhinos mean something?’” she said. To find that meaning, she’s focusing on how the physical differences between the species are a product of their different diets and environments and whether those same mechanisms shape species today.

For all of its phenomenal fossil preservation and the profound impact it has had on those who have worked there, the park is still a bit of a hidden gem. “The one thing that amazes me,” Tucker admitted, “is how many people in Nebraska don’t even know this exists.”

As the world races to decarbonize everything from the electricity grid to industry, it faces particular problems with transportation—which alone is responsible for about a quarter of our planet’s energy-related greenhouse gas emissions. The fuels for transport need to be not just green, cheap, and powerful, but also lightweight and safe enough to be carried around.

Fossil fuels—mainly gasoline and diesel—have been extraordinarily effective at powering a diverse range of mobile machines. Since the Industrial Revolution, humanity has perfected the art of dredging these up, refining them, distributing them and combusting them in engines, creating a vast and hard-to-budge industry. Now we have to step away from fossil fuels, and the world is finding no one-size-fits-all replacement.

Each type of transportation has its own peculiarities—which is one reason we have different formulations of hydrocarbons today, from gasoline to diesel, bunker fuel to jet fuel. Cars need a convenient, lightweight power source; container ships need enough oomph to last months; planes absolutely need to be reliable and to work at subzero temperatures. As the fossil fuels are phased out, the transport fuel landscape is “getting more diverse,” says Timothy Lipman, co-director of the Transportation Sustainability Research Center at the University of California, Berkeley.

Every energy solution has its pros and cons. Batteries are efficient but struggle with their weight. Hydrogen—the lightest element in the universe—packs a huge energy punch, but it’s expensive to make in a “green” way and, as a gas, it takes up a lot of space. Liquid fuels that carry hydrogen can be easier to transport or drop into an existing engine, but ammonia is toxic, biofuels are in short supply, and synthetic hydrocarbons are hard to produce.

The scale of this energy transition is massive, and the amount of renewable energy the world will require to make the needed electricity and alternative fuels is “a little bit mind-blowing,” says mechanical engineer Keith Wipke, manager of the fuel cell and hydrogen technologies program at the National Renewable Energy Laboratory in Colorado. Everything, from the electrical grid to buildings and industry, is also thirsty for renewable power: It’s estimated that overall, the global demand for electricity could more than double by 2050. Fortunately, analyses suggest that renewables are up to the task. “We need our foot on the accelerator pedal of renewables 100 percent, as fast as we can, and it will all get used,” says Wipke.

In order to stay below 1.5° of planetary warming and limit some of the worst effects of climate change, the Intergovernmental Panel on Climate Change recommends that the world hit net-zero emissions by 2050—meaning that whatever greenhouse gases we still put into the air we take out in other ways, such as through forests or carbon capture. Groups including the International Energy Agency (IEA)—a Paris-based intergovernmental organization that analyzes the global energy sector—have laid out pathways that can get the world to net zero.

The IEA’s pathway describes a massive, hard-to-enact shift across the entire world, including all kinds of transport. Their goal: to replace fossil fuels (which release long-captured carbon into the air, where it wreaks havoc on the climate) with something more sustainable, like green hydrogen or biofuels (which either don’t produce greenhouse gases at all or recycle the ones that are already in the air).

Although some transportation sectors are still in flux, we can now get a pretty good glimpse of what will likely be powering the ships, planes, trains, and automobiles of tomorrow. Here’s a peek into that future.

Cars

Road passenger vehicles (including taxis, buses, and motorcycles) together make up the biggest chunk of global transport emissions—about 45 percent of them.

Today, the clear winner for light-duty traffic is electric batteries. (Of course, to cut emissions you need a green, renewable grid to provide the electricity; that transition is happening independently of transport.) More than a dozen nations have declared that all new cars must be electric by 2035 or earlier, and we’re on track to get there: About 14 million electric cars were sold in 2023, making up about 18 percent of new car sales. It wasn’t a clear path, though. “You learn more from your failures than you do your successes,” says Wipke: “There have been a lot of learnings along the way.”

Surprisingly, electric cars date back to the 1800s, when they were popular because they were simpler, quieter, and less smelly to drive than gasoline versions. It was the invention of Henry Ford’s Model T in the early 1900s that made gas cars the winner; these were less than half the price of electric roadsters of the time and had broader reach. They were a hit: Today there are over a billion gasoline-fueled vehicles on the road.

In the early 2000s, it looked like hydrogen fuel cells would be the solution to decarbonizing cars. These chemical cells are filled with hydrogen gas and then run like a battery—combining hydrogen with oxygen in the air to make power and water. Swapping to fuel cells would have given drivers a regimen similar to the one they were used to: the ability to go hundreds of miles between minutes-long refueling sessions. “The thought was, let’s not make people sacrifice or change their behaviors. Let’s give them something just like gasoline, but just a different fuel,” says Wipke.

But there were problems, predominantly in the logistical challenges of building a network of hydrogen filling stations, and the economics of producing all the needed hydrogen in a green way. “The big problem is not the vehicles — the vehicles are great. It’s the infrastructure,” says Lipman.

In the face of those issues, battery cars swung past fuel cells to market dominance, even though early versions of electric cars struggled to realize 100 miles in range and took hours, sometimes tens of hours, to fully recharge. The fact that you could just plug them in to existing electrical infrastructure was a huge bonus. And the overall efficiency of a battery is high—you don’t lose energy through the multiple steps of first creating a fuel and then powering your car. Plus, R&D promised ever better and cheaper batteries.

The challenge is achieving a high energy density (a lighter battery means a lighter car, which uses less energy per mile and so can go farther on a single charge), while keeping the battery cheap, safe, quick to charge, capable of powering bursts of acceleration, and operational across wide temperature ranges. Most electric cars today are powered by lithium-ion batteries, which have come a long way and are still improving. Since they were first commercialized in 1991, their average energy density by weight has more than doubled and prices have dropped by an order of magnitude. But there’s a limit to how good they can get, and lithium metal is prone to price spikes in the face of skyrocketing battery demand. So researchers and companies are pursuing two dramatic changes to battery tech.

As of 2023, some Chinese companies have started commercial production of sodium-ion batteries. Sodium is plentiful—it’s the sixth most common element on Earth—so it’s far, far cheaper than lithium, making it a great option for budget EVs. The trade-off is that sodium is heftier than lithium—each atom weighs 3.3 times more—which limits the energy that can be packed into any given battery weight. In other words, these batteries are heavy. Chinese cars with sodium batteries are expected to cost around $10,000 but go just 150 miles or so. Compare that to, say, a Tesla 3 (with a modern lithium-ion battery), which sells for more than four times as much but has over twice that range.

Car companies are also starting to promise solid-state batteries sometime within the next five years. Solid-state batteries get their name from the fact that they swap the liquid that’s typically in lithium-ion batteries with a thin layer of solid ceramic or polymer. This small-sounding shift offers safety benefits and opens the door to better options for the electrode ends of the battery. As a result, solid-state batteries promise much higher energy densities, though they haven’t yet hit the vehicle market. By 2027-28, Toyota plans to release a car with a solid-state battery that goes more than 600 miles on a single charge.

Overall, experts foresee roads filled with electric cars by 2050, but those cars will sport a variety of different types of batteries to suit users with different priorities: price or performance. We’re going to need a lot of batteries. In the IEA’s pathway to net-zero emissions by 2050, 60 percent of new car sales will be electric by 2030, requiring nearly 20 new gigascale battery factories to start up every year. That’s an epic—but doable—mission.

Trucks

Road freight vehicles—including massive semitrucks—make up the next-largest slice of the transport emissions pie, accounting for nearly 30 percent. For these heavy-duty road vehicles, especially long-haul ones, one preferred solution now harkens back to the original plan for decarbonizing cars: fuel cells.

Say you have an 18-wheeler pulling 80,000 pounds and need to go 500 to 600 miles. “To store that much energy in batteries could require up to 10,000 pounds of batteries on your truck,” says Wipke, “whereas maybe it’s 1,000 to 2,000 pounds of hydrogen storage, including the fuel cell.” And a hydrogen tank can be refilled in minutes. This translates to easier logistics for trucking companies, and less weight means less energy needed.

Like batteries, fuel cells have improved since their invention. “Hydrogen has made a lot of strides in the last 20 years, technically,” Wipke says. The pressure that the hydrogen can be stored under in a car has doubled, for example, so more fuel can be packed into a given space. And designers have overcome the problem of water freezing inside the fuel cell and breaking it.

Though the fiery inferno of the 1937 Hindenburg airship disaster gave hydrogen fuel an enduring bad reputation, experts point out that all fuels are flammable. Researchers typically say that a well-built hydrogen car is generally no riskier than a gasoline one—hydrogen, for example, is so light that it tends to float away quickly if a crash or leak occurs. There are also fail-safe technologies at hydrogen filling stations to prevent someone from just spraying it around, notes Wipke—which don’t exist for gasoline. But hydrogen filling stations are hard to make reliable. “You have compressors, you have flow valves. As a result, there’s more things that could break,” Wipke says.

Those kinks should be ironed out as fuel cell usage ramps up. In May, the Atlanta-based nonprofit Center for Transportation and the Environment opened the world’s largest-yet hydrogen fueling station. Located near Berkeley, California, it is designed to power 30 trucks that will take shipping containers and cars from the Port of Oakland to their next stop. Lipman is involved, with his team crunching all the numbers on the station’s reliability and usage, along with overseeing the trucks themselves. If all goes well, he says, it will expand. “We’re hoping to have thousands of trucks in 10 years.”

California isn’t alone in its pursuit of hydrogen. As of 2023, the US Department of Energy has invested $8 billion in a Regional Clean Hydrogen Hubs Program, establishing up to 10 centers that can make and distribute hydrogen fuel. Globally, hydrogen use in road transport increased by around 45 percent in 2022 over 2021 (although that’s still just tens of thousands of trucks and buses in total around the world).

A big challenge, though, is to make all the needed hydrogen in a green way. Although hydrogen is plentiful (it’s the most abundant element in the universe) and there are some natural geological deposits to mine, creating a pure, concentrated supply takes energy. The cheapest way to get hydrogen is to steam-reform fossil fuels, but this produces carbon dioxide. The cleanest way is to use renewable electricity to crack water into hydrogen and oxygen but making such “green hydrogen” is much, much more expensive.

As of 2022, hydrogen demand hit nearly 100 million metric tons, but less than 1 percent of this was made in a low-emissions way. According to the IEA’s net-zero pathway, the world will need twice this amount of hydrogen for fuels by 2030, including 11 million metric tons of straight hydrogen power for transport. The IEA has documented a lot of political support for green hydrogen, and a steep increase in the rate at which low-emission hydrogen production projects are being announced, which is all good news. But actual, real-world deployment, the agency notes, is “not taking off” and a lot more policy support is needed to get it to ramp up.

Trains

Rail is already the most electrified transport subsector, according to the IEA, and makes up only a slim 1 percent of transport emissions. So this is the smallest, most-solved problem of the batch.

Trains, like trucks, are heavy beasts that need a lot of power. But many trains already run on electric wires or rails. Others use a fuel, usually diesel, but turn that into electricity on board in order to power an electric motor (which has better torque than a fossil-fuel-fed engine). It’s a relatively simple step to swap out that diesel for something else, like hydrogen or batteries, to supply power for an already-existing electric motor. “Trains are pretty easy to electrify,” says chemical engineer Hartej Singh, who analyzes decarbonization for the nonprofit Rocky Mountain Institute in Washington, DC.

Expanding electric rail, the IEA says, is a good idea—especially if it replaces flights. Today, every mile a passenger travels on a train has, on average, one-fifth the emissions of the same distance traveled on a plane. But, the IEA notes, putting in a new electric rail line is an expensive proposition.

Ships

Shipping—accounting for about 10 percent of transport emissions—has a particular need to go extraordinary distances and lengths of time before refueling: Crossing an ocean calls for weeks-long journeys of thousands of miles.

Shipping currently predominantly uses bunker fuel—a high-sulfur variant of fossil fuel often described as the gunk left over at the bottom of an oil barrel. But that’s changing fast, thanks to International Maritime Organization goals, adopted in 2023, to hit net-zero emissions by close to 2050. “That’s basically the entire global fleet needing to transition off fossil fuels,” says Tristan Smith, an engineer at University College London who studies shipping. For now, just 1.2 percent of the ships in the global fleet use lower-emission fuels, but 21 percent of the new ships on order are designed to run on these alternatives. Smith sees a clear path ahead to get where shipping needs to go.

For now, one popular low-emission alternative is bio-methanol (made from plants). But this is a short-term distraction, says Smith: There’s simply not enough land to grow enough biofuel stock for the global fleet. For the long term, he’s betting on ammonia—NH₃—as the best solution.

This is a hydrogen-rich liquid fuel that provides a lot of oomph. Plus, we already know how to make it and move it around; globally some 150 million metric tons are produced every year, mainly for fertilizer. Ammonia counterintuitively works out to be cheaper than straight hydrogen, notes Smith (even though it has hydrogen as an ingredient), because pure hydrogen comes with the extra energy and cost burden of putting it under pressure and keeping it cold to store it. Ammonia, by contrast, is relatively easy to keep liquid. And though ammonia requires more storage space than fossil fuels, this matters less for ships than for, say, cars.

You do have to redesign your engine to run on ammonia, though. Ammonia is hard to ignite, and the engine needs catalysts to remove other pollutants, like the greenhouse gas nitrous oxide. All of this is being tackled: The Green Pioneer, run by Australian mining and green energy company Fortescue, is the first ship to trial an ammonia-burning engine (with some diesel in the mix), along with refueling strategies and safety protocols. The main problem with ammonia, says Smith, is that it’s toxic, so spills are nasty. All in all, Smith sees a clear path ahead for ammonia. “We can see a situation where there’s an explosion of ordering [of ammonia-engine ships] from the middle of next year,” he says.

Ammonia will put yet more strain on the demand for green hydrogen. By 2030, the IEA calls for an additional 8 million metric tons of hydrogen for ammonia-based transport fuels, on top of the 11 million metric tons of straight hydrogen for transport uses. There’s billions of dollars of investment already being plowed into green ammonia, Smith says. “We need lots of billions.”

There are additional ways to reduce emissions from ships—including shipping less cargo to begin with, improving logistics to run fewer ships shorter distances, designing sleeker hulls, and even putting up modern sails. That includes strange rotating poles called Flettner rotors that can help to propel a ship in a way similar to how a spinning baseball moves sideways in the air. All of them could help to whittle down shipping’s carbon burden.

Planes

Perhaps the hardest sector to decarbonize is aviation, which makes up about 12 percent of the transport emission pie. A plane must fight gravity, so it can’t carry a fuel that’s too heavy. The fuel can’t take up too much room, needs to work at the freezing temperatures found at altitude, and above all, it must be reliable. “It’s one thing if a truck or a car loses its propulsion and it coasts to the side of the road. It’s much different if you’re in the air and you lose power,” says Wipke.

In 2022, the United Nations’ International Civil Aviation Organization pledged for the industry to become carbon neutral by 2050, so the race is on to swap out the current fuel, kerosene, for something cleaner: sustainable aviation fuels. Most of these fuels still spew carbon dioxide out of the tailpipe, but since many are made from something, such as plants, that originally removed carbon dioxide from the air, the net effect can be to cut emissions at least in half, if not almost entirely. As of 2022, around 300 million to 450 million liters of “sustainable fuels” were being used in aviation — but that’s less than 0.15 percent of the total market.

For now, the most cost-effective option for sustainable fuel is biofuel made from fats, oils, and greases (such as used cooking oil) that have been chemically converted into kerosene. This is a mature, already-commercial technology, says the RMI’s Singh, who focuses on aviation fuels. But long-term, there simply isn’t enough of this source material. “We could probably only cover about 6 percent of demand by 2050,” says Singh.

The next option is biofuel made from forestry residue, such as fallen branches and logs or even nut husks. This source material could provide about as much fuel as waste oils, but the chemical conversion is more complicated; the one company Singh knew of trying to make this work commercially recently shut down its biggest plant.

One long-term option for sustainable jet fuel is to make hydrocarbons from recycled air. These synthetic fuels (sometimes called power-to-liquid fuels, or e-fuels) take carbon dioxide from the air and combine that carbon with low-emission hydrogen (yes, yet more low-emission hydrogen). Direct air capture plants, as they’re called, are industrial facilities that use liquids or solids like a sponge to sop up CO₂ from the ambient air. These are just now ramping up to large-scale commercial operation: The planet’s first megaton-scale plant — sucking around half a million metric tons of CO₂ from the air each year — should be opening in Texas in 2025.

Using straight hydrogen is also a possible long-term option, either by burning it in an engine (the way NASA launches rockets) or using it to run a fuel cell. But that requires special tanks to store hydrogen at high enough pressures and low enough temperatures to fit into a plane. “You need to reconfigure the entire way we think about airplane design,” says Singh. A few companies are taking the possibility of hydrogen flight very seriously, including H2FLY, a subsidiary of Joby Aviation, which ran a test flight of a small demonstration hydrogen plane in September 2023. Airbus and a partner are now working toward building a liquid hydrogen airport-refueling facility in Toulouse, France.

“I think we underestimate this skill of the engineers,” says Smith, who sees the difficulties with ammonia-powered ship engines and hydrogen-fuel-cell-powered planes as surmountable obstacles. “You just put some good engineers on a project, and they systematically work through everything.”

Batteries are also a possibility, especially for shorter, smaller flights like those taken by electric vertical takeoff and landing craft (eVTOLs), which are essentially flying taxis. A lot of long-shot research is being done now on batteries that are hard to make work but would have spectacular potential. Lithium-air batteries, for example would pull oxygen from the air on the go as one vital electrode ingredient, making them incredibly lightweight and well suited to aviation.

“We need to think of this as a jigsaw puzzle,” says Singh, with different pieces filling in different parts of the problem. Batteries might end up powering short hops, while fuel cells tackle regional traffic, and sustainable fuels get saved up for the long-haul flights that are too hard to electrify.

In fact, the whole transport sector is a puzzle, with many pieces needed to complete a picture that’s not quite clear yet. “I can’t see the future any better than anybody, or I probably would be retired right now,” says Wipke. “But I do really enjoy watching things evolve. The pace of development is tremendous.”

Welcome to Edition 7.01 of the Rocket Report! We're compiling this week's report a day later than usual due to the Independence Day holiday. Ars is beginning its seventh year publishing this weekly roundup of rocket news, and there's a lot of it this week despite the holiday here in the United States. Worldwide, there were 122 launches that flew into Earth orbit or beyond in the first half of 2024, up from 91 in the same period last year.

As always, we welcome reader submissions, and if you don't want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Firefly launches its fifth Alpha flight. Firefly Aerospace placed eight CubeSats into orbit on a mission funded by NASA on the first flight of the company’s Alpha rocket since an upper stage malfunction more than half a year ago, Space News reports. The two-stage Alpha rocket lifted off from Vandenberg Space Force Base in California late Wednesday, two days after an issue with ground equipment aborted liftoff just before engine ignition. The eight CubeSats come from NASA centers and universities for a range of educational, research, and technology demonstration missions. This was the fifth flight of Firefly's Alpha rocket, capable of placing about a metric ton of payload into low-Earth orbit.

Anomaly resolution ... This was the fifth flight of an Alpha rocket since 2021 and the fourth Alpha flight to achieve orbit. But the last Alpha launch in December failed to place its Lockheed Martin payload into the proper orbit due to a problem during the relighting of its second-stage engine. On this week's launch, Alpha deployed its NASA-sponsored payloads after a single burn of the second stage, then completed a successful restart of the engine for a plane change maneuver. Engineers traced the problem on the last Alpha flight to a software error. (submitted by Ken the Bin)

Two companies added to DoD's launch pool. Blue Origin and Stoke Space Technologies — neither of which has yet reached orbit — have been approved by the US Space Force to compete for future launches of small payloads, Breaking Defense reports. Blue Origin and Stoke Space join a roster of launch companies eligible to compete for launch task orders the Space Force puts up for bid through the Orbital Services Program-4 (OSP-4) contract. Under this contract, Space Systems Command buys launch services for payloads 400 pounds (180 kilograms) or greater, enabling launch from 12 to 24 months of the award of a task order. The OSP-4 contract has an "emphasis on small orbital launch capabilities and launch solutions for Tactically Responsive Space mission needs," said Lt. Col. Steve Hendershot, chief of Space Systems Command's small launch and targets division.

Italian startup test-fires small rocket. Italian rocket builder Sidereus Space Dynamics has completed the first integrated system test of its EOS rocket, European Spaceflight reports. This test occurred Sunday, culminating in a firing of the rocket's kerosene/liquid oxygen MR-5 main engine for approximately 11 seconds. The EOS rocket is a novel design, utilizing a single-stage-to-orbit architecture, with the reusable booster returning to Earth from orbit for recovery under a parafoil. The rocket stands less than 14 feet (4.2 meters) tall and will be capable of delivering about 29 pounds (13 kilograms) of payload to low-Earth orbit.

A lean operation ... After it completes integrated testing on the ground, the company will conduct the first low-altitude EOS test flights. Founded in 2019, Sidereus has raised 6.6 million euros ($7.1 million) to fund the development of the EOS rocket. While this is a fraction of the funding other European launch startups like Isar Aerospace, MaiaSpace, and Orbex have attracted, the Sidereus’s CEO, Mattia Barbarossa, has previously stated that the company intends to “reshape spaceflight in a fraction of the time and with limited resources.” (submitted by EllPeaTea and Ken the Bin)

"I want to break free." One of the most promising Chinese space startups, Space Pioneer, experienced a serious anomaly last weekend while testing the first stage of its Tianlong 3 rocket near the city of Gongyi, Ars reports. The rocket was undergoing a static fire test of the stage, in which a vehicle is clamped to a test stand while its engines are ignited, when the booster broke free. According to a statement from the company, the rocket was not sufficiently clamped down and blasted off from the test stand "due to a structural failure." The Tianlong 3 is a medium-lift rocket modeled on SpaceX's Falcon 9, with nine engines clustered on its first stage, and Space Pioneer aims to make the first stage recoverable and reusable eventually. But with this accident, Space Pioneer won't be achieving its goal of intentionally launching Tianlong 3 later this year.

"It's strange, but it's true" ... The videos of Tianlong 3's accidental ascent are remarkable, showing the rocket climbing several hundred meters into the sky before crashing explosively into a mountain about 1.5 kilometers from the test site. (See various angles of the accident here, on the social media site X, or on Weibo.) The statement from Space Pioneer sought to downplay the incident, saying it had implemented safety measures before the test, and there were no casualties as a result of the accident. "The test site is far away from the urban area of Gongyi," the company said. However, the test stand is located about 5 kilometers from downtown Gongyi, a city of about 800,000 people. (submitted by Ken the Bin, Marakai, and gizmo23)

Checking in on Firefly's reusable rocket. The new medium-lift rocket under development by Firefly Aerospace and Northrop Grumman will eventually incorporate a recoverable booster that will return to its launch site in Virginia for reuse, Ars reports. Firefly has previously suggested rocket reuse is on the roadmap for the new rocket—known, for now, only as the Medium Launch Vehicle (MLV)—but officials revealed new details of the plan during a recent visit by Ars to Firefly's rocket factory in rural Central Texas. MLV's first stage booster is designed for propulsive landings back at its launch site at Wallops Island, Virginia, and Firefly officials said they will begin experimenting with recovery techniques on MLV's first flight.

Necessary to compete ... "Northrop and Firefly have a similar perspective and that is, for that class of rocket, reusability is a requirement for a bunch of reasons," said Bill Weber, Firefly's CEO. "Economically, it becomes an advantage because we don't have to go build additional floor space... Similarly, the pricing structure for customers starts to get super competitive." Firefly and Northrop Grumman announced a partnership in 2022 to develop the MLV, which includes a kerosene-fueled first stage and second stage. Initially, though, Firefly will build MLV first stages to marry with Northrop's solid-fueled upper stage used on the Antares rocket to continue launching cargo to the International Space Station.

Eumetsat ditches Ariane 6. In a shocking announcement this week, the European intergovernmental organization responsible for launching and operating the continent's weather satellites has pulled its next mission off a future launch of Europe's new Ariane 6 rocket, Ars reports. Instead, the valuable MTG-S1 satellite will now reach geostationary orbit on SpaceX's Falcon 9 rocket in 2025. “This decision was driven by exceptional circumstances,” said Phil Evans, director general of the organization Eumetsat. “It does not compromise our standard policy of supporting European partners, and we look forward to a successful SpaceX launch for this masterpiece of European technology.”

Intriguing timing ... The decision, taken at a council meeting of Eumetsat's 30 member nations last week, comes shortly before the debut of the Ariane 6 rocket, scheduled for July 9. Outwardly, at least, this decision reflects a lack of confidence in the reliability of the Ariane 6, the ability of European companies ArianeGroup and Arianespace to produce future versions of the Ariane 6, or both. It comes not just on the eve of the long-awaited debut of the Ariane 6, but also at a time when European officials are trying to close ranks and ensure that satellites built in Europe get launched on European rockets. (submitted by Ken the Bin)

H3's first operational flight. The Japan Aerospace Exploration Agency (JAXA) successfully put an advanced Earth observation satellite into orbit via its new flagship H3 rocket on Monday, the Japan Times reports. The H3 rocket launched the Daichi 4 satellite, also known as ALOS-4, with a synthetic aperture radar instrument for all-weather observations of Earth's surface. “It was truly a perfect launch, a perfect 100 out of 100,” said Makoto Arita, the JAXA H3 project team manager. Japan's H3 rocket launched for the first time last year, following a decade of development, but it failed to reach orbit due to a malfunction on its second stage. A $200 million Earth observation satellite was lost on the doomed rocket. A second test flight of the H3 rocket in February was successful, and this time the launcher only carried small test payloads.

Entry into service ... This was the third flight of the expendable H3 rocket, and the first launch that Japan's space agency considered to be operational. The H3 will become the workhorse for Japan's space program over the next decade or more, launching scientific probes, spy satellites, and cargo missions to the International Space Station. It will fly about six times per year, according to JAXA, up from the cadence of three flights per year achieved by the H-IIA rocket, the vehicle the H3 will replace. There are two more H-IIA rockets left to fly later this year. (submitted by tsunam and Ken the Bin)

SpaceX wins new NASA launch contract. A small research satellite designed to study the violent processes behind the creation and destruction of chemical elements will launch on a SpaceX Falcon 9 rocket in 2027, Ars reports. The Compton Spectrometer and Imager (COSI) mission features a gamma-ray telescope that will scan the sky to study gamma rays emitted by the explosions of massive stars and the end of their lives. These supernova explosions generate reactions that fuse new atomic nuclei, a process called nucleosynthesis, of heavier elements. NASA awarded SpaceX a firm-fixed-price contract valued at $69 million to launch the COSI mission, but the agency didn't have much of a decision to make in the COSI launch contract. The Falcon 9 is the only rocket certified by NASA that can launch a satellite with the mass of COSI into its desired orbit.

An unusual orbit ... COSI is a relatively small spacecraft, built by Northrop Grumman and weighing less than a ton, but it will ride alone into orbit on top of a Falcon 9 rocket. That's because COSI will operate in an unusual orbit about 340 miles (550 kilometers) over the equator, an orbit chosen to avoid interference from radiation over the South Atlantic Anomaly, the region where the inner Van Allen radiation belt comes closest to Earth’s surface. The Falcon 9 will deliver COSI directly into its operational orbit after taking off from Cape Canaveral, Florida, and then will fire its upper stage in a sideways maneuver to make a turn at the equator. This type of maneuver—called a plane change— takes a lot of energy, or delta-V, on par with the delta-V required to put a heavier satellite into a much higher orbit. (submitted by Ken the Bin)

Polaris Dawn launching later this month. The Polaris Dawn mission, an all-private spaceflight that will include the first commercial spacewalk, is scheduled for launch no earlier than July 31 from Florida's Space Coast, the group behind the mission announced on X. This is a few weeks later than the mission's previous target launch date of July 12, but officials didn't explain the delay. Jared Isaacman, a billionaire businessman and pilot who has flown in space before, will command the Polaris Dawn mission. Former US Air Force fighter pilot Scott Poteet and two SpaceX engineers, Sarah Gillis and Anna Menon, will also fly on Polaris Dawn.

Going higher ... The foursome of commercial astronauts will launch aboard a SpaceX Falcon 9 rocket and Crew Dragon spacecraft, reaching an altitude of 870 miles (1,400 kilometers), higher than anyone has flown since the last Apollo mission in 1972. They will depressurize the Dragon spacecraft and Isaacman and Gillis will exit the capsule for a brief spacewalk, the first ever without involvement of a government space agency. The mission will last approximately five days.

SpaceX soon plans to catch a Super Heavy booster. In a short video released Thursday, possibly to celebrate the US Fourth of July holiday with the biggest rocket's red glare of them all, SpaceX provided new footage of the most recent test of its Starship launch vehicle. This flight of Starship on June 6 marked significant progress for SpaceX's mega-rocket, including an on-target splashdown of the rocket's Super Heavy booster in the Gulf of Mexico. At the end of the new highlights video, there is a simulated view showing Starship's first stage descending back toward the launch tower with the title "Flight 5." And then it fades out. This supports the idea that SpaceX is working toward attempting a Starship booster catch on its next flight test, which likely will occur later this summer, Ars reports. Doubtless, the company still has both technical and regulatory work before this can happen.

Beryl bearing down … Meanwhile, activities at the South Texas launch site may well be curtailed for a couple of days as Hurricane Beryl enters the Gulf of Mexico later on Friday and then tracks toward the Texas coast early next week. The center of Beryl is expected to pass near or north of the launch site late on Sunday night or Monday, bringing winds and surges. However, because Beryl is not expected to be a major hurricane in terms of wind speed, these impacts should not prove catastrophic to SpaceX facilities.

Not enough room for Starship? United Launch Alliance and Blue Origin are worried about SpaceX's plans to launch its enormous Starship rocket from Florida, Ars reports. In documents submitted to the Federal Aviation Administration last month, ULA and Blue Origin raised concerns about the impact of Starship launch operations on their own activities on Florida's Space Coast. Blue Origin, Jeff Bezos' space company, urged the federal government to consider capping the number of Starship launches and landings, test-firings, and other operations, and limiting SpaceX's activities to particular times. ULA suggested the FAA consider outright denying SpaceX's proposal to launch Starship from Kennedy Space Center, supposedly out of concern it would have to evacuate its nearby launch pad for every Starship launch and landing.

A pattern of protest … It's understandable that ULA and Blue Origin wouldn't want to halt work at their launch pads for several Starship launches every week. But this isn't the first time SpaceX's top two rivals in the US launch industry have tried to block Elon Musk's space company from establishing a new launch site. In 2013, Blue Origin and SpaceX fought for rights to lease Launch Complex 39A from NASA after the retirement of the space shuttle. SpaceX won, signed a lease with NASA the next year, and began launching Falcon 9 rockets from the launch pad in 2017. Musk offered to let Blue Origin also use the launch pad if it could launch a human-rated spacecraft to the International Space Station within five years. This led to one of the most famous Elon Musk quotes in the long-running rivalry: "Frankly, I think we are more likely to discover unicorns dancing in the flame duct."

Next three launches

July 8: Falcon 9 | Türksat 6A | Cape Canaveral Space Force Station, Florida | 21:20 UTC

July 9: Falcon 9 | Starlink 9-3 | Vandenberg Space Force Base, California | 02:46 UTC

July 9: Ariane 62 | Demo Flight | Guiana Space Center, French Guiana | 18:00 UTC

Supermassive black holes are ravenous. Clumps of dust and gas are prone to being disrupted by the turbulence and radiation when they are pulled too close. So why are some of them orbiting on the edge of the Milky Way’s own supermassive monster, Sgr A*? Maybe these mystery blobs are hiding something.

After analyzing observations of the dusty objects, an international team of researchers, led by astrophysicist Florian Peißker of the University of Cologne, have identified these clumps as potentially harboring young stellar objects (YSOs) shrouded by a haze of gas and dust. Even stranger is that these infant stars are younger than an unusually young and bright cluster of stars that are already known to orbit Sgr A*, known as the S-stars.

Finding both of these groups orbiting so close is unusual because stars that orbit supermassive black holes are expected to be dim and much more ancient. Peißker and his colleagues “discard the en vogue idea to classify [these] objects as coreless clouds in the high energetic radiation field of the supermassive black hole Sgr A*,” as they said in a study recently published in Astronomy & Astrophysics.

More than just space dust

To figure out what the objects near Sgr A* might be the, researchers needed to rule out things they weren’t. Embedded in envelopes of gas and dust, they maintain especially high temperatures, do not evaporate easily, and each orbits the supermassive black hole alone.

The researchers determined their chemical properties from the photons they emitted, and their mid- and near-infrared emissions were consistent with those of stars. They used one of them, object G2/DSO, as a case study to test their ideas about what the objects might be. The high brightness and especially strong emissions of this object make it the easiest to study. Its mass is also similar to the masses of known low-mass stars.

YSOs are low-mass stars that have outgrown the protostar phase but have not yet developed into main sequence stars, with cores that fuse hydrogen into helium. These objects like YSO candidates because they couldn’t possibly be clumps of gas and space dust. Gaseous clouds without any objects inside to hold them together via gravity could not survive so close to a supermassive black hole for long. Its intense heat causes the gas and dust to evaporate rather quickly, with heat-excited particles crashing into each other and flying off into space.

The team figured out that a cloud comparable in size to G2/DSO would evaporate in about seven years. A star orbiting at the same distance from the supermassive black hole would not be destroyed nearly as fast because of its much higher density and mass.

Another class of object that the dusty blobs could hypothetically be—but are not—is a compact planetary nebula or CPN. These nebulae are the expanding outer gas envelopes of small to medium stars in their final death throes. While CPNs have some features in common with stars, the strength of a supermassive black hole’s gravity would easily detach their gas envelopes and tear them apart.

It is also unlikely that the YSOs are binary stars, even though most stars form in binary systems. The scorching temperatures and turbulence of SGR A* would likely cause stars that were once part of binaries to migrate.

Seeing stars

Further observations determined that some of the dust-obscured objects are nascent stars, and while others are thought to be stars of some kind, but haven’t been definitively identified.

The properties that made G2/DSO an exceptional case study are also the reason it has been identified as a YSO. D2 is another high-luminosity object about as massive as a low-mass star, which is easy to observe in the near- and mid-infrared. D3 and D23 also have similar properties. These are the blobs near the black hole that the researchers think are most likely to be YSOs.

There are other candidates that need further analysis. These include additional objects that may or may not be YSOs, but still show stellar characteristics: D3.1 and D5, which are difficult to observe. The mid-infrared emissions of D9 are especially low when compared to the other candidates, but it is still thought to be some type of star, though possibly not a YSO. Objects X7 and X8 both exhibit bow shock—the shockwave that results from a star’s stellar wind pushing against other stellar winds. Whether either of these objects is actually a YSO remains unknown.

Where these dusty objects came from and how they formed is unknown for now. The researchers suggest that the objects formed together in molecular clouds that were falling toward the center of the galaxy. They also think that, no matter where they were born, they migrated towards Sgr A*, and any that were in binary systems were separated by the black hole’s immense gravity.

While it is unlikely that the YSOs and potential YSOs originated in the same cluster as the slightly older S-stars, they still might be related in some way. They might have experienced similar formation and migration journeys, and the younger stars might ultimately reach the same stage.

“Speculatively, the dusty sources will evolve into low-mass S stars,” Peißker’s team said in the same study.

Even black holes look better with a necklace of twinkling diamonds.

Astronomy and Astrophysics, 2024.  DOI: 10.1051/0004-6361/202449729

Because most things about Earth change so slowly, it's difficult to imagine them being any different in the past. But Earth's rotation has been slowing due to tidal interactions with the Moon, meaning that days were considerably shorter in the past. It's easy to think that a 22-hour day wouldn't be all that different, but that turns out not to be entirely true.

For example, some modeling has indicated that certain day lengths will be in resonance with other effects caused by the planet's rotation, which can potentially offset the drag caused by the tides. Now, a new paper looks at how these resonances could affect the climate. The results suggest that it would shift rain to occurring in the morning and evening while leaving midday skies largely cloud-free. The resulting Earth would be considerably warmer.

On the Lamb

We're all pretty familiar with the fact that the daytime Sun warms up the air. And those of us who remember high school chemistry will recall that a gas that is warmed will expand. So, it shouldn't be a surprise to hear that the Earth's atmosphere expands due to warming on its day side and contracts back again as it cools (these lag the daytime peak in sunlight). These differences provide something a bit like a handle that the gravitational pulls of the Sun and Moon can grab onto, exerting additional forces on the atmosphere. This complicated network of forces churns our atmosphere, helping shape the planet's weather.

Two researchers, Russell Deitrick and Colin Goldblatt at Canada's University of Victoria, were curious as to what would happen to these forces as the day length got shorter. Specifically, they were interested in a period where the day's length would be at resonance with phenomena called Lamb waves.

Lamb waves aren't specific to the atmosphere. Rather, they're a specific manner in which a disturbance can travel through a medium, from vibrations in a solid to sound through the air.

Although various forces can create Lamb waves in the atmosphere, they'll travel with a set of characteristic frequencies. One of those is roughly 10.5 to 11 hours. As you go back in time to shorter days, you'll reach a point where the Earth's day was a bit shorter than 22 hours, or twice the period of the Lamb waves. At this point, any disturbances in the atmosphere related to day length would have the ability to interact with the Lamb waves that were set off the day prior. This resonance could potentially strengthen the impact of any atmospheric phenomena related to day length.

Figuring out whether they do turned out to be a bit of a challenge. There are plenty of climate models to let researchers explore what's going on in the modern atmosphere. But a lot of these have key features, like day length and solar output, hard coded into them. Others don't let you do things like rearrange the Earth's continents or change some atmospheric components.

The researchers did find a model that would allow them to change day length, solar intensity, and carbon dioxide concentrations to those present when Earth's day length was 22 hours (which was likely to be in the pre-Cambrian). But it wasn't able to reset the ozone concentrations, and ozone is also a greenhouse gas. So, they ran simulations without ozone, which are expected to be an under-estimate, and one where they elevated methane concentrations in order to mimic ozone's greenhouse effect.

Nothing but sunshine

As the researchers tested day lengths between 16 and 24 hours, the point of resonance was obvious. Things like average temperatures and the difference between day and night pressures started rising when day lengths reached 21 hours and peaked at a 22-hour day length before declining again. And the differences were substantial. The present-day difference between minimal and peak daily pressures is about 110 Pascals. At a day length of 22 hours, it was 330 Pascals, a threefold increase.

The increase in average temperatures is on the order of 2 Kelvin. We're currently trying to avoid that sort of temperature rise due to the potential for widespread ecological disruptions. The addition of methane to mimic ozone leads to an increase of 4 Kelvin. Accordingly, atmospheric moisture goes up by about 10 percent, and the amount of precipitation by five percent.

But why does the Earth get warmer when the days are shorter? In part due to the altered pressure changes, the organization of tropical clouds changes. Now, peaks in cloud cover and precipitation occur in the morning and evening; the daytime in between is largely cloud-free. This means that the peak of absorption of solar energy now coincides with the peak in sunshine.

Deitrick and Goldblatt note that, given how long the Moon has been slowing down the Earth's rotation, a period like this is inevitable at some point in our past. The question is when.

As we noted above, there's a similar atmospheric/orbital resonance that may offset the Moon's drag on our rotation, leading to an extended period where the Earth's day length remains largely unchanged. Deitrick and Goldblatt see no clear evidence of that resonance in this work. And a simple extrapolation back suggests that this resonance may have occurred shortly (in geological terms) before the Cambrian.

And that's an interesting time. Thanks to the contribution of a fainter Sun, the Earth went through a number of global glaciations immediately prior to the Cambrian. The ice is thought to have blocked the exchange of carbon dioxide with the ocean, allowing it to build up in the atmosphere and eventually warm the planet enough to melt it out of the snowball phase. But this resonance has the potential to drive a melt even without the greenhouse gas buildup.

If this holds up in further studies, that may mean that a lot of the complex life on Earth owes its existence to the warming driven by this atmospheric resonance.

Nature Geoscience, 2024. DOI: 10.1038/s41561-024-01469-3  (About DOIs).

Ah, cats. We love our furry feline overlords despite the occasional hairball and their propensity to scratch the furniture to sharpen their claws. The latter is perfectly natural kitty behavior, but overly aggressive scratching is usually perceived as a behavioral problem. Veterinarians frown on taking extreme measures like declawing or even euthanizing such "problematic" cats. But there are alternative science-backed strategies for reducing or redirecting the scratching behavior, according to the authors of a new paper published in the journal Frontiers in Veterinary Science.

This latest study builds on the group's prior research investigating the effects of synthetic feline facial pheromones on undesirable scratching in cats, according to co-author Yasemin Salgirli Demirbas, a veterinary researcher at Ankara University in Turkey. "From the beginning, our research team agreed that it was essential to explore broader factors that might exacerbate this issue, such as those influencing stress and, consequently, scratching behavior in cats," she told Ars. "What’s new in this study is our focus on the individual, environmental, and social dynamics affecting the level of scratching behavior. This perspective aims to enhance our understanding of how human and animal welfare are interconnected in different scenarios."

The study investigated the behavior of 1,211 cats, with data collected via an online questionnaire completed by the cats' caregivers. The first section collected information about the caregivers, while the second asked about the cats' daily routines, social interactions, environments, behaviors, and temperaments. The third and final section gathered information about the frequency and intensity of undesirable scratching behavior in the cats based on a helpful "scratching index."

The team concluded that there are several factors that influence the scratching behavior of cats, including environmental factors, high levels of certain kinds of play, and increased nocturnal activity. But stress seems to be the leading driver. "Cats might scratch more as a way to relieve stress or mark their territory, especially if they feel threatened or insecure," said Demirbas. And the top source of such stress, the study found, is the presence of small children in the home.

Cats + kids = stress

"The presence of children can definitely influence a cat's stress levels, but it is a complex situation," said Demirbas. "Children, especially when young, tend to move quickly and unpredictably, which can be challenging for cats. Their loud noises and sudden movements can be distressing for cats. Additionally, children might not always understand how to approach cats properly. Rough handling, in particular, can make cats feel threatened and stressed. Another factor is that children can invade the cat's safe spaces, playing or resting in areas the cat considers its own core territories."

How stressful any given cat finds said children also depends in part on the cat's temperament. "A cat’s reaction to children can vary based on its personality and past experiences," said Demirbas. "Cats that are naturally more nervous or have had negative encounters with children before are likely to be more stressed. Conversely, well-socialized cats or those accustomed to being around different people and situations tend to handle the presence of children better."

However, the authors caution that the link between small children in the home and increased scratching is not well understood and requires more research. "If children are taught to respect and handle cats properly, they are less likely to stress the cats out," said Demirbas. "If a cat has enough space to retreat to a safe, quiet area when feeling overwhelmed, they can manage their stress better. Overall, the specific dynamics between cats and children can vary widely. Further detailed studies on these factors can help manage the situation better."

And while too little playtime can adversely affect cat behavior, overstimulation by too much play—or the wrong kind of play—can also have a negative impact. "For cats, structured and routine play is crucial," said Demirbas. "Since play in cats, especially solitary play, originates from hunting behaviors, organized play sessions that mimic hunting are crucial for their well-being. Extended play sessions that do not result in successful hunting or satisfaction (often caused by toys like laser pointers) can induce stress responses due to frustration, overstimulation, and hyperarousal. Similarly, inadequate or lack of play contradicts cats' biology and can lead to distress. The optimal approach involves offering short yet repetitive and successful play sessions. This method mentally and physically stimulates cats, enhances their well-being, and helps prevent undesirable behaviors."

Some of these factors are more easily addressed than others. Providing items such as proper scratching posts placed near the areas a cat frequents, toys, elevated observation spots, and other enrichment options, including pheromone products, can help. Our cat Caliban, for instance, loves to scratch a particular spot on the living room sofa. We placed a scratching post in front of it and now he scratches that—an effective redirection of his otherwise normal scratching behavior.

What you shouldn't do is punish the cat or engage in what's known as "positive punishment": essentially a kind of behavioral aversion therapy akin to positive reinforcement, in which every time a cat engages in unwanted scratching, the caregiver adds an adverse stimulus immediately after. Per Demirbas, positive punishment is more likely to lead to confusion, distress, and increased stress in cats—the opposite of what one should be trying to achieve.

“Understanding the underlying emotional motivations of scratching behavior, such as frustration, which seem to be linked to personality traits and environmental factors, allows caregivers to address these issues directly," said Demirbas. “Our findings can help caregivers redirect scratching to appropriate materials, which could help foster a more harmonious living environment for both cats and their caregivers.”

Frontiers in Veterinary Science, 2024. DOI: 10.3389/fvets.2024.1403068  (About DOIs).

Officially, of course, the Atlantic hurricane season begins on June 1, But most years, the tropics remain fairly sleepy for the first month or two, allowing coastal residents to ease into the season.

Yes, a tropical storm might form here or a modest hurricane there. But the really big and powerful hurricanes, which develop from tropical waves in the central Atlantic and roar into the Caribbean Sea, do not spin up until August or September when seas reach their peak temperatures.

Not so this year, in which the Atlantic Ocean is boiling already. The seas in the main development region of the Atlantic have already reached temperatures not normally seen until August or September. This has led to the rapid intensification of Hurricane Beryl, which crashed through the Windward Islands on Monday and is now traversing the Caribbean Sea toward Jamaica.

Beryl is, to put it mildly, a freak storm.

It intensified on Monday night into a Category 5 hurricane, with sustained winds of 165 mph. Like other meteorologists, I had to check my calendar to verify that it really just was the first day of July. Remember, we're still in the traditionally "sleepy" part of hurricane season. Prior to Beryl, in more than a century of hurricane records, the earliest a Category 5 hurricane has ever developed in the Atlantic was July 16. That was Hurricane Emily, in 2005, the notorious hurricane season that delivered Katrina to New Orleans about a month later.

Getting stronger, faster

The rapid transformation of Beryl from a tropical depression into a major hurricane in 48 hours would have been super impressive for an Atlantic storm in September. Although not quite record-setting for the peak of the Atlantic hurricane season, this kind of intensification is absolutely unheard of for June or July. This graphic, from meteorologist Sam Lillo, puts the unprecedented nature of Beryl's rapid intensification into perspective.

Writing about the strengthening of Beryl on Sunday, University of Miami atmospheric scientist Brian McNoldy summed up how meteorologists feel observing such a storm so early in the season. "It's hard to communicate how unbelievable this is," he wrote. "With La Niña on the way and the ocean temperatures already looking like the second week of September, this is precisely the type of outlier event that people have been talking about for months heading into this season. When you have an unprecedented favorable environment, you're bound to see unprecedented tropical cyclone activity."

The superlatives for Beryl don't stop there. According to seasonal hurricane forecaster Phil Klotzbach, Beryl formed farther east in the Atlantic than any previous hurricane on record, beating even the 1933 season (another notorious outlier in terms of activity). That's another sign that the main development region of the Atlantic tropics is heating up way ahead of schedule this year.

Fortunately, Beryl is now likely at its peak intensity. Over the next 24 hours, it should begin to encounter higher levels of wind shear, which is kryptonite for the organization of a tropical cyclone. The hurricane should also start to run into some drier air.

However, Beryl will still probably be a major hurricane when it strikes or passes just south of the Caribbean island of Jamaica on Wednesday. And it will probably remain at hurricane strength when it nears Mexico's Yucatan peninsula late on Thursday or Friday morning. After this, the storm should move into the southern Gulf of Mexico. There, it is unlikely to regain hurricane strength, but it could bring some rain showers to Mexico and Texas. We'll have to see.

The climate changes, storms get stronger

The point here is not really to discuss the threat of Beryl to the United States, which at this point seems in the modest-to-minimal range. Rather, it's the implications of Beryl both for the rest of the Atlantic season and as a harbinger for what to expect from the tropics in a world where we see warmer seas on the regular.

For this year, forecasters have been consistently predicting a hyperactive season due to the combination of roasting sea surface temperatures and the onset of La Niña during the critical months of August, September, and October. That forecast seems to be right on track and will be of concern to all coastal residents in the United States, Mexico, and the Caribbean islands. If Beryl is smashing records from 2005 and 1933 already, we're in "this is fine" territory.

Longer term, the implications are sobering for hurricanes in a world modified by climate change. The emerging consensus from scientists has been that there will be a 1 to 10 percent increase in tropical cyclone intensities and that the proportion of major hurricanes will increase. But even in such a world, Beryl would be an outlier. That we're already seeing superstorms develop in late June and early July should concern everyone everywhere.

One of the most promising Chinese space startups, Space Pioneer, experienced a serious anomaly this weekend while testing the first stage of its Tianlong-3 rocket near the city of Gongyi.

The rocket was undergoing a static fire test of the stage, in which a vehicle is clamped to a test stand while its engines are ignited, when the booster broke free. According to a statement from the company, the rocket was not sufficiently clamped down and blasted off from the test stand "due to a structural failure."

Video of the accidental ascent showed the rocket rising several hundred meters into the sky before it crashed explosively into a mountain 1.5 km away from the test site. (See various angles of the accident here, on the social media site X, or on Weibo.) The statement from Space Pioneer sought to downplay the incident, saying it had implemented safety measures before the test, and there were no casualties as a result of the accident. "The test site is far away from the urban area of Gongyi," the company said.

This is not entirely true, however. Located in the Henan province in eastern China, alongside the Yellow River, Gongyi has a population of about 800,000 people. The test stand is only about 5 km away from the city's downtown and less than a kilometer from a smaller village.

Such accidents are rare in the launch industry but not unprecedented. Typically, during a static fire test, the mass of propellant on board a vehicle combined with strong clamps hold a rocket down. However, in 1952, a US Viking rocket broke loose of its moorings at White Sands Missile Range in New Mexico. It crashed 6 km downrange of the launch site without casualties.

How big of a setback?

It is unclear how big of a setback this will be for Space Pioneer, a quasi-private company founded in 2019. A little more than a year ago, Space Pioneer became the first Chinese company to reach orbit with a liquid-fueled rocket. It did so, impressively, on the first attempt of its small Tianlong-2 rocket. This was a notable achievement, but the rocket's engines were provided by a Chinese state-operated firm, the Academy of Aerospace Liquid Propulsion Technology, rather than the private company.

For the larger Tianlong-3 rocket, Space Pioneer says it is manufacturing its own kerosene-fueled engines, known as TH-12. (They appear to have performed as expected this weekend.) Nine of these engines will power the Tianlong-3 rocket, which is intended to have a thrust of 17 tons to low-Earth orbit. The rocket's design and the planned reuse of its first stage mimic the Falcon 9 rocket developed by SpaceX.

Space Pioneer had been prepping the vehicle for its debut launch later this summer or fall—and first-stage static-fire tests are indicative of a rocket's final testing phase before liftoff. The company's statement did not set a new timeline for a launch attempt but said it would complete the fault analysis "as soon as possible."

China has the most vibrant commercial space industry in the world after the United States. Nearly a decade ago, the country's leadership committed to sharing state-owned technology with companies that raised private funding, seeking to emulate the commercial success of SpaceX and other US companies.

Today, there are dozens of Chinese firms developing rockets, satellites, and other spaceflight products. Space Pioneer has been among the most promising, having raised more than $400 million since its inception five years ago.

A small group of woolly mammoths became trapped on Wrangel Island around 10,000 years ago when rising sea levels separated the island from mainland Siberia. Small, isolated populations of animals lead to inbreeding and genetic defects, and it has long been thought that the Wrangel Island mammoths ultimately succumbed to this problem about 4,000 years ago.

A paper in Cell on Thursday, however, compared 50,000 years of genomes from mainland and isolated Wrangel Island mammoths and found that this was not the case. What the authors of the paper discovered not only challenges our understanding of this isolated group of mammoths and the evolution of small populations, it also has important implications for conservation efforts today.

A severe bottleneck

It’s the culmination of years of genetic sequencing by members of the international team behind this new paper. They studied 21 mammoth genomes—13 of which were newly sequenced by lead author Marianne Dehasque; others had been sequenced years prior by co-authors Patrícia Pečnerová, Foteini Kanellidou, and Héloïse Muller. The genomes were obtained from Siberian woolly mammoths (Mammuthus primigenius), both from the mainland and the island before and after it became isolated. The oldest genome was from a female Siberian mammoth who died about 52,300 years ago. The youngest were from Wrangel Island male mammoths who perished right around the time the last of these mammoths died out (one of them died just 4,333 years ago).

It’s a remarkable and revealing time span: The sample included mammoths from a population that started out large and genetically healthy, went through isolation, and eventually went extinct.

Mammoths, the team noted in their paper, experienced a “climatically turbulent period,” particularly during an episode of rapid warming called the Bølling-Allerød interstadial (approximately 14,700 to 12,900 years ago)—a time that others have suggested might have led to local woolly mammoth extinctions. However, the genomes of mammoths studied through this time period don’t indicate that the warming had any adverse effects.

Adverse effects only appeared—and drastically so—once the population was isolated on that island.

The team's simulations indicate that, at its smallest, the total population of Wrangel Island mammoths was fewer than 10 individuals. This represents a severe population bottleneck. This was seen genetically through increased runs of homozygosity within the genome, caused when both parents contribute nearly identical chromosomes, both derived from a recent ancestor. The runs of homozygosity within isolated Wrangel Island mammoths were four times as great as those before sea levels rose.

Despite that dangerously tiny number of mammoths, they recovered. The population size, as well as inbreeding level and genetic diversity, remained stable for the next 6,000 years until their extinction. Unlike the initial population bottleneck, genomic signatures over time seem to indicate inbreeding eventually shifted to pairings of more distant relatives, suggesting either a larger mammoth population or a change in behavior.

Within 20 generations, their simulations indicate, the population size would have increased to about 200–300 mammoths. This is consistent with the slower decrease in heterozygosity that they found in the genome.

Long-lasting negative effects

The Wrangel Island mammoths may have survived despite the odds, and harmful genetic defects may not have been the reason for their extinction, but the research suggests their story is complicated.

At about 7,608 square kilometers today, a bit larger than the island of Crete, Wrangel Island would have offered a fair amount of space and resources, although these were large animals. For 6,000 years following their isolation, for example, they suffered from inbreeding depression, which refers to increased mortality as a result of inbreeding and its resulting defects.

That inbreeding also boosted the purging of harmful mutations. That may sound like a good thing—and it can be—but it typically occurs because individuals carrying two copies of harmful mutations die or fail to reproduce. So it’s good only if the population survives it.

The team’s results show that purging genetic mutations can be a lengthy evolutionary process. Lead author Marianne Dehasque is a paleogeneticist who completed her PhD at the Centre for Palaeogenetics. She explained to Ars that, “Purging harmful mutations for over 6,000 years basically indicates long-lasting negative effects caused by these extremely harmful mutations. Since purging in the Wrangel Island population went on for such a long time, it indicates that the population was experiencing negative effects from these mutations up until its extinction.”

Co-author Love Dalén is a professor of evolutionary genomics at the Centre for Palaeogenetics in Stockholm. He said “When individuals have a double copy of harmful mutations (e.g., inherited from both parents that are related) these individuals become sick. And this subsequently means that these mutations are removed from the population through natural selection.” In other words, they die, but they take harmful mutations with them.

“We also see that mildly harmful mutations accumulate in the population up until its extinction,” Dehasque added. “The higher the amount of mildly harmful mutations, the bigger the potential negative fitness effects.” These might have ultimately led to the population’s end, either directly or by making it more vulnerable to environmental changes.

Vincent Lynch, associate professor at the University of Buffalo, was also not involved in the research, but he was part of a team that did earlier genetic research on Wrangel Island mammoths.

He was surprised by the results of this paper, noting that even with the persistent genetic impacts of inbreeding depression, they continued to survive. And, he said, he liked the two suggestions the team made about what may have caused their eventual extinction. In one, “the accumulation of many [harmful] mutations of small effects added up to a burden they couldn’t afford,” a scenario he compared to the straw that broke the horse’s back. In the other, “it is also possible they didn’t have the genetic diversity needed to deal with a sudden change in the climate or the introduction of an infectious disease (like white-nose syndrome in little brown bats); or some combination of these,” he explained.

And then they were gone

While the results of the research don’t elucidate the reason behind the Wrangel Island mammoth extinction, they do indicate it happened remarkably fast.

“From archeological evidence, we know that humans only arrived after mammoths went extinct,” Dehasque said,  “Something sudden like disease or a fire could have definitely caused the population to collapse, but this remains very speculative. With more research we will hopefully unravel in the near future what caused the mammoth’s final extinction.”

Are there lessons for current populations in this data? This bird’s-eye view of genetic changes over thousands of years is in stark contrast to current conservation studies of similarly isolated populations, where scientists have access to only a handful of generations’ worth of genetics to study.  This is significant because the long-term genetic effects of these mammoths show that “just restoring population size may not be sufficient to ensure a viable population,” Dehasque said.

At a time when the habitats for many forms of life are shrinking, climate change is impacting the world, and there are increasing numbers of endangered species, it is more important than ever to understand possible extinction risks.

“Conservation biologists have, in the past, thought that as long as one brings the population size up to a level where inbreeding doesn’t increase (and genetic diversity stops going down), then the genetic threat has been largely removed,” Dalén said. “But our results show that even when inbreeding/diversity has been stabilized, the population will still continue to be affected by inbreeding depression for hundreds of generations.”

“This is not good news for endangered species. However, when we now know this, we can factor this into models that predict extinction risks,” he continued. “Moreover, we can in some cases take actions such as facilitating gene flow between populations in order to bring inbreeding levels down.”

Jacqueline Robinson is an evolutionary geneticist at the University of California San Francisco. She was not involved in the research, but her work on island foxes was referenced in this paper. She told Ars that she was “fascinated and impressed” by this research, noting that it’s “a valuable study for how this process—bottleneck and long-term isolation—has played out over time. We can study contemporary populations all we want, but we’re not going to be able to see what the impacts of their population decline will be in the future. We can make predictions. But that’s different than being able to actually look at something that has happened in the past and directly observe those effects.”

She finds it “very encouraging” that the Wrangel Island mammoths stabilized after a severe population bottleneck, as it indicates species in similar circumstances today might do the same. “To me,” she said, “it’s a sign that species and populations are more resilient than we would expect. I just feel like it gives us more hope and greater reasons to invest in protecting species that have declined to unfortunately small numbers.”

Robinson says this research “will hopefully further boost the message that we shouldn’t give up on populations” even if their numbers are tiny.

A near miss?

For Dalén, who started working on Wrangel Island mammoth DNA more than 20 years ago, there are two key takeaways from this research, the first of which is “that bottlenecks cause a genetic debt in the form of harmful mutations, and that it can take many thousands of years for this debt to be paid.”

The other key takeaway, he suggested, is “that the mammoth’s extinction seems likely to have been caused by some random environmental event, meaning that perhaps they simply were unlucky. If it hadn’t been for that, we may still have had mammoths living today.”

The idea of their potential continued existence is one that Dehasque considered as well, wondering, “If the mammoths had survived until now, would the harmful mutations have kept accumulating? And how bad would their combined fitness effects have been by now?”

Cell, 2024.  DOI: 10.1016/j.cell.2024.05.033

Welcome to Edition 6.50 of the Rocket Report! SpaceX launched its 10th Falcon Heavy rocket this week with the GOES-U weather satellite for NOAA, and this one was a beauty. The late afternoon timing of the launch and atmospheric conditions made for great photography. Falcon Heavy has become a trusted rocket for the US government, and its next flight in October will deploy NASA's Europa Clipper spacecraft on the way to explore one of Jupiter's enigmatic icy moons.

As always, we welcome reader submissions, and if you don't want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Sir Peter Beck dishes on launch business. Ars spoke with the recently knighted Peter Beck, founder and CEO of Rocket Lab, on where his scrappy company fits in a global launch marketplace dominated by SpaceX. Rocket Lab racked up the third-most number of orbital launches by any US launch company (it's headquartered in California but primarily assembles and launches rockets in New Zealand). SpaceX's rideshare launch business with the Falcon 9 rocket is putting immense pressure on small launch companies like Rocket Lab. However, Beck argues his Electron rocket is a bespoke solution for customers desiring to put their satellite in a specific place at a specific time, a luxury they can't count on with a SpaceX rideshare.

Ruthlessly efficient ... A word that Beck returned to throughout his interview with Ars was "ruthless." He said Rocket Lab's success is a result of the company being "ruthlessly efficient and not making mistakes." At one time, Rocket Lab was up against Virgin Orbit in the small launch business, and Virgin Orbit had access to capital through billionaire Richard Branson. Now, SpaceX is the 800-pound gorilla in the market. "We have a saying here at Rocket Lab that we have no money, so we have to think. We've never been in a position to outspend our competitors. We just have to out-think them. We have to be lean and mean."

Firefly reveals plans for new launch sites. Firefly Aerospace plans to use the state of Virginia-owned launch pad at NASA’s Wallops Flight Facility for East Coast launches of its Alpha small-satellite rocket, Aviation Week reports. The company plans to use Pad 0A for US military and other missions, particularly those requiring tight turnaround between procurement and launch. This is the same launch pad previously used by Northrop Grumman's Antares rocket, and it's the soon-to-be home of the Medium Launch Vehicle (MLV) jointly developed by Northrop and Firefly. The launch pad will be configured for Alpha launches beginning in 2025, according to Firefly, which previously planned to develop an Alpha launch pad at Cape Canaveral Space Force Station in Florida. Now, Alpha and MLV rockets will fly from the same site on the East Coast, while Alpha will continue launching from the West Coast at Vandenberg Space Force Base, California.

Hello, Sweden... A few days after the announcement for launches from Virginia, Firefly unveiled a collaborative agreement with Swedish Space Corporation to launch Alpha rockets from the Esrange Space Center in Sweden as soon as 2026. Esrange has been the departure point for numerous suborbital and sounding rocket for nearly 50 years, but the spaceport is being upgraded for orbital satellite launches. A South Korean startup named Perigee Aerospace announced in May it signed an agreement to be the first user of Esrange's orbital launch capability. Firefly is the second company to make plans to launch satellites from the remote site in northern Sweden. (submitted by Ken the Bin and brianrhurley)

China hops closer to reusable rockets. The Shanghai Academy of Spaceflight Technology (SAST), part of China's apparatus of state-owned aerospace companies, has conducted the country's highest altitude launch and landing test so far as several teams chase reusable rocket capabilities, Space News reports. A 3.8-meter-diameter (9.2-foot) test article powered by three methane liquid-oxygen engines lifted off from the Gobi Desert on June 23 and soared to an altitude of about 12 kilometers (7.5 miles) before setting down successfully for a vertical propulsive touchdown on landing legs at a nearby landing area. SAST will follow up with a 70-kilometer (43.5-mile) suborbital test using grid fins for better control. A first orbital flight of the new reusable rocket is planned for 2025.

Lots of players ... If you don't exclusively follow China's launch sector, you should be forgiven for being unable to list all the companies working on new reusable rockets. Late last year, a Chinese startup named iSpace flew a hopper rocket testbed to an altitude of several hundred meters as part of a development program for the company's upcoming partially reusable Hyperbola 2 rocket. A company named Space Pioneer plans to launch its medium-class Tianlong 3 rocket for the first time later this year. Tianlong 3 looks remarkably like SpaceX's Falcon 9, and its first stage will eventually be made reusable. China recently test-fired engines for the government's new Long March 10, a partially reusable rocket planned to become China's next-generation crew launch vehicle. These are just a few of the reusable rocket programs in China. (submitted by Ken the Bin)

Spanish launch startup invests in Kourou. PLD Space says it is ready to start construction at a disused launch complex at the Guiana Space Center in Kourou, French Guiana. The Spanish launch startup announced this week a 10 million euro ($10.7 million) investment in the launch complex for its Miura 5 rocket, with preparations of the site set to begin "after the summer." The launch pad was previously used by the French Diamant rocket in the 1970s and is located several miles away from the launch pads used by the European Ariane 6 and Vega rockets. PLD Space is on track to become the first fully commercial company to launch from the spaceport in South America.

Free access to space ... Also this week, PLD Space announced a new program to offer space aboard the first two flights of its Miura 5 rocket for free, European Spaceflight reports. The two-stage Miura 5 rocket will be capable of delivering about a half-ton of payload mass into a Sun-synchronous orbit. PLD Space will offer free launch services aboard the first two Miura 5 flights, which are expected to take place in late 2025 and early 2026. The application process will close on July 30, and winning proposals will be announced on November 30. (submitted by Ken the Bin and EllPeaTea)

Starship not a threat to Ariane 6, ESA manager says. Toni Tolker-Nielsen, who oversees rocket development at the European Space Agency, isn't particularly worried about competition from SpaceX's giant Starship rocket, Ars reports. In an interview with Space News, Tolker-Nielsen said Starship won't eradicate Europe's Ariane 6 rocket, which is finally set to debut next month after years of delays. "Honestly, I don’t think Starship will be a game-changer or a real competitor," he said. "This huge launcher is designed to fly people to the Moon and Mars. Ariane 6 is perfect for the job if you need to launch a four- or five-ton satellite." Ariane 6, of course, is entirely expendable, and Tolker-Nielsen defended the decision not to pursue reusability with Europe's new flagship rocket by saying it won't fly often enough to make investing in recovery and reuse worthwhile. "Our launch needs are so low that it wouldn't make sense economically," he said. On its face, this seems like a defeatist attitude.

Will they ever learn? ... European space officials are starting to say publicly what has been known for years: Ariane 6 will not compete with SpaceX's Falcon 9 or Starship in any sustained or meaningful way, according to Space Intel Report. This is a far cry from the commanding position Europe's launch industry found itself in 10 to 20 years ago. In 2013, an official from the French launch service provider Arianespace famously dismissed SpaceX's ambition to field a reusable rocket and launch 100 times per year as a dream. Well, the dream is alive. (submitted by Ken the Bin)

SpaceX sets new reuse records. Continuing the theme of rocket reusability, SpaceX launched a Falcon 9 rocket Thursday from Cape Canaveral with a first-stage booster making its 22nd trip to space, a new record, Spaceflight Now reports. This booster, designated B1062, has been active in SpaceX's rocket fleet since November 2020. Thursday's launch delivered 23 more Starlink Internet satellites into orbit, and the first stage returned to land on a drone ship in the Atlantic Ocean. SpaceX also recently flew a Falcon 9 mission with a payload fairing shell that made its 20th launch, also a record for fairing reuse.

350 ... Thursday's launch was also the 350th flight by a Falcon 9 rocket, and SpaceX's 68th launch of the year overall, including 65 Falcon 9s, two Starships, and one Falcon Heavy. One more Falcon 9 flight is on SpaceX's schedule to close out the first half of the year, and SpaceX aims for an even higher number of flights in the second half of 2024, with the goal of nearly 150 launches for the entire year. Most of these missions will carry satellites into orbit for the Starlink network. (submitted by brianrhurley)

Look out! Video recorded downrange from China's inland Xichang launch site shows a booster from a Long March rocket falling to the ground alarmingly close to a community. The video shows people running in the direction away from the rocket debris. The booster left a trail of toxic gas as it tumbled back to Earth. Unfortunately, this is not all that unusual, and it often happens after rockets take off from Xichang, which is positioned closer to population centers than China's other launch sites. This has been going on for decades, and although China is moving toward new rockets that burn non-toxic propellants, they continue to use inland spaceports, and there's no sign this will stop happening any time soon.

In the name of science ... The Long March 2C that created the debris lifted off with the Space Variable Objects Monitor (SVOM) mission, a joint project by the Chinese and French space agencies. The SVOM astrophysics mission will study gamma-ray bursts—violent electromagnetic explosions that can release as much energy in a few seconds as the Sun will emit over its entire 10-billion-year lifetime, Space News reports. (submitted by Ken the Bin and EllPeaTea)

India's diminished role in small satellite launch. The head of the Indian Space Organization, S. Somanath, says his country's once leading position in the market for launching small satellites has eroded in recent years. A few years ago, Russian launchers and India's PSLV rocket were the prime players in the nascent commercial rideshare launch market. SpaceX's Transporter missions have changed the equation, and Somanath says India will only launch four satellites from customers from other countries, after tallying 435 in total to date.

Competitiveness ... "We could only get this much, but our launch capabilities are three times the demand," Somanath said, according to The Economic Times. "We are not able to use our capacity because satellites are not there." The kinds of satellites that used to fly on PSLV rideshare missions now fly on SpaceX's Transporter missions, which offer lower prices, taking advantage of SpaceX's rocket reuse program. While it's true more than 70 percent of SpaceX's missions so far this year have been for the company's own Starlink network, the addressable commercial market for launch services is growing. The problem for India and other launch providers is that most of these satellites are flying on SpaceX rockets. "At ISRO, we have PSLVs, but we have no demand," Somanath said. "I have a problem: Rockets are built and kept in stock but not finding customers."

Vulcan's second flight won't have a payload. The second flight of United Launch Alliance's Vulcan rocket will take off in September with a dummy payload in place of Sierra Space's Dream Chaser spaceplane, preserving a chance for ULA to begin launching US military satellites on the new rocket by the end of the year, Ars reports. There was little hope Dream Chaser would be ready to make its first resupply run to the International Space Station before the end of the summer, so ULA opted to complete the second Vulcan test flight as soon as possible to allow the Space Force to certify the new rocket for national security missions. This will allow ULA to begin launching a backlog of 25 military space missions assigned to Vulcan.

An update on BE-4 reuse … Tory Bruno, ULA's CEO, also provided an update on the company's progress on efforts to eventually recover and reuse BE-4 engines from the Vulcan first stage. He said ULA has spent "tens of millions of dollars" on technology development to enable engine recovery and reuse, but he declined to provide a timetable for when the company will actually introduce engine reuse on the Vulcan program. ULA is working with NASA on an inflatable heat shield to allow the engines to survive reentry and redesigning the aft engine section of the Vulcan booster to make the engine pod detachable in flight. The rest of the booster, including the main airframe and propellant tanks, will still be expended.

Falcon Heavy flies again. A powerful SpaceX Falcon Heavy rocket boosted a hurricane-hunting GOES weather satellite into orbit Tuesday, the final member of a four-satellite fleet at the heart of an $11 billion upgrade to the nation's forecasting infrastructure, CBS News reports. "NOAA's geostationary satellites are an indispensable tool for protecting the United States and the 1 billion people who live and work in the Americas," said Pam Sullivan, GOES program director. "They provide a constant real-time view of weather and dangerous environmental phenomena across the Western hemisphere." This satellite, known as GOES-U and soon to be renamed GOES-19, will provide constant vigil from geostationary orbit to track severe storms and tropical cyclones, wildfires, and other phenomena.

Fresh from the factory … This was the 10th flight of a Falcon Heavy rocket and one of two Falcon Heavy flights SpaceX has on its schedule this year. All three first-stage boosters were brand new, and the two side boosters returned to landing at Cape Canaveral Space Force Station for reuse. The upper stage deployed the GOES-U spacecraft, built by Lockheed Martin, into a transfer orbit. GOES-U will use its own propulsion to maneuver into its final operational orbit over the equator to begin a 10-year operational lifetime.

Next three launches

June 29: Falcon 9 | NROL-186 | Vandenberg Space Force Base, California | 03:14 UTC

June 29: Long March 7A | Unknown Payload | Wenchang Space Launch Site, China | 12:00 UTC

June 30: H3 | ALOS-4 | Tanegashima Space Center, Japan | 03:06 UTC

NASA has awarded an $843 million contract to SpaceX to develop a "US Deorbit Vehicle." This spacecraft will dock to the International Space Station in 2029 and then ensure the large facility makes a controlled reentry through Earth's atmosphere before splashing into the ocean in 2030.

"Selecting a US Deorbit Vehicle for the International Space Station will help NASA and its international partners ensure a safe and responsible transition in low Earth orbit at the end of station operations," said Ken Bowersox, NASA's associate administrator for Space Operations, in a statement. "This decision also supports NASA’s plans for future commercial destinations and allows for the continued use of space near Earth."

NASA has a couple of reasons for bringing the space station's life to a close in 2030. Foremost among these is that the station is aging. Parts of it are now a quarter of a century old. There are cracks on the Russian segment of the space station that are spreading. Although the station could likely be maintained beyond 2030, it would require increasing amounts of crew time to keep flying the station safely.

Additionally, NASA is seeking to foster a commercial economy in low-Earth orbit. To that end, it is working with several private companies to develop commercial space stations that would be able to house NASA astronauts, as well as those from other countries and private citizens, by or before 2030. By setting an end date for the station's lifetime and sticking with it, NASA can help those private companies raise money from investors.

Do we have to sink the station?

The station, the largest object humans have ever constructed in space, is too large to allow it to make an uncontrolled return to Earth. It has a mass of 450 metric tons and is about the size of an American football field. The threat to human life and property is too great. Hence the need for a deorbit vehicle.

The space agency considered alternatives to splashing the station down into a remote area of an ocean. One option involved moving the station into a stable parking orbit at 40,000 km above Earth, above geostationary orbit. However, the agency said this would require 3,900 m/s of delta-V, compared to the approximately 47 m/s of delta-V needed to deorbit the station. In terms of propellant, NASA estimated moving to a higher orbit would require 900 metric tons, or the equivalent of 150 to 250 cargo supply vehicles.

NASA also considered partially disassembling the station before its reentry but found this would be much more complex and risky than a controlled deorbit that kept the complex intact.

The NASA announcement did not specify what vehicle SpaceX would use to perform the deorbit burn, but we can draw some clues from the public documents for the contract procurement. For example, NASA will select a rocket for the mission at a later date, but probably no later than 2026. This would support a launch date in 2029, to have the deorbit vehicle docked to the station one year before the planned reentry.

How will they do it?

Because of the sensitivity of the mission, NASA is likely to require a "Category 3" rocket under the auspices of its Launch Services Program, which are rockets that have a robust launch history. The agency notes that some rockets that fit this category are SpaceX's Falcon 9 rocket and Northrop Grumman's Pegasus and Minotaur rockets. Because SpaceX is the contractor for the deorbit vehicle, it stands to reason that it likely will launch on a Falcon 9 or Falcon Heavy. It's possible that SpaceX bid Starship for this mission, although I think that is unlikely because the vehicle is not classified as a Category 3 rocket now, nor is it likely to be for at least a couple of years.

Without seeing SpaceX's actual bid, it's impossible to know what the company's plan is. An unmodified Dragon 2 spacecraft would probably not have the propulsive capability to accomplish this task. At a minimum, it would require much larger propellant tanks, perhaps by significantly modifying the trunk.

Another option is the "Dragon XL" spacecraft, which SpaceX is designing to supply NASA's Lunar Gateway station near the Moon. This vehicle could conceivably have the propulsive capability to deorbit the station, and, critically, it is being designed to have the capability to remain docked to a space station for 12 months or longer, similar to the requirement for the deorbit vehicle. Therefore, this seems like the most probable choice.

The bidding process for the US Deorbit Vehicle was opaque, but there are a few intriguing clues. Initially, the contract was offered as a hybrid. NASA's original documents said the "design" portion of the contract would be cost-plus and the development portion firm-fixed-price. Then a couple of things happened. Perhaps because there were not that many bidders (one source suggested to Ars that SpaceX did not even bid initially), NASA modified the process to allow flexibility on the contracting mechanism. Then, earlier this year, NASA Administrator Bill Nelson estimated that the US Deorbit Vehicle would cost $1.5 billion.

This week's announcement of a contract price came in well below that—indicating that the space agency got a better deal than Nelson anticipated. And notably, the award is entirely based on a firm-fixed-price contract, which is SpaceX's preferred way of working with NASA.

"The contract is a single-award firm-fixed-price core with indefinite delivery, indefinite quantity, firm-fixed-price task orders," NASA spokesman Joshua Finch told Ars on Wednesday night. "To maximize value to the government and enhance competition, the acquisition allowed offerors flexibility in proposing firm-fixed-price or a cost-plus incentive fee for the design, development, test and evaluation phase, as well as for the production, assembly, integration, and test phase."

Their feet left copious traces in muddy Permian floodplains, leaving tracks scattered across ancient sediments. But in one slab of such trackways, scientists uncovered something more: the trace of an animal’s tail as it dragged across the ground. Strikingly, these tail prints come complete with scale impressions—at 300 million years old, they’re among the earliest scale impressions we have.

This may seem small, but it shows us that some of the hardened skin structures necessary for our ancestors to survive on land had evolved much earlier than previously suspected. A paper published in Biology Letters this past May describes this discovery in detail.

A rare find

The particular slab holding these traces was discovered in 2020 at the Piaskowiec Czerwony quarry in Poland. Mining had stopped to enable paleontologists to search the red sandstone rocks for fossils. Gabriela Calábková described climbing upon “a huge pile of rubble” only to discover a sizable slab of fossil tracks at the very top. There, among one set of footprints, was something new.

She called to her colleagues to join her at the top of the pile. None of them, she said, had ever encountered that kind of trace fossil before, but they “quickly understood that it must be a body impression,” she explained to Ars.

Calábková is a paleontologist at the Moravian Museum. She and her co-authors are part of a joint effort by Polish, Czech, and German scientists studying the Permian in Poland—a geologic time period that stretches from 289.9 to 252 million years ago. The Piaskowiec Czerwony quarry is the world’s second-largest producer of one particularly recognizable type of Permian track known as Ichniotherium cottae. (If you were asked to draw hands, you might come up with something that looks like Ichniotherium cottae. The five bulbous imprints of the digits are almost cartoonish.)

Footprints and tail drags are examples of ichnofossils, or trace fossils. As their name suggests, these are the fossilized marks or traces made during the life of an animal. Matching the exact animal to its trace is almost impossible, especially when body fossils are absent, so traces themselves are often given scientific names.

In this case, however, we may have identified the source, which is why the world’s leading site of these same tracks is in nearby Germany, where the spectacular Bromacker site has not only produced abundant Permian tracks, it has also provided the fossils of animals with feet that appear to match the prints. They belong to diadectimorphs, four-legged vertebrates (tetrapods) that were distant forerunners of mammals.

Bromacker has also provided a helpful verification of the exceedingly rare tail drag found in the Piaskowiec Czerwony quarry. The only two other known tail drags associated with I. cottae trackways were found there. They, too, have similar corn cob-shaped scales.

Tipping the scales

Sebastian Voigt is the director of the Urweltmuseum GEOSKOP in Germany and the lead author of this paper. Evidence of segmentation within the toes of their footprints along with the tail drag scale impressions are “a further argument that diadectids had scales at least on the underside of the tail and feet,” he told Ars. “One cannot automatically assume that scales developed evenly and quickly all over the body. For example, scales could have developed first on the parts of the body that were most likely to be in contact with the ground in terrestrial vertebrates (feet, belly, underside of the tail).”

But either way, “the epidermal scales in diadectids and other terrestrial tetrapods prevented the evaporation of water from their bodies in a dry environment,” Calábková noted, which may have helped them survive “the desert climate that prevailed on [the supercontinent of] Pangea during the Permian.”

Adriana Cecilia Mancuso is a researcher from Argentina who specializes in the evolution of terrestrial ecosystems. She was not involved in the research, but says this discovery is “highly significant. Fossil skin impressions are rare in the deep geological record. Furthermore, the quality of the reported impressions provides strong evidence regarding the origin of epidermal scales in early tetrapods.”

“By studying these fossil traces,” she explained to Ars, “scientists can reconstruct ancient ecosystems, understand how organisms responded to environmental and climatic changes, and trace the evolution of key features in the history of life on Earth. This information not only helps us better understand our geological and biological past but also offers insights into how modern ecosystems may respond to current and future environmental challenges.”

Help on the ground

Access to the two Polish quarries where these fossils are found is a direct result of “support from the employees and management of the quarries,” said Izabela Ploch, co-author and stratigrapher and paleontologist with the Polish Geological Institute. She added that “in the case of very heavy sandstone slabs, they help us extract them from the quarry, often using heavy equipment.”

“We often talk about fossils to quarry workers,” she continued, “which really piques their interest. The result of this is, for example, the creation of [an exhibit space] in Radków, initiated by the management of a nearby quarry after they saw what beautiful trace fossils we found there.”

“We want local people to understand what they have in this area and what interesting stories the ichnofossils tell,” she said. And that includes plans to encourage geotourism to the area as well as exhibits displaying the trace fossils found in the quarries.

Ploch mused about how much we have yet to uncover. “There are so many mysteries still to be discovered,” she said. “Without knowing our past, we will not know our future and the processes that guide the evolution of life on Earth. By learning about even a modest fragment of the Earth's past, we add an element to a larger puzzle.”

Biology Letters, 2024.  DOI: 10.1098/rsbl.2024.0041

While CRISPR is probably the most prominent gene-editing technology, there are others, some developed before and since. And people have been developing CRISPR variants to perform more specialized functions, like altering specific bases. In all of these cases, researchers are trying to balance a number of competing factors: convenience, flexibility, specificity and precision for the editing, low error rates, and so on.

So, having additional options for editing can be a good thing, enabling new ways of balancing those different needs. On Wednesday, a pair of papers in Nature describe a DNA-based parasite that moves itself around bacterial genomes through a mechanism that hasn't been previously described. It's nowhere near ready for use in humans, but it may have some distinctive features that make it worth further development.

Going mobile

Mobile genetic elements, commonly called transposons, are quite common in many species—they make up nearly half the sequences in the human genome, for example. They are indeed mobile, showing up in new locations throughout the genome, sometimes by cutting themselves out and hopping to new locations, other times by sending a copy out to a new place in the genome. For any of this to work, they need to have an enzyme that cuts DNA and specifically recognizes the right transposon sequence to insert into the cut.

The specificity of that interaction, needed to ensure the system only inserts new copies of itself, and the cutting of DNA, are features we'd like for gene editing, which places a value on better understanding these systems.

Bacterial genomes tend to have very few transposons—the extra DNA isn't really in keeping with the bacterial reproduction approach of "copy all the DNA as quickly as possible when there's food around." Yet bacterial transposons do exist, and a team of scientists based in the US and Japan identified one with a rather unusual feature. As an intermediate step in moving to a new location, the two ends of the transposon (called IS110) are linked together to form a circular piece of DNA.

In its circular form, the DNA sequences at the junction act as a signal that tells the cell to make an RNA copy of nearby DNA (termed a "promoter"). When linear, each of the two bits of DNA on either side of the junction lacks the ability to act as a signal; it only works when the transposon is circular. And the researchers confirmed that there is in fact an RNA produced by the circular form, although the RNA does not encode for any proteins.

So, the research team looked at over 100 different relatives of IS110 and found that they could all produce similar non-protein-coding RNAs, all of which shared some key features. These included stretches where nearby sections of the RNA could base-pair with each other, leaving an unpaired loop of RNA in between. Two of these loops contained sequences that either base-paired with the transposon itself or at the sites in the E. coli genome where it inserted.

That suggests that the RNA produced by the circular form of the transposon helped to act as a guide, ensuring that the transposon's DNA was specifically used and only inserted into precise locations in the genome.

Editing without precision

To confirm this was right, the researchers developed a system where the transposon would produce a fluorescent protein when it was properly inserted into the genome. They used this to show that mutations in the loop that recognized the transposon would stop it from being inserted into the genome—and that it was possible to direct it to new locations in the genome by changing the recognition sequences in the second loop.

To show this was potentially useful for gene editing, the researchers blocked the production of the transposon's own RNA and fed it a replacement RNA that worked. So, you could potentially use this system to insert arbitrary DNA sequences into arbitrary locations in a genome. It could also be used with targeting RNAs that caused specific DNA sequences to be deleted. All of this is potentially very useful for gene editing.

Emphasis on "potentially." The problem is that the targeting sequences in the loops are quite short, with the insertion site targeted by a recognition sequence that's only four to seven bases long. At the short end of this range, you'd expect that a random string of bases would have an insertion site about once every 250 bases.

That relatively low specificity showed. At the high end, various experiments could see an insertion accuracy ranging from a close-to-being-useful 94 percent down to a positively threatening 50 percent. For deletion experiments, the low end of the range was a catastrophic 32 percent accuracy. So, while this has some features of an interesting gene-editing system, there's a lot of work to do before it could fulfill that potential. It's possible that these recognition loops could be made longer to add the sort of specificity that would be needed for editing vertebrate genomes, but we simply don't know at this point.

Getting mechanistic

We do, however, know a surprising amount about the exact mechanism by which this system cuts and re-links DNA, since the researchers published a second paper in which they describe the structure of the enzyme that does the cutting, along with the DNA that's being cut and the RNA that guides the cuts.

The cutting takes place through a four-step process. The whole thing starts out with the two separate DNA double helices (or two locations of a single double helix) both inserted into the enzyme, with the DNA strands looking a bit like two U's with their bottoms facing each other. In the first step, two of the four individual DNA strands involved are cut, with two of the newly formed ends being left chemically linked to the enzyme.

In the second step, the enzyme swivels those breaks around and links them to a different DNA molecule. This converts the structure from something that looks like two U's to something that looks like a single X, with both halves of the double helix swapping partners at the middle of the X.

The next two steps involve the same set of reactions with the two strands that haven't reacted yet. At the end of this process, the four strands/two double helices have swapped partners. (You can think of the resulting structure as looking like two parentheses facing each other— )( —although the physical placement of the strands doesn't look like this.)

For IS110, this works because four copies of a protein it produces can form a single complex, with each of the copies hanging onto a single double helix as it either enters or exits the complex. At each of the stages of these reactions, only two of the four copies are active at any single time, helping to keep everything coordinated. The structure shows that at least one RNA molecule is present to enable the targeting of the right sequences, though various bits of evidence indicate there are probably two around.

The RNA molecules serve a number of additional roles during the reaction. They base-pair with individual strands of the DNA molecules, disrupting their pairing with each other and making it easier for the proteins to break links and swap partners. And they also base-pair on both sides of the break. They may dedicate seven base pairs to recognition for the sequence they target but will have a couple of additional base pairs for that DNA strand's eventual partner.

This probably helps ensure that the cut and re-join process doesn't result in the accidental insertion or deletion of bases. So, while the IS110 system may not be accurate in terms of the sites it recognizes, it appears to be very precise in terms of what it does after they're recognized. Which would be a nice feature if we could boost the accuracy.

Nature, 2024. DOI: 10.1038/s41586-024-07552-4, 10.1038/s41586-024-07570-2  (About DOIs).