As a summer wave of COVID-19 infections swells once again, a study published this week in the New England Journal of Medicine offers some positive news about the pandemic disease: Rates of long COVID have declined since the beginning of the health crisis, with rates falling from a high of 10.4 percent before vaccines were available to a low of 3.5 percent for those vaccinated during the omicron era, according to the new analysis.

The study, led by Ziyad Al-Aly, chief of research at the VA Saint Louis Health Care System, used data from a wealth of health records in the Department of Veterans Affairs. The researchers ultimately included data from over 440,000 veterans who contracted COVID-19 sometime between March 1, 2020, and January 31, 2022, as well as over 4.7 million uninfected veterans who acted as controls.

Al-Aly and colleagues divided the population into eight groups. People who were infected during the study period were divided into five groupings by the dates of their first infection and their vaccination status. The first group included those infected in the pre-delta era before vaccines were available (March 1, 2020, to June 18, 2021). Then there were vaccinated and unvaccinated groups who were infected in the delta era (June 19, 2021, to December 18, 2021) and the omicron era (December 19, 2021, and January 31, 2022). The uninfected controls made up the final three of eight groups, with the controls assigned to one of the three eras.

On the decline

In the pre-delta/pre-vaccine era, 10.42 out of 100 unvaccinated people infected developed long COVID in the year after their infection, which the researchers referred to as PASC, or postacute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In the delta era, the rate of long COVID among the unvaccinated fell slightly to 9.51 out of 100. But for the vaccinated, the rate fell much further, to 5.35 out of 100. A similar pattern was seen in the omicron era. For the unvaccinated, the rate of long COVID again fell slightly to 7.76 per 100 people, while the vaccinated saw their rate fall to 3.5 per 100.

In a secondary statistical analysis, called a decomposition analysis, the researchers found that vaccines could explain about 72 percent of the cumulative decline in long COVID rates across the eras, while era-related factors explained about 28 percent. Those era-related factors could include differences in the virus, improved treatments, and use of anti-viral medications.

Further, looking at data on the disease categories related to long COVID cases, the researchers also did an analysis finding a shift in symptoms over the eras. The researchers looked at over 10 disease categories: cardiovascular, coagulation and hematologic, fatigue, gastrointestinal, kidney, mental health, metabolic, musculoskeletal, neurologic, and pulmonary. Compared to the two earlier eras, the researchers noted an increase in gastrointestinal, metabolic, and musculoskeletal diseases involved in long COVID cases in the omicron era.

Overall, the study points to a welcomed decline in the rates of long COVID among the infected, particularly for those who are vaccinated. But, it also makes clear that long COVID isn't a thing of the past: "a substantial residual risk of PASC remains among vaccinated persons who had SARS-CoV-2 infection during the omicron era," Al-Aly and his colleagues conclude.

The study also has some limitations, leaving lingering questions for further study. One is whether the type or number of vaccines affect the risk of long COVID—that was not included in the study. The study also didn't allow researchers to assess whether repeat infections increase the burden of long COVID.

NASA has spent $450 million designing and building a first-of-its-kind robot to drive into eternally dark craters at the Moon's south pole, but the agency announced Wednesday it will cancel the rover due to delays and cost overruns.

"NASA intends to discontinue the VIPER mission," said Nicky Fox, head of the agency's science mission directorate. "Decisions like this are never easy, and we haven’t made this one, in any way, lightly. In this case, the projected remaining expenses for VIPER would have resulted in either having to cancel or disrupt many other missions in our Commercial Lunar Payload Services (CLPS) line."

NASA has terminated science missions after development delays and cost overruns before, but it's rare to cancel a mission with a spacecraft that is already built.

The Volatiles Investigating Polar Exploration Rover (VIPER) mission was supposed to be a robotic scout for NASA's Artemis program, which aims to return astronauts to the lunar surface in the next few years. VIPER was originally planned to launch in late 2023 and was slated to fly to the Moon aboard a commercial lander provided by Pittsburgh-based Astrobotic, which won a contract from NASA in 2020 to deliver the VIPER rover to the lunar surface. Astrobotic is one of 14 companies in the pool of contractors for NASA's CLPS program, with the goal of transporting government-sponsored science payloads to the Moon.

But VIPER has been delayed at least two years—the most recent schedule projected a launch in September 2025—causing its cost to grow from $433 million to more than $609 million. The ballooning costs automatically triggered a NASA review to determine whether to proceed with the mission or cancel it. Ultimately, officials said they determined NASA couldn't pay the extra costs for VIPER without affecting other Moon missions.

"Therefore, we’ve made the decision to forego this particular mission, the VIPER mission, in order to be able to sustain the entire program," Fox said.

“We're disappointed," said John Thornton, CEO of Astrobotic. "It's certainly difficult news... VIPER has been a great team to work with, and we're disappointed we won't get the chance to fly them to the Moon."

NASA said it will consider "expressions of interest" submitted by US industry and international partners by August 1 for use of the existing VIPER rover at no cost to the government. If NASA can't find anyone to take over VIPER who can pay to get it to the Moon, the agency plans to disassemble the rover and harvest instruments and components for future lunar missions.

Scientists were dismayed by VIPER's cancellation.

“It's absurd, to be honest with you," said Clive Neal, a planetary geologist at the University of Notre Dame. "It made no sense to me in terms of the economics. You’re canceling a mission that is complete, built, ready to go. It's in the middle of testing."

"This is a bad mistake," wrote Phil Metzger, a planetary physicist at the University of Central Florida, in a post on X. "This was the premier mission to measure lateral and vertical variations of lunar ice in the soil. It would have been revolutionary. Other missions don’t replace what is lost here."

Built with nowhere to go

Engineers at NASA's Johnson Space Center in Houston finished assembling the VIPER rover last month, and managers gave approval to put the craft through environmental testing to make sure VIPER could withstand the acoustics and vibrations of launch and the extreme temperature swings it would encounter in space.

Instead, NASA has canceled the mission after spending $450 million to get it to this point. "This is a very tough decision, but it is a decision based on budgetary concerns in a very constrained budget environment," Fox told reporters Wednesday.

VIPER is about the size of a golf cart, with four wheels, headlights, a drill, and three science instruments to search for water ice in depressions near the Moon's south pole that have been shaded from sunlight for billions of years. This has allowed these so-called permanently shadowed regions to become cold traps, allowing water ice to accumulate at or near the surface, where it could be accessible for future astronauts to use as drinking water or an oxygen source or to convert into electricity and rocket fuel.

But first, scientists need to know exactly where the water is located and how easy it is to reach. VIPER was supposed to be the next step in mapping resources on the Moon, providing ground truth measurements to corroborate remote sensing data from satellites in lunar orbit.

But late parts deliveries delayed construction of the VIPER rover, and in 2022, NASA ordered additional testing of Astrobotic's Griffin lunar lander to improve the chances of a successful landing with VIPER. This delayed VIPER's launch from late 2023 until late 2024, and at the beginning of this year, more supply chain issues with the VIPER rover and the Griffin lander pushed back the launch until September 2025.

This most recent delay raised the projected cost of VIPER more than 30 percent over the original cost of the mission, prompting a NASA termination review. While the rover is now fully assembled, NASA still needed to put it through a lengthy series of tests, complete development of the ground systems to control VIPER on the Moon, and deliver the craft to Astrobotic for integration onto the Griffin lander.

The remaining work to complete VIPER and operate it for 100 days on the lunar surface would have cost around $84 million, according to Kearns.

Kearns said it was possible the $84 million figure could grow if the VIPER mission faced another delay. If it didn't launch by November 2025, the mission's next launch opportunity would not come until the second half of 2026, when the solar-powered rover would have the proper lighting conditions at its polar landing site.

"So we were taking into account the cost it would take to continue VIPER, and also the risk that it would still be possible that either VIPER or Griffin would not be ready at the launch date that was desired in 2025," Kearns said.

NASA officials said they worried they would have to scavenge funding from other missions to pay for more VIPER cost overruns. The agency's science mission directorate is facing budget cuts, with its funding level this year nearly $500 million less than last year's budget, and $900 million below the White House's request.

"We cancel a half-billion dollar rover, that is built, to save $84 million, plus the mission costs," Neal said. "It still doesn't add up to me, but NASA is reacting to the situation they find themselves in because of Congress."

NASA's contract with Astrobotic for the Griffin lander mission remains in effect. The value of NASA's contract with Astrobotic increased from $200 million to $323 million since the initial award in 2020, partially to cover NASA's desire for additional testing on the Griffin lander to gain confidence the unproven craft could safely deliver VIPER to the Moon. Combining VIPER's development cost with Astrobotic's transportation and delivery contract brings the anticipated total mission cost to $932 million.

A disappointment

Astrobotic's first lunar lander, named Peregrine, failed to reach the Moon after launching in January. John Thornton, Astrobotic's CEO, told Ars on Wednesday that engineers have completed the investigation into what happened on the Peregrine mission. The inquiry confirmed what Astrobotic first thought—a helium valve in the spacecraft's propulsion system didn't reseat properly, causing pressure to rise in a propellant tank until it ruptured.

The Griffin lander is significantly larger and more complex than Peregrine. Kearns said NASA would like to see Astrobotic demonstrate a successful landing with the Griffin spacecraft, which could be used to deliver heavier cargo to the Moon than the landers available from other CLPS companies.

"The mission is still a go," Thornton said. "We have an opportunity to put some other payloads on this manifest, and we're excited about that. We've got some interesting ideas around that. One of the ones that we're looking at is an idea of putting our LunaGrid program on that lander."

Astrobotic's LunaGrid program involves deploying vertical solar arrays to generate electricity, an architecture that is particularly useful at the Moon's poles, where some high-elevation points receive near-continuous sunlight. The power generated from these locations could be distributed to landers and rovers in darkness nearby, allowing them to survive the two-week-long lunar night. Some elements of LunaGrid could now be demonstrated on the Griffin lander.

"It's a possibility of creating the first infrastructure on the moon with a pop-up deployable solar array, and the possibility of power infrastructure on the Moon," Thornton said in an interview with Ars. "We're basically trying to turn these lemons into lemonade, and I think we have that opportunity here. The business development side of me is interested and excited about that, but certainly it's been challenging news. We would rather be in a position to fly VIPER, but we're going to do the best with what we’ve got here."

NASA doesn't plan to add any of its own science instruments to the Griffin lander. Thornton said Astrobotic is open to ideas for commercial payloads that could fly on the Griffin mission, but with a launch potentially next year, there's little time to search for customers. "We will need to make a decision very quickly if we're going to be trying to make a push for another payload, or if we're going to be flying the lander as is," he said.

Last month, NASA's inspector general released a report on the CLPS program that highlighted rising costs and delays in the program. The CLPS contract with the largest cost growth was Astrobotic's delivery of the VIPER rover. The value of that contract rose by 62 percent after NASA asked Astrobotic to perform extra tests to mitigate the risks of using a new lander design to deliver a half-billion-dollar rover to the Moon.

NASA established the CLPS program in 2018 with the goal of fostering the nascent industry for commercial lunar missions, and to provide a cost-effective way to transport science payloads to the Moon. The first CLPS missions launched in January and February of this year, several years later than originally planned. Astrobotic's lander didn't make it, but a robotic lander from a Texas-based company named Intuitive Machines became the first US spacecraft to land on the Moon since 1972.

The first two CLPS missions were relatively modest, well short of the capability required to land a mission like VIPER.

“We and the companies have not yet accrued enough experience to properly understand how to smoothly deliver such a large and sophisticated payload as VIPER to the lunar surface," Kearns said.

Ceding leadership

NASA approved development of the VIPER rover after the agency canceled a similar mission named Resource Prospector in 2018, hours before former NASA Administrator Jim Bridenstine officially took the helm of the space agency. NASA changed its strategy to pursue commercial missions to the Moon, and the CLPS program was born.

VIPER was designed to answer some of the same questions as Resource Prospector: Where is the water ice? How much of it is there? How accessible is it?

"Everybody agrees that a serious prospecting campaign is crucial, and VIPER is the best start," Metzger wrote. "So now, if it is cancelled again (after Resource Prospector), we will get several more years of delay or longer. This will be harmful to sustainability in space exploration, to geopolitical challenges in space, and to the most important science. Congress needs to find the money to continue VIPER."

China plans to land astronauts on the Moon by 2030 and establish a lunar base called the International Lunar Research Station. An end goal of NASA's Artemis program is to support a sustained human presence on the Moon. "Part of making that happen is understanding where the resources are to properly locate the base, and yet, we've canceled the only mission that is doing that," Neal said.

"There is also geopolitical concern about nations competing over lunar resources," Metzger wrote. "We believe it is crucial for nations that support the international rules-based order to be leading in lunar exploration to influence and help establish fair and just policy. So it is vital for democratic nations to operate missions like VIPER as quickly as possible. Another couple years' delay could be disproportionately harmful to the world’s future in space."

"China has already stated that Chang’e 7 and 8, to be launched in ’26 and ’28 respectively, are going to the south pole to prospect for volatiles in order to inform China where to correctly site their International Lunar Research Station," Neal told Ars. "So we're ceding leadership. 'Hey, China, go for it.'"

Kearns said some future CLPS missions, and eventually NASA astronauts, could go after similar goals as Resource Prospector and VIPER. But there's no one-for-one replacement on the books at NASA—no mission that combines VIPER's scientific instrumentation and ability to go into dark craters for up to two days at a time.

"The science that VIPER would get would far exceed the other CLPS missions that we have in line," Neal said.

NASA eventually plans to include lunar rovers for astronauts to drive on Artemis missions, and these could allow for human exploration of permanently shadowed craters harboring water ice. But the first rover won't fly until NASA's third Artemis landing, slated for 2030 or later.

If Congress doesn't save the VIPER mission, perhaps another international space agency or a commercial company could take over. But it would be expensive, and NASA hasn't allowed much time for outside entities to express interest. Thornton said Astrobotic probably doesn't have the money to pay for the rest of VIPER's testing and mission operations on its own. "That's a pretty tall order for us and anyone else," he said.

Archaeologists have hotly debated the precise cause of death of those who perished in Pompeii when Mount Vesuvius erupted in 79 CE. Did they die of asphyxiation, from the extreme heat, or from a combination of factors? A new paper published in the journal Frontiers in Earth Science examines the complicating effects of earthquakes that occurred just prior to and concurrently with the eruption. Of most interest was the discovery of two skeletons of people who likely died when their shelter collapsed around them, weakened by the seismic tremors.

As previously reported, the eruption of Mount Vesuvius released thermal energy roughly equivalent to 100,000 times the atomic bombs dropped on Hiroshima and Nagasaki at the end of World War II, spewing molten rock, pumice, and hot ash over the cities of Pompeii and Herculaneum in particular. Archaeologists believed that the vast majority of the victims died of asphyxiation, choking to death on the thick clouds of noxious gas and ash.

However, a 2001 study in Nature, co-authored by University of Naples archaeologist Pierpaolo Petrone, estimated a temperature of 500° Celsius (932° Fahrenheit) for the pyroclastic surge that destroyed Pompeii, sufficient to kill inhabitants in fractions of a second. In 2018, we reported on Petrone's conclusion that inhabitants of Herculaneum may have suffered a similar fate. He observed fracturing in the bones of some 100 excavated skeletons, as well as "cracking and explosion" of the skullcaps, consistent with forensic cases where skulls burst from extreme heat.

Petrone's 2020 follow-up study offered additional evidence that extreme heat killed many victims, based on analysis of one victim's skull in particular, first excavated in the 1960s from Herculaneum. There was evidence of brain matter remains in the skull. Usually such brain matter would be "saponified" by the extreme heat—that is, it turned to soap (glycerol and fatty acids). But this victim's brain matter had been vitrified, i.e., fused into glass. Later that year, Petrone reported fresh evidence that this might, indeed, have been the case, announcing his discovery of preserved human neurons in the victim with the "glassified" brain, although other scientists expressed skepticism about that finding.

A 2023 multidisciplinary analysis of seven plaster casts from Pompeii concluded that these victims, at least, likely survived the early eruption and died some 20 hours later from asphyxiation, although the authors were careful to emphasize that their findings were only applicable to these particular cases. "It is likely that the catastrophic eruption killed people in different ways," the authors of that 2023 study wrote, concluding that "generalizing and supporting a sole hypothesis of death becomes overly reductive."

Seismic shocks

Now we have yet another twist: Some Pompeii residents may have perished due to the cumulative effects of earthquakes and aftershocks. According to Domenico Sparice, a volcanologist at INGV-Osservatorio Vesuviana, and co-authors, there is historical evidence of seismic activity in the decades prior to the 79 CE eruption. For instance, an earthquake in 62–63 CE caused extensive damage to buildings in Pompeii such that repairs were still underway 17 years later.

Many houses in Pompeii had goods and furniture set aside, with piles of lime and other building materials stacked, as well as incomplete wall decorations and frescoes—all indications of ongoing repairs. "The picture that emerges is of a city that, between 62 and 79 CE, suffered the effects of recurring earthquakes and volcanic tremors that forced the inhabitants to undertake continuous reconstruction, renovation, and restoration works until the eruption," Sparice et al. wrote.

Pliny the Younger reported seismic shakings for several days before the eruption but noted that people weren't particularly alarmed because they were accustomed to it. During the eruption itself, Pliny reported tremors in Misenum, some 29 kilometers west of Vesuvius during the night of the first day of eruption, as well as violent aftershocks at the dawn of the second day. He wrote that the "earthquakes... that night became so intense that everything seemed not only to be shaken but overturning." As for the following morning. "the chariots we had ordered to be brought out, though on a level ground, were shaken back and forth and did not remain steady in their places even wedged with stones."

Seismic activity was clearly a factor, yet it can be difficult to identify specific evidence of seismic damage during archaeological excavations at Pompeii since most of the devastation was primarily caused by volcanic phenomena, and the two types of damage intertwine. "For example, earthquakes may trigger the collapse of buildings already conditioned by a vertical load of a fall deposit," Sparice et al. wrote. "Alternatively, the dynamic pressure of a pyroclastic current may affect buildings already weakened by seismic shakings."

The discovery of two male skeletons with traumatic injuries consistent with collapsing structures provides key evidence for this scenario. The remains were found at the Insula dei Casti Amanti, a name derived from a fresco depicting two lovers kissing. Excavations of the site have been ongoing, with the most recent efforts revealing two adjoining rooms (designated A and 22) with evidence of wall failures and damage consistent with structural collapse.

The two skeletons found in Room A were male, around 50 years of age. The first (Individual 1) was lying on its right side with wall debris covering the skull, torso, upper limbs, and part of the lower limbs; the back was exposed and facing the center of the room. The second (Individual 2) was lying on its left side on top of a heap of small rocks and ashes (pumice lapilli). A large masonry fragment lay on top of the right lower limb and pelvis, and the skeleton was covered in a layer of wall fragments and pumice.

The position of Individual 1 is consistent with a man being suddenly crushed by the collapse of a large wall, causing trauma that would have led to immediate death. Individual 2 met a similar fate but may have been trying to protect himself with some kind of round wooden object. Excavators found traces of such an object in the volcanic deposits. It seems unlikely these two men choked to death on thick clouds of hot ash, or perished from extreme heat, since their skeletons were found on top of the pumice lapilli layer rather than under it. According to the authors, it seems the two men survived the initial phase of the eruption and took temporary shelter, only to be crushed under collapsing walls weakened by all the seismic activity before the onset of the pyroclastic flows.

“These complexities are like a jigsaw puzzle in which all the pieces must fit together to unravel the complete picture,” said Sparice of their findings. “We proved that seismicity during the eruption played a significant role in the destruction of Pompeii and, possibly, influenced the choices of the Pompeiians who faced an inevitable death.”

Frontiers in Earth Science, 2024. DOI: 10.3389/feart.2024.1386960  (About DOIs).

“Language is a huge field, and we are novices in this. We know a lot about how different areas of the brain are involved in linguistic tasks, but the details are not very clear,” says Mohsen Jamali, a computational neuroscience researcher at Harvard Medical School who led a recent study into the mechanism of human language comprehension.

“What was unique in our work was that we were looking at single neurons. There is a lot of studies like that on animals—studies in electrophysiology, but they are very limited in humans. We had a unique opportunity to access neurons in humans,” Jamali adds.

Probing the brain

Jamali’s experiment involved playing recorded sets of words to patients who, for clinical reasons, had implants that monitored the activity of neurons located in their left prefrontal cortex—the area that’s largely responsible for processing language. “We had data from two types of electrodes: the old-fashioned tungsten microarrays that can pick the activity of a few neurons; and the Neuropixel probes which are the latest development in electrophysiology,” Jamali says. The Neuropixels were first inserted in human patients in 2022 and could record the activity of over a hundred neurons.

“So we were in the operation room and asked the patient to participate. We had a mixture of sentences and words, including gibberish sounds that weren’t actual words but sounded like words. We also had a short story about Elvis,” Jamali explains. He said the goal was to figure out if there was some structure to the neuronal response to language. Gibberish words were used as a control to see if the neurons responded to them in a different way.

“The electrodes we used in the study registered voltage—it was a continuous signal at 30 kHz sampling rate—and the critical part was to dissociate how many neurons we had in each recording channel. We used statistical analysis to separate individual neurons in the signal,” Jamali says. Then, his team synchronized the neuronal activity signals with the recordings played to the patients down to a millisecond and started analyzing the data they gathered.

Putting words in drawers

“First, we translated words in our sets to vectors,” Jamali says. Specifically, his team used the Word2Vec, a technique used in computer science to find relationships between words contained in a large corpus of text. What Word2Vec can do is tell if certain words have something in common—if they are synonyms, for example. “Each word was represented by a vector in a 300-dimensional space. Then we just looked at the distance between those vectors and if the distance was close, we concluded the words belonged in the same category,” Jamali explains.

Then the team used these vectors to identify words that clustered together, which suggested they had something in common (something they later confirmed by examining which words were in a cluster together). They then determined whether specific neurons responded differently to different clusters of words. It turned out they did.

“We ended up with nine clusters. We looked at which words were in those clusters and labeled them,” Jamali says. It turned out that each cluster corresponded to a neat semantic domain. Specialized neurons responded to words referring to animals, while other groups responded to words referring to feelings, activities, names, weather, and so on. “Most of the neurons we registered had one preferred domain. Some had more, like two or three,” Jamali explained.

The mechanics of comprehension

The team also tested if the neurons were triggered by the mere sound of a word or by its meaning. “Apart from the gibberish words, another control we used in the study was homophones,” Jamali says. The idea was to test if the neurons responded differently to the word “sun” and the word “son,” for example.

It turned out that the response changed based on context. When the sentence made it clear the word referred to a star, the sound triggered neurons triggered by weather phenomena. When it was clear that the same sound referred to a person, it triggered neurons responsible for relatives. “We also presented the same words at random without any context and found that it didn’t elicit as strong a response as when the context was available,” Jamali claims.

But the language processing in our brains will need to involve more than just different semantic categories being processed by different groups of neurons.

“There are many unanswered questions in linguistic processing. One of them is how much a structure matters, the syntax. Is it represented by a distributed network, or can we find a subset of neurons that encode structure rather than meaning?” Jamali asked. Another thing his team wants to study is what the neural processing looks like during speech production, in addition to comprehension. “How are those two processes related in terms of brain areas and the way the information is processed,” Jamali adds.

The last thing—and according to Jamali the most challenging thing—is using the Neuropixel probes to see how information is processed across different layers of the brain. “The Neuropixel probe travels through the depths of the cortex, and we can look at the neurons along the electrode and say like, 'OK, the information from this layer, which is responsible for semantics, goes to this layer, which is responsible for something else.' We want to learn how much information is processed by each layer. This should be challenging, but it would be interesting to see how different areas of the brain are involved at the same time when presented with linguistic stimuli,” Jamali concludes.

Nature, 2024.  DOI: 10.1038/s41586-024-07643-2

Inspired by the electric shock capabilities of electric eels, scientists have developed a soft, stretchable "jelly" battery ideal for wearable devices or soft robotics, according to a new paper published in the journal Science Advances. With further testing in living organisms, the batteries might even be useful as brain implants for targeted drug delivery to treat epilepsy, among other conditions.

As previously reported, the electric eel produces its signature electric discharges—both low and high voltages, depending on the purpose for discharging—via three pairs of abdominal organs composed of modified muscle cells called electrocytes, located symmetrically along both sides of the eel. The brain sends a signal to the electrocytes, opening ion channels and briefly reversing the polarity. The difference in electric potential then generates a current, much like a battery with stacked plates.

Vanderbilt University biologist and neuroscientist Kenneth Catania is one of the most prominent scientists studying electric eels these days. He has found that the creatures can vary the degree of voltage in their electrical discharges, using lower voltages for hunting purposes and higher voltages to stun and kill prey. Those higher voltages are also useful for tracking potential prey, akin to how bats use echolocation. One species, Volta's electric eel (Electrophorus voltai), can produce a discharge of up to 860 volts. In theory, if 10 such eels discharged at the same time, they could produce up to 8,600 volts of electricity—sufficient to power 100 light bulbs.

Mimicking Mother Nature

For soft robotics or wearable electronics applications, soft and stretchy devices with tissue-like electronic properties are required. However, “It’s difficult to design a material that is both highly stretchable and highly conductive since those two properties are normally at odds with one another,” said co-author Stephen O’Neill of the University of Cambridge. “Typically, conductivity decreases when a material is stretched.” So he and his colleagues decided to model their jelly battery design on the layered structure of the electric eel's electrocytes. Whereas conventional electronics employ rigid materials with electrons to carry the charges, this battery would use ions as charge carriers, like the electric eels.

Hydrogels—3D polymer networks composed of 60 percent water—were the obvious choice since they confer the ability to precisely control mechanical properties and can mimic human skin. They are usually made of neutrally charged polymers, but O'Neill et al. added a charge to their polymers, altering the salt component to make them sticky enough to squish together into multiple layers. This builds up a larger energy potential.

The stickiness of the hydrogels comes from the reversible bonds that form between the different layers, thanks to barrel-shaped molecules that act a bit like "molecular handcuffs," per the authors. So, the jelly batteries can stretch without separating the layers and without any loss of conductivity. Furthermore, “We can customize the mechanical properties of the hydrogels so they match human tissue,” said co-author Oren Scherman. “Since they contain no rigid components such as metal, a hydrogel implant would be much less likely to be rejected by the body or cause the build-up of scar tissue.” That makes them promising for future biomedical applications.

Another stretchy battery

In related research, a new paper published in the journal ACS Energy Letters described the fabrication of a lithium-ion battery with stretchable components, including an electrolyte layer that can expand by 5,000 percent. The battery can retain its charge storage capacity after nearly 70 charge/discharge cycles. Rather than using a liquid electrolyte, a team of Chinese scientists incorporated the electrolyte into a polymer layer fused between two flexible electrode films.

The electrodes consisted of a thin film of conductive paste embedded with silver nanowires, carbon black, and lithium-based cathode or anode materials onto a plate. They applied a layer of flexible polydimethylsiloxane (used in contact lenses) on top of the paste, followed by a lithium salt, highly conductive liquid, and stretchy polymer ingredients. When zapped with light, all those components formed a solid rubber-like stretchy layer that could still transport lithium ions. This was topped with another electrode film, and the entire device was then sealed in a protective coating. This battery had a roughly six times higher average charge capacity at a fast-charging rate than a similar device with a traditional liquid electrolyte.

Science Advances, 2024. DOI: 10.1126/sciadv.adn5142  (About DOIs).

ACS Energy Letters, 2024. DOI: 10.1021/acsenergylett.4c01254  (About DOIs).

The highly pathogenic avian influenza H5N1 virus that spilled from wild birds into US dairy cows late last year may have recently seeped from a dairy farm in Colorado to a nearby poultry farm, where it then infected five workers tasked with culling the infected chickens

In a press briefing Tuesday, federal officials reported that four of the avian influenza cases have been confirmed by the Centers for Disease Control and Prevention, while the fifth remains a presumptive positive awaiting CDC confirmation.

All five people have shown mild illnesses, though they experienced variable symptoms. Some of the cases involved conjunctivitis, as was seen in other human cases linked to the H5N1 outbreak in dairy cows. Others in the cluster of five had respiratory and typical flu-like symptoms, including fever, chills, sore throat, runny nose, and cough. None of the five cases required hospitalization.

The virus infecting the five people is closely related to the virus infecting the chickens on the poultry farm, which, in turn, is closely related to virus seen in infected dairy herds and in other human cases that have been linked to the dairy outbreak. The affected poultry farm is in Colorado's northern county of Weld, which has also reported about two dozen outbreaks of avian influenza in dairy herds.

Dairy to poultry hypothesis

In one fell swoop, Colorado's poultry farm outbreak has more than doubled the number of human avian influenza cases linked to the dairy cow spillover, bringing the previous tally of four cases to nine. While officials have previously noted instances where it appeared that H5N1 on dairy farms had moved to nearby poultry farms, this appears to be the first time such spread has led to documented human infections.

The link between the poultry farm cases and neighboring dairy farms is still just a hypothesis, however, Nirav Shah, the principal deputy director at the CDC, emphasized to reporters Tuesday. "It is a hypothesis that needs and requires a full investigation. But that is a hypothesis at this point," he said of the link between the dairy farms and the poultry farm. So far, there is no direct evidence of a specific source of the poultry farm's infection, and the route of infection is also unclear.

Throughout the outbreak of H5N1 on dairy farms, officials have noted that the primary way the virus appears to spread to new farms is via the movement of cows, people, and machinery between those facilities. There remains no evidence of human-to-human transmission. But milk from infected cows has been found to be brimming with high levels of infectious virus, and milk-contaminated equipment is a prime suspect in the spread.

In the press briefing Tuesday, Eric Deeble, acting senior advisor for H5N1 response with the US Department of Agriculture, noted the poultry are very susceptible to avian influenza and are easily infected. "It does not take much to introduce this into a flock," Deeble said. The USDA is now working on a "trace-back" investigation on how the Colorado poultry farm was infected.

Searing spread

As for how the farm workers specifically became infected with the virus, health officials pointed to high temperatures that prevented workers from donning protective gear. The poultry farm is a commercial egg layer operation with around 1.8 million birds. Given the presence of bird flu on the premises, all 1.8 million birds need to be culled, aka "depopulated." This is being carried out using mobile carts with carbon dioxide gas chambers, a common culling method. Workers are tasked with placing the birds in the chambers, which only hold a few dozen birds at a time. In all, the method requires workers to have a high degree of contact with the infected birds, going from bird to bird and batch to batch with the carts.

Amid this grim task, temperatures in the area reached over 100° Fahrenheit, and massive industrial fans were turned on in the facility to try to cool things down. Between the heat and the fans, the approximately 160 people involved in the culling struggled to use personal protective equipment (PPE). The required PPE for the depopulation involves a full Tyvek suit, boots, gloves, goggles, and an N95 respirator.

"The difficulty with wearing all that gear in that kind of heat, you can imagine," said Julie Gauthier, executive director for field operations at the USDA's Animal and Plant Health Inspection Service (APHIS). The industrial fans blowing large amounts of air made it yet more difficult for workers to keep goggles and respirators on their faces, she said.

The CDC and the USDA are both involved in further investigations of the poultry farm outbreak. CDC's Shah noted that the team the agency deployed to Colorado included an industrial hygienist, who can work on strategies to prevent further transmission.

To date, at least 161 herds in 13 states have tested positive for avian influenza since the dairy outbreak was confirmed in March. Since January 2022, when US birds first tested positive for the H5N1 virus, 99 million birds in the US have been affected in 48 states, which involved 1,165 individual outbreaks.

Mars trembles with marsquakes, but not all of them are driven by phenomena that occur beneath the surface—many are the aftermath of meteorite strikes.

Meteorites crash down to Mars every day. After analyzing data from NASA’s InSight lander, an international team of researchers noticed that its seismometer, SEIS, detected six nearby seismic events. These were linked to the same acoustic atmospheric signal that meteorites generate when whizzing through the atmosphere of Mars. Further investigation identified all six as part of an entirely new class of quakes known as VF (very high frequency) events.

The collisions that generate VF marsquakes occur in fractions of a second, much less time than the few seconds it takes tectonic processes to cause quakes similar in size. This is some of the key seismological data that has helped us understand the occurrence of earthquakes caused by meteoric impacts on Mars. This is also the first time seismic data was used to determine how frequently impact craters are formed.

“Although a non-impact origin cannot be definitively excluded for each VF event, we show that the VF class as a whole is plausibly caused by meteorite impacts,” the researchers said in a study recently published in Nature.

Seismic shift

Scientists had typically determined the approximate meteorite impact rate on Mars by comparing the frequency of craters on its surface to the expected rate of impacts calculated using counts of lunar craters that were left behind by meteorites. Models of the lunar cratering rate were then adjusted to fit Martian conditions.

Looking to the Moon as a basis for comparison was not ideal, as Mars is especially prone to being hit by meteorites. The red planet is not only a more massive body that has greater gravitational pull, but it is located near the asteroid belt.

Another issue is that lunar craters are often better preserved than Martian craters because there is no place in the Solar System dustier than Mars. Craters in orbital images are often partly obscured by dust, which makes them difficult to identify. Sandstorms can complicate matters by covering craters in more dust and debris (something that cannot occur on the Moon due to the absence of wind).

InSight deployed its SEIS instrument after it landed in the Elysium Planitia region of Mars. In addition to detecting tectonic activity, the seismometer can potentially determine the impact rate through seismic data. When meteorites strike Mars, they produce seismic waves just like tectonic marsquakes do, and the waves can be detected by seismometers when they travel through the mantle and crust. An immense quake picked up by SEIS was linked to a crater 150 meters (492 feet) wide. SEIS would later detect five more marsquakes that were all associated with an acoustic signal (detected by a different sensor on InSight) that is a telltale sign of a falling meteorite.

A huge impact

Something else stood out about the six impact-driven marsquakes detected with seismic data. Because of the velocity of meteorites (over 3,000 meters or 9,842 feet per second), these events happened faster than any other type of marsquake, even faster than quakes in the high frequency (HF) class. That’s how they earned their own classification: very high frequency, or VF, quakes. When the InSight team used the Mars Reconnaissance Orbiter’s (MRO) Context Camera (CTX) to image the locations of the events picked up by SEIS, there were new craters present in the images.

There are additional seismic events that haven’t been assigned to craters yet. They are thought to be small craters formed by meteorites about the size of basketballs, which are extremely difficult to see in orbital images from MRO.

The researchers were able to use SEIS data to estimate the diameters of craters based on distance from InSight (according to how long it took seismic waves to reach the spacecraft) and the magnitude of the VF marsquakes associated with them. They were also able to derive the frequency of quakes picked up by SEIS. Once a frequency estimate based on the data was applied to the entire surface area of Mars, they estimated that around 280 to 360 VF quakes occur each year.

“The case is strong that the unique VF marsquake class is consistent with impacts,” they said in the same study. “It is, therefore, worthwhile considering the implications of attributing all VF events to meteoroid impacts.”

Their detection has added to the estimated number of impact craters on Mars since many could not be seen from space before. What can VF impacts tell us? The impact rate on a planet or moon is important for determining the age of that object’s surface. Using impacts has helped us determine that the surface of Venus is constantly being renewed by volcanic activity, while most of the surface of Mars has not been covered in lava for billions of years.

Figuring out the rate of meteorite impacts can also help protect spacecraft and, someday, maybe Martian astronauts, from potential hazards. The study suggests that there are periods where impacts are more or less frequent, so it might be possible to predict when the sky is a bit more likely to be clear of falling space rocks—and when it isn’t. Meteorites are not much of a danger to Earth since most of them burn up in the atmosphere. Mars has a much thinner atmosphere that more can make it through, and there is no umbrella for a meteor shower.

Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02301-z

The first earthquake struck while the town was still asleep. Around 2:00 am on Dec. 16, 1811, New Madrid—a small frontier settlement of 400 people on land now located in Missouri—was jolted awake. Panicked townsfolk fled their homes as buildings collapsed and the smell of sulfur filled the air.

The episode didn’t last long. But the worst was yet to come. Nearly two months later, after dozens of aftershocks and another massive quake, the fault line running directly under the town ruptured. Thirty-one-year-old resident Eliza Bryan watched in horror as the Mississippi River receded and swept away boats full of people. In nearby fields, geysers of sand erupted, and a rumble filled the air.

In the end, the town had dropped at least 15 feet. Bryan and others spent a year and a half living in makeshift camps while they waited for the aftershocks to end. Four years later, the shocks had become less common. At last, the rattled townspeople began “to hope that ere long they will entirely cease,” Bryan wrote in a letter.

Whether Bryan’s hope will stand the test of time is an open question.

The US Geological Survey released a report in December 2023 detailing the risk of dangerous earthquakes around the country. As expected on the hazard map, deep red risk lines run through California and Alaska. But the map also sports a big bull’s eye in the middle of the country—right over New Madrid.

The USGS estimates that the region has a 25 to 40 percent chance of a magnitude 6.0 or higher earthquake in the next 50 years, and as much as a 10 percent chance of a repeat of the 1811-1812 sequence. While the risk is much lower compared to, say, California, experts say that when it comes to earthquake resistance, the New Madrid region suffers from inadequate building codes and infrastructure.

Caught in this seismic splash zone are millions of people living across five states—mostly in Tennessee and Missouri, as well as Kentucky, Illinois, and Arkansas—including two major cities, Memphis and St. Louis. Mississippi, Alabama, and Indiana have also been noted as places of concern.

In response to the potential for calamity, geologists have learned a lot about this odd earthquake hotspot over the last few decades. Yet one mystery has persisted: why earthquakes even happen here in the first place.

This is a problem, experts say. Without a clear mechanism for why New Madrid experiences earthquakes, scientists are still struggling to answer some of the most basic questions, like when—or even if—another large earthquake will strike the region. In Missouri today, earthquakes are “not as front of mind” as other natural disasters, said Jeff Briggs, earthquake program manager for the Missouri State Emergency Management Agency.

But when the next big shake comes, “it’s going to be the biggest natural disaster this state has ever experienced.”

Risk assessment

Sizing up earthquake risk isn’t easy—especially when a seismic zone is smack dab in the middle of a tectonic plate.

Up until recently, the 1811 and 1812 quakes were considered “freak events,” said Martitia Tuttle, a paleoseismologist at M. Tuttle and Associates, an earthquake risk consulting company. Earthquakes occur when subterranean strain, building over centuries, is released in seconds. That usually happens near plate tectonic boundaries, where massive plates rub against each other.

But exceptions happen. For instance, the New York area was jolted by a sudden seismic shock in April, despite being thousands of miles from the closest plate boundary.

But just because areas like New York are far from a plate boundary today doesn’t mean that was always the case—and they have the scars to prove it. Researchers have mapped out three currently active ancient fault lines—fissures in the Earth’s crust—in the New Madrid area that formed around 500 million years ago, at a time when the North American plate tried and failed to pull itself apart. Now those fault lines form weak zones where stress in the earth can build and eventually break into earthquakes.

Why these fault lines are seismically active, while neighboring ones aren’t, is less clear. “It’s really one of the most enigmatic seismic zones on the planet,” said Eric Sandvol, a seismologist at the University of Missouri. “We’re not supposed to have earthquakes here.”

Scientists have suggested that the movement of the North American plate westward is driving stress, or that earth bounding back after the crush of massive glaciers during the Ice Age is to blame. Some have also pointed to a pillow-shaped rock underneath the seismic zone as a factor.

But researchers simply "don't have a smoking gun stress source" and are unlikely to any time soon, explained Eunseo Choi, a computational geodynamicist at the Center for Earthquake Research and Information at the University of Memphis.

That matters because measuring stress buildup is a great way to predict earthquake hazards. The tell-tale ripping of earth along the surface—a sign of stress buildup—is easy to see in places like California, where scientists can track the movement of the earth thanks to key geological features in that area. Yet until recently, researchers working in the New Madrid area weren’t even able to prove that the ground in the region was moving at all because the movement there is far harder to detect. The lack of obvious stress buildup led some scientists to suggest that New Madrid might not be gearing up for another earthquake. In 2015, scientists published data that showed that the ground near fault lines was in fact creeping—albeit slowly.

But researchers still don't know exactly how much stress is building below the surface, said Choi.

With modern technology, people can look at celestial bodies light years away, he said. “But ironically, we don’t really see that well just a few kilometers down from our surface.”

Reconstructing seismic history

On a cloudy day in May, geologist Roy Van Arsdale is driving on top of the Reelfoot fault line in western Tennessee. The Mississippi River valley extends on terrain as flat as Kansas for miles. Only some towns have the slightest bit of elevation.

Settlers in the region built anywhere they could escape the annual spring floods. In New Madrid, that meant building where earthquakes have uplifted the earth. Van Arsdale pulls off the main road to park behind a prison complex. At odds with the rest of the countryside, a long, linear mound of earth juts out from beneath a prison fence and into a neighboring cornfield. It’s the fault line. If another major earthquake were to happen, “they’d be in trouble,” Van Arsdale said.

Van Arsdale has spent his career trying to understand why the region experiences earthquakes. In the 1970s, the nuclear power industry planned on building power plants along the Mississippi and Ohio rivers. But the specter of the 1811 and 1812 quakes raised concerns, so geologists like Van Arsdale were brought in to try and reconstruct the seismic history of the area.

The geologist treks across a small drainage ditch and onto the fault line. Dragonflies dart everywhere as Van Arsdale points to where the fault line hits a levee to the north—the massive, engineered earthworks that hold back the annual Mississippi floods. When Van Arsdale and other research groups dug down into this fault line decades ago, they found traces of the 1811 and 1812 quakes, as well as older ruptures dating back to the 15th and 10th centuries.

This work helped reveal that the New Madrid Seismic Zone has popped out major 7.0 magnitude or greater earthquakes every 500 years or so for the last five millennia. Traces of older earthquakes could also exist, but scientists have yet to find them. Work by other researchers on sand blows—those geysers of sand Bryan saw back in 1812—revealed that the 1811-1812 pattern of three earthquakes hitting one right after the other wasn’t an aberration. The 15th and 10th century earthquakes also likely involved multiple major quakes one right after the other.

This research suggested that another major set of quakes was possible—and that if one happened, the area “should expect two more” in quick succession, said Van Arsdale.

Five hundred years between major earthquakes puts a lot of time before the next big one. But many experts say the region is still largely unprepared for even moderate shaking. Many parts of Alaska—which experiences large quakes more frequently—put in strict building codes after an earthquake devastated the state in 1964. Those building codes are thought to be why Anchorage survived a 7.0 earthquake in 2018 with only minimal damage and no deaths.

By contrast, many states in the New Madrid region only included earthquake provisions in their building codes in the early 2000s, meaning anything built prior to that is prone to collapse. In Tennessee, jurisdictions can decide whether to opt in to building codes with earthquake provisions, while other states—like Missouri—don’t have state-wide building codes at all, though there are efforts to change that.

That has experts worried. “Human bodies don’t stand up well to falling building parts,” said Chris Cramer, a geophysicist who works on earthquake hazard at the Center for Earthquake Research and Information at the University of Memphis. He estimated that a major earthquake near New Madrid would cost the US an average of $10 billion a year for 100 years from damaged buildings and lost infrastructure. For an aging Memphis, which is only around 40 miles from the southern edge of one fault line in the New Madrid system, even a moderate earthquake could cause considerable damage.

St. Louis is another city near the bullseye. Like other places in Missouri, “we know that a lot of people are living in buildings that are not ready for a big earthquake,” said Briggs, who works for Missouri’s Seismic Safety Commission, a committee of experts appointed by the governor to help the state prepare for earthquakes.

Memphis and St. Louis have started to retrofit bridges in preparation. Newer buildings, especially taller ones, are built with shaking in mind. But “while progress has been made, there’s still a considerable way to go to ensure the resilience of buildings and infrastructure,” Alicia Tate-Nadeau, director of the Illinois Emergency Management Agency and Office of Homeland Security, wrote in an email to Undark. To deal with this, the state has adopted international building codes with seismic provisions. These won’t become mandatory across the state until 2025.

But federal funding for earthquake preparation is also not thick on the ground, said Patrick Sheehan, director of the Tennessee Emergency Management Agency. He highlighted that in 2024, the Federal Emergency Management Agency will have a little over $ 2 million to distribute to states and territories for earthquake education and risk reduction. “That’s a pittance,” said Sheehan. “I think our nation could do a better job of investing in this.”

When contacted for comment, the FEMA press office confirmed that the 2024 fiscal year budgeted more than $2 million for individual state earthquake assistance, to be distributed through grants. But it said that the total amount allocated for the National Earthquake Hazards Reduction Program, or NEHRP—a major government initiative to reduce risk, educate the public, and research earthquake impacts in the US—totals $8.5 million. The press office also added that there are natural hazard mitigation funds through other programs that states, tribes, and territories can apply for as well.

Much of the funding distributed through the NEHRP goes toward raising awareness of earthquake risk. Arkansas, for example, qualifies for a grant of roughly $70,000, which can go toward increasing “community preparedness and knowledge of the threat of an earthquake,” wrote Hilda Booth, earthquake program manager at the Arkansas Department of Public Safety, in an email to Undark.

Kentucky, Indiana, and Alabama’s emergency management agencies did not respond to requests for comment. The Emergency Management Agency of Mississippi did not answer written questions sent by Undark.

In the New Madrid region, at least, “there’s a long way to go,” said Briggs. “I don’t know that we’ll ever get there.”

A seismic wind-down?

To work on earthquakes in the central United States is to trade in uncertainty. The region experiences about 200 small earthquakes every year. And still, when it comes to major quakes, “they can’t say that it will happen, because we don’t know that," said Seth Stein, an earthquake seismologist and emeritus professor at Northwestern University.

Even Van Arsdale can see an earthquake-free future for New Madrid. His theory is that the Reelfoot fault and other rifts in the area were strained and activated only when the Mississippi River Valley eroded the land above them—creating a way for that pressure to be released. In this scenario, New Madrid might be winding down seismically.

But to others the trend is clear: "It's not whether they'll occur, but when and where," said Tuttle.

Not knowing the physics behind earthquakes in the area has made predicting future events tough. So, while scientists try to untangle the mysteries of the New Madrid Seismic Zone, some states and nonprofits are doing their best to get locals ready for the next earthquake.

“We know from research and past events that we’re capable of having large earthquakes in this area again and at any time,” said Brian Blake, executive director of the Central United States Earthquake Consortium, a nonprofit devoted to earthquake planning, education, and mitigation. “Our job, regardless of the mechanism that causes earthquakes, is to prepare.”

In Missouri, Briggs and his agency have developed an emergency plan for the next big one. The agency’s headquarters in Jefferson City has an underground facility that they can use to coordinate relief after the disaster. In the meantime, his team heads out to test the structural integrity of schools and other significant buildings in the southeastern corner of Missouri to see whether they can withstand shaking.

Despite this preparation, there appears to be no sense of urgency in the town of New Madrid, which now boasts some 2,700 residents and a largely empty main street.

On the levee, a sign incorrectly announces the location of a fault line. The actual rift runs west of town, said Jeff Grunwald, administrator at the New Madrid Historical Museum. The 1811 and 1812 quakes are a major draw for the 5,000 or so annual visitors to the museum.

But locals think about earthquakes—and the risk they pose—“very, very, little,” he said. “People have lives to lead.”

Is space-based solar power a costly, risky pipe dream? Or is it a viable way to combat climate change? Although beaming solar power from space to Earth could ultimately involve transmitting gigawatts, the process could be made surprisingly safe and cost-effective, according to experts from Space Solar, the European Space Agency, and the University of Glasgow.

But we’re going to need to move well beyond demonstration hardware and solve a number of engineering challenges if we want to develop that potential.

Designing space-based solar

Beaming solar energy from space is not new; telecommunications satellites have been sending microwave signals generated by solar power back to Earth since the 1960s. But sending useful amounts of power is a different matter entirely.

“The idea [has] been around for just over a century,” said Nicol Caplin, deep space exploration scientist at the ESA, on a Physics World podcast. “The original concepts were indeed sci-fi. It’s sort of rooted in science fiction, but then, since then, there’s been a trend of interest coming and going.”

Researchers are scoping out multiple designs for space-based solar power. Matteo Ceriotti, senior lecturer in space systems engineering at the University of Glasgow, wrote in The Conversation that many designs have been proposed.

The Solaris initiative is exploring two possible technologies, according to Sanjay Vijendran, lead for the Solaris initiative at the ESA: one that involves beaming microwaves from a station in geostationary orbit down to a receiver on Earth and another that involves using immense mirrors in a lower orbit to reflect sunlight down onto solar farms. He said he thinks that both of these solutions are potentially valuable. Microwave technology has drawn wider interest and was the main focus of these interviews. It has enormous potential, although high-frequency radio waves can also be used.

“You really have a source of 24/7 clean power from space,” Vijendran said. The power can be transmitted regardless of weather conditions because of the frequency of the microwaves.

“A 1-gigawatt power plant in space would be comparable to the top five solar farms on earth. A power plant with a capacity of 1 gigawatt could power around 875,000 households for one year,” said Andrew Glester, host of the Physics World podcast.

But we’re not ready to deploy anything like this. “It will be a big engineering challenge,” Caplin said. There are a number of physical hurdles involved in successfully building a solar power station in space.

Using microwave technology, the solar array for an orbiting power station that generates a gigawatt of power would have to be over 1 square kilometer in size, according to a Nature article by senior reporter Elizabeth Gibney. “That’s more than 100 times the size of the International Space Station, which took a decade to build.” It would also need to be assembled robotically, since the orbiting facility would be uncrewed.

The solar cells would need to be resilient to space radiation and debris. They would also need to be efficient and lightweight, with a power-to-weight ratio 50 times more than the typical silicon solar cell, Gibney wrote. Keeping the cost of these cells down is another factor that engineers have to take into consideration. Reducing the losses during power transmission is another challenge, Gibney wrote. The energy conversion rate needs to be improved to 10–15 percent, according to the ESA. This would require technical advances.

Space Solar is working on a satellite design called CASSIOPeiA, which Physics World describes as looking “like a spiral staircase, with the photovoltaic panels being the ‘treads’ and the microwave transmitters—rod-shaped dipoles—being the ‘risers.’” It has a helical shape with no moving parts.

“Our system's comprised of hundreds of thousands of the same dinner-plate-sized power modules. Each module has the PV which converts the sun's energy into DC electricity,” said Sam Adlen, CEO of Space Solar.

“That DC power then drives electronics to transmit the power… down toward Earth from dipole antennas. That power up in space is converted to [microwaves] and beamed down in a coherent beam down to the Earth where it's received by a rectifying antenna, reconverted into electricity, and input to the grid.”

Adlen said that robotics technologies for space applications, such as in-orbit assembly, are advancing rapidly.

Ceriotti wrote that SPS-ALPHA, another design, has a large solar-collector structure that includes many heliostats, which are modular small reflectors that can be moved individually. These concentrate sunlight onto separate power-generating modules, after which it’s transmitted back to Earth by yet another module.

Space-based safety

These plans involve large fluxes of microwave or radio radiation. But space-based solar power is relatively safe. For microwave radiation from a space-based solar power installation, “the only known effect of those frequencies on humans or living things is tissue heating,” Vijendran said. “If you were to stand in such a beam at that power level, it would be like standing in the… evening sun.” Still, Caplin said that more research is needed to study the effects of these microwaves on humans, animals, plants, satellites, infrastructure, and the ionosphere.

Getting that across to the public may remain a challenge, however. “There’s still a public perception issue to work through, and it’s going to need strong engagement to bring this to market successfully,” Adlen said.

Military attacks using space-based solar power might also raise concerns. But even if a space-based solar power station was hijacked for military reasons, the hardware would limit the beam to a safe intensity so that it could not be used to harm people or ecosystems on Earth, Ceriotti said.

Beyond the environmental issues, there are additional concerns that will need to be sorted out before deployment. Interference with communications signals is another potential risk, although Gibney wrote that the beam’s frequency would not disrupt aircraft communication. Some other physical risks are important to take into account.

Orbiting debris such as meteorites or space junk could strike the station and damage it, Vijendran said. If the impacts on the solar power station generate debris, that could cause problems as well. Plus the hardware itself will have to be deorbited when it reaches end-of-life. “ESA has a Clean Space Initiative. Anything that we’re sending to space, we have to think about the whole lifecycle, cradle to grave,” Caplin said.

Finally, the project would still have an environmental impact. Putting the solar power station hardware in orbit, constructing it, and controlling it would generate pollution and use a substantial amount of fuel, Ceriotti wrote. Hundreds of launches might be required.

Launch economics

Beyond their environmental impact, those launches will cost money. Cost has usually been the main barrier to building a space solar power station so far, Caplin said. “As that landscape is changing and things are generally becoming cheaper to send to space, we can put it on the table again. Money talks. We have the advice of two independent studies on cost-benefit analyses, and they both determined that this could be viable.”

The expense of space-based solar power would include manufacturing costs, maintenance costs, and launch costs, Ceriotti said.

“We expect [the] cost to fall in future,” Vijendran said. “We can start with a power that is competitive with what we pay for nuclear today… between $100 and $200 per megawatt-hour… which is higher than intermittent renewables like solar and wind, but has a role to play because it is reliable and available 24/7.”

Vijendran said he expects the cost of space-based solar power will eventually fall to a point where it is competitive with solar and wind power on Earth, which is below $50 per megawatt-hour. According to the Energy Information Administration’s 2022 publication on this subject, both solar power and onshore wind cost around $20–$45 per megawatt-hour in 2021.

Adlen’s cost estimate is much lower—around a quarter of the cost of nuclear power.

SpaceX and Blue Origin are designing launch vehicles that can handle heavy lifts, Ceriotti wrote. These vehicles’ parts can be reused, and their high capacity and reusability can drop the cost of some aspects of construction by 90 percent.

Looking toward the future, what are the next steps in the development of space-based solar power? The ESA plans to make a decision next year about its goals in developing an uncrewed space station, Vijendran said. The process has been slowed by a shortage of financial support from some European countries.

“The first major decision point would be to implement a… small-scale in-space demo mission for launch sometime around 2030,” Vijendran said.

Outside of the ESA, Caltech has demonstrated a lightweight prototype that converts sunlight to radio-frequency electrical power and transmits it as a beam. The university has been researching modular, foldable, ultralight space-based solar power equipment.

“My view is that much like the world of connectivity went from wired to wireless, so we're going to see the world of power move in a similar direction,” Adlen said. International cooperation will be key to creating space-based solar power stations if projects like these move forward.

Kat Friedrich is a former mechanical engineer who started out as an applied mathematics, engineering, and physics major at the University of Wisconsin-Madison. She has completed a graduate degree focusing on science and environmental journalism and has edited seven news publications, two of which she co-founded. She is the editor-in-chief of the energy magazine Solar Today. 

Know your enemy, know yourself. It's a centuries-old strategy. But even in the present-day war against cancer, achieving it remains elusive. In many cases, cancer cells blend in with healthy ones. They bear no unique molecular markers or targets that we can aim clinical defenses at. That means any deadly strike on enemy cancer cells could result in casualties among healthy ones as well. The untenable toxicity of this artless warfare has led some researchers to rethink the ancient script—and flip it: know yourself, know your enemy.

In a set of clever and highly technical tricks, researchers are working on ways to precisely mark and shield healthy cells from chemical weapons, abandoning the effort to pick out enemy cancer cells specifically. By exploiting molecular markers common among many types of cells, researchers can safeguard healthy cells, leaving only the cancer cells in harm's way.

A drug or therapy that targets common markers would normally lay waste to cancerous and healthy cells alike. But that's not the case in this radical approach, which is first being used to treat blood cancers. For the strategy, researchers collect healthy blood stem cells and genetically engineer tiny, benign changes to a common molecular marker on them. Those tiny changes make the healthy cells essentially invisible to killer treatments. After the engineered cells are transplanted into a patient, clinicians can deploy the treatments. The cancerous cells that lack the genetic tweak are now easily killed by the drug or therapy, while the healthy engineered cells are left untouched.

The utility of the tactic doesn't end there. While cloaking healthy cells means researchers no longer need to know their specific enemy from healthy cells with precision, that imprecision opens vast possibilities. For one, it has the potential to create a virtually universal treatment for blood cancers. Whatever specific type of cancer is present, targeting a ubiquitous marker on blood cells and cloaking healthy cells will eradicate whatever strain of cancer is lurking among them.

"We no longer have to worry whether a tumor originated from a B cell or from a T cell or from a myeloid cell. It doesn't matter," transplantation immunologist Lukas Jeker of the University of Basel in Switzerland told Ars. "As long as it is a blood cell, we can use [the strategy], and that's why we think it's going to be almost universal."

For now, the results are still in the pre-clinical realm—mouse studies and Petri dishes—but researchers are swiftly marching toward clinical trials with compelling results in hand. Those trials using the strategy "are eagerly anticipated by the scientific and medical community," oncologist Miriam Kim of the Washington University School of Medicine wrote in Trends in Cancer in December. Those trials are now expected in the next few years.

A universal target

Last month, Jeker and his colleagues published the early results of their nearly universal strategy. It targets CD45, a molecular marker found only on blood cells, with the exceptions of red blood cells and platelets. It's called a pan-hematopoietic marker. In the study published in Nature, the researchers successfully used a potent treatment that kills anything with an unaltered CD45. The treatment is an antibody-drug conjugate (ADC). The antibody part of the ADC is a protein that can uniquely latch onto CD45 and, once attached, deliver a toxic payload bound to it, which contains an existing cell-killing drug. Normally, a CD45-targeting ADC would wipe out the entire hematopoietic cell population. But with healthy blood stem cells shielded by a tweak to their CD45, the ADC selectively kills off the unprotected and cancerous cells.

In mouse experiments, the strategy worked. "It was just unbelievably effective. I mean, the first time I saw the results, I didn't believe it. I thought something must be wrong," Jeker said.

First, the researchers injected mice with four different cancerous cell lines. After a single dose of the CD45-targeting ADC, all the rodents' tumors shrank rapidly. They then tested it out with a cancer patient's cells. The patient had a type of blood cancer called AML, Acute Myeloid Leukemia, which is a kind of blood cancer that originates in the bone marrow. The researchers transplanted the patient's AML cells into mice that had already gotten a transplant of healthy CD45-shielded blood stem cells. They then treated the mice with their CD45-targeting ADC.

"The results were really just black or white. It's just like, it just works," Jeker said. The CD45-shielded cells were protected. The researchers saw no evidence of them being killed. Meanwhile, the patient's AML cells were eradicated. "So we really get the dream result," Jeker said. "We have the complete protection, and we get complete elimination of the disease, which is what we want, ultimately."

How the shielding works

Of course, getting to those dream results took a lot of work. Jeker's study builds on results published last year by two other research groups, one led by researchers at the University of Pennsylvania and the other at Boston Children's Hospital and Harvard. In both cases, researchers used new gene-editing tools for a technique called "base editing" on blood cell markers. Base editing, which uses CRISPR/Cas9 machinery, allows researchers to precisely edit a single base—a nucleotide building block of DNA—in a gene. Unlike other editing techniques, this doesn't require double-stranded breaks of the genetic material, which can be toxic to cells. It's a precise and less toxic editing method.

The goal of the single base edit is to change the molecular marker just enough to keep an antibody from recognizing it. Mouse-generated antibodies are critical tools in the fight against cancer. Researchers train the antibodies to precisely recognize and bind specific molecules on the outside of cells. Once bound, antibodies can deliver toxic payloads, neutralize the function of a target, or recruit immune responses to attack and kill bound cells, among other useful tasks. But without molecular markers that are specific only to cancer cells, antibodies can be toxic to healthy cells. That's where the base editing comes in.

The goal is to "find a mutation that avoids the binding but at the same time preserve the functionality" of the marker, said gene therapy researcher Pietro Genovese of Harvard and Boston Children's Hospital. Genovese's group was behind one of the papers last year that provided a springboard for the development of the strategy. In the paper published in Nature, Genovese and his team base edited three markers present at high levels on AML cells: CD123, CD135, and CD117. Researchers already had antibodies against all these markers, which are used in the development of AML immunotherapies. So they just needed to find small tweaks that prevent the antibodies from binding in order to shield healthy cells.

Finding the right spot to base edit is another "trick we exploit," Genovese explained. Because researchers use mice to generate therapeutic antibodies, the result is a mouse anti-human antibody. Mice also have the blood cell markers researchers are targeting here, such as CD45, CD123, and so on. Parts of these markers are conserved—that is, the same—between humans and mice.

But the antibody "will never mount an antibody response against a self-antigen," Geneovese said, meaning that any parts that are mouse-specific or conserved between mice and humans likely won't be targeted by the mouse anti-human antibody. That leaves non-conserved, human-specific places for the antibodies to bind on the markers. If the area where the antibody binds is not conserved, it's likely not important for the marker's function, which could play a role in cell signaling or another activity.

Thus, targeting the area where the antibody recognizes the marker—an area called an epitope—takes advantage of known biases. Any changes in the epitope are likely to thwart both the antibody's binding and preserve the marker's function. Of course, all of those things still require testing to confirm and ensure the safety of the approach.

For the epitope binding, we're looking for a "minimal" genetic change to shield the cells, Jeker explained. "The minimal change is that we really change, ideally, just one amino acid from the hundreds of amino acids that are found in a protein," Jeker said of the base-editing technique. "We went through quite some lengths to identify, first, which antibody is the best one, which region is the best one, which exchange or which amino acid is the best position, and then also which substitution per position is the best one, because each position you can exchange against different amino acids." Jeker and his team further characterized the thermal stability, structural changes, and biophysical characteristics for potential base edits. Since this edit will persist in healthy stem cells, it's critical that this shielding edit is completely benign.

Clinical attack plans

In future patients, the approach would combine all the different moving parts. Currently, blood stem cell transplants (hematopoietic stem cell transplantation, or HSCTs) are used to try to cure a variety of blood cancers. Typically, the treatment starts with an unspecific chemotherapy that kills cancer cells as well as healthy cells, followed by a transplant of healthy stem cells, sometimes from the patient or sometimes from a cancer-free, healthy donor.

The healthy, transplanted stem cells go on to replenish the population of blood cells. In some cases, such as in leukemia patients, white blood cells from a donor transplant can attack lingering cancer cells from the patient, an effect called graft-vs-tumor or graft-vs-leukemia. This indiscriminate killing-then-replenishing approach can work for some patients. But aggressive cancers often return. Not all of the cancer cells may be killed by the chemotherapy; some may develop resistance to the drug treatment, and sometimes, the graft-versus-tumor effect doesn't work at all.

With the new base-editing cloaking strategy, the risk of a relapse could be dashed. The treatment could start with chemotherapy, but the subsequent HSCT would introduce the shielded stem cells with base-edited CD45s or CD123s, for example. Once the transplanted stem cells are established, clinicians could treat the patients with targeted cancer-killing therapies such as anti-CD45 ADCs. The treatment would then kill off any lingering cancer cells and cells leftover from the original blood cell population.

If this initial strategy works in further pre-clinical testing as well as in early clinical trials in patients, Jeker said researchers could move to a next-level approach. That would involve skipping the toxic chemotherapy step in the beginning, and using the targeted therapies, such as anti-CD45 ADCs, instead. This approach could be safer for patients because it would selectively kill only blood cells, efficiently depleting the population before a transplant and potentially reducing toxicity.

Killer weapons

Further, the approach could also use different killing strategies. Jeker's group started with an antibody linked to an existing cancer drug. But Genovese's group used another genetic engineering tool called CAR T cells. In this strategy, researchers alter T cells—which are white blood cells involved in immune responses—to carry highly engineered receptors known as chimeric antigen receptors, or CARs. The CARS reach out from the T cell's surface and have a receptor made from components of synthetic antibodies.

These synthetic antibody domains on the CAR T cells work similarly to the antibody therapies described earlier; they can be trained to bind to specific molecular markers. Those molecular markers can be base-edited to prevent binding on healthy cells. After such shielding, the CAR T cells can target unaltered cancerous cells by binding to the targeted molecular marker. Once bound, the T cells directly kill the cancerous cell and recruit immune responses.

Genovese and his colleagues used CAR T cells to target two markers, CD123 and CD135 (aka FLT3). In this case, the researchers weren't working to target a universal blood marker like CD45 but instead markers that are known to be present at high levels in AML cells. "I would prefer ... to focus and concentrate the therapy only on the cells that you really need to kill in order to achieve the proof of concept [and] to provide therapeutic benefit" for early patients, he said.

So far, this approach has presented impressively positive results in mice. In mice that were transplanted with shielded (CD123 and CD135) stem cells and also patient-derived AML cells, treatments with anti-CD123 and anti-CD135 CAR T cell treatments worked—the shielded stem cells were protected, while the AML cells were eradicated.

In the other study published last year by the group at Penn, hematologist Saar Gill and immunologist and oncologist Carl June added yet another level of complexity to the approach. They, like Jeker, went for a universal marker, base-editing CD45 to shield healthy blood stem cells. They also used an anti-CD45 CAR T cells to kill off cancerous cells. The trouble is that T cells also contain CD45. For the approach to work—and keep the CAR T cells from simply massacring each other (called fratricide)—the researchers had to shield the CD45 on the T cells and those on the healthy stem cells.

As in the other studies, the strategy worked in mouse models. The base-edited shielding of CD45 didn't appear to alter cell functions and protected both the T cells and the stem cells from the anti-CD45 CAR T cells. The anti-CD45 CAR T cells, meanwhile, efficiently killed off patient-derived AML cells, B cell lymphoma cells, and acute T cell leukemia cells. The results were published in Science Translational Medicine.

"We’re very determined to get this into a clinical trial," Gill told the NIH last year. "It’s the only way we’ll know if it’s going to work."

March to trials

Genovese and Jeker both think they can have their strategies in clinical trials in a few years—less than five, Jeker said. The variations between their cloaking strategies have their own pros and cons, which will likely play out in clinical trial designs and the data. For now, Genovese is focusing on markers found at high levels in cancer cells, hoping they lead to a potent and highly effective therapy, while Jeker is optimistic about the universal approach with CD45.

Not all cancer cells contain high levels of CD45, Jeker noted—some are so low that they've been considered CD45-negative. But Jeker's group tested its anti-CD45 ADC on such a cell line in its experiments, finding that the cells were almost completely killed off in transplanted mice. Though tumor cells later relapsed in those mice, Jeker was still pleased with the result. "I'm actually very happy that even if they express very low levels, they still initially responded," he said.

The different killing strategies also present a choice for future development. Immunotherapies, like the ADC that Jeker's group used, have the advantage of combining off-the-shelf products (an antibody and an existing cancer drug) that are known to be effective. CAR T cell therapies, meanwhile, have the benefit of being a living cell line. The engineered T cells can persist in patients and have immunological memory to prevent relapses. But they also add a second layer of genetically edited cells to the strategy, making a regulatory review of safety and efficacy more complicated. Because the two components work together, it will be difficult to test their safety and efficacy separately.

"The real challenge will be to explain all this complex stuff to the regulatory agency and get the proper feedback to design a trial," Genovese said.

He also worries about the ethical considerations of their dual cell therapy approach. To ensure the strategy is not toxic to humans, we'll want to start with low doses in early clinical trials. But at low doses, a patient must go through a complex, risky treatment with low chances of efficacy—tipping the risk-benefit analysis against the trial. So the challenge, he says, is finding a way of starting with low doses and then scaling up to reach "a level in which you can really get efficacy."

Both Genovese and Jeker note that having two genetically engineered products in a clinical trial is not unprecedented. Currently, Vor Bio, a Boston-based biotechnology company, has a shielding strategy in early-stage clinical trials. It involves using an anti-CD33 ADC after fully deleting CD33 from blood stem cells in patients with relapsed AML. The company recently began moving forward with testing anti-CD33 CAR T Cells. (Both Genovese and Gill are clinical advisors to Vor).

If all goes well, Genovese and Jeker see the potential for the shielding strategy to move beyond AML to other blood cancers that could be treated with stem cell transplants—leukemias, lymphomas, severe myelodysplastic syndromes, and myeloproliferative neoplasms like high-risk polycythemia vera. Further, the treatment could move to other types of cancers, such as melanoma and colorectal cancer, auto-immune diseases, or even HIV infections.

"Of course, it's very complicated," Genovese said of the strategy. "But at the same time, I also feel pretty confident that it is feasible." Gene therapies and technologies such as these are already making their way into clinic, and "they are really effective therapies the moment some of them are becoming approved," he said.

The launch date for the Europa Clipper mission to study the intriguing moon orbiting Jupiter, which ranks alongside the Cassini spacecraft to Saturn as NASA's most expensive and ambitious planetary science mission, is now in doubt.

The $4.25 billion spacecraft had been due to launch in October on a Falcon Heavy rocket from Kennedy Space Center in Florida. However, NASA revealed that transistors on board the spacecraft may not be as radiation-hardened as they were believed to be.

"The issue with the transistors came to light in May when the mission team was advised that similar parts were failing at lower radiation doses than expected," the space agency wrote in a blog post Thursday afternoon. "In June 2024, an industry alert was sent out to notify users of this issue. The manufacturer is working with the mission team to support ongoing radiation test and analysis efforts in order to better understand the risk of using these parts on the Europa Clipper spacecraft."

The moons orbiting Jupiter, a massive gas giant planet, exist in one of the harshest radiation environments in the Solar System. NASA's initial testing indicates that some of the transistors, which regulate the flow of energy through the spacecraft, could fail in this environment. NASA is currently evaluating the possibility of maximizing the transistor lifetime at Jupiter and expects to complete a preliminary analysis in late July.

To delay or not to delay

NASA's update is silent on whether the spacecraft could still make its approximately three-week launch window this year, which gets Clipper to the Jovian system in 2030.

Ars reached out to several experts familiar with the Clipper mission to gauge the likelihood that it would make the October launch window, and opinions were mixed. The consensus view was between a 40 to 60 percent chance of becoming comfortable enough with the issue to launch this fall. If NASA engineers cannot become confident with the existing setup, the transistors would need to be replaced.

The Clipper mission has launch opportunities in 2025 and 2026, but these could lead to additional delays. This is due to the need for multiple gravitational assists. The 2024 launch follows a "MEGA" trajectory, including a Mars flyby in 2025 and an Earth flyby in late 2026—Mars-Earth Gravitational Assist. If Clipper launches a year late, it would necessitate a second Earth flyby. A launch in 2026 would revert to a MEGA trajectory. Ars has asked NASA for timelines of launches in 2025 and 2026 and will update if they provide this information.

Another negative result of delays would be costs, as keeping the mission on the ground for another year likely would result in another few hundred million dollars in expenses for NASA, which would blow a hole in its planetary science budget.

NASA's blog post this week is not the first time the space agency has publicly mentioned these issues with the metal-oxide-semiconductor field-effect transistor, or MOSFET. At a meeting of the Space Studies Board in early June, Jordan Evans, project manager for the Europa Clipper Mission, said it was his No. 1 concern ahead of launch.

“What keeps me awake at night”

"The most challenging thing we're dealing with right now is an issue associated with these transistors, MOSFETs, that are used as switches in the spacecraft," he said. "Five weeks ago today, I got an email that a non-NASA customer had done some testing on these rad-hard parts and found that they were going before (the specifications), at radiation levels significantly lower than what we qualified them to as we did our parts procurement, and others in the industry had as well."

At the time, Evans said things were "trending in the right direction" with regard to the agency's analysis of the issue. It seems unlikely that NASA would have put out a blog post five weeks later if the issue were still moving steadily toward a resolution.

"What keeps me awake right now is the uncertainty associated with the MOSFETs and the residual risk that we will take on with that," Evans said in June. "It's difficult to do the kind of low-dose rate testing in the timeframes that we have until launch. So we're gathering as much data as we can, including from missions like Juno, to better understand what residual risk we might launch with."

These are precisely the kinds of issues that scientists and engineers don't want to find in the final months before the launch of such a consequential mission. The stakes are incredibly high—imagine making the call to launch Clipper only to have the spacecraft fail six years later upon arrival at Jupiter.

The basic outline of the interactions between modern humans and Neanderthals is now well established. The two came in contact as modern humans began their major expansion out of Africa, which occurred roughly 60,000 years ago. Humans picked up some Neanderthal DNA through interbreeding, while the Neanderthal population, always fairly small, was swept away by the waves of new arrivals.

But there are some aspects of this big-picture view that don't entirely line up with the data. While it nicely explains the fact that Neanderthal sequences are far more common in non-African populations, it doesn't account for the fact that every African population we've looked at has some DNA that matches up with Neanderthal DNA.

A study published on Thursday argues that much of this match came about because an early modern human population also left Africa and interbred with Neanderthals. But in this case, the result was to introduce modern human DNA to the Neanderthal population. The study shows that this DNA accounts for a lot of Neanderthals' genetic diversity, suggesting that their population was even smaller than earlier estimates had suggested.

Out of Africa early

This study isn't the first to suggest that modern humans and their genes met Neanderthals well in advance of our major out-of-Africa expansion. The key to understanding this is the genome of a Neanderthal from the Altai region of Siberia, which dates from roughly 120,000 years ago. That's well before modern humans expanded out of Africa, yet its genome has some regions that have excellent matches to the human genome but are absent from the Denisovan lineage.

One explanation for this is that these are segments of Neanderthal DNA that were later picked up by the population that expanded out of Africa. The problem with that view is that most of these sequences also show up in African populations. So, researchers advanced the idea that an ancestral population of modern humans left Africa about 200,000 years ago, and some of its DNA was retained by Siberian Neanderthals. That's consistent with some fossil finds that place anatomically modern humans in the Mideast at roughly the same time.

There is, however, an alternative explanation: Some of the population that expanded out of Africa 60,000 years ago and picked up Neanderthal DNA migrated back to Africa, taking the Neanderthal DNA with them. That has led to a small bit of the Neanderthal DNA persisting within African populations.

To sort this all out, a research team based at Princeton University focused on the Neanderthal DNA found in Africans, taking advantage of the fact that we now have a much larger array of completed human genomes (approximately 2,000 of them).

The work was based on a simple hypothesis. All of our work on Neanderthal DNA indicates that their population was relatively small, and thus had less genetic diversity than modern humans did. If that's the case, then the addition of modern human DNA to the Neanderthal population should have boosted its genetic diversity. If so, then the stretches of "Neanderthal" DNA found in African populations should include some of the more diverse regions of the Neanderthal genome.

There and back again

In this work, non-Africans acted as a control group. The researchers identified the regions of the Neanderthal genome that they carry and checked how diverse those are within the Neanderthal genomes. They then made the same comparison with the sections of Neanderthal DNA that are found in African populations. This showed there was a clear difference: the Neanderthal DNA carried in Africans tended to come from areas of the Neanderthal genome that were much more diverse. (Meaning the six Neanderthal chromosomes we have sequences from are more likely to have differences between their DNA bases in these areas.)

A second analysis focused in on the most diverse regions of the Neanderthal genome (the top fifth percentile). Fully 60 percent of these regions were included in the Neanderthal DNA identified in African populations. By contrast, they accounted for only 23 percent of the Neanderthal DNA in non-African populations. The team also reran the analysis without the top 10 percent of diverse Neanderthal sequences and found that the matches with African genomes largely disappeared.

So, it's clear that the most diverse parts of the Neanderthal genome are largely shared with human genomes in African populations. The conclusion is that this isn't Neanderthal DNA that somehow made its way to Africans. Instead, it's modern human DNA that was picked up by Neanderthals and maintained in their population. Overall, the researchers estimate that roughly 3 to 4 percent of Neanderthal genomes consist of modern human DNA from this early interbreeding.

This doesn't explain all of the matches with Neanderthal DNA found in African populations, though—the researchers estimate that there is still somewhere between 20 and 40 percent of these matching sequences it doesn't account for. This suggests that some Neanderthal DNA did arrive in Africa through back-migration of populations that had left during the out-of-Africa expansion.

This modern human→Neanderthal DNA shows up in the populations that left Africa, as well. But it only accounts for about 10 percent of the DNA they share with Neanderthals. All of the rest is distinctly Neanderthal→modern human DNA that was picked up during the expansion out of Africa.

A vanishing population

The converse of this finding is that the distinctly Neanderthal portions of the genome are much less diverse than the complete Neanderthal genome. And that's significant, because genetic diversity is a measure of the effective population size—small populations tend to be much less genetically diverse, in part because there are simply fewer chromosomes overall, and in part because it's more likely that individuals will mate with distant relatives.

In the case of Neanderthals, the existing estimates of genetic diversity from the genomes we had suggested that the Neanderthal population was small, far smaller than those of contemporary modern humans. The new work suggests that about 20 percent of that diversity came through interbreeding with modern humans, implying that the Neanderthal population was even smaller than those estimates.

The two other Neanderthal genomes we have date from around the time of the major out-of-Africa expansion of modern humans. And the new analysis suggests that they'd also picked up a tiny bit of additional human DNA at this time. But the researchers propose that the population was so small that this made very little difference. "The assimilation of Neanderthals into modern human populations as they spread throughout Eurasia would have effectively increased the size of modern human populations while simultaneously decreasing the size of an already at-risk Neanderthal population," the authors suggest.

Science, 2024. DOI: 10.1126/science.adi1768  (About DOIs).

Welcome to Edition 7.02 of the Rocket Report! The highlight of this week was the hugely successful debut of Europe's Ariane 6 rocket. They will address the upper stage issue, I am sure. Given Europe's commitment to zero debris, stranding the second stage is not great. But for a debut launch of a large new vehicle, this was really promising.

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.

Chinese launch company suffers another setback. Chinese commercial rocket firm iSpace suffered a launch failure late Wednesday in a fresh setback for the company, Space News reports. The four-stage Hyperbola-1 solid rocket lifted off from Jiuquan spaceport in the Gobi Desert at 7:40 pm ET (23:40 UTC) on Wednesday. Beijing-based iSpace later issued a release stating that the rocket’s fourth stage suffered an anomaly. The statement did not reveal the name nor nature of the payloads lost on the flight.

Early troubles are perhaps to be expected ... Beijing Interstellar Glory Space Technology Ltd., or iSpace, made history in 2019 as the first privately funded Chinese company to reach orbit, with the solid-fueled Hyperbola-1. However the rocket suffered three consecutive failures following that feat. The company recovered with two successful flights in 2023 before the latest failure. The loss could add to reliability concerns over China’s commercial launch industry as it follows Space Pioneer’s recent catastrophic static-fire explosion. (submitted by EllPeaTea)

Feds backtrack on former Firefly investor. A long, messy affair between US regulators and a Ukrainian businessman named Max Polyakov seems to have finally been resolved, Ars reports. On Tuesday, Polyakov's venture capital firm Noosphere Venture Partners announced that the US government has released him and his related companies from all conditions imposed upon them in the run-up to the Russian invasion of Ukraine. This decision comes more than two years after the Committee on Foreign Investment in the United States and the US Air Force forced Polyakov to sell his majority stake in the Texas-based launch company Firefly.

Not a spy ... This rocket company was founded in 2014 by an engineer named Tom Markusic, who ran into financial difficulty as he sought to develop the Alpha rocket. Markusic had to briefly halt Firefly's operations before Polyakov, a colorful and controversial Ukrainian businessman, swooped in and provided a substantial infusion of cash into the company. "The US government quite happily allowed Polyakov to pump $200 million into Firefly only to decide he was a potential spy just as the company's first rocket was ready to launch," Ashlee Vance, a US journalist who chronicled Polyakov's rise, told Ars. It turns out, Polyakov wasn't a spy.

Pentagon ICBM costs soar. The price tag for the Pentagon's next-generation nuclear-tipped Sentinel ICBMs has ballooned by 81 percent in less than four years, The Register reports. This triggered a mandatory congressional review. On Monday, the Department of Defense released the results of this review, with Under-secretary of Defense for Acquisition and Sustainment William LaPlante saying the Sentinel missile program met established criteria for being allowed to continue after his "comprehensive, unbiased review of the program."

Trust us, the military says ... The Sentinel project is the DoD's attempt to replace its aging fleet of ground-based nuclear-armed Minuteman III missiles (first deployed in 1970) with new hardware. When it passed its Milestone B decision (authorization to enter the engineering and manufacturing phase) in September 2020, the cost was a fraction of the $141 billion the Pentagon now estimates Sentinel will cost, LaPlante said. To give that some perspective, the proposed annual budget for the Department of Defense for its fiscal 2025 is nearly $850 billion. (submitted by EllPeaTea)

Polish rocket reaches space for the first time. The Łukasiewicz Institute of Aviation has made history with the launch of its ILR-33 Amber 2K rocket from the Andøya Space Centre in Norway on July 3, European Spaceflight reports. Powered by a hybrid core stage and two solid-fuel boosters, the rocket reached an altitude of 101 km, the first time a Polish rocket has reached outer space.

Operational flights next ... "This is a historic day for the Łukasiewicz Institute of Aviation, but also a historic moment for the entire Polish rocket community," said Michał Wierciński, vice president of the Polish Space Agency. With the rocket successfully reaching space for the first time, operational flights can now commence. The rocket has already secured a customer with Polish company Thorium Space expected to conduct research missions aboard ILR-33 Amber 2K flights between 2025 and 2027. (submitted by Ken the Bin)

Dawn Aerospace obtains flight clearance. New Zealand-based Dawn Aerospace announced Thursday it has received certification from the Civil Aviation Authority in that country to fly its Mk-II Aurora space plane at unlimited speeds, including supersonic, up to an altitude of 80,000 feet. The Mk-II Aurora is a rocket-powered aircraft, designed to be the first vehicle ever to fly to 100 km altitude twice in a single day. "This unlocks the next major performance milestone for the Mk-II vehicle, namely supersonic flight," said the company's chief executive, Stefan Powell.

Seeking to go supersonic ... In the last three years, Dawn has completed 50 flight tests under both jet and rocket power, operating under more restrictive licenses. This Mk-II Aurora vehicle measures 4.5 meters long and is powered by a combustion rocket engine fueled by kerosene and hydrogen peroxide. The upcoming flight test campaign, scheduled from July through September, will consist of up to a dozen flights. The primary objective is to test the vehicle's speed up to Mach 1.1.

Virgin Galactic completes manufacturing facility. On Wednesday, the suborbital space tourism company said it had completed a new manufacturing facility in Phoenix, where final assembly of its next-generation Delta spaceships is scheduled to take place in the first quarter of 2025. The facility is scheduled to have tooling installed beginning during the final quarter of this year. The Delta class ships are designed to be capable of supporting a higher flight rate, up to eight missions a month.

Building the machine to build the machine ... The company plans to assemble the Delta ships at the new facility and perform some ground testing. Then, Virgin Galactic’s mothership will ferry completed spaceships to Spaceport America, New Mexico, for flight testing ahead of commercial operations. The company hopes to begin commercial operations with the Delta ships in 2026. (submitted by Ken the Bin)

A positive step for European space sector. A Germany-based fund, Alpine Space Ventures, said in a news release Thursday it has raised 170 million euros to invest primarily in the European space sector. The fund will invest in a concentrated portfolio of no more than 10 to 15 selected targets, which will receive up to 5 million euros initially, with capital reserved for follow-on rounds. One of the founding partners is Bulent Altan, an early leader at SpaceX.

VC funding needed ... Altan told me that the majority of the firm's investments would be "one to two steps further downstream from launch," with "satellites and components right now being the focus." Although the firm is not likely to invest directly in launch companies, this development is important for a couple of reasons. One, to thrive, the commercial space sector in Europe needs a more robust venture capital environment. And two, a more vibrant in-space sector could drive demand for European launch services.

Ariane 6 makes a largely successful debut. The first European Ariane 6 rocket fired off its launch pad at the edge of the Amazon rainforest and climbed into orbit Tuesday, restoring Europe's ability to put its own large satellites into space, Ars reports. The European Space Agency paid more than $4 billion to get the Ariane 6 rocket to this point, with the goal of replacing the Ariane 5 with a cheaper, more capable launcher. But there are still pressing questions about Ariane 6's cost per launch, and whether the rocket will ever be able to meet its price target and compete with SpaceX and other companies in the commercial market.

Only a slight sting in the tail ... European officials were celebratory after the launch. “Europe is back," said Josef Aschbacher, ESA's director general. "This powers Europe back into space.” The flight went essentially perfectly until a malfunction on the upper stage prevented the Vinci engine from completing a third burn to steer back into Earth's atmosphere for a targeted, destructive reentry. The restartable Vinci engine is intended to allow Ariane 6 to deploy payloads at different altitudes, or inject satellites directly into high-energy geosynchronous orbits, like SpaceX's Falcon launchers or United Launch Alliance's Atlas V and Vulcan rockets.

Some intrigue surrounds Vega C customers. The manufacturer of the Vega C rocket, Avio, has reached an agreement to break its rocket away from Arianespace for marketing and operations. Under the terms of the resolution, Arianespace will remain the launch service provider for the final Vega flight scheduled for later this year, and all Vega C flights up to and including flight VV29, which is currently expected to occur in the fourth quarter of 2025, European Spaceflight reports.

A request rather than a requirement ... Following that, all customers who have contracted Vega C flights through Arianespace will be offered the opportunity to transfer their contracts to Avio as the new launch service provider for their missions. When asked if the agreement would allow customers to shop around instead of transferring their contracts to Avio, the European Space Agency’s head of strategy and institutional launches, Lucia Linares, gave a diplomatic non-answer. “Arianespace will request agreement for the transfer of those launch service contracts to the clients, which are European institutional customers,” Linares told European Spaceflight. (submitted by Ken the Bin)

Congress to NASA: find more customers for SLS rocket. As part of the new NASA reauthorization bill working its way through Congress, there is a curious section on the Space Launch System rocket, Ars reports. The section is titled "Reaffirmation of the Space Launch System," and in it Congress asserts its commitment to a flight rate of twice per year for the rocket. The reauthorization legislation, which cleared a House committee on Wednesday, also said NASA should identify other customers for the rocket.

Subsidized launch system ... Congress is asking for NASA to study demand for the SLS rocket and estimate "cost and schedule savings for reduced transit times" for deep space missions due to the "unique capabilities" of the rocket. The space agency also must identify any "barriers or challenges" that could impede use of the rocket by other entities other than NASA, and estimate the cost of overcoming those barriers. It seems preposterous that Congress would ask NASA to identify subsidies to lower the cost of the SLS rocket in order to sell more of them to commercial customers, but here we are.

SpaceX rolls next Super Heavy booster to the pad. The company rolled Starship's giant first-stage booster, known as Super Heavy, out to the launch pad at Starbase on Wednesday, Space.com reports. This booster will be used for the fifth flight test of the Starship rocket. Video of the rollout provided by SpaceX also showcased the company's new "Starfactory" facility in South Texas.

Flight test possibly in August ... When it's complete and fully optimized, Starfactory is intended to churn out one Starship every day, SpaceX representatives have said. As for the fifth flight test, SpaceX founder Elon Musk has said it could come in about four weeks, so perhaps during the first half of August.

Next three launches

July 12: Falcon 9 | Starlink 9-3 | Vandenberg Space Force Base, California | 02:35 UTC

July 14: Falcon 9 | Starlink 10-4 | Cape Canaveral Space Force Station, Florida | 07:35 UTC

July 16: Falcon 9 | Arctic Satellite Broadband Mission | Vandenberg Space Force Base | 03:40 UTC

In the early 2000s, local fossil collector Mohamed ‘Ou Said’ Ben Moula discovered numerous fossils at Fezouata Shale, a site in Morocco known for its well-preserved fossils from the Early Ordovician period, roughly 480 million years ago. Recently, a team of researchers at the University of Lausanne (UNIL) studied 100 of these fossils and identified one of them as the earliest ancestor of modern-day chelicerates, a group that includes spiders, scorpions, and horseshoe crabs.

The fossil preserves the species Setapedites abundantis, a tiny animal that crawled and swam near the bottom of a 100–200-meter-deep ocean near the South Pole 478 million years ago. It was 5 to 10 millimeters long and fed on organic matter in the seafloor sediments. “Fossils of what is now known as S. abundantis have been found early on—one specimen mentioned in the 2010 paper that recognized the importance of this biota. However, this creature wasn’t studied in detail before simply because scientists focused on other taxa first,” Pierre Gueriau, one of the researchers and a junior lecturer at UNIL, told Ars Technica.

The study from Gueriau and his team is the first to describe S. abundantis and its connection to modern-day chelicerates (also called euchelicerates). It holds great significance, because “the origin of chelicerates has been one of the most tangled knots in the arthropod tree of life, as there has been a lack of fossils between 503 to 430 million years ago,” Gueriau added.

An ancestor of spiders

The study authors used X-ray scanners to reconstruct the anatomy of 100 fossils from the Fezouata Shale in 3D. When they compared the anatomical features of these ancient animals with those of chelicerates, they noticed several similarities between S. abundantis and various ancient and modern-day arthropods, including horseshoe crabs, scorpions, and spiders.

For instance, the nature and arrangement of the head appendages or ‘legs’ in S. abundantis were homologous with those of present-day horseshoe crabs and Cambrian arthropods that existed between 540 to 480 million years ago. Moreover, like spiders and scorpions, the organism exhibited body tagmosis, where the body is organized into different functional sections.

“Setapedites abundantis contributes to our understandings of the origin and early evolution of two key euchelicerate characters: the transition from biramous to uniramous prosomal appendages, and body tagmosis,” the study authors note.

Currently, two Cambrian-era arthropods, Mollisonia plenovenatrix and Habelia optata are generally considered the earliest ancestors of chelicerates (not all scientists accept this idea). Both lived around 500 million years ago. When we asked how these two differ from S. abundantis, Gueriau replied, “Habelia and Mollisonia represent at best early-branching lineages in the phylogenetic tree. While S. abundantis is found to represent, together with a couple of other fossils, the earliest branching lineage within chelicerates.”

This means Habelia and Mollisonia are relatives of the ancestors of modern-day chelicerates. On the other side, S. abundantis represents the first group that split after the chelicerate clade was established, making it the earliest member of the lineage. “These findings bring us closer to untangling the origin story of arthropods, as they allow us to fill the anatomical gap between Cambrian arthropods and early-branching chelicerates,” Gueriau told Ars Technica.

S. abundantis connects other fossils

The researchers faced many challenges during their study. For instance, the small size of the fossils made observations and interpretation complicated. They overcame this limitation by examining a large number of specimens—fortunately, S. abundantis fossils were abundant in the samples they studied. However, these fossils have yet to reveal all their secrets.

“Some of S. abundantis’ anatomical features allow for a deeper understanding of the early evolution of the chelicerate group and may even link other fossil forms, whose relationships are still highly debated, to this group,” Gueriau said. For instance, the study authors noticed a ventral protrusion at the rear of the organism. Such a feature is observed for the first time in chelicerates but is known in other primitive arthropods.

“This trait could thus bring together many other fossils with chelicerates and further resolve the early branches of the arthropod tree. So the next step for this research is to investigate deeper this feature on a wide range of fossils and its phylogenetic implications,” Gueriau added.

Nature Communications, 2023. DOI: 10.1038/s41467-024-48013-w  (About DOIs)

Rupendra Brahambhatt is an experienced journalist and filmmaker. He covers science and culture news, and for the last five years, he has been actively working with some of the most innovative news agencies, magazines, and media brands operating in different parts of the globe.

A SpaceX Falcon 9 rocket suffered an upper stage engine failure and deployed a batch of Starlink Internet satellites into a perilously low orbit after launch from California Thursday night, the first blemish on the workhorse launcher's record in more than 300 missions since 2016.

Elon Musk, SpaceX's founder and CEO, posted on X that the rocket's upper stage engine failed when it attempted to reignite nearly an hour after the Falcon 9 lifted off from Vandenberg Space Force Base, California, at 7:35 pm PDT (02:35 UTC).

Frosty evidence

After departing Vandenberg to begin SpaceX's Starlink 9-3 mission, the rocket's reusable first stage booster propelled the Starlink satellites into the upper atmosphere, then returned to Earth for an on-target landing on a recovery ship parked in the Pacific Ocean. A single Merlin Vacuum engine on the rocket's second stage fired for about six minutes to reach a preliminary orbit.

A few minutes after liftoff of SpaceX's Starlink 9-3 mission, veteran observers of SpaceX launches noticed an unusual build-up of ice around the top of the Merlin Vacuum engine, which consumes a propellant mixture of super-chilled kerosene and cryogenic liquid oxygen. The liquid oxygen is stored at a temperature of several hundred degrees below zero.

Numerous chunks of ice fell away from the rocket as the upper stage engine powered into orbit, but the Merlin Vacuum, or M-Vac, engine appeared to complete its first burn as planned. A leak in the oxidizer system or a problem with insulation could lead to ice accumulation, although the exact cause, and its possible link to the engine malfunction later in flight, will be the focus of SpaceX's investigation into the failure.

A second burn with the upper stage engine was supposed to raise the perigee, or low point, of the rocket's orbit well above the atmosphere before releasing 20 Starlink satellites to continue climbing to their operational altitude with their own propulsion.

"Upper stage restart to raise perigee resulted in an engine RUD for reasons currently unknown," Musk wrote in an update two hours after the launch. RUD (rapid unscheduled disassembly) is a term of art in rocketry that usually signifies a catastrophic or explosive failure.

"Team is reviewing data tonight to understand root cause," Musk continued. "Starlink satellites were deployed, but the perigee may be too low for them to raise orbit. Will know more in a few hours."

Telemetry from the Falcon 9 rocket indicated it released the Starlink satellites into an orbit with a perigee just 86 miles (138 kilometers) above Earth, roughly 100 miles (150 kilometers) lower than expected, according to Jonathan McDowell, an astrophysicist and trusted tracker of spaceflight activity. Detailed orbital data from the US Space Force was not immediately available.

Ripple effects

While ground controllers scramble to salvage the 20 Starlink satellites, SpaceX engineers began probing what went wrong with the second stage's M-Vac engine. For SpaceX and its customers, the investigation into the rocket malfunction is likely the more pressing matter.

SpaceX could absorb the loss of 20 Starlink satellites relatively easily. The company's satellite assembly line can produce 20 Starlink spacecraft in a few days. But the Falcon 9 rocket's dependability and high flight rate have made it a workhorse for NASA, the US military, and the wider space industry. An investigation will probably delay several upcoming SpaceX flights.

Depending on the cause of the problem and what SpaceX must do to fix it, it's possible the company can recover from the upper stage failure and resume launching Starlink satellites soon. Most of SpaceX's launches aren't for external customers, but deploy satellites for the company's own Starlink network. This gives SpaceX a unique flexibility to quickly return to flight with the Falcon 9 without needing to satisfy customer concerns.

The Federal Aviation Administration, which licenses all commercial space launches in the United States, will require SpaceX to conduct a mishap investigation before resuming Falcon 9 flights.

"The FAA will be involved in every step of the investigation process and must approve SpaceX’s final report, including any corrective actions," an FAA spokesperson said. "A return to flight is based on the FAA determining that any system, process, or procedure related to the mishap does not affect public safety."

Two crew missions are supposed to launch on SpaceX's human-rated Falcon 9 rocket in the next six weeks, but those launch dates are now in doubt.

The all-private Polaris Dawn mission, commanded by billionaire Jared Isaacman, is scheduled to launch on a Falcon 9 rocket on July 31 from NASA's Kennedy Space Center in Florida. Isaacman and three commercial astronaut crewmates will spend five days in orbit on a mission that will include the first commercial spacewalk outside their Crew Dragon capsule, using new pressure suits designed and built by SpaceX.

NASA's next crew mission with SpaceX is slated to launch from Florida aboard a Falcon 9 rocket around August 19. This team of four astronauts will replace a crew of four who have been on the International Space Station since March.

Some customers, especially NASA's commercial crew program, will likely want to see the results of an in-depth inquiry and require SpaceX to string together a series of successful Falcon 9 flights with Starlink satellites before clearing their own missions for launch. SpaceX has already launched 70 flights with its Falcon family of rockets since January 1, an average cadence of one launch every 2.7 days, more than the combined number of orbital launches by all other nations this year.

With this rapid-fire launch cadence, SpaceX could quickly demonstrate the fitness of any fixes engineers recommend to resolve the problem that caused Thursday night's failure. But investigations into rocket failures often take weeks or months. It was too soon, early on Friday, to know the true impact of the upper stage malfunction on SpaceX's launch schedule.

SpaceX reported its ground team established contact with five of the 20 Starlink satellites soon after they separated from the Falcon 9's failed upper stage. Officials hope to quickly activate their ion thrusters to overcome the effects of atmospheric drag. At their current altitude, without orbit-raising, the satellites will be naturally dragged back into the atmosphere to burn up in a matter of hours or days.

"The satellite thrusters need to raise orbit faster than atmospheric drag pulls them down or they burn up," Musk said, adding that the efforts to save the satellites "will probably not work, but it's worth a shot."

By the numbers

Going into Thursday's mission, the current version of SpaceX's Falcon 9 rocket, known as the Falcon 9 Block 5, was indisputably the most reliable launch vehicle in history. Since debuting in May 2018, the Falcon 9 Block 5, which NASA has certified for astronaut flights, never had a mission failure in all of its 297 launches before the ill-fated Starlink 9-3 mission.

Assuming the Starlink satellites can't be saved, and if Thursday night's launch is scored as a complete mission failure, the Falcon 9 Block 5 still has a 99.7 percent success rate. This is still an enviable number for any launch company.

Since 2010, SpaceX has launched 354 flights of the Falcon 9 rocket, including retired versions of the vehicle. The more powerful Falcon Heavy, which uses three Falcon 9 rocket boosters connected together, has flown 10 times.

There were several failures in the early years of the Falcon 9 rocket. A first stage engine failure on the fourth Falcon 9 launch in 2012 prevented the rocket from deploying a secondary payload into the correct orbit, but SpaceX was still able to complete the primary mission of delivering cargo to the International Space Station.

The Falcon 9's only total in-flight launch failure occurred on its 19th flight on June 28, 2015, when the upper stage's liquid oxygen tank burst a couple of minutes after launch from Cape Canaveral Space Force Station, Florida. The rocket disintegrated in the upper atmosphere, dooming a Dragon cargo capsule en route to the space station.

SpaceX resumed Falcon 9 launches six months later in December 2015. On that flight, SpaceX landed the Falcon 9's first stage booster back at Cape Canaveral for the first time, a historic achievement and a harbinger of the company's later success in reusing rockets.

Nine SpaceX missions flawlessly launched before a Falcon 9 rocket exploded on the launch pad during a prelaunch test on September 3, 2016. This wasn't an in-flight failure, but the fireball destroyed the Israeli Amos-6 communications satellite mounted on top of the Falcon 9. Engineers traced the cause to a helium tank failure in the upper stage.

Since then, it's been smooth sailing for SpaceX's Falcon family of rockets, which counted 335 consecutive successful launches since the on-pad explosion in 2016, or 344 flights since an in-flight failure. Both numbers are all-time industry records.

The first Falcon Heavy rocket launched in 2018, and SpaceX launched its first astronaut mission under contract with NASA in May 2020. SpaceX ramped up the flight rate from 18 launches in 2017 to 96 Falcon rocket flights in 2023. SpaceX aims to launch Falcon rockets 144 times this year, but even a brief halt in launches could jeopardize that goal.

Through it all, SpaceX mastered the recovery and reuse of Falcon 9 boosters and payload fairings while maintaining a perfect launch success record. The upper stage of the Falcon 9, though, remains expendable, and every launch flies with a brand-new second stage engine. This is the element that failed Thursday night.

This story was updated with the FAA's statement on SpaceX's mishap investigation. 

Gaiasia jennyae, a newly discovered freshwater apex predator with a body length reaching 4.5 meters, lurked in the swamps and lakes around 280 million years ago. Its wide, flattened head had powerful jaws full of huge fangs, ready to capture any prey unlucky enough to swim past.

The problem is, to the best of our knowledge, it shouldn’t have been that large, should have been extinct tens of millions of years before the time it apparently lived, and shouldn’t have been found in northern Namibia. “Gaiasia is the first really good look we have at an entirely different ecosystem we didn’t expect to find,” says Jason Pardo, a postdoctoral fellow at Field Museum of Natural History in Chicago. Pardo is co-author of a study on the Gaiasia jennyae discovery recently published in Nature.

Common ancestry

“Tetrapods were the animals that crawled out of the water around 380 million years ago, maybe a little earlier,” Pardo explains. These ancient creatures, also known as stem tetrapods, were the common ancestors of modern reptiles, amphibians, mammals, and birds. “Those animals lived up to what we call the end of Carboniferous, about 370–300 million years ago. Few made it through, and they lasted longer, but they mostly went extinct around 370 million ago,” he adds.

This is why the discovery of Gaiasia jennyae in the 280 million-year-old rocks of Namibia was so surprising. Not only wasn’t it extinct when the rocks it was found in were laid down, but it was dominating its ecosystem as an apex predator. By today’s standards, it was like stumbling upon a secluded island hosting animals that should have been dead for 70 million years, like a living, breathing T-rex.

“The skull of gaiasia we have found is about 67 centimeters long. We also have a front end of her upper body. We know she was at minimum 2.5 meters long, probably 3.5, 4.5 meters—big head and a long, salamander-like body,” says Pardo. He told Ars that gaiasia was a suction feeder: she opened her jaws under water, which created a vacuum that sucked her prey right in. But the large, interlocked fangs reveal that a powerful bite was also one of her weapons, probably used to hunt bigger animals. “We suspect gaiasia fed on bony fish, freshwater sharks, and maybe even other, smaller gaiasia,” says Pardo, suggesting it was a rather slow, ambush-based predator.

But considering where it was found, the fact that it had enough prey to ambush is perhaps even more of a shocker than the animal itself.

Location, location, location

“Continents were organized differently 270–280 million years ago,” says Pardo. Back then, one megacontinent called Pangea had already broken into two supercontinents. The northern supercontinent called Laurasia included parts of modern North America, Russia, and China. The southern supercontinent, the home of gaiasia, was called Gondwana, which consisted of today’s India, Africa, South America, Australia, and Antarctica. And Gondwana back then was pretty cold.

“Some researchers hypothesize that the entire continent was covered in glacial ice, much like we saw in North America and Europe during the ice ages 10,000 years ago,” says Pardo. “Others claim that it was more patchy—there were those patches where ice was not present,” he adds. Still, 280 million years ago, northern Namibia was around 60 degrees southern latitude—roughly where the northernmost reaches of Antarctica are today.

“Historically, we thought tetrapods [of that time] were living much like modern crocodiles. They were cold-blooded, and if you are cold-blooded the only way to get large and maintain activity would be to be in a very hot environment. We believed such animals couldn’t live in colder environments. Gaiasia shows that it is absolutely not the case,” Pardo claims. And this turned upside-down lots of what we knew about life on Earth back in gaiasia’s time.

Exploring the Skull Island

Most of our understanding of how the world looked in the late Carboniferous comes from fossils found in North America and Europe, which were in the tropical, equatorial regions of Laurasia back then. “Let’s take the example of Texas. We have been working on this ecosystem for 140 years. We know these rocks and these animals pretty well," explains Prado. The Field Museum of Natural History alone has drawers upon drawers filled with fossils of different Laurasian life forms from that period, Pardo says.

Southern Gondwana, on the other hand, was thought to host mostly lifeless fields of ice and snow. But instead, it may have been something like Kong’s Skull Island, with abundance of animals that went extinct in hotter climate but fared well in colder weather. “Modern giant salamanders live in colder, mountainous environments. It takes time for them to get big, but they are the largest salamanders living today. Maybe we didn’t necessarily have the right mindset approaching these animals,” Prado wonders. And gaiasia may be just the beginning.

“We have gaiasia, those huge predators, but there are more animals found in Namibia with lots of material still in the field that shows there was a diverse ecosystem surrounding this fantastic animal,” Pardo says. Life in the south of Gondwana must have been quite abundant to support a large predator like gaiasia, he argued. “You can’t get big without plenty of food. There were fish there and we found pieces of other tetrapods. A little piece here and there, a piece of the jaw. We just took a first look—a couple of field studies with a very small team. When it comes to Namibia, we are in 1880s compared to the work that has been done in Texas. Perhaps we will learn more about this ecosystem in the next 100 years,” Pardo says.

Nature, 2024. DOI: 10.1038/s41586-024-07572-0