There appear to be two separate arms originating from the same general location at the crust-mantle boundary. One branch slopes northeast to feed the Yellowstone caldera, while a second branches off toward the Snake River Plain. The branches split in a way that the volcano-free zone between the two features results.

The researchers reasoned that, whatever else was going on to provide molten material, the paths to the surface were likely to be enabled by stresses in the crust. And that was going to depend on both the existing features in the crust (obtained largely through seismic data) as well as larger-scale processes going on in the mantle underneath. So, the model included both basic geological details, known physical processes, and a bit of history in the sense of what we know about how that section of the crust came to be.

And that’s where we come back to the Farallon plate. Its remains, having been driven beneath the North American plate, are continuing to sink and move through the mantle. That, the researchers surmise, is driving a general eastward flow of material through the viscous mantle. Just east of Yellowstone, however, that flow runs into the older border of the North American plate, where the crust is thicker and denser than the portion of the continent that was put in place by the Farallon plate.

New pathways

This thick crust causes the flow of the mantle to dip downward. And that change in flow causes a series of stresses in the crust, most notably a compressive force between the older and newer sections of the North American plate, as well as a downward drag on the older section. Adding to the local stresses is the fact that all the material that erupted to form the Snake River Plain is denser than much of the surrounding rock, which generates strain on nearby rocks as it tries to sink.

https://arstechnica.com/science/2026/04/new-paper-argues-history-not-mantle-plume-powers-yellowstone/

Mixing corn starch and water in appropriate amounts produces a slurry that is liquid when stirred slowly but hardens when you punch it—a substance colorfully dubbed “oobleck.” (The name derives from a 1949 Dr. Seuss children’s book, Bartholomew and the Oobleck.) High-speed imaging and force measurements have revealed another surprising property of oobleck drops hitting a flat surface, according to a new paper published in the journal Physical Review Letters.

As previously reported, in an ideal fluid, viscosity largely depends on temperature and pressure: Water will continue to flow regardless of other forces acting on it, such as stirring or mixing. In a non-Newtonian fluid, the viscosity changes in response to an applied strain or shearing force, thereby straddling the boundary between liquid and solid behavior. Stirring a cup of water produces a shearing force, and the water shears to move out of the way. The viscosity remains unchanged. But for non-Newtonian fluids like oobleck, the viscosity changes when a shearing force is applied.

Ketchup, for instance, is a shear-thickening non-Newtonian fluid, which is one reason smacking the bottom of the bottle doesn’t make the ketchup come out any faster; the application of force increases the viscosity. Yogurt, gravy, mud, pudding, and thickened pie fillings are other examples. And so is oobleck.

The underlying physics principles of this simple substance are surprisingly nuanced and complex, and thus fascinating to scientists. For instance, back in 2023, molecular engineers at the University of Chicago used dense suspensions of piezoelectric nanoparticles to measure what is happening at the molecular level when oobleck transitions from liquid to solid behavior.

https://arstechnica.com/science/2026/04/oobleck-still-holds-some-surprises/

Finding a radula, the chitinous, toothed, conveyor-belt-like tongue used by mollusks to scrape food, was the definitive proof that Pohlsepia was indeed a mollusk. A more precise answer came in the form of the teeth. The synchrotron scan was sharp enough to let researchers count the tiny, individual tooth impressions across the radula’s transverse rows. They observed a central rachidian tooth, pairs of lateral teeth, marginal teeth, and smooth marginal plates, adding up to at least 11 distinct elements per row. The only animals matching this exact 11-element configuration are Nautiloids, ancient, shelled relatives of modern cephalopods.

“Pohlsepia mazonensis is a nautiloid that died, decomposed, lost its protective shell and was subsequently flattened into the mud and preserved as an ambiguous stain,” Clements said.

Switching titles

But while the fossil’s “oldest octopus” badge is most likely gone, it managed to earn itself some new superlatives. “The first is of course the most difficult fossil to work on that I’ve ever worked on,” Clements said. “The second would probably be the most fun fossil I’ve ever worked on.”

The results of his study also made Pohlsepia the oldest unequivocal piece of evidence of nautiloid soft tissues ever found in the entire Paleozoic fossil record. “I’d say unequivocal because other nautiloid soft tissue fossils are a bit questionable,” Clements said.

His team now plans to use the same advanced imaging on other fossils. “Mazon Creek in particular is full of very interesting and very weird fossils which have not been looked at for a long time, and you know, all of these new techniques can be used on them,” Clements said.

He thinks that even for Pohlsepia itself, it’s not yet the end of the story. “It’s the oldest nautiloid now, so it would be interesting to study it more.”

Clements’ study on the Pohlsepia mazonensis is published in Proceedings of the Royal Society B Biological Sciences: https://doi.org/10.1098/rspb.2025.2369

https://arstechnica.com/science/2026/04/oldest-octopus-fossil-found-to-not-be-an-octopus/

NASA’s schedule currently puts the launch of Artemis III in 2027 and Artemis IV in 2028. Kshatriya said he was confident that NASA, working with the European Space Agency and Airbus, which builds the service module, will be able to fix the valve problem in time for Artemis IV. Manufacturing of the Artemis IV service module is largely complete.

“I’m pretty sure we’re going to need to, at a minimum, tweak the design to prevent the leak rate that we have, if not fundamentally change the way the valve works,” he said.

Valves are a common bugaboo on rockets and spacecraft. Nearly every US human spaceflight program has dealt with malfunctioning or leaky valves. Boeing’s Starliner crew capsule suffered helium leaks in its propulsion system, along with other issues, during a test flight to the International Space Station in 2024. Helium valves on the Space Launch System rocket had to be replaced in the run-up to the Artemis I and Artemis II launches. SpaceX has also scrubbed launches due to valve problems. The list goes on.

“There are a lot of options for how to take care of this problem,” Kshatriya said of the issue on the Orion spacecraft. “If anything, I’d characterize it as a production redesign risk for the Artemis IV mission, which I think we can get in front of, and which is why we put so much attention on it during this mission to make sure [we understand] what we’re seeing.”

The big lesson NASA learned on Artemis I involved the capsule’s heat shield. The ablative thermal barrier burned away unevenly as the craft reentered the atmosphere, but Orion still made it to a safe, on-target splashdown. NASA officials said they are confident the heat shield will hold up on Artemis II after adjusting the path Orion will take through the upper atmosphere. A new heat shield design will debut on Artemis III.

NASA engineers spent two years investigating the heat shield issue after Artemis I. Kshatriya does not expect the valve redesign to take as long.

“It’s not a safety of flight, safety of crew, must-work function like the heat shield investigation sent us down,” he said. “It’s going to take work to get it right, but it’s not of that magnitude.”

https://arstechnica.com/space/2026/04/nasa-homes-in-on-likely-redesign-to-fix-orion-spacecrafts-leaky-valves/

Almost as soon as researchers started exploring the capabilities of the CRISPR/Cas9 system, they recognized its potential use in targeted gene editing. But the intervening decades have seen slow progress as people worked to determine how to do so in a way that would be safe for use in humans. It was only a little over two years ago, decades after CRISPR’s discovery, that the FDA approved the first CRISPR-based therapy, for sickle-cell anemia.

Now, following up on that success, a large Chinese collaboration has followed up with a description of an improved gene editing system that produces more focused changes and fewer mistakes. And they’ve used it to produce a therapy that addresses a disease that’s closely related to sickle-cell anemia: β-Thalassaemia.

Gene editing and its limits

The CRISPR/Cas-9 system provides bacteria with a form of immunity. It uses specially structured RNAs (called guide RNAs) that can base-pair with a targeted sequence. The Cas-9 protein then recognizes this structure and cuts the DNA nearby. This is quite effective when the guide RNA can base-pair with a DNA virus, as the resulting cut will inactivate the virus.

There are a couple of ways to use this for DNA editing in organisms such as ourselves. Both of these take advantage of the fact that the DNA repair systems in cells will often chew back the ends of these cuts before linking them back together again. This will frequently lead to small deletions at the site of the cut, which can be used to disable genes. The size of these deletions will vary, so you have to do some DNA sequencing to find one that disables the gene you’re interested in, but doesn’t do any additional damage.

Alternately, any deleted sequence can sometimes be repaired using a matching sequence, which is typically found on the other copy of the same chromosome. If the CRISPR-based cut is accompanied by lots of copies of a modified sequence, then it’s possible for repair systems to insert the modifications into the genome, providing a true editing capability. But again, this process is error-prone, so people typically need to edit a bunch of cells and sequence the DNA to make sure the right changes are made.

https://arstechnica.com/science/2026/04/clinical-trial-shows-gene-editing-works-for-%ce%b2-thalassaemia-too/

Even those factors might not have been sufficient, but the authors also identified three possible catalysts. In 2014, five adult males and one adult female died of unknown causes, although several had shown signs of illness. Those losses likely disrupted the social network by weakening social ties across clusters. There was also a new alpha male from the western cluster the following year, coincidentally, the same time when the first sustained separation occurred. The two prior alphas had been from the central cluster, so that change in the dominance hierarchy may have exacerbated inter-group tensions.

Finally, there was a respiratory outbreak in January 2017 that killed 25 chimps, which could have sped up the final separation. “Taken together, these events suggest how networks may fracture in the face of multiple demographic and social changes,” the authors concluded.

“A hostile split among wild chimpanzees is a reminder of the danger that group divisions can present to human societies,” Brooks wrote in his perspective. “However, humans also engage with, bond, and cooperate at multiple levels across intersecting groups. The group relationships of humans are nuanced, diverse, and flexible. This flexibility enables deep cooperation but also underlies acts of violence. Humans must learn from studying the group-based behavior of other species, both in war and at peace, while remembering that their evolutionary past does not determine their future.

“If relational dynamics alone can drive polarization and lethal conflict in chimps without language, ethnicity, or ideology, then in humans, those cultural markers might be secondary to something more basic,” said Sandel. “If that’s true, then we may have the potential to reduce societal conflicts in our personal lives, and that gives me hope. As our paper concludes, it may be in the small, daily acts of reconciliation and reunion between individuals that we find opportunities for peace.”

Science, 2026. DOI: 10.1126/science.adz4944 (About DOIs).

https://arstechnica.com/science/2026/04/ugandan-chimps-split-into-two-factions-then-killed-rivals/

“We have loved living in Orion,” said Christina Koch, mission specialist on Artemis II. “In fact, we’ve all said that sometimes you can forget where you really are, because we’re in this small space that just gives us everything we need.”

Living in microgravity makes the cramped quarters seem a little more accommodating. The astronauts can take advantage of every corner of the spacecraft.

“It is bigger in microgravity, and yes, we are bumping into each other 100 percent of the time,” Koch said. “A phrase that you often hear in the cabin is, ‘Don’t move your foot. I’m just going to reach for something right under it.’”

NASA named the crew members for the Artemis II mission three years ago. Now, the astronauts will have their names in the history books. With Artemis II, the number of people alive who have traveled to the vicinity of the Moon has nearly doubled. Just five of the 24 men who flew to the Moon are still alive. Four of them walked on its surface.

“I will miss this camaraderie. I will miss being this close with this many people and having a common purpose, a common mission,” Koch said. “This sense of teamwork is something that you don’t usually get as an adult. I mean, we are close, like brothers and sisters, and that is a privilege we will never have again.”

One of the most poignant moments of the mission was a tribute to Wiseman’s late wife, Carroll, who died of cancer in 2020. On Monday, as the crew neared the Moon, Hansen radioed down the crew’s request to name a crater for Carroll.

“When Jeremy spelled Carol’s name, C-A-R-R-O-L- L, I think, for me, that’s when I was overwhelmed with emotion,” Wiseman said. “And I looked over and Christina was crying. I put my hand down on Jeremy’s hand as he was still talking. I could just tell he was trembling, and we all pretty much broke down right there. And just for me, personally, that was kind of the pinnacle moment of the mission. For me, that was, I think, where the four of us were the most forged, the most bonded, and we came out of that really focused on the day ahead.”

https://arstechnica.com/space/2026/04/astronauts-recall-the-sci-fi-experience-of-flying-in-the-shadow-of-the-moon/

If the star is sufficiently massive, this will cause the near-instantaneous onset of oxygen fusion, releasing a massive burst of energy. That energy is thought to be enough to completely destroy the star without leaving a remnant black hole behind. Alternatively, smaller bursts of oxygen fusion may blast away the star’s outer layers, leaving a much smaller star behind that will ultimately create a far less massive black hole.

While that’s pretty well established through modeling, it’s a very difficult process to confirm. There have been a number of proposed examples of potential pair-instability events, and we don’t have a clear picture of what observations would distinguish them from more run-of-the-mill stellar explosions. And while we’ve been able to estimate the mass of the black holes we’ve observed merging, that hasn’t been as helpful as we would like.

The problem is that several of the mergers we’ve seen involve black holes that seem to have merged previously. So they’re big enough to be above the cutoff where pair-instability should have blocked the formation of a black hole, but they might have gotten that hefty by swallowing another black hole.

Numbers to the rescue

The international team behind the new work considered what kinds of collisions we might see. One is two first-generation (G1) black holes merging, in which case both should be below the mass at which pair-instability destroys everything. Then there’s a G1 colliding with a second-generation (G2) that’s the product of a previous merger, with the G2 potentially being above the mass cutoff. Finally, there’s a G2-G2 merger, where both are above the cutoff.

Any black hole mergers are likely to take place within a structure filled with lots of high-mass stars, such as a globular cluster. But the merger itself tends to impart a lot of energy to the resulting black hole, which could potentially kick it out of the cluster. As a result, G2-G2 mergers would likely be far more rare than G1-G2 mergers; the team estimates that only about 1 percent of all mergers would be G2-G2.

https://arstechnica.com/science/2026/04/black-hole-mergers-put-limits-on-star-destroying-supernovae/

Fälth noted that proponents of reform believe that “basic skills—especially reading, writing, and numeracy—must be firmly established first, and that physical textbooks are often better suited for that purpose.”

Between 2000 and 2012, Swedish students’ scores on standardized tests steadily declined in reading, math, and science. Though they recovered ground between 2012 and 2018, those scores had dropped again by 2022.

Though it’s unclear precisely how much of the decline is due to digitization, there is some evidence that analog teaching materials for reading may be superior to screen learning. However, this applies to expository as opposed to narrative texts. Narrative texts tell a story, whether fiction or non-fiction, while expository texts are designed to inform, describe, or explain a topic in a logical, factual manner.

Swedish officials emphasize that digital technology isn’t being removed from schools altogether. Rather, digital aids “should only be introduced in teaching at an age when they encourage, rather than hinder, pupils’ learning.” Achieving digital competence remains an important objective, particularly in higher grades.

Historically, the technology industry has pushed for more use of digital learning, seeing itself as a transformer of education. In the 1980s, Apple helped bring about the use of computers in schools. Then, starting with the use of the Internet, and later integrating mobile devices, technology reshaped the educational landscape. Education experts suggest it can foster a learning experience that is more interactive, accessible, and tailored to the needs of individual students.

In the US, the trend nationally in recent years has been toward the use of increasingly sophisticated methods of digital learning, such as providing children with laptops or devices like the iPad. According to a survey conducted by the EdWeek Research Center, part of the trade publication Education Week, 90 percent of school district leaders were providing devices for every middle and high school student as of March 2021. More than 80 percent of school district leaders said the same was true for elementary school students.

https://arstechnica.com/science/2026/04/sweden-goes-back-to-basics-swapping-screens-for-books-in-the-classroom/

KENNEDY SPACE CENTER, Florida—Launching to the Moon is an all-day undertaking, something the four astronauts waiting to climb aboard NASA’s Artemis II rocket know well.

“It is actually a very long day,” said Victor Glover, the pilot on Artemis II. “We wake up about eight hours before launch, and there’s a pretty tight schedule of things to get out there.”

Glover and his three crewmates have their schedules planned to the minute throughout the nine-day Artemis II mission. If all goes according to plan, their mission will carry them more than a quarter-million miles from Earth, farther from home than anyone has ventured in human history. After looping behind the Moon, the astronauts and their Orion capsule will fall back to Earth at some 25,000 mph (40,000 km/hr), setting another record for the fastest that humans have ever traveled.

Reid Wiseman, the mission commander, will join Glover at the controls inside the Orion spacecraft’s cockpit. Mission specialist Christina Koch and Canadian astronaut Jeremy Hansen round out the crew. All four have critical roles during the mission to test the Orion spaceship, which is flying with humans for the first time after 20 years in development.

The journey could begin as soon as Wednesday at NASA’s Kennedy Space Center in Florida. The mission has a two-hour launch window opening at 6:24 pm EDT (22:24 UTC). You can watch NASA’s live coverage of the countdown and launch in the YouTube stream embedded below.

[embedded content]

The full Moon, Artemis II’s destination, will rise over the eastern horizon at the spaceport during the launch window.

Looking at the Moon has taken on a new meaning for the Artemis II astronauts since their selection for the mission three years ago. Artemis II is the first crew mission for NASA’s Artemis program. The long-term goal of Artemis is to build a sustained human presence at the Moon, with a lunar base at the Moon’s south pole, to set the stage for future expeditions to Mars.

https://arstechnica.com/space/2026/04/launch-day-has-arrived-for-nasas-artemis-ii-mission-heres-what-to-expect/