The confused wiggles on the graph above have a simple message: Most years, even years with record-high temperatures, have some months that aren't especially unusual. Month to month, temperatures dip and rise, with the record years mostly being a matter of having fewer, shallower dips.

As the graph shows, last year was not at all like that. The first few months of the year were unusually warm. And then, starting in June, temperatures rose to record heights and simply stayed there. Every month after June set a new record for high temperatures for that month. So it's not surprising that 2023 will enter the record books as far and away the warmest year on record.

The EU makes it official

Several different organizations maintain global temperature records; while they use slightly different methods, they tend to produce very similar numbers. So, over the next few weeks, you can expect each of these organizations to announce record temperatures (NASA and the National Oceanic and Atmospheric Administration will do so on Friday). On Tuesday, it was the European Union's turn, via its Copernicus Earth-observation program.

Copernicus rates 2023 as being nearly 1.5° C above pre-industrial temperatures and about 0.17° C above 2016, the previous holder of the warmest year on record. The difference between 2023 and 2022 was the largest single-year change in the record as well, confirming that the amount of warming this past year was exceptional.

The 1.5° C landmark is significant because many countries have committed to trying to limit global warming to that mark. This doesn't mean we've failed; the average temperature for the last decade is still below that. But it does highlight how little time we have left to act before we potentially experience more radical consequences of climate change.

The Copernicus analysis notes a couple of additional daily landmarks within the yearly record. It defines pre-industrial temperatures as those experienced between 1850–1900. The records from this period are sparse enough that, rather than daily temperature data, it's been handled as a monthly average. So, the best Copernicus could do is compare 2023's daily temperatures to the equivalent month in the pre-industrial record.

Even given that limitation, some of the results of this comparison were striking. For the first time ever, individual days in 2023 were 2.0° C above the preindustrial monthly average. Nearly half the days in 2023 were 1.5° C warmer than preindustrial records, and it was the first time every day was at least 1.0° C warmer.

Why so extreme?

The simplest answer is El Niño. The past few years have been spent in a reasonably strong La Niña, the cooler phase of the Southern Oscillation. But that started fading throughout the spring, and by mid-year, a weak El Niño had arrived. Normally, a relatively feeble El Niño like this would have a limited effect on global temperatures, and in any case, it would normally take some time for its effect to be felt in global temperatures.

But with temperatures poised near record levels to begin with, just a little push appeared to be all 2023 needed to soar to record heights.

Still, there are plenty of indications that the year wasn't only the result of El Niño, which is a phenomenon that occurs in the tropical Pacific. For example, the North Atlantic, which is not directly connected to the Tropical Pacific, experienced exceptionally warm sea surface temperatures over the second half of the year.

Copernicus suggests that several additional, weak factors could have contributed to the year's warmth. These include lower emissions of cooling aerosols from shipping, a peak in the solar cycle, and high levels of water vapor in the stratosphere due to the eruption of the Hunga Tonga volcano. On its own, the impact of any of these would likely be minimal. In combination with the weak El Niño and the continued emission of greenhouse gasses, however, they might have enhanced what was already an exceptionally warm year.

The announcement of 2023's warmth comes only months after a set of UN climate negotiations that many have derided as lacking the sort of urgency the record might have provided. Instead, Copernicus notes that carbon dioxide and methane emissions increased last year.

Listing image by Marco Bottigelli

What do we need to find if we want to discover another Earth? If an exoplanet is too far away for even the most powerful telescopes to search directly for water or certain biosignatures, is there something else that may tell us about the possibility of habitability? The answer could be carbon dioxide.

Led by Amaury Triaud and Julien de Wit, an international team of researchers is now proposing that the absence of CO₂ in a planet’s atmosphere potentially increases the chances of liquid water on its surface. Earth’s own atmosphere is depleted of CO₂. Unlike dry Mars and Venus, which have high concentrations of CO₂ in their atmospheres, oceans on our planet have taken immense amounts of carbon dioxide out of the atmosphere because the gas dissolves in water. CO₂ deficits in exoplanet atmospheres might mean the same.

Another molecule could be a sign of a habitable planet: ozone. Many organisms on Earth (especially plants) breathe carbon dioxide and release oxygen. This oxygen reacts with sunlight and becomes O₃, or ozone, which is easier to detect than atmospheric oxygen. The presence of ozone and the absence of carbon dioxide could mean a habitable, and even inhabited, planet.

Anyone—or anything—out there?

There is a difference between a planet orbiting within what is considered a habitable zone and actual habitability. Habitability is defined by the researchers as “a planet’s capacity to retain large reservoirs of surface liquid water,” as they state in a study recently published in Nature Astronomy.

Proving that water actually exists could hypothetically be done in many ways. The problem is that most existing telescopes, no matter how advanced, are incapable of pulling them all off. Finding liquid water from light years away is not as easy as seeing the glimmer of a lake, though that is possible at short distances, like those within our own Solar System. (When sunlight reflects off a body of surface liquid, what scientists refer to as a “glint” can be seen, which is how the lakes and oceans on Saturn’s moon Titan were discovered.)

Beyond water, other factors could determine habitability. Besides atmospheric properties, these include (but are not limited to) the orbit of a planet, plate tectonics, magnetic fields, and how it is affected by its star.

When less is more

Triaud, de Wit, and their team argue that it’s worth trying to identify potentially habitable planets that belong to a system similar to ours. If there is a system with several terrestrial planets that are close in size and have atmospheres, this makes it possible to compare carbon dioxide content in their atmospheres and see if there is a significant deficit in one or more planets compared to the others.

While a CO₂ deficit does not guarantee that there is liquid water on the surface, it should give scientists a reason to observe the planet or planets in question more closely. We don’t have to look far from Earth to see why this makes sense. Not only has most of the carbon dioxide in our planet’s atmosphere been depleted by its oceans, but plate tectonics also bury it in the crust. The amount of early Earth’s atmospheric carbon dioxide that ended up trapped in rocks is almost equal to the amount of CO₂ in the entire atmosphere of Venus.

There is another advantage to searching for this deficit. Because it's an especially strong infrared light absorber, CO₂ is rather easy to detect. Telescopes that are around today, including NASA’s James Webb Telescope and ESO’s Very Large Telescope, as well as ESO’s upcoming Extremely Large Telescope, have infrared vision that can easily search for CO₂ signatures.

So what if we did find a planet that showed a deficit of CO₂ and the presence of ozone? The researchers think the combination of both could mean not just a few microbial life forms but, at least hypothetically, a planet alive with organisms.

“Life on Earth is planet-shaping,” the team said in the same study. “Planet-shaping life is really what astronomers are after.”

Nature Astronomy, 2023.  DOI:  10.1038/s41550-023-02157-9

Good morning. It's January 9, and today's image showcases the Milky Way Galaxy rising above the visitor's center on Mauna Kea on the Big Island of Hawaii.

The Big Island is one of my favorite places on Earth. It has some of the world's best beaches, some of its most active volcanoes, wonderful people, and a world-class observatory on the great mountain, which climbs about 13,800 feet above sea level. Astronomers say the atmosphere up there, so remote from major landmasses, has some of the best "seeing" quality in the world.

The visitor's center, at 9,200 feet, is accessible with a rental car. It features a two-fer: If you get there during the evening hours, you can climb a little hill to see a gorgeous sunset above the clouds. And then, if you wait about an hour, the skies darken nicely to afford some of the best views of the heavens on Earth. I first saw the zodiacal light on Mauna Kea seven years ago. Stunning. But bring a jacket; it gets cold quickly.

This photo of the Milky Way from Samuel Miller is great because it's pretty simple, with no significant processing. Muller told me he hasn't done much astrophotography, and he shot this with a Sony A7R 2 camera. What I like about this is, if you go to Mauna Kea and let your eyes adapt to the dark skies, this photo is not that much different from what you'll see with the naked eye.

Yes, it's that brilliant.

Source: Samuel Muller

A few hours after a successful liftoff on United Launch Alliance's Vulcan rocket, Astrobotic's first commercial lunar lander ran into serious trouble. The robotic Peregrine lander, still in orbit around Earth, appears to have a propellant leak that will prevent it from reaching the Moon.

There are 20 payloads aboard the Peregrine lunar lander, including five from NASA, which is paying Astrobotic about $108 million for delivery of its science instruments to the Moon's surface. Peregrine was the first US-owned lunar lander to launch to the Moon in more than 50 years, and Astrobotic is one of 14 companies selected by NASA to deliver the agency's scientific instruments to the lunar surface.

This program, called Commercial Lunar Payload Services (CLPS), is aimed at flying robotic precursor missions to the Moon before NASA astronauts land on the lunar surface in the agency's Artemis program. Astrobotic's CLPS mission was first to the launch pad.

Propulsion anomaly

Astrobotic's ground controllers, working out of a control center at the company's Pittsburgh headquarters, struggled to stabilize the spacecraft throughout Monday. The problem with the lander's propulsion system initially prevented Peregrine from maneuvering into a Sun-pointing orientation needed to recharge its battery using solar power.

In additional updates, Astrobotic said the propulsion system malfunction would probably threaten the spacecraft's ability to soft-land on the Moon. Engineers uplinked commands for the spacecraft to perform an "improvised maneuver"  to reorient its solar panels toward the Sun. That apparently worked, at least temporarily, and Astrobotic reported Peregrine was recharging its battery.

Another statement from Astrobotic released Monday afternoon painted a bleaker picture of the status of Peregrine Mission One.

"Unfortunately, it appears the failure within the propulsion system is causing a critical loss of propellant," the company said. "The team is working to try and stabilize this loss, but given the situation, we have prioritized maximizing the science and data we can capture. We are currently assessing what alternative mission profiles may be feasible at this time."

Astrobotic released an image from the Peregrine lander appearing show a section of distributed multi-layer insulation on the exterior of the spacecraft.  This was the "first visual clue" aligning with telemetry data indicating a propulsion system problem, Astrobotic posted on the social media platform X.

"Nonetheless, the spacecraft’s battery is now fully charged, and we are using Peregrine’s existing power to perform as many payload and spacecraft operations as possible," Astrobotic said.

Peregrine's control thrusters are struggling to keep the lander from an uncontrollable tumble, Astrobotic said. If the thrusters hold up to the extra burden, Astrobotic said Monday evening that the lander could remain in a stable Sun-pointing state for about 40 more hours, based on current fuel consumption.

An unmitigated propellant leak would certainly prevent Peregrine from achieving Astrobotic's goal of landing on the Moon. If the mission went according to plan, the Peregrine lander would complete two long phasing loops around Earth before intercepting the Moon and entering lunar orbit in late January. Then, the Peregrine spacecraft would have ignited its main engines for a powered descent to the lunar surface around February 23.

But that's not going to happen for this mission. "At this time, the goal is to get Peregrine as close to lunar distance as we can before it loses the ability to maintain its Sun-pointing position and subsequently loses power," Astrobotic said Monday.

The Peregrine lander's propulsion system uses a hypergolic propellant mixture, combining hydrazine fuel and a solution of nitric oxide and nitrogen tetroxide as the oxidizer. This is a tried-and-true architecture because hydrazine and nitrogen tetroxide immediately combust upon contact with one another, meaning the propulsion system doesn't need an ignition source.

According to Astrobotic, the spacecraft has two tanks each of fuel and oxidizer, plus a fifth tank for helium pressurant. There are five main engines and 12 smaller attitude control engines.

Sharad Bhaskaran, Astrobotic's Peregrine mission director, told Ars before the launch that the design for the lander's propulsion system was "fairly simple and straightforward."

But this was Astrobotic's first space mission, so engineers were eager to learn how the spacecraft operated in orbit. "This is about proving the technology, proving the spacecraft can operate successfully and carry out its mission," Bhaskaran said Friday. “You can do all the testing you want on the ground, and you can do all the simulations, but once you get to space, that's when everything gets proven."

A risky endeavor

NASA is going into these CLPS missions, like the Astrobotic lander launched Monday, aware of the risks. A second CLPS mission from a Houston-based company named Intuitive Machines is scheduled to launch in mid-February on a SpaceX Falcon 9 rocket.

“Each success and setback are opportunities to learn and grow," said Joel Kearns, deputy associate administrator for exploration at NASA’s science mission directorate. "We will use this lesson to propel our efforts to advance science, exploration, and commercial development of the Moon."

NASA officials know there was a chance that the first CLPS landing mission could miss the mark. The agency's managers have smartly set low expectations for these early commercial lunar missions, but these first landers are several years late, and a series of failures would inevitably raise questions about the program's future.

Thomas Zurbuchen, who led NASA's science mission directorate for six years, was instrumental in setting up the CLPS program in 2018. Early in the program, Zurbuchen guessed the initial batches of CLPS lander missions might have a 50-50 chance of success. NASA officials watched intently as private ventures like the Israeli Beresheet lunar lander and the Hakuto-R lander from the Japanese company ispace crashed on the Moon. Those missions had no significant NASA involvement, but they were successful until the final stage before landing.

A lander developed by India's space agency also crashed in 2019, but Indian engineers overcame the setback, tried again, and succeeded with a landing in August. Russia's Luna 25 mission also launched in August, but it plummeted to the Moon's surface after a botched engine burn.

China is three-for-three with robotic lunar landers since 2013, a remarkable streak of success that included the first landing on the far side of the Moon and an ambitious mission to return lunar rock samples to Earth.

All told, the world's roster of lunar landers has achieved a 50 percent success rate over the last decade, perfectly in line with Zurbuchen's prediction for the first few CLPS missions. Intuitive Machines needs to be successful with their lunar landing for those 50-50 odds to hold.

But even if Intuitive Machines is unsuccessful, NASA has more CLPS missions on contract. Including Astrobotic's first Peregrine lander, the space agency has awarded nine CLPS mission orders to five companies—eight landings and one lunar orbit mission.

Next steps for CLPS

Astrobotic is developing a larger lunar lander named Griffin to ferry a one-ton NASA rover to the Moon's south pole. This mission, known as VIPER, will search for water ice in dark polar craters, and will cost about $500 million, significantly more than NASA's financial commitment on the Peregrine mission launched Monday.

The commercial approach underpinning CLPS is intended to lower the cost of transporting equipment to the Moon and help foster a stronger market for business activity on the Moon. Astrobotic's Peregrine lander carried privately funded payloads along with NASA science instruments.

While one CLPS failure doesn't spell disaster for the program, Zurbuchen said it would be natural for NASA to reassess its assumptions regarding CLPS if the commercial contractors run into multiple setbacks.

“Suppose we’re at the end of ’24, we’ve done multiple landings, and none of them work; I think it’s worth looking at the game. Did it make sense?" Zurbuchen told Ars last year. "I really considered it an experiment when I came up with the idea. Generally speaking, NASA has done well to bet on entrepreneurial entities to do very, very hard challenges.

"Of course, I believe this will be successful. I think it’s really important, come 2025 or so, to really look at the program and say, hey, is it successful? Are there things that NASA should do to affect the program one way or another?"

NASA's payload complement on Astrobotic's Peregrine lander includes a radiation sensor, spectrometers, and a laser retroreflector array. The mission also includes a small lunar rover developed at Carnegie Mellon University and five tiny robots—each less than a tenth of a pound—from the Mexican Space Agency that will deploy onto the lunar surface. Some of Astrobotic's customers are sending commemorative plaques and mementos to the Moon.

NASA officials told reporters before the launch that, in the event Astrobotic's Peregrine mission failed to reach the Moon, the agency would not plan to rebuild any of its instruments aboard the lander. But some of NASA's future CLPS missions are booked to fly similar science payloads to the Moon.

"If this particular mission does not successfully soft land, NASA does not, today, plan to rebuild the instruments and then fly additional copies on future missions, other than what we've already planned today," Kearns said last week.

This story was updated to add a statement from Astrobotic.

Good morning. It's January 6, and today's image features a newish star cluster in the constellation Cepheus.

The stars in this cluster are relatively young, estimated at an age of about 4 million–12 million years old. The cluster is formally known as NGC 7380, and the feature is known more informally as the Wizard Nebula. It was first reported by German astronomer William Herschel, who said it was discovered by his sister, Caroline Herschel, in 1787.

The Herschels were born in Hanover, Germany, so fittingly, today's submission comes from an amateur astronomer in Hanover, George Amanakis. He described his process, with a total integration time of 36 hours, as follows, "I acquired RGB for stars for a more star-full composition. So the process was: SHO->starless->starless+RGB stars. I used a 5-inch triplet apochromatic refractor and a monochrome camera."

It certainly looks like a wizard's magic to me.

Source: George Amanakis

The version of evolution proposed by Charles Darwin focused on slow, incremental changes that only gradually build into the sort of differences that separate species. But that doesn't rule out the potential for sudden, dramatic changes. Indeed, some differences make it difficult to understand what a transitional state would look like, suggesting that a major leap might be needed.

A new study looks at one major transition: the shift from egg-laying to live births in a set of related snail species. By sequencing the genomes of multiple snails, the researchers identified the changes in DNA that are associated with egg-laying. It turns out that a large number of genes are associated with the change despite its dramatic nature.

Giving up eggs

The snails in question are in a genus called Littorina, which are largely distributed around the North Atlantic. Many of these species lay eggs, but a number of them have transitioned to live births. In these species, an organ that coats eggs with a protein-rich jelly in other species instead acts as an incubator, allowing eggs to develop until young snails can crawl out of their parent's shells. This is thought to be an advantage for animals that would otherwise have to lay eggs in environments that aren't favorable for their survival.

The egg laying species are so similar to their relatives that they were sometimes thought to just be a variant of an egg-laying species. All of which suggests that live birth has evolved relatively recently, giving us a good opportunity to understand the genetic changes that enabled it.

So, a large international team of researchers sequenced the genomes of over 100 individual snails, both egg-laying and live birth. The resulting data was used to analyze things like how closely related different species are, and what genetic changes are associated with live birth.

The results suggest that there are two separate clusters of species that reproduce through live births. Put differently, on an evolutionary tree of these snail species, there's a branch full of egg-laying species separating two groups that give birth to live snails. Typically, this structure is viewed as an indication that live births evolved twice, once for each of the two clusters.

But that doesn't seem to be the case here, for reasons that we'll get into.

Lots of variations

Separately, the researchers looked for regions of the genome that are associated with giving live births. And they found lots of them—88 in total. These 88 regions were identified in both clusters of live-birth species, and the DNA sequences within them were very similar. This suggests that these regions had a single origin and were maintained in both these lineages.

One possibility to explain this is that a population of live-birth animals reverted to egg-laying at some point in their evolution. Alternatively, hybridization between egg-layers and live-birthers could have let these variations spread within an egg-laying population and ultimately re-enable live births when enough of them were present in individual animals, producing a separate live-birth lineage.

The 88 regions identified as underlying live births have very little genetic diversity, suggesting that a specific genetic variant in each region is so advantageous that it swept through the population, displacing all other versions of the stretch of DNA. They have, however, picked up some distinct variations that are rare outside the egg-laying populations—enough to allow the researchers to estimate the age when these pieces of DNA came under evolutionary selection.

The answer varies depending on which of the 88 segments you're looking at, but it ranges from about 10,000 to 100,000 years ago. That range suggests that the genetic regions that enable live births were put together gradually over many years—exactly as the traditional view of evolution suggests.

The researchers acknowledge that at least some of these regions are likely to have evolved after live births were already the norm and simply improve the efficiency of the internal incubation. And there's no way to know how many variants (or which) need to be present before live births are possible. However, the researchers now have an extensive list of genes to look into to understand things better.

Science, 2024. DOI: 10.1126/science.adi2982  (About DOIs).

A new experimental antibiotic can handily knock off one of the world's most notoriously drug-resistant and deadly bacteria —in lab dishes and mice, at least. It does so with a never-before-seen method, cracking open an entirely new class of drugs that could yield more desperately needed new therapies for fighting drug-resistant infections.

The findings appeared this week in a pair of papers published in Nature, which lay out the extensive drug development work conducted by researchers at Harvard University and the Swiss-based pharmaceutical company Roche.

In an accompanying commentary, chemists Morgan Gugger and Paul Hergenrother of the University of Illinois at Urbana-Champaign discussed the findings with optimism, noting that it has been more than 50 years since the Food and Drug Administration has approved a new class of antibiotics against the category of bacteria the drug targets: Gram-negative bacteria. This category—which includes gut pathogens such as E. coli, Salmonella, Shigella, and the bacteria that cause chlamydia, the bubonic plague, gonorrhea, whooping cough, cholera, and typhoid, to name a few—is extraordinarily challenging to kill because it's defined by having a complex membrane structure that blocks most drugs, and it's good at accumulating other drug-resistance strategies

Weighty finding

In this case, the new drug—dubbed zosurabalpin—fights off the Gram-negative bacterium carbapenem-resistant Acinetobacter baumannii, aka CRAB. Though it may sound obscure, it's an opportunistic, invasive bacteria that often strikes hospitalized and critically ill patients, causing deadly infections worldwide. It is extensively drug-resistant, with ongoing emergence of pan-resistant strains around the world—in other words, strains that are resistant to every current antibiotic available. Mortality rates of invasive CRAB infections range from 40 to 60 percent. In 2017, the World Health Organization listed it as a priority 1: critical pathogen, for which new antibiotics are needed most urgently.

Zosurabalpin may just end up being that urgently needed drug, as Gugger and Hergenrother write in their commentary: "Given that zosurabalpin is already being tested in clinical trials, the future looks promising, with the possibility of a new antibiotic class being finally on the horizon for invasive CRAB infections."

An international team of researchers, led by Michael Lobritz and Kenneth Bradley at Roche, first identified a precursor of zosurabalpin through an unusual screen. Most new antibiotics are small molecules—those that have molecular weights of less than 600 daltons. But in this case, researchers searched through a collection of 45,000 bigger, heavier compounds, called tethered macrocyclic peptides (MCPs), which have weights around 800 daltons. The molecules were screened against a collection of Gram-negative strains, including an A. baumannii strain. A group of compounds knocked back the bacteria, and the researchers selected the top one—with the handy handle of RO7036668. The molecule was then optimized and fine-tuned, including charge balancing, to make it more effective, soluble, and safe. This resulted in zosurabalpin.

Deadly drug

In further experiments, zosurabalpin proved effective at killing a collection of 129 clinical CRAB isolates, many of which were difficult-to-treat isolates. The experimental drug was also effective at ridding mice of infections with a pan-resistant A. baumannii isolate, meaning however the drug worked, it could circumvent existing resistance mechanisms.

Next, the researchers worked to figure out how zosurabalpin was killing off these pan-resistant, deadly bacteria. They did this using a standard method of subjecting the bacteria to varying concentrations of the antibiotic to induce spontaneous mutations. For bacteria that developed tolerance to zosurabalpin, the researchers used whole genome sequencing to identify where the mutations were. They found 43 distinct mutations, and most were in genes encoding LPS transport and biosynthesis machinery.

LPS—lipopolysaccharide—is a key bacterial toxin on the outside of Gram-negative bacteria, which are uniquely encased in two menacing layers. There's an outer membrane, which contains LPS, and an inner membrane made of peptidoglycan, a large polymer that forms a rigid mesh scaffold around the bacterial cytoplasm. In between the inner and outer members is a squishy periplasmic space. Any drug that wants to get into a Gram-negative bacterium's cell must traverse both membranes and the periplasm—no small feat. (In contrast, Gram-positive bacteria contain only one thick peptidoglycan layer around their cells. The two types of bacteria are distinguished from each other using a staining method developed by Danish bacteriologist Hans Christian Gram in the 1880s.)

Based on the mutations, it seemed zosurabalpin didn't need to get into the cells to kill the bacteria—it was working in the membranes. Researchers at Harvard, led by Andrew Kruse and Daniel Kahne, worked to figure out exactly what zosurabalpin was up to with LPS-related machinery. The researchers took a multi-pronged approach, using structure, genetic, and biochemical approaches to create a complete picture. First, they solved the structure that revealed what zosurabalpin was up to: It was binding to a complex of lipopolysaccharide transport proteins (Lpt). This transporter complex (aka LptB₂FGC) creates a protein bridge that spans from the cytoplasm, through the inner membrane, across the periplasm, and to the outer surface of the outer membrane. Its job is to transport LPS from the inner membrane to its final resting place in the outer membrane. And zosurabalpin was gumming up the works.

Toxic blockage

However, the researchers found that zosurabalpin is not the wrench in the machinery; rather, the drug clamped onto the transporter complex when LPS was in it, in transit. Zosurabalpin trapped the LPS in the transporter, preventing its movement to the outer membrane. This alone isn't lethal for the bacteria—A. baumannii can survive without LPS on its outer membrane. But, while LPS jammed in the transporter en route to the outer membrane, the parts of the machinery at the inner membrane keep working, the researchers found. This creates a toxic buildup of LPS biosynthesis intermediates in the cell. And that is how zosurabalpin kills CRAB.

The LPS transport system has never been the target of an antibiotic before—other classes target things like peptidoglycan, protein synthesis, and DNA replication. The finding opens up a new class of drugs, giving researchers new targets for their drug candidates.

But there are some caveats. For one, zosurabalpin doesn't seem to work on any other Gram-negative bacteria besides A. baumannii. The proteins in the LPS transporter complex are not conserved across different bacteria. Thus, targeting the LPS transporters of other nefarious Gram-negative bacteria will take yet more drug development research. One bright side of this, as Gugger and Hergenrother note in their commentary, is that it may produce species-specific antibiotics, which could protect patients' microbiomes from being obliterated by broad-spectrum drugs, which we now appreciate is bad for human health.

And, of course, with any new antibiotic, there's the inevitability that bacteria will develop resistance. The researchers already found that select mutations in the LPS transporter machinery can knock back the drug's potency. Also, A. baumannii doesn't need LPS to stay alive. That said, simply blocking LPS production would leave A. baumannii more vulnerable, and it's unclear how that trade-off will play out in clinical settings.

For now, zosurabalpin is in early phase clinical trials and researchers are hopeful that it will be the long-sought new antibiotic that's urgently needed.

"With this significant breakthrough, zosurabalpin has the potential to address a major unmet need in the fight against antimicrobial resistance," Kenneth Bradley, lead author on one of the new papers and Global Head of Infectious Disease Discovery at Roche, said in a statement.

Welcome to Edition 6.25 of the Rocket Report! We hope all our readers had a peaceful holiday break. While many of us were enjoying time off work, launch companies like SpaceX kept up the pace until the final days of 2023. Last year saw a record level of global launch activity, with 223 orbital launch attempts and 212 rockets successfully reaching orbit. Nearly half of these missions were by SpaceX.

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's fourth launch puts payload in wrong orbit. The fourth flight of Firefly Aerospace's Alpha rocket on December 22 placed a small Lockheed Martin technology demonstration satellite into a lower-than-planned orbit after lifting off from Vandenberg Space Force Base, California. US military tracking data indicated the Alpha rocket released its payload into an elliptical orbit ranging between 215 and 523 kilometers in altitude, not the mission's intended circular target orbit. Firefly later confirmed the Alpha rocket's second stage, which was supposed to reignite about 50 minutes after liftoff, did not deliver Lockheed Martin's satellite into the proper orbit. This satellite, nicknamed Tantrum, was designed to test Lockheed Martin's new wideband Electronically Steerable Antenna technology to demonstrate faster on-orbit sensor calibration to deliver rapid capabilities to US military forces.

Throwing a tantrum? ... This was the third time in four flights that Firefly's commercial Alpha rocket, designed to loft payloads up to a metric ton in mass, has not reached its orbital target. The first test flight in 2021 suffered an engine failure on the first stage before losing control shortly after liftoff. The second Alpha launch in 2022 deployed its satellites into a lower-than-planned orbit, leaving them unable to complete their missions. In September, Firefly launched a small US military satellite on a responsive launch demonstration. Firefly and the US Space Force declared that mission fully successful. Atmospheric drag will likely pull Lockheed Martin's payload back into Earth's atmosphere for a destructive reentry in a matter of weeks. The good news is ground teams are in contact with the satellite, so there could be a chance to complete at least some of the mission's objectives. (submitted by Ken the Bin)

Australian startup nears first launch. The first locally made rocket to be launched into space from Australian soil is scheduled for liftoff from a commercial facility in Queensland early next year, the Australian Broadcasting Corporation reports. A company named Gilmour Space says it hopes to launch its first orbital-class Eris rocket in March, pending final approval from Australian regulatory authorities. This would be the first Australian-built orbital rocket, although a US-made rocket launched Australia's first satellite from a military base in South Australia in 1967. The UK's Black Arrow rocket also launched a satellite from the same remote Australian military base in 1971.

Getting to know Eris ... The three-stage Eris rocket stands 25 meters (82 feet) tall with the ability to deliver up to 300 kilograms (660 pounds) of payload into low-Earth orbit, according to Gilmour Space. The company says the Eris rocket will be powered by Gilmour's "new and proprietary hybrid rocket engine." These kinds of propulsion systems use a solid fuel and a liquid oxidizer. We'll be watching to see if Gilmour shares more tangible news about the progress toward the first Eris launch in March. In late 2022, the company targeted April 2023 for the first Eris flight, so this program has a history of delays. (submitted by Marzipan and Onychomys)

A commander's lament on the loss of a historic SpaceX booster. The Falcon 9 rocket that launched NASA astronauts Doug Hurley and Bob Behnken on SpaceX's first crew mission in 2020 launched and landed for the 19th and final time just before Christmas, then tipped over on its recovery ship during the trip back to Cape Canaveral, Florida, Ars reports. This particular booster, known by the tail number B1058, was special among SpaceX's fleet of reusable rockets. It was the fleet leader, having tallied 19 missions over the course of more than three-and-a-half years. More importantly, it was the rocket that thundered into space on May 30, 2020, on a flight that made history.

A museum piece? ... The lower third of the booster was still on the deck of SpaceX's recovery ship as it sailed into Port Canaveral on December 26. This portion of the rocket contains the nine Merlin engines and landing legs, some of which appeared mangled after the booster tipped over in high winds and waves. Hurley, who commanded SpaceX's Crew Dragon spacecraft on the booster's historic first flight in 2020, said he hopes to see the remaining parts of the rocket in a museum. “Hopefully they can do something because this is a little bit of an inauspicious way to end its flying career, with half of it down at the bottom of the Atlantic Ocean," said Hurley.

SpaceX opens 2024 campaign with a new kind of Starlink satellite. SpaceX has launched the first six Starlink satellites that will provide cellular transmissions for customers of T-Mobile and other carriers, Ars reports. A Falcon 9 rocket launched from California on January 2 carried 21 Starlink satellites overall, including the first six Starlinks with Direct to Cell capabilities. SpaceX says these satellites, and thousands of others to follow, will "enable mobile network operators around the world to provide seamless global access to texting, calling, and browsing wherever you may be on land, lakes, or coastal waters without changing hardware or firmware." T-Mobile said that field testing of Starlink satellites with the T-Mobile network will begin soon. "The enhanced Starlink satellites have an advanced modem that acts as a cellphone tower in space, eliminating dead zones with network integration similar to a standard roaming partner," SpaceX said.

Two of 144 ... SpaceX followed this launch with another Falcon 9 flight from Florida on January 3 carrying a Swedish telecommunications satellite. These were the company's first two missions of 2024, a year when SpaceX officials aim to launch up to 144 rockets, an average of 12 per month, exceeding the 98 rockets it launched in 2023. A big focus of SpaceX's 2024 launch manifest will be delivering these Starlink Direct to Cell satellites into orbit. (submitted by Ken the Bin)

Chinese booster lands near homes. China added a new pair of satellites to its Beidou positioning and navigation system on December 25, but spent stages from the launch landed within inhabited areas, Space News reports. Meanwhile, a pair of the side boosters from the Long March 3B rocket used for the launch appeared to fall to the ground near inhabited areas in Guangxi region, downrange of the Xichang spaceport in Sichuan province, according to apparent bystander footage on Chinese social media. One video shows a booster falling within a forested area and exploding, while another shows a falling booster and later, wreckage next to a home.

Life downrange ... Chinese government authorities reportedly issue warnings and evacuation notices for citizens living in regions where spent rocket boosters are likely to fall after launch, but these videos clearly show people are still close by as the rockets fall from the sky. We've seen this kind of imagery before, including views of a rocket that crashed into a rural building in 2019. What's more, the rockets return to Earth with leftover toxic propellants—hydrazine and nitrogen tetroxide—that could be deadly to breathe or touch. Clouds of brownish-orange gas are visible around the rocket wreckage, an indication of the presence of nitrogen tetroxide. China built its three Cold War-era spaceports in interior regions to protect them from possible military attacks, while its newest launch site is at a coastal location on Hainan Island, allowing rockets launched there to drop boosters into the sea. (submitted by Ken the Bin and EllPeaTea)

Launch date set for next H3 test flight. The second flight of Japan's new flagship H3 rocket is scheduled for February 14 (US time; February 15 in Japan), the Japan Aerospace Exploration Agency announced on December 28. This will come nearly one year after the first H3 test flight failed to reach orbit last March when the rocket's second stage failed to ignite a few minutes after liftoff. This failure destroyed a pricey Japanese Earth observation satellite and dealt a setback to Japan's rocket program. The H3 is designed to be cheaper and more capable than the H-IIA and H-IIB rockets it will replace. Eventually, the H3 will launch Japan's scientific research probes, spy satellites, and commercial payloads.

Fixes since the first flight ... Engineers narrowed the likely cause for the first H3 launch failure to an electrical issue, although Japanese officials have not provided an update on the investigation for several months. In August, Japan's space agency said investigators had narrowed the cause of the H3's second-stage malfunction to three possible failure scenarios. Nevertheless, officials are apparently satisfied the H3 is ready to fly again. But this time, there won't be an expensive satellite aboard. A dummy payload will fly inside the H3 rocket's nose cone, along with two relatively low-cost small satellites hitching a piggyback ride to orbit. (submitted by Ken the Bin and EllPeaTea)

India's PSLV launches first space mission of 2024. The first orbital launch of the new year, as measured in the globally recognized Coordinated Universal Time, or UTC, was the flight of an Indian Polar Satellite Launch Vehicle (PSLV) on January 1 (December 31 in the United States). This launch deployed an X-ray astronomy satellite named XPoSat, which will measure X-ray emissions from black holes, neutron stars, active galactic nuclei, and pulsars. This is India's first X-ray astronomy satellite, and its launch is another sign of India's ascendence among the world's space powers. India has some of the world's most reliable launch vehicles, is developing a human-rated capsule to carry astronauts into orbit, and landed its first robotic mission on the Moon last year.

Going lower ... After releasing the XPoSat payload, the PSLV's fourth stage lowered its orbit to begin an extended mission hosting 10 scientific and technology demonstration experiments. These payloads will test new radiation shielding technologies, green propulsion, and fuel cells in orbit, according to the Indian Space Research Organization. On missions with excess payload capacity, India has started offering researchers and commercial companies the opportunity to fly experiments on the PSLV fourth stage, which has its own solar power source to essentially turn itself from a rocket into a satellite platform. (submitted by EllPeaTea and Ken the Bin)

Mixed crews will continue flying to the International Space Station. NASA and the Russian space agency, Roscosmos, will extend an agreement on flying each other's crew members to the International Space Station through 2025, Interfax reports. This means SpaceX's Crew Dragon spacecraft and Boeing's Starliner capsule, once operational, will continue transporting Russian cosmonauts to and from the space station, as several recent SpaceX crew missions have done. In exchange, Russia will continue flying US astronauts on Soyuz missions.

There's a good reason for this… Despite poor relations on Earth, the US and Russian governments continue to be partners on the ISS. While NASA no longer has to pay for seats on Soyuz spacecraft, the US space agency still wants to fly its astronauts on Soyuz to protect against the potential for a failure or lengthy delay with a SpaceX or Boeing crew mission. Such an event could lead to a situation where the space station has no US astronauts aboard. Likewise, Roscosmos benefits from this arrangement to ensure there's always a Russian on the space station, even in the event of a problem with Soyuz. (submitted by Ken the Bin)

SpaceX sets new records to close out 2023. SpaceX launched two rockets, three hours apart, to wrap up a record-setting 2023 launch campaign, Ars reports. On December 28, SpaceX launched a Falcon Heavy rocket from NASA's Kennedy Space Center in Florida with the US military's super-secret X-37B spaceplane. Less than three hours later, a Falcon 9 rocket took off a few miles to the south with another batch of Starlink Internet satellites. These were SpaceX's final launches of 2023. SpaceX ended the year with 98 flights, including 91 Falcon 9s, five Falcon Heavy rockets, and two test launches of the giant new Super Heavy-Starship rocket. These flights were spread across four launch pads in Florida, California, and Texas. It was also the shortest turnaround between two SpaceX flights in the company's history, and set a modern-era record at Cape Canaveral, Florida, with the shortest span between two orbital-class launches there since 1966.

Where's the X-37B?… The military's reusable X-37B spaceplane that launched on the Falcon Heavy rocket apparently headed into an unusually high orbit, much higher than the spaceplane program's previous six flights. But the military kept the exact orbit a secret, and amateur skywatchers will be closely watching for signs of the spaceplane passing overhead in hopes of estimating its apogee, perigee, and inclination. What the spaceplane is doing is also largely a mystery. The X-37B resembles a miniature version of NASA's retired space shuttle orbiter, with wings, deployable landing gear, and black thermal protection tiles to shield its belly from the scorching heat of reentry.

Elon Musk says SpaceX needs to built a lot of Starships. Even with reusability, SpaceX will need to build Starships as often as Boeing builds 737 jetliners in order to realize Elon Musk's ambition for a Mars settlement, Ars reports. "To achieve Mars colonization in roughly three decades, we need ship production to be 100/year, but ideally rising to 300/year," Musk wrote on his social media platform X. SpaceX still aims to make the Starship and its Super Heavy booster rapidly reusable. The crux is that the ship, the part that would travel into orbit, and eventually to the Moon or Mars, won't be reused as often as the booster. These ships will come in a number of different configurations, including crew and cargo transports, refueling ships, fuel depots, and satellite deployers.

Laws of physics… The first stage of the giant launch vehicle, named Super Heavy, is designed to return to SpaceX's launch sites about six minutes after liftoff, similar to the way SpaceX recovers its Falcon boosters today. Theoretically, Musk wrote, the booster could be ready for another flight in an hour. With the Starship itself, the laws of physics and the realities of geography come into play. As an object flies in low-Earth orbit, the Earth rotates underneath it. This means that a satellite, or Starship, will find itself offset some 22.5 degrees in longitude from its launch site after a single 90-minute orbit around the planet. It could take several hours, or up to a day, for a Starship in low-Earth orbit to line up with one of the recovery sites. "The ship needs to complete at least one orbit, but often several to have the ground track line back up with the launch site, so reuse may only be daily," Musk wrote. "This means that ship production needs to be roughly an order of magnitude higher than booster production."

Next three launches

January 5: Kuaizhou 1A | Unknown Payload | Jiuquan Satellite Launch Center, China | 11:20 UTC

January 7: Falcon 9 | Starlink 6-35 | Cape Canaveral Space Force Station, Florida | 21:00 UTC

January 8: Falcon 9 | Starlink 7-10 | Vandenberg Space Force Base, California | 05:00 UTC

Good morning. It's January 5, and today's photo reveals the Crab Nebula in all of its glory.

This object, known more formally as Messier 1 or M1, earned its colloquial name when Anglo-Irish astronomer William Parsons observed and drew this object in the early 1840s. It looked something like a crab with arms, and the appellation stuck. The nebula had been discovered about a century earlier by English astronomer John Bevis.

The nebula is actually a supernova remnant from a star that was observed popping in 1054 and recorded by Chinese astronomers. That must have been quite a sight, because the supernova occurred only about 2,000 light-years from Earth, which is relatively close as these things go. It likely was as bright as Venus and visible during daylight hours for a few weeks.

This image was captured by amateur astronomer Paul Macklin in Indiana. And it's quite spectacular.

Source: Paul Macklin

There is only so much heat—or cold—that the human body can take. This can be a problem in extreme environments, from subzero polar temperatures to the ruthless heat of the Sahara, and it doesn’t stop at Earth. Maintaining temperature is also an issue for astronauts. The vacuum of space is a gargantuan freezer, and exposure to direct sunlight out there can be just as brutal as the cold.

Clothing tech that regulates body temperature usually goes only one way: heating or cooling. It also tends to be bulky and needs substantial energy that eventually drains any batteries. What if there was a system that both heat and cool while running on a constant renewable energy source?

A team of researchers, led by Ziyuan Wang of Nankai University in Tianjin, China, has created a flexible, solar-powered device that can be incorporated into clothing and regulate the body by actively heating or cooling the skin. It also works continuously for 24 hours and only needs sunlight to recharge.

“To achieve the required sustainability and flexibility as well as light weight, the thermal-management unit for the body must be highly efficient in transferring energy and have a low energy consumption,” the team said in a study recently published in Science.

Batteries not included

Wang’s new system combines the power of a solar cell with that of an electrocaloric device. Solar cells, also known as photovoltaic cells, are made of materials that are semiconductors, which can absorb energy from sunlight and convert it to electricity. In this case, the photovoltaic material used is a flexible polymer.

The other component is an electrocaloric device that changes temperature when placed in an electric field applying the field will heat the material, while removing it will cool it.

The system developed by Wang and his colleagues is made of a type of polyvinyl. This flexible material functions as an insulator, integrating a solar cell outside the polyvinyl with an electrocaloric device underneath. When exposed to sunlight, the solar cell did exactly what it was expected to by turning sunlight into electrical energy. This electricity is then transferred to the electrocaloric device, where (assuming the device is in cooling mode) the appearance of an electric field will heat the device. Enough power is produced by the solar cell to keep the entire system going, and any extra energy is kept in a separate energy storage device.

Turn it up or turn it down

Whatever energy stored during the day becomes especially useful after the sun goes down. In the dark, the system automatically taps into energy from the storage attachment to keep going through the night.  Heating and cooling modes can be easily switched as it gets hotter or colder. And, when the system runs out of energy, there is no need to plug anything in—exposure to direct sunlight for 12 hours will recharge it.

“With these two working modes, bidirectional controllable thermoregulation for cooling and warming can be implemented as needed,” the researchers said in the same study.

So how can an explorer, astronaut, or anyone in an extreme environment wear this device? Wang proposes a suit with heating-cooling panels attached to the front and back of the chest, arms and legs. Because the panels are so flexible and lightweight, a garment like this would not weigh down someone facing blistering heat.

While this thermoregulatory tech may not be available yet, Wang is hopeful that it could be a significant breakthrough for those who have to work in extreme environments, even astronauts who have to brave the freezing darkness to go out on a spacewalk.

Science, 2023.  DOI:  10.1126/science.adj3654

Good morning. It's January 4, and today's image is a photo of our star, Sol. The image was captured by NASA's Solar Dynamics Observatory, a spacecraft in geosynchronous orbit, on Wednesday.

So why a picture of the Sun? Because we've just passed perihelion, the point at which planet Earth reaches its closest point to the Sun. This year perihelion came at 00:38 UTC on Wednesday, January 3. We got to within about 91.4 million miles (147 million km) of the star. Due to its slightly elliptical orbit around the Sun, Earth will reach aphelion this year on July 5, at a distance of 94.5 million miles (152 million km).

There is a bit of irony for those of us who live in the Northern Hemisphere, of course. We approach nearest to the Sun at almost the coldest time of year, just a couple of weeks after the winter solstice. Our planet's seasons are determined by Earth's axial tilt, however, not its proximity to the Sun.

In any case, happy new year, a time when the world can seem full of possibility—shiny and bright like a star.

Source: NASA SDO

We've all heard the common folk wisdom that when it comes to forming romantic partnerships, opposites attract. Researchers at the University of colourado, Boulder, contend that this proverbial wisdom is largely false, based on the findings of their sweeping September study, published in the journal Nature Human Behavior. The saying, "birds of a feather flock together," is a more apt summation of how we choose our partners.

“These findings suggest that even in situations where we feel like we have a choice about our relationships, there may be mechanisms happening behind the scenes of which we aren't fully aware,” said co-author Tanya Horwitz, a psychology and neuroscience graduate student at UCB. “We’re hoping people can use this data to do their own analyses and learn more about how and why people end up in the relationships they do.”

Horwitz et al. conducted a systematic review of peer-reviewed studies in the English language involving comparisons of the same or similar complex traits in partners, all published before August 17, 2022, with the oldest dated 1903. They excluded same-sex/gender partners, maintaining that these partnerships warranted a separate analysis since the patterns could differ significantly. The meta-analysis focused on 22 distinct traits. The team also conducted a raw data analysis of an additional 133 traits, drawing from the UK's Biobank dataset, one of the largest and most detailed in the world for health-related information on more than 500,000 people. All told, the study encompassed millions of couples spanning over a century: co-parents, engaged pairs, married pairs, and cohabitating pairs.

The personality traits included were based on the so-called Big Five basic personality traits: neuroticism, extraversion, openness, agreeableness, and conscientiousness. (The Big Five is currently the professional standard for social psychologists who study personality. Here's a good summary of what those traits mean to psychologists.) The other traits studied included such things as educational attainment, IQ score, political values, religiosity, problematic alcohol use, drinking, quitting smoking, starting smoking, quantity of smoking, smoker status, substance use disorder, BMI, height, waist-to-hip ratio, depression, diabetes, generalized anxiety, whether they were breastfed as a child, and age of first intercourse, among others.

The meta-analysis and Biobank analysis revealed that the strongest correlations for couples were for birth year and traits like political and religious attitudes, educational attainment, and certain IQ measures. Couples tend to be similar when it comes to their substance use, too: heavy drinkers tend to be with other heavy drinkers, and teetotalers tend to pair with fellow teetotalers. There were a handful of traits among the Biobank couples where opposites did seem to attract, most notably whether one is a morning person or a night owl, tendency to worry, and hearing difficulty.

The weakest correlations were for traits like height, weight, medical conditions, and personality traits, although these were still mostly positive, apart from extroversion, which somewhat surprisingly showed almost no correlation. “People have all these theories that extroverts like introverts or extroverts like other extroverts, but the fact of the matter is that it’s about like flipping a coin," said Horwitz. "Extroverts are similarly likely to end up with extroverts as with introverts."

Horwitz et al. cautioned that even the strongest correlations they found were still fairly modest. As for why couples show such striking similarities, the authors write that there could be many reasons. Some people might just be attracted to similar sorts, or couples might become more similar over time. (The study also found that the strength of the correlations changed over time.) Perhaps two people who grow up in the same geographical area or a similar home environment might naturally find themselves drawn to each other.

The authors were careful to note several limitations to their meta-analysis. Most notably, most of those partners sampled came from Europe and the United States, with only a handful coming from East and South Asia, Africa, Latin America, and the Caribbean. Furthermore, all participants in the UK Biobank dataset were between the ages of 40 and 69 when they were originally recruited, all of whom were less likely to smoke, be socioeconomically deprived, or drink daily. The studies included in the meta-analysis also varied widely regarding sample sizes used to draw correlations across traits. For these reasons, the authors caution that their findings "are unlikely to be generalizable to all human populations and time periods."

Nature Human Behavior, 2023. DOI: 10.1038/s41562-023-01672-z  (About DOIs).

It's not an exaggeration to suggest that the most significant event on Earth was the evolution of photosynthesis. The ability to harvest energy from light freed life from the need to scavenge energy from its environment. With this new capability, life grew in complexity and invaded new environments, ultimately reshaping the Earth.

For such a pivotal event, we know remarkably little about it. Tracing the presence of oxygen in the atmosphere suggests photosynthesis evolved at least 2.4 billion years ago, although the rise in oxygen levels turns out to be impressively complicated. Tracing the variations of present-day genes places photosynthesis' origin at about 3 billion years ago. That timing is similar to the origin of the photosynthetic cyanobacteria, which both continue to live independently and have been incorporated into plant cells as chloroplasts.

What we don't have is clear evidence of photosynthetic cells of similar age. A few microfossils with similarities to cyanobacteria have been identified, but it's impossible to determine whether they were making the proteins that power photosynthesis. Now, new fossils described by a team at the University of Liège push unambiguous evidence of photosynthesis back over a billion years to 1.7 billion years ago.

What’s a thylakoid?

The work relies on the identification of structures called thylakoid membranes. These are stacks of disc-shaped membranes that increase the surface area within the cell that can play host to photosynthetic protein complexes. Not all present-day cyanobacteria have thylakoid membranes, but they're present in the chloroplasts of plant cells.

To search for thylakoids, the researchers obtained small cell-like bodies from sedimentary rocks in several sites. They made ultra-thin sections of these rocks and then performed electron microscopy to resolve some of the details in the interior of the cells. This allowed them to pick up features that were only a few tens of nanometers across.

Two of the sites had cells with multi-layered internal membranes that are typical of thylakoids. These were the McDermott Formation in Australia and the Grassy Bay Formation in Arctic Canada. The latter is over a billion years old, which is substantially older than any previous evidence of thylakoids. But the McDermott Formation is over 1.7 billion years old, which means the fossil evidence for these structures now goes back 1.2 billion years earlier than it had.

At the same time, apparent cyanobacteria fossils from the Democratic Republic of the Congo that are a billion years old do not have indications of thylakoid membranes. As noted, there are still species of cyanobacteria around today that lack these structures, so it appears these lineages have been separate for quite some time.

Going back in time

While important in its own right, the findings are mostly significant for their implications. Molecular data suggests that the split between the two groups of cyanobacteria—with and without thylakoids—goes back even earlier. There have also been some proposals that the evolution of thylakoid membranes gave photosynthesis the boost needed to set off the Great Oxygenation Event, where the atmosphere's oxygen levels rose significantly for the first time.

By showing it was possible to identify thylakoid membranes despite the immense age, the researchers behind this work provide a strong impetus to check for their presence around the time of key evolutionary events. The fossil evidence might ultimately catch up with the genetic and chemical evidence when it comes to the evolution of photosynthesis.

Nature, 2024. DOI: 10.1038/s41586-023-06896-7  (About DOIs).

The mythical Hydra may have been able to grow one of its many heads back every time it suffered a decapitation, but there are actual creatures capable of regenerating parts of their bodies bitten off by hungry predators. Jellyfish are one of them.

From salamanders to starfish to the actual hydra (a tiny hydrozoan named for the fearsome beast of legend), animals that are capable of regeneration all start the repair process by forming a blastema. This clump of proliferative cells, which are similar to stem cells, can repopulate body parts by dividing over and over again. While the cells are still undifferentiated in the beginning, they eventually form specific cell types like muscle and skin.

The process of blastema formation in some other animals has been studied, but how they form in jellyfish was still a mystery. Led by postdoctoral researcher Sosuke Fujita, the team at the University of Tokyo and Tohoku University in Japan wanted to establish a baseline for non-bilaterian regeneration by finding out how a blastema helps regrow tentacles in jellyfish. Would their blastema formation process be different from that in bilaterians?

“In particular, the current understanding of blastema formation largely relies on bilaterian models, and thus the mechanisms of blastema formation outside of bilaterians remain poorly understood,” the researchers said in a study recently published in PLOS Biology.

The regeneration process in jellyfish has been a mystery. The Japanese team finally gained new insight into this process in the jellyfish Cladonema pacificum. They found that the proliferative cells that create the blastema only appear where there is an injury—they aren’t the same as localized stem cells found at the tentacle base. But both types of cells work together to repair and regrow a severed tentacle.

An arm and a leg

Jellyfish are cnidarians, a phylum of soft-bodied invertebrates. Cnidaria also includes corals, hydras, and anemones, which all have stinging tentacles. Unlike bilaterians such as salamanders (and humans), which have bilateral symmetry (meaning a symmetrical right and left side), cnidarians have radial body symmetry, with body sections that extend out from the middle and are symmetrical all around. They have no right and left or front and back.

Because jellyfish rely on their tentacles to capture and paralyze prey, they need a lost tentacle to grow back as fast as possible. When a tentacle from Cladonema was severed with the base, or bulb, left in place, the wound at the site of the cut completely healed in as little as 24 hours. A blastema formed right after healing; the new tentacle then began growing.

The longer it grew, the more nematocytes, or stinging cells, multiplied. This suggested to Fujita and his team that regeneration occurs regardless of whether the jellyfish has recently eaten because its body automatically prioritizes regrowing a tentacle to catch food.

They just keep growing

When the blastema forms, most cell proliferation happens toward the regenerating tip of the new tentacle. Three types of differentiated cells were later found in the blastema. These are epithelial cells, which form the inner layers of the tentacle; i-cells, which help the jellyfish sense and handle food; and stinging nematocytes. Undifferentiated cells showed a tendency to turn into epithelial cells because those are the most common cells in a completely developed tentacle.

Most cells making up the blastema are not stem cells from the bulb that migrate to the tip. But there’s still something the bulb stem cells do. The team believes the cells help the newly forming tentacle grow outward from the base, adding some length while the proliferative cells elongate it from the tip. Elimination of the stem cells at the base would also delay blastema formation by a week or two.

Overall, blastema formation in jellyfish turned out to be very similar to that seen in bilaterians that are capable of regeneration. However, exactly how and where proliferative cells originate is still unclear. The researchers think it is possible that these cells are derived from already differentiated cells that dedifferentiate to form the blastema. Examples of dedifferentiated cells that form blastema have been seen in starfish and crickets.

Could humans ever be capable of regeneration? It might happen. Some experiments on animals that do not normally regenerate have successfully induced to regrow tissues. As mechanisms behind this phenomenon are better understood, human treatments using regenerative processes may someday be developed, but for now, this remains in the realm of science fiction.

PLOS Biology, 2023.  DOI:  10.1371/journal.pbio.3002435