An ancient and enormous organism called Prototaxites, initially found to be a type of fungus, may actually be an unknown branch of life, researchers say. When you purchase through links on our site, we may earn an affiliate commission. Here's how it works. A bizarre ancient life-form, considered to be the first giant organism to live on land, may belong to a totally unknown branch of the tree of life, scientists say. These organisms, named Prototaxites, lived around 420 million to 375 million years ago during the Devonian period and resembled branchless, cylindrical tree trunks. These organisms would have been massive, with some species growing up to 26 feet (8 meters) tall and 3 feet (1 meter) wide. Since the first Prototaxites fossil was discovered in 1843, scientists haven't been sure whether they were a plant, fungus or even a type of algae. However, chemical analyses of Prototaxites fossils in 2007 suggested they were likely a giant ancient fungus. Now, according to a paper published March 17 on the preprint server bioRxiv, Prototaxites might not have been a humongous fungus after all — rather, it may have been an entirely different and previously unknown life-form. The study has not yet been peer-reviewed. All life on Earth is classified within three domains — bacteria, archaea and eukarya — with eukarya containing all multicellular organisms within the four kingdoms of fungi, animals, plants and protists. Bacteria and archaea contain only single-celled organisms. Previous chemical analysis of Prototaxites fossils indicated that they likely fed off decaying organisms, just like many fungi do today, rather than making their food from carbon dioxide in the air like plants. However, according to this new research, Prototaxites may actually have been part of a totally different kingdom of life, separate from fungi, plants, animals and protists. Get the world's most fascinating discoveries delivered straight to your inbox. The researchers studied the fossilized remains of one Prototaxites species named Prototaxites taiti, found preserved in the Rhynie chert, a sedimentary deposit of exceptionally well-preserved fossils of early land plants and animals in Scotland. This species was much smaller than many other species of Prototaxites, only growing up to a few inches tall, but it is still the largest Prototaxites specimen found in this region. Upon examining the internal structure of the fossilized Prototaxites, the researchers found that its interior was made up of a series of tubes, similar to those within a fungus. But these tubes branched off and reconnected in ways very unlike those seen in modern fungi. "We report that Prototaxites taiti was the largest organism in the Rhynie ecosystem and its anatomy was fundamentally distinct from all known extant or extinct fungi," the researchers wrote in the paper. "We therefore conclude that Prototaxites was not a fungus, and instead propose it is best assigned to a now entirely extinct terrestrial lineage." True fungi from the same period have also been preserved in the Rhynie chert, enabling the researchers to chemically compare them to Prototaxites. In addition to their unique structural characteristics, the team found that the Prototaxites fossils left completely different chemical signatures to the fungi fossils, indicating that the Prototaxites did not contain chitin, a major building block of fungal cell walls and a hallmark of the fungal kingdom. The Prototaxites fossils instead appeared to contain chemicals similar to lignin, which is found in the wood and bark of plants. "We conclude that the morphology and molecular fingerprint of P. taiti is clearly distinct from that of the fungi and other organism preserved alongside it in the Rhynie chert, and we suggest that it is best considered a member of a previously undescribed, entirely extinct group of eukaryotes," the researchers wrote. Kevin Boyce, a professor at Stanford University, led the 2007 study that posited Prototaxites is a giant fungus and was not involved in this new research. However, he told the New Scientist that he agreed with the study's findings. —Scientists discover new 15 million-year old fish with last meal fossilized inside its stomach —30,000-year-old fossilized vulture feathers 'nothing like what we usually see' preserved in volcanic ash —Iguanas sailed one-fifth of the way around the world on rafts 34 million years ago "Given the phylogenetic information we have now, there is no good place to put Prototaxites in the fungal phylogeny," Boyce said. "So maybe it is a fungus, but whether a fungus or something else entirely, it represents a novel experiment with complex multicellularity that is now extinct and does not share a multicellular common ancestor with anything alive today." More research into Prototaxites fossils needs to be done to determine if they were fungi or a completely different type of life, and what caused them to go extinct millions of years ago. "The conclusion that it is a completely unknown eukaryote certainly creates an air of mystery and intrigue around it — probably not likely to be solved until more fossils are discovered or new analytical techniques developed," Brett Summerell, a plant pathologist and fungi expert at the Botanic Gardens of Sydney, Australia, who not involved in this new study, told the New Scientist. Jess Thomson is a freelance journalist. She previously worked as a science reporter for Newsweek, and has also written for publications including VICE, The Guardian, The Cut, and Inverse. Jess holds a Biological Sciences degree from the University of Oxford, where she specialised in animal behavior and ecology. Please logout and then login again, you will then be prompted to enter your display name. How many species of insects are there on Earth? Scientists thought sharks didn't make sounds — until this accidental discovery James Webb telescope zooms in on bizarre 'Einstein ring' caused by bending of the universe Live Science is part of Future US Inc, an international media group and leading digital publisher. Visit our corporate site. © Future US, Inc. Full 7th Floor, 130 West 42nd Street, New York, NY 10036.

The strange sight is actually two galaxies, with the light of the second warped around the one at the front as a result of its massive gravity. When you purchase through links on our site, we may earn an affiliate commission. Here's how it works. The James Webb Space Telescope (JWST) has captured a stunning image of a bizarre astronomical optical illusion. This "rare cosmic phenomenon", called an Einstein ring, appears as a single eye-like orb in the darkness of space, but is actually a distorted view of two distant galaxies in the constellation Hydrus. In the bright center of this cosmic spectacle is one galaxy, while the stretched orange and blue color surrounding it is the light from another galaxy located behind it. The light from the more distant galaxy looks like a ring because it has been distorted by gravitational lensing. Gravitational lensing occurs when the gravity of a massive object — like a galaxy or a black hole — bends the light from a more distant object. This effect is a direct consequence of Einstein's theory of relativity, which states that mass warps the fabric of space-time, causing light to follow curved paths, like a ball rolling down a curved slope. "This effect is much too subtle to be observed on a local level, but it sometimes becomes clearly observable when dealing with curvatures of light on enormous, astronomical scales," ESA representatives wrote in a statement. This latest image was released by ESA and the Canadian Space Agency today (March 27) as their March picture of the month. It was captured by JWST's Near-InfraRed Camera instrument and also includes data from the Wide Field Camera 3 and the Advanced Camera for Surveys instruments on the Hubble Space Telescope. Related: 42 jaw-dropping James Webb Space Telescope images Get the world's most fascinating discoveries delivered straight to your inbox. Einstein rings like these are created when the distant light source, the massive lensing object, and the observer are perfectly aligned, resulting in the light appearing as a complete ring wrapped around the lensing object. As a result, they are rare. In this case, the elliptical galaxy in the foreground — which is part of a galaxy cluster named SMACSJ0028.2-7537 — is so massive that it is bending the light of the spiral galaxy situated far behind it. "Even though its image has been warped as its light travelled around the galaxy in its path, individual star clusters and gas structures are clearly visible," according to the statement The fascinating phenomenon of gravitational lensing also allows astronomers to better understand the universe. —James Webb telescope captures auroras on Neptune for first time ever —James Webb telescope reveals 'cosmic tornado' in best detail ever — and finds part of it is not what it seems —'Unlike any objects we know': Scientists get their best-ever view of 'space tornadoes' howling at the Milky Way's center Light emitted from distant galaxies, which existed long ago in the past, is often too faint to be observed directly from Earth. Strong gravitational lensing magnifies these galaxies, making them appear larger and brighter, and allowing astronomers to study some of the first galaxies formed after the Big Bang. "Objects like these are the ideal laboratory in which to research galaxies too faint and distant to otherwise see," the ESA statement noted. Additionally, because black holes and dark matter don't emit light, scientists can use gravitational lensing to detect and study these phenomena by measuring how they bend and magnify background stars. Jess Thomson is a freelance journalist. She previously worked as a science reporter for Newsweek, and has also written for publications including VICE, The Guardian, The Cut, and Inverse. Jess holds a Biological Sciences degree from the University of Oxford, where she specialised in animal behavior and ecology. Please logout and then login again, you will then be prompted to enter your display name. How to watch Saturday's sunrise 'devil horn' solar eclipse online for free James Webb telescope captures auroras on Neptune for first time ever How to watch Saturday's sunrise 'devil horn' solar eclipse online for free Live Science is part of Future US Inc, an international media group and leading digital publisher. Visit our corporate site. © Future US, Inc. Full 7th Floor, 130 West 42nd Street, New York, NY 10036.

Only $2.99 a month The evidence for Majorana qubits didn't win over many skeptics at the Global Physics Summit Microsoft's topological quantum chip, the Majorana 1 (pictured), could be a boon to quantum computing, but some physicists are skeptical that the chip does what's claimed. Microsoft By Emily Conover 4 hours ago ANAHEIM, CALIF. — At the world's largest gathering of physicists, a talk about Microsoft's claimed new type of quantum computing chip was perhaps the main attraction. Microsoft's February announcement of a chip containing the first topological quantum bits, or qubits, has ignited heated blowback in the physics community. The discovery was announced by press release, without publicly shared data backing it up. A concurrent paper in Nature fell short of demonstrating a topological qubit. Microsoft researcher Chetan Nayak, a coauthor on that paper, promised to provide solid evidence during his March 18 talk at the American Physical Society's Global Physics Summit. Before the talk, the chair of the session made an announcement: Follow the code of conduct; treat others with respect. The room, jam-packed with hundreds of eager physicists filling the seats and standing along the walls, chuckled knowingly at the implication that decorum might be lost. Topological quantum computing has had a dark shadow cast upon it by a series of retracted claims. Nevertheless, the concept holds great promise. The qubits that make up quantum computers are notoriously fragile and error-prone. Qubits that harness the concepts of topology, the mathematical discipline that describes structures with holes or loops, might improve on this. With topological quantum computing, “you can have very low error rates,” Nayak, of Microsoft's Station Q in Santa Barbara, Calif., said during his talk. Scientists were not wowed by the data he presented. A key plot looked like random jitter, rather than an identifiable signal. Nayak claimed that an analysis of that apparent randomness revealed a pattern underlying the noise, suggesting a working qubit. That argument wasn't enough to flip the harshest critics. “The data was incredibly unconvincing. It is as if Microsoft Quantum was attempting a simultaneous Rorschach test on hundreds of people,” says physicist Henry Legg of the University of St. Andrews in Scotland, one of the fiercest critics of Microsoft's work. Still, others were optimistic that, with additional effort, Microsoft could improve their device to produce a clearer signal. “I felt like it was maybe a bit premature to call it a qubit,” says physicist Kartiek Agarwal of Argonne National Laboratory in Lemont, Ill. But “there's very many positive signs.” Quantum computers promise to unlock new types of calculations, but only if they can be made reliable. The idea of building a qubit that is intrinsically less error-prone has excited scientists. “It's one of the more creative, more original approaches to quantum computing, and in this sense, I've really been rooting for it,” says physicist Ivar Martin of Argonne National Laboratory. But the idea has struggled to get off the ground, trailing decades behind more conventional qubit technologies. Creating a topological qubit requires provoking electrons in a material to dance just-so. The electron collective behaves like a hypothetical, particle-ish thing: a quasiparticle known as a Majorana. But creating Majoranas, and proving they exist, has been extremely challenging. Sponsor Message Microsoft has made impressive strides, Martin notes. But “as far as demonstrating things which people at this meeting would care about the most — really convincingly showing physics of Majoranas — it's underwhelming to many.” If it's possible to be less-than-underwhelmed, that would describe Legg, who gave a talk the day before Nayak's. He expressed doubts about the very foundation of Microsoft's method in a room filled to bursting — albeit a significantly smaller room than Nayak's headliner venue. In his talk, squeezed into the meeting's schedule at the last minute, Legg listed a litany of criticisms. The critique centered on the method used to demonstrate that the device is topological in the first place — the “topological gap protocol,” laid out in a 2023 Microsoft paper in Physical Review B. That protocol was flawed, he argued in his talk and in a paper submitted March 11 to arXiv.org. For example, Legg argued, the protocol gives different results for the same data, depending on the range of the parameters included, such as the spread of magnetic field or voltage values. “Any company claiming to have a topological qubit in 2025 is essentially selling a fairytale, and I think it's a dangerous fairytale,” Legg said. “It undermines the field of quantum computation and, in general, I think it undermines, actually, the public's confidence in science.” During a Q&A immediately after Legg's talk, Microsoft researcher Roman Lutchyn rose with a forceful rebuttal: “A lot of statements here are just simply incorrect,” he said, ticking through several of Legg's claims, which he also addressed in a LinkedIn post. “We stand behind the results in these papers.” At their most basic level, Microsoft's devices consist of aluminum nanowires, just 60 nanometers wide, laid atop a semiconductor. When cooled, this aluminum becomes superconducting, allowing it to transmit electricity without resistance. This induces superconductivity in the semiconductor, creating ideal conditions for Majoranas. Once the device is tuned to particular values of magnetic field and voltage, Majoranas should theoretically appear at each end of the nanowires. Disorder in these devices is a big problem for topological qubits. Surface roughness or material defects can result in spurious signals or ambiguous results. In recent years, Microsoft's devices have improved enormously in that regard, says physicist Sankar Das Sarma of the University of Maryland in College Park. But, he says, “some more improvement is needed.… I think disorder still needs to go down by another factor of two.” When the aluminum threads are arranged in an H shape, they create a qubit with Majoranas at each of its four ends. To claim a working qubit, Microsoft needed to show that they could perform measurements on it. This involves probing quantum dots, hot dog–shaped nanoparticles laid out near the nanowires. Two types of measurements, known as X and Z, are necessary. Microsoft's new qubit looks like a H on its side. It's made of two nanowires (green, in this rendering) connected by a third (gray). Two quantum dots (hot dog shapes) allow two different types of measurements, X and Z (indicated by dotted lines). The qubit is based on quasiparticles called Majoranas which should reside at the wires' ends (red). In the February Nature paper, Microsoft demonstrated a Z measurement, which involves probing the quantum dot associated with a single wire. Repeated Z measurements revealed the qubit switching between two possible states, the expected outcome for a topological qubit. These transitions purportedly indicated flips in parity, essentially reflecting whether there were an even or odd number of electrons within a wire. During Nayak's talk, he unveiled their X measurement, which probes a quantum dot adjacent to two nanowires. The plot of these data looked random, lacking the same obvious flip-flopping between two values. The audience did not seem particularly impressed. During the Q&A, Cornell University physicist Eun-Ah Kim said, “I would have loved this to just come out screaming at me that there's only two, but I don't think that's what I see.” Nayak said that a statistical analysis of the random-looking data revealed a hidden pattern. But, in an email, Kim questioned the validity of Nayak's method for teasing out this pattern. Even regarding the clearer Z measurement, scientists still don't agree whether this flipping constitutes evidence for Majoranas. “I'm persuaded,” Das Sarma says, “but people of goodwill could disagree.” During the talk, attendees raised smartphones high to snap photos of Nayak's slides, which rocketed around the physics community. Just after the presentation, physicist Sergey Frolov of the University of Pittsburgh, who was not at the meeting, posted a detailed rebuttal on the social media platform BlueSky. “[T]he data shown are … just noise. They are simply disappointing,” wrote Frolov. This, he suggested, doesn't bode well for the chip containing eight qubits that Microsoft announced in February: “That chip cannot possibly work, given what we saw today.” Not all scientists are quite as critical as Legg and Frolov. Agarwal, for example, thinks Microsoft's topological gap protocol, the foundation of their current work, is sound. But, he notes, the device Nayak presented is impractical, given that its values appear essentially random. “It certainly can't be used as a qubit in its present state. That's also clearly obvious,” Agarwal says. Nayak is confident that his team will improve their devices further, until skeptics are convinced. Frolov, for one, is confident that more paper retractions are coming. Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ C. Nayak. Towards topological quantum computing using InAs-Al hybrid devices. Global Physics Summit, Anaheim, Calif., March 18, 2025. H.F. Legg. Can we build a topological qubit in 2025? Global Physics Summit, Anaheim, Calif., March 17, 2025. H.F. Legg. Comment on "Interferometric single-shot parity measurement in InAs-Al hybrid devices", Microsoft Quantum, Nature 638, 651-655 (2025). arXiv:2503.08944. Submitted March 11, 2025. Microsoft Azure Quantum. Interferometric single-shot parity measurement in InAs–Al hybrid devices. Nature. Vol. 638, February 20, 2025, p. 651. doi: 10.1038/s41586-024-08445-2. Microsoft Quantum. InAs-Al hybrid devices passing the topological gap protocol. Physical Review B. Vol. 107, June 21, 2023, 245423. doi: 10.1103/PhysRevB.107.245423. Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. 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Archaeologists are unsure why unrelated teenagers were buried in an elaborate Bronze Age tomb but think their age may be a clue. When you purchase through links on our site, we may earn an affiliate commission. Here's how it works. Five millennia ago, Bronze Age people in Mesopotamia built elaborate stone tombs full of spectacular grave goods and human sacrifices. Researchers are unsure of the meaning of this ritual, but a new study of the skeletons points to a clue: the age at which people were sacrificed and their biological sex. "The fact that they are mostly adolescents is fascinating and surprising," David Wengrow, a professor of comparative archaeology at University College London, told Live Science. "It highlights how little thought scientists and historians have really given to the importance of adolescence as a crucial stage in the human life cycle." The finding may also upend assumptions about the type of government this culture practiced. Previously, it was thought to be a king-led hierarchical society, but these burials hint at a more egalitarian organization. Wengrow and colleagues have studied a series of skeletons found at the archaeological site of Başur Höyük on the Upper Tigris River in southeastern Turkey. Once part of ancient Mesopotamia, Başur Höyük is dated to between 3100 and 2800 B.C. Several stone tombs were discovered there a decade ago, full of hundreds of copper artifacts, textiles and beads. In a previous study, researchers identified a burial of two 12-year-old children flanked by eight violently killed people and suggested the funeral ritual indicated the rise of an early state that included "royal" tombs with "retainer sacrifice." But in a new study, published March 17 in the Cambridge Archaeological Journal, the researchers conducted ancient DNA analysis on a separate set of skeletons and presented a more nuanced view of the cemetery, focusing on the idea of adolescence as an important life stage in this society. Related: Massive Mesopotamian canal network unearthed in Iraq Get the world's most fascinating discoveries delivered straight to your inbox. Ancient DNA analysis of nine skeletons from Başur Höyük showed that the people were not biologically related to one another. The DNA also showed that most of the people the researchers tested were female. "So we are dealing with adolescents brought together, or coming together voluntarily, from biologically unrelated groups to carry out a very extreme form of ritual," Wengrow said. The meaning of the ritual, however, is still unclear. Previously, researchers thought that the main burials represented young royals with their sacrificed attendants. But this interpretation was based on the idea that early Bronze Age societies had evolved into large-scale states with a king at the top of the social hierarchy. There is now more archaeological evidence that Bronze Age political systems were more flexible. Societies in Mesopotamia could have regularly switched between hierarchical, king-based rule and a more egalitarian social organization where people collectively make decisions. "The idea that humans evolved to live in just one form of society almost all the time is almost certainly wrong," Wengrow said. If Başur Höyük was one of these more fluid societies, the "royal" burial may be better explained as a complex and potentially age-related funeral tradition. "Much more likely, what we see in the cemetery is a subset of a larger group, other members of which survived the ritual process and went on to full adulthood," Wengrow said. This larger group can be called an "age set," according to the study. In general, in egalitarian societies, leadership is earned instead of inherited, but "age sets" and gender can also come into play. For instance, elders may be valued for their wisdom and experience, while adolescents may be valued for their hunting skills. In the case of the Bronze Age burials in Turkey, this "age set" of adolescents could represent initiates into an ancient cult or victims of inter-group competition or violence, the researchers note in their study. —Origins of world's earliest writing point to symbols on 'seals' used in Mesopotamian trade —5,000-year-old artifacts in Iraq hint at mysterious collapse of one of the world's 1st governments —People have been dumping corpses into the Thames since at least the Bronze Age, study finds Few researchers focus on adolescence in ancient societies, the researchers noted in their study, so the Başur Höyük burials suggest that it is important to investigate age sets in early Bronze Age states rather than assuming the society was led by kings and other royals at the top of a political hierarchy. Further research on the skeletons is forthcoming, Wengrow said, in terms of stable isotope analysis to figure out the origins of the people buried at Başur Höyük. "For now, all we can say is that many of the teenagers buried in the tombs were not local to the area of the cemetery," he said. Kristina Killgrove is a staff writer at Live Science with a focus on archaeology and paleoanthropology news. Her articles have also appeared in venues such as Forbes, Smithsonian, and Mental Floss. Killgrove holds postgraduate degrees in anthropology and classical archaeology and was formerly a university professor and researcher. She has received awards from the Society for American Archaeology and the American Anthropological Association for her science writing. Please logout and then login again, you will then be prompted to enter your display name. Why modern humans have smaller faces than Neanderthals and chimpanzees Archaeologists may have finally discovered famous 'lost' canal built by Julius Caesar's uncle Sony A7R V review: A 61-megapixel giant Live Science is part of Future US Inc, an international media group and leading digital publisher. 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The James Webb Space Telescope has successfully detected auroras on Neptune for the first time ever, finishing a job that NASA's Voyager 2 probe began decades ago. When you purchase through links on our site, we may earn an affiliate commission. Here's how it works. New James Webb Space Telescope (JWST) images have captured auroras on Neptune for the first time. The telescope spotted infrared auroras that create exotic molecules known as trihydrogen cations, according to a study published March 26 in Nature. Scientists identified auroras on Jupiter, Saturn, and Uranus more than 30 years ago, but Neptune's auroras staunchly evaded detection until now. Auroras form when energetic, charged particles from the sun get caught up in a planet's magnetic field. The field funnels the particles toward the planet's magnetic poles, where they collide with — and ionize — atmospheric molecules along the way, causing them to glow. Unlike auroras on Earth, which occur at extreme northern and southern latitudes near our planet's North and South Pole, Neptune's auroras appear near the planet's mid-latitudes. That's because Neptune's magnetic field is tilted 47 degrees off its rotational axis, so the planet's magnetic poles lie between the geographic poles and the equator — around where South America would be located on Earth. And unlike the Northern Lights, Neptune's auroras aren't visible to the naked eye. "Turns out, actually imaging the auroral activity on Neptune was only possible with Webb's near-infrared sensitivity," Henrik Melin, a planetary scientist at Northumbria University in the U.K., said in a statement. "It was so stunning to not just see the auroras, but the detail and clarity of the signature really shocked me." In June 2023, researchers used JWST's Near-Infrared Spectrograph to look for the trihydrogen cation (H3+), a hallmark of auroral activity in the hydrogen-rich atmospheres of the solar system's gas giants. NASA's Voyager 2 probe flew by Neptune in 1989, but it didn't have the right equipment to detect the cation. Since then, scientists at ground-based facilities, such as Hawaii's Keck telescope and NASA Infrared Telescope Facility, have looked for this molecule in Neptune's atmosphere without success, despite predictions that it should be present. Get the world's most fascinating discoveries delivered straight to your inbox. Related: 'Hidden' rings of Uranus revealed in dazzling new James Webb telescope images This time, JWST detected H3+, but researchers also noted unexpected changes in Neptune's atmosphere. "I was astonished — Neptune's upper atmosphere has cooled by several hundreds of degrees [since the Voyager flyby]," Melin said in the statement. "In fact, the temperature in 2023 was just over half of that in 1989." —Mystery of Jupiter's powerful X-ray auroras finally solved —Do extraterrestrial auroras occur on other planets? —James Webb telescope to zoom in on Uranus and Saturn in study of mysterious auroras These cold temperatures could be why scientists haven't detected H3+ on Neptune until now. The auroras appear much fainter at cold temperatures, and light reflecting off Neptune's clouds may have drowned them out, the researchers said. "As we look ahead and dream of future missions to Uranus and Neptune, we now know how important it will be to have instruments tuned to the wavelengths of infrared light to continue to study the auroras," study coauthor Leigh Fletcher, a planetary scientist at Leicester University in the U.K., said in the statement. "This observatory has finally opened the window onto this last, previously hidden ionosphere of the giant planets." Skyler Ware is a freelance science journalist covering chemistry, biology, paleontology and Earth science. She was a 2023 AAAS Mass Media Science and Engineering Fellow at Science News. Her work has also appeared in Science News Explores, ZME Science and Chembites, among others. Skyler has a Ph.D. in chemistry from Caltech. Please logout and then login again, you will then be prompted to enter your display name. Current AI models a 'dead end' for human-level intelligence, scientists agree 'We will fight for him': Author John Green meets Henry Reider, a young tuberculosis patient with drug-resistant disease 'Fish odor syndrome': A rare metabolic condition that makes sweat smell like rotten fish Live Science is part of Future US Inc, an international media group and leading digital publisher. Visit our corporate site. © Future US, Inc. Full 7th Floor, 130 West 42nd Street, New York, NY 10036.

Every print subscription comes with full digital access A U.S. return to underground detonations would have wide-ranging implications In 1946, the United States conducted this nuclear test at Bikini Atoll. Tests moved underground in the 1960s to limit nuclear fallout. After decades of hiatus, the United States may resume underground tests, some experts say. Science History Images/Alamy Stock Photo By Emily Conover 4 hours ago When the countdown hit zero on September 23, 1992, the desert surface puffed up into the air, as if a giant balloon had inflated it from below. It wasn't a balloon. Scientists had exploded a nuclear device hundreds of meters below the Nevada desert, equivalent to thousands of tons of TNT. The ensuing fireball reached pressures and temperatures well beyond those in Earth's core. Within milliseconds of the detonation, shock waves rammed outward. The rock melted, vaporized and fractured, leaving behind a cavity oozing with liquid radioactive rock that puddled on the cavity's floor. As the temperature and pressure abated, rocks collapsed into the cavity. The desert surface slumped, forming a subsidence crater about 3 meters deep and wider than the length of a football field. Unknown to the scientists working on this test, named Divider, it would be the end of the line. Soon after, the United States halted nuclear testing. Beginning with the first explosive test, known as Trinity, in 1945, more than 2,000 atomic blasts have rattled the globe. Today, that nuclear din has been largely silenced, thanks to the norms set by the Comprehensive Nuclear-Test-Ban Treaty, or CTBT, negotiated in the mid-1990s. Only one nation — North Korea — has conducted a nuclear test this century. But researchers and policy makers are increasingly grappling with the possibility that the fragile quiet will soon be shattered. Some in the United States have called for resuming testing, including a former national security adviser to President Donald Trump. Officials in the previous Trump administration considered testing, according to a 2020 Washington Post article. And there may be temptation in coming years. The United States is in the midst of a sweeping, decades-long overhaul of its aging nuclear arsenal. Tests could confirm that old weapons still work, check that updated weapons perform as expected or help develop new types of weapons. Meanwhile, the two major nuclear powers, the United States and Russia, remain ready to obliterate one another at a moment's notice. If tensions escalate, a test could serve as a signal of willingness to use the weapons. Testing “has tremendous symbolic importance,” says Frank von Hippel, a physicist at Princeton University. “During the Cold War, when we were shooting these things off all the time, it was like war drums: ‘We have nuclear weapons and they work. Better watch out.' ” The cessation of testing, he says, was an acknowledgment that “these [weapons] are so unusable that we don't even test them.” Many scientists maintain that tests are unnecessary. “What we've been saying consistently now for decades is there's no scientific reason that we need to test,” says Jill Hruby, who was the administrator of the National Nuclear Security Administration, or NNSA, during the Biden administration. That's because the Nevada site, where nuclear explosions once thundered regularly, hasn't been mothballed entirely. There, in an underground lab, scientists are performing nuclear experiments that are subcritical, meaning they don't kick off the self-sustaining chains of reactions that define a nuclear blast. Many scientists argue that subcritical experiments, coupled with computer simulations using the most powerful supercomputers on the planet, provide all the information needed to assess and modernize the weapons. Subcritical experiments, some argue, are even superior to traditional testing for investigating some lingering scientific puzzles about the weapons, such as how they age. Others think that subcritical experiments and simulations, no matter how sophisticated, can't replace the real thing indefinitely. But so far, the experiments and detailed assessments of the stockpile have backed up the capabilities of the nuclear arsenal. And those experiments avoid the big drawbacks of tests. Sponsor Message “A single United States test could trigger a global chain reaction,” says geologist Sulgiye Park of the Union of Concerned Scientists, a nonprofit advocacy group. Other nuclear powers would likely follow by setting off their own test blasts. Countries without nuclear weapons might be spurred to develop and test them. One test could kick off a free-for-all. “It's like striking a match in a roomful of dynamite,” Park says. The logic behind nuclear weapons involves mental gymnastics. The weapons can annihilate entire cities with one strike, yet their existence is touted as a force for peace. The thinking is that nuclear weapons act as a deterrent — other countries will resist using a nuclear weapon, or making any major attack, in fear of retaliation. The idea is so embedded in U.S. military circles that a type of intercontinental ballistic missile developed during the Cold War was dubbed Peacekeeper. Since the end of testing, the world seems to have taken a slow, calming exhale. Global nuclear weapons tallies shrunk from more than 70,000 in the mid-1980s to just over 12,000 today. That pullback was due to a series of treaties between the United States and Russia (previously the Soviet Union). Nuclear weapons largely fell from the forefront of public consciousness. Since the first nuclear weapons test in 1945, there have been more than 2,000 tests. In the 1960s, countries began performing tests underground over fears of radioactive fallout. In the 1990s, nuclear testing largely ended with the arrival of the Comprehensive Nuclear-Test-Ban Treaty. The only country to test nuclear weapons in the 21st century is North Korea. Its last known test was in 2017. But now there's been a sharp inhale. The last remaining arms-control treaty between the United States and Russia, New START, is set to expire in 2026, giving the countries free rein on numbers of deployed weapons. Russia already suspended its participation in New START in 2023 and revoked its ratification of the Comprehensive Nuclear-Test-Ban Treaty to mirror the United States and a handful of other countries that signed but never ratified the treaty. (The holdouts prevented the treaty from officially coming into force, but nations have abided by it anyway.) Nuclear threats by Russia have been a regular occurrence during the ongoing war in Ukraine. And China, with the third-largest stockpile, is rapidly expanding its cache, highlighting a potential future in which there are three main nuclear powers, not just two. “There is this increasing perception that this is a uniquely dangerous moment.… We're in this regime where all the controls are coming off and things are very unstable,” says Daniel Holz, a physicist at the University of Chicago and chair of the Science and Security Board of the Bulletin of the Atomic Scientists, a nonprofit that aims to raise awareness of the peril of nuclear weapons and other threats. In January, the group set its metaphorical Doomsday Clock at 89 seconds to midnight — the closest it has ever been. Some see the ability to test as a necessity for a world in which nuclear weapons are a rising threat. “We are seeing an environment in which the autocrats are increasingly relying on nuclear weapons to threaten and coerce their adversaries,” says Robert Peters, a research fellow at the Heritage Foundation, a conservative think tank. “If you're in an acute crisis or conflict in which your adversary is threatening to employ nuclear weapons, you don't want to limit the options of the president to get you out of that crisis.” Testing, and the signal it sends to an adversary, he argues, should be such an option. Peters advocates for shortening the time window for test preparations — currently estimated at two or three years — to three to six months. The Heritage Foundation's Project 2025 calls for “immediate test readiness.” The United States regularly considers the possibility of testing nuclear weapons. “It's a question that actually gets asked every year,” says Thom Mason, director of Los Alamos National Laboratory in New Mexico. Los Alamos is one of the three U.S. nuclear weapons labs, alongside Lawrence Livermore National Laboratory in California and Sandia National Laboratories in Albuquerque. Each year, the directors of the three labs coordinate detailed assessments of the stockpile's status, including whether tests are needed. “Up until this point, the answer has been ‘no,' ” Mason says. But if scientific concerns arose that couldn't be resolved otherwise or if weapons began unexpectedly deteriorating, that assessment could change. If a test were deemed necessary, exactly how long it would take to prepare would depend on the reasons for it. “If you're trying to answer a scientific question, then you probably need lots of instrumentation and that could take time,” Mason says. “If you're just trying to send a signal, then maybe you don't need as much of that; you're just trying to make the ground shake.” The area of the Nevada desert encompassing the test site is speckled with otherworldly Joshua trees and the saucer-shaped craters of past tests. In addition to 828 underground tests, 100 atmospheric tests were performed there, part of what's now known as the Nevada National Security Sites. Carved out of Western Shoshone lands, it sits 120 kilometers from Las Vegas. Radioactive fallout from atmospheric tests, which ceased in 1962, reached nearby Indian reservations and other communities — a matter that is still the subject of litigation. By moving tests underground, officials aimed to contain the nuclear fallout and limit its impact on human health. Before an underground test, workers outfitted a nuclear device with scientific instruments and lowered it into a hole drilled a few hundred meters into the earth. The hole was then filled with sand, gravel and other materials. As personnel watched a video feed from the safety of a bunker, the device was detonated. “You see the ground pop, and you see the dust come up and then slowly settle back down. And then eventually you see the subsidence crater form. It just falls in on itself,” says Marvin Adams, a nuclear engineer who was deputy administrator for NNSA's Defense Programs during the Biden administration. “There was always a betting pool on how long that would take before the crater formed. And it could be seconds, or it could be days.” Kilometers' worth of cables fed information from the equipment to trailers where data were recorded. Meanwhile, stations monitored seismic signals and radioactivity. Later, another hole would be drilled down into the cavity and rock samples taken to determine the explosion's yield. Today, such scenes have gone the way of the '90s hairstyles worn in photos of underground test preparation. They've been replaced by subcritical experiments, which use chemical explosives to implode or shock plutonium, the fuel at the heart of U.S. weapons, in a facility called the Principal Underground Laboratory for Subcritical Experimentation, PULSE. The experiments mimic what goes on in a real weapon but with one big difference. Weapons are supercritical: The plutonium is compressed enough to sustain chains of nuclear fission reactions, the splitting of atomic nuclei. The chain reactions occur because fission spits out neutrons that, in a supercritical configuration, can initiate further fissions, which release more neutrons, and so on. A subcritical experiment doesn't smoosh the plutonium enough to beget those fissions upon fissions that lead to a nuclear explosion. The PULSE facility consists of 2.3 kilometers of tunnels nearly 300 meters below the surface. There, a machine called Cygnus takes X-ray images of the roiling plutonium when it's blasted with chemical explosives in subcritical experiments. X-rays pass through the plutonium and are detected on the other side. Just as a dentist uses an X-ray machine to see inside your mouth, the X-rays illuminate what's happening inside the experiment. Glimpses of such experiments are rare. A video of a 2012 subcritical experiment shows a dimly lit close-up of the confinement vessel that encloses the experiment over audio of a countdown and a piercing beeping noise, irritating enough that it must be signifying something important is about to happen. When the countdown ends, there's a bang, and the beeping stops. That's it. It's a far cry from the mushroom clouds of yesteryear. The experiments are a component of the U.S. stockpile stewardship program, which ensures the weapons' status via a variety of assessments, experiments and computer simulations. PULSE is now being expanded to beef up its capabilities. A new machine called Scorpius is planned to begin operating in 2033. It will feature a 125-meter-long particle accelerator that will blast electrons into a target to generate X-rays that are more intense and energetic than Cygnus', which will allow scientists to take images later in the implosion. What's more, Scorpius will produce four snapshots at different times, revealing how the plutonium changes throughout the experiment. And the upcoming ZEUS, the Z-Pinched Experimental Underground System, will blast subcritical experiments with neutrons and measure the release of gamma rays, a type of high-energy radiation. ZEUS will be the first experiment of its kind to study plutonium. Subcritical experiments help validate computer simulations of nuclear weapons. Those simulations then inform the maintenance and development of the real thing. The El Capitan computer, installed for this purpose at Lawrence Livermore in 2024, is the fastest supercomputer ever reported. That synergy between powerful computing and advanced experiments is necessary to grapple with the full complexity of modern nuclear weapons, in which materials are subject to some of the most extreme conditions known on Earth and evolve dramatically over mere instants. To maximize the energy released, modern weapons don't stop with fission. They employ a complex interplay between fission and fusion, the merging of atomic nuclei. First, explosives implode the plutonium, which is contained in a hollow sphere called a “pit.” This allows fission reactions to proliferate. The extreme temperatures and pressures generated by fission kick off fusion reactions in hydrogen contained inside the pit, blasting out neutrons that initiate additional fission. X-rays released by that first stage compress a second stage, generating additional fission and fusion reactions that likewise feed off one another. These principles have produced weapons 1,000 times as powerful as the bomb dropped on Hiroshima. To mesh simulations and experiments, scientists must understand their measurements in detail and carefully quantify the uncertainties involved. This kind of deep understanding wasn't as necessary, or even possible, in the days of explosive nuclear weapons test, says geophysicist Raymond Jeanloz of the University of California, Berkeley. “It's actually very hard to use nuclear explosion testing to falsify hypotheses. They're designed mostly to reassure everyone that, after you put everything together and do it, that it works.” Laboratory experiments can be done repeatedly, with parameters slightly changed. They can be designed to fail, helping delineate the border between success and failure. Nuclear explosive tests, because they were expensive, laborious one-offs, were designed to succeed. Stockpile stewardship has allowed scientists to learn the ins and outs of the physics behind the weapons. “We pay attention to every last detail,” Hruby says. “Through the science program, we now better understand nuclear weapons than we ever understood them before.” For example, Jeanloz says, in the era of testing, a quantity called the energy balance wasn't fully understood. It describes how much energy gets transferred from the primary to the secondary component in a weapon. In the past, that lack of understanding could be swept aside, because a test could confirm that the weapons worked. But with subcritical experiments and simulations, fudge factors must be eliminated to be certain a weapon will function. Quantifying that energy balance and determining the uncertainty was a victory of stockpile stewardship. This type of work, Jeanloz says, brought “the heart and soul, the guts of the scientific process into the [nuclear] enterprise.” Subcritical experiments are focused in particular on the quandary over how plutonium ages. Since 1989, the United States hasn't fabricated significant numbers of plutonium pits. That means the pits in the U.S. arsenal are decades old, raising questions about whether weapons will still work. An aging pit, some scientists worry, might cause the multistep process in a nuclear warhead to fizzle. For example, if the implosion in the first stage doesn't proceed properly, the second stage might not go off at all. Plutonium ages not only from the outside in — akin to rusting iron — but also from the inside out, says Siegfried Hecker, who was director of Los Alamos from 1986 to 1997. “It's constantly bombarding itself by radioactive decay. And that destroys the metallic lattice, the crystal structure of plutonium.” The decay leaves behind a helium nucleus, which over time may result in tiny bubbles of helium throughout the lattice of plutonium atoms. Each decay also produces a uranium atom that zings through the material and “beats the daylights out of the lattice,” Hecker says. “We don't quite know how much the damage is … and how that damaged material will behave under the shock and temperature conditions of a nuclear weapon. That's the tricky part.” One way to circumvent this issue is to produce new pits. A major effort under way will ramp up production. In 2024, the NNSA “diamond stamped” the first of these pits, meaning that the pit was certified for use in a weapon. The aim is for the United States to make 80 pits per year by 2030. But questions remain about new plutonium pits as well, Hecker says, as they rely on an updated manufacturing process. Hecker, whose tenure at Los Alamos straddled the testing and post-testing eras, thinks nuclear tests could help answer some of those questions. “Those people who say, ‘There is no scientific or technical reason to test. We can do it all with computers,' I disagree strongly.” But, he says, the benefits of performing a test would be outweighed by the big drawback: Other countries would likely return to testing. And those countries would have more to learn than the United States. China, for instance, has performed only 45 tests, while the United States has performed over 1,000. “We have to find other ways that we can reassure ourselves,” Hecker says. Other experts similarly thread the needle. Nuclear tests of the past produced plenty of surprises, such as yields that were higher or lower than predicted, physicist Michael Frankel, an independent scientific consultant, and colleagues argued in a 2021 report. While the researchers advise against resuming testing in the current situation, they expect that stockpile stewardship will not be sufficient indefinitely. “Too many things have gone too wrong too often to trust Lucy with the football one more time,” Frankel and colleagues wrote, referring to Charles Schulz's comic strip Peanuts. If we rely too much on computer simulations to conclude an untested nuclear weapon will work, we might find ourselves like Charlie Brown — flat on our backs. But other scientists have full faith in subcritical experiments and stockpile stewardship. “We have always found that there are better ways to answer these questions than to return to nuclear explosive testing,” Adams says. For many scientists, subcritical experiments are preferable, especially given the political ramifications of full-fledged tests. But the line between a nuclear test prohibited by the Comprehensive Nuclear-Test-Ban Treaty and an experiment that is allowed is not always clear. The CTBT is a “zero yield” treaty; experiments can release no energy beyond that produced by the chemical explosives. But, Adams says, “there's no such thing as zero yield.” Even in an idle, isolated hunk of plutonium, some nuclear fission happens spontaneously. That's a nonzero but tiny nuclear yield. “It's a ridiculous term,” he says. “I hate it. I wish no one had ever said it.” The United States has taken zero yield to mean that self-sustaining chain reactions are prohibited. U.S. government reports claim that Russia has performed nuclear experiments that surpass this definition of the zero yield benchmark and raise concerns about China's adherence to the standard. The confusion has caused finger-pointing and increased tensions. But countries might honestly disagree on the definition of a nuclear test, Adams says. For example, a country might allow “hydronuclear” experiments, which are supercritical but the amount of fission energy released is dwarfed by the energy from the chemical explosive. Such experiments would violate U.S. standards, but perhaps not those of Russia or another country. Even if everyone could agree on a definition, monitoring would be challenging. The CTBT provides for seismic and other monitoring, but detecting very-low-yield tests would demand new inspection techniques, such as measuring the radiation emanating from a confinement vessel used in an experiment. Tests that clearly break the rules, however, can be swiftly detected. The CTBT monitoring system can spot underground explosions as small as 0.1 kilotons, less than a hundredth that of the bomb dropped on Hiroshima. That includes the most recent nuclear explosive test, performed by North Korea in 2017. Despite being invisible, underground nuclear explosive tests have an impact. While an underground test is generally much safer than an open-air nuclear test, “it's not not risky,” Park says. The containment provided by an underground test isn't assured. In the 1970 Baneberry test in Nevada, a misunderstanding of the site's geology led to a radioactive plume escaping in a blowout that exposed workers on the site. While U.S. scientists learned from that mistake and haven't had such a major containment failure since, the incident suggests that performing an underground test in a rushed manner could increase the risks for an accident, Park says. Hecker is not too concerned about that possibility. “For the most part, I have good confidence that we could do underground nuclear testing without a significant insult to the environment,” he says. “It's not an automatic given.… Obviously there's radioactive debris that stays down there. But I think enough work has been done to understand the geology that we don't think there will be a major environmental problem.” While the United States knows its test sites well and has practice with underground testing, “other countries might not be as knowledgeable,” Hruby says. So if the United States starts testing and others follow, “the chance of a non-containment, a leak of some kind, certainly goes up.” A U.S. test, she says, is “a very bad idea.” Even if the initial containment is successful, radioactive materials could travel via groundwater. Although tests are designed to avoid groundwater, scientists have detected traces of plutonium in groundwater from the Nevada site. The plutonium traveled a little more than a kilometer in 30 years. “To a lot of people, that's not very far,” Park says. But “from a geology time scale, that's really fast.” Although not at a level where it would cause health effects, the plutonium had been expected to stay put. The craters left in the Nevada desert are a mark of each test's impact on structures deep below the surface. “There was a time when detonating either above ground or underground in the desert seemed like — well, that's just wasteland,” Jeanloz says. “Many would view it very differently now, and say, ‘No, these are very fragile ecosystems, so perturbing the water table, putting radioactive debris, has serious consequences.' ” The weight of public opinion is another hurdle. In the days of nuclear testing, protests at the site were a regular occurrence. That opposition persisted to the very end. On the day of the Divider test in 1992, four protesters made it to within about six kilometers of ground zero before being arrested. The disarmament movement continues despite the lack of testing. At a recent meeting of nuclear experts, the Nuclear Deterrence Summit in Arlington, Va., a few protesters gathered outside in the January cold, demanding that the United States and Russia swear off nuclear weapons for good. But that option was not on the meeting's agenda. During a break between sessions, the song that played — presumably unintentionally — was “Never Gonna Give You Up.” Questions or comments on this article? E-mail us at feedback@sciencenews.org | Reprints FAQ S. Park and R.C. Ewing. Environmental impacts of underground nuclear weapons testing. Bulletin of the Atomic Scientists. Published online March 7, 2024. doi: 10.1080/00963402.2024.2314439. U.S. Government Accountability Office. Nuclear weapons: Program management improvements would benefit U.S. efforts to build new experimental capabilities. Published online August 30, 2023. J. Scouras, G. Ullrich and M. Frankel. Tickling the sleeping dragon's tail: Should We Resume Nuclear Testing? Defense Technical Information Center. Published online May 10, 2021. Accession Number: AD1132778. Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers' Association Newsbrief award. We are at a critical time and supporting science journalism is more important than ever. Science News and our parent organization, the Society for Science, need your help to strengthen scientific literacy and ensure that important societal decisions are made with science in mind. Please subscribe to Science News and add $16 to expand science literacy and understanding. 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