'Bouncing' comets could deliver building blocks for life to exoplanets

How did the molecular building blocks for life end up on Earth? One long-standing theory is that they could have been delivered by comets. Now, researchers from the University of Cambridge have shown how comets could deposit similar building blocks to other planets in the galaxy.

In order to deliver organic material, comets need to be travelling relatively slowly -- at speeds below 15 kilometres per second. At higher speeds, the essential molecules would not survive -- the speed and temperature of impact would cause them to break apart.

The most likely place where comets can travel at the right speed are 'peas in a pod' systems, where a group of planets orbit closely together. In such a system, the comet could essentially be passed or 'bounced' from the orbit of one planet to another, slowing it down.

At slow enough speeds, the comet would crash on a planet's surface, delivering the intact molecules that researchers believe are the precursors for life. The results, reported in the Proceedings of the Royal Society A, suggest that such systems would be promising places to search for life outside our Solar System if cometary delivery is important for the origins of life.

Comets are known to contain a range of the building blocks for life, known as prebiotic molecules. For example, samples from the Ryugu asteroid, analysed in 2022, showed that it carried intact amino acids and vitamin B3. Comets also contain large amounts of hydrogen cyanide (HCN), another important prebiotic molecule. The strong carbon-nitrogen bonds of HCN make it more durable to high temperatures, meaning it could potentially survive atmospheric entry and remain intact.

"We're learning more about the atmospheres of exoplanets all the time, so we wanted to see if there are planets where complex molecules could also be delivered by comets," said first author Richard Anslow from Cambridge's Institute of Astronomy. "It's possible that the molecules that led to life on Earth came from comets, so the same could be true for planets elsewhere in the galaxy."

The researchers do not claim that comets are necessary to the origin of life on Earth or any other planet, but instead they wanted to place some limits on the types of planets where complex molecules, such as HCN, could be successfully delivered by comets.

Most of the comets in our Solar System sit beyond the orbit of Neptune, in what is known as the Kuiper Belt. When comets or other Kuiper Belt objects (KBOs) collide, they can be pushed by Neptune's gravity toward the Sun, eventually getting pulled in by Jupiter's gravity. Some of these comets make their way past the Asteroid Belt and into the inner Solar System.

"We wanted to test our theories on planets that are similar to our own, as Earth is currently our only example of a planet that supports life," said Anslow. "What kinds of comets, travelling at what kinds of speed, could deliver intact prebiotic molecules?"

Using a variety of mathematical modelling techniques, the researchers determined that it is possible for comets to deliver the precursor molecules for life, but only in certain scenarios. For planets orbiting a star similar to our own Sun, the planet needs to be low mass and it is helpful for the planet to be in close orbit to other planets in the system. The researchers found that nearby planets on close orbits are much more important for planets around lower-mass stars, where the typical speeds are much higher.

In such a system, a comet could be pulled in by the gravitational pull of one planet, then passed to another planet before impact. If this 'comet-passing' happened enough times, the comet would slow down enough so that some prebiotic molecules could survive atmospheric entry.

"In these tightly-packed systems, each planet has a chance to interact with and trap a comet," said Anslow. "It's possible that this mechanism could be how prebiotic molecules end up on planets."

For planets in orbit around lower-mass stars, such as M-dwarfs, it would be more difficult for complex molecules to be delivered by comets, especially if the planets are loosely packed. Rocky planets in these systems also suffer significantly more high-velocity impacts, potentially posing unique challenges for life on these planets.

The researchers say their results could be useful when determining where to look for life outside the Solar System.

"It's exciting that we can start identifying the type of systems we can use to test different origin scenarios," said Anslow. "It's a different way to look at the great work that's already been done on Earth. What molecular pathways led to the enormous variety of life we see around us? Are there other planets where the same pathways exist? It's an exciting time, being able to combine advances in astronomy and chemistry to study some of the most fundamental questions of all."

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Nature photographers posting to social media help with protecting biodiversity

Nature photographers posting to social media are helping improve biodiversity conservation mapping in South Asia, and the method could go global.

Dr Shawan Chowdhury from UQ's School of the Environment led an international team which scoured images on Facebook nature photography groups in Bangladesh, to add to the existing Global Biodiversity Information Facility database.

"We found 44,000 photos of almost 1,000 animal species, including many birds and insects, 288 of which are considered threatened in Bangladesh," Dr Chowdhury said.

"This has vastly improved habitat mapping across the country where only 4.6 per cent of land is designated as protected.

"We identified many more high-priority areas for conservation, spanning 4,000 square kilometres for birds and 10,000 square kilometres for butterflies.

"We'd been missing out on the distribution data of hundreds of endangered species in Bangladesh so this is a big result.

"This could change the way scientists gather biodiversity information in the future, especially in regions where there is a lack of reliable and up-to-date structured monitoring to inform conservation efforts."

In Australia, social media posts are being used to track pest species.

"A South Asian butterfly, called the tawny coster, entered Australia in 2012," Dr Chowdhury said.

"We've searched for additional locality records from Facebook to analyse the movement, ecology and colonisation status of this species and shown that it expanded at about 135 kilometres per year in Australia between 2012 and 2020."

Co-author Professor Richard Fuller from UQ said while Facebook had been helpful, there are some big opportunities for social media companies.

"There is currently no automated way to collect this information, and it was a very arduous task for us to do it manually." Professor Fuller said.

"We hope our research can inspire the development of technology such as an app that transfers biodiversity data posted on Facebook directly to the global biodiversity databases.

"This way, conservation scientists can easily access that data and use it."

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Birds set foot near South Pole in Early Cretaceous, Australian tracks show

The discovery of 27 avian footprints on the southern Australia coast -- dating back to the Early Cretaceous when Australia was still connected to Antarctica -- opens another window onto early avian evolution and possible migratory behavior.

PLOS ONE published the discovery of some of the oldest, positively identified bird tracks in the Southern Hemisphere, dated to between 120 million and 128 million years ago.

"Most of the bird tracks and body fossils dating as far back as the Early Cretaceous are from the Northern Hemisphere, particularly from Asia," says Anthony Martin, first author of the study and a professor in Emory University's Department of Environmental Sciences. "Our discovery shows that there were many birds, and a variety of them, near the South Pole about 125 million years ago."

Martin is a geologist and paleontologist focused primarily on ichnology -- the study of traces of life such as tracks, burrows, nests and tooth marks.

The international team of co-authors also includes researchers from Monash University and the Museums Victoria Research Institute in Australia; the Benemérita Normal School of Coahuila in Mexico and the Smithsonian Institution.

A possible migratory route

The 27 bird tracks vary in form and size and are among the largest known from the Early Cretaceous. They range from seven to 14 centimeters wide, which is similar to tracks of modern-day shorebirds, such as small herons and oystercatchers.

The tracks were found in the Wonthaggi Formation south of Melbourne. The rocky coastal strata mark where the ancient supercontinent Gondwana began to break up around 100 million years ago when Australia separated from Antarctica.

The polar environment at that time was a rift valley with braided rivers. Although the mean annual air temperature was higher during the Cretaceous than today, during the polar winters the ecosystem experienced deep, freezing temperatures and months of darkness.

The Wonthaggi avian tracks occurred on multiple stratigraphic levels, indicating a recurrent presence of a variety of birds. It also suggests seasonal formation of the tracks during polar summers, perhaps on a migratory route.

"The birds would likely have been stepping on soft sand or mud," Martin says. "Then the tracks may have been buried by a gentle river flow that deposited more sand or mud on top of them."

A scarcity of bird fossils

The Wonthaggi Formation is famous for its variety of polar dinosaur bones, although bird-fossil finds are extremely rare. The Cretaceous strata of the formation has yielded only one tiny bird bone -- a wishbone -- and a few feathers.

"Birds have such thin and tiny bones," Martin says. "Think of the likelihood of a sparrow being preserved in the geologic record as opposed to an elephant."

Birds are also lightweight and don't leave much of a foot impression, he adds.

Martin and colleagues discovered two 105-million-year-old bird tracks in Australia's Eumeralla Formation in 2013, making them the oldest from Australia at the time.

An eagle eye

Co-author Melissa Lowery, a local volunteer fossil hunter, first spotted some of the tracks in the current discovery in 2020. Dubbed "the doyenne of dinosaur discovery," Lowery has found hundreds of bones and more than 100 dinosaur footprints.

"Melissa is incredibly skilled at finding fossil tracks," Martin says. "Some of these tracks are subtle even for me, and I have lots of experience and training."

Most of the tracks were only exposed at low tide and some of them were encrusted by marine life such as algae, barnacles and mollusks.

Due to international travel restrictions in Australia during the COVID-19 pandemic, Martin had to wait until 2022 before he could travel to the site to lead the analyses of the tracks.

He was joined in the field by co-authors Patricia Vickers-Rich, professor of paleontology at Monash University, and Thomas Rich, curator of vertebrate aleontology at Museums Victoria Research Institute. The couple have led a major effort since the 1970s to uncover fossils in the Australian state of Victoria and to interpret the biota of Gondwana.

Also assisting in the field analyses were co-authors Mike Hall, a geologist at Monash University, and Peter Swinkels, a taxidermist at Museums Victoria Research Institute and an expert at preserving specimens through moldings and casts.

The thinness of the toes relative to the track lengths, the wide angles between the toes and the thin sharp claws and rear toes on some of the tracks helped Martin to verify their avian identity.

Co-author Claudia Serrano-Brañas, a paleontologist at the Benemérita Normal School of Coahuila and the National Museum of Natural History, Smithsonian Institution, verified similarities between the Australian bird footprints and ancient bird footprints from other parts of the world.

Swinkels created resin casts of the Australian tracks that brought into greater relief some of the nuances of the impressions. The casts provide a tool for further study. They also serve to preserve the finds. The silty, sandstone beds containing the footprints are rapidly eroding under the coastal tides and waves.

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An old star with ring-like structure: ALMA demonstrates highest resolution yet

ALMA (Atacama Large Millimeter/submillimeter Array) has demonstrated the highest resolution yet with observations of an old star. The observations show that the star is surrounded by a ring-like structure of gas and that gas from the star is escaping to the surrounding space. Future observations with the newly demonstrated high resolution are expected to elucidate, not only the end of a star's life, but also the beginning, when planets are still forming.

ALMA is a radio interferometric array telescope, in which individual antennas work together to observe a celestial object. ALMA's resolution, the ability to see small details, is determined by the maximum separation between the antennas and the frequency of the observed radio waves. In this research, an international team comprised mainly of astronomers from the Joint ALMA Observatory, National Astronomical Observatory of Japan (NAOJ), National Radio Astronomy Observatory, and European Southern Observatory used ALMA's maximum antenna separation of 16 km and highest frequency receivers (known as Band 10, up to 950 GHz) to achieve the best resolution possible. Pushing ALMA's resolution to new limits also required a new calibration technique to correct for fluctuations in Earth's atmosphere above the antennas. The calibration technique the team used, known as "band-to-band (B2B)," was originally tested in the 1990s at Nobeyama Radio Observatory of NAOJ for future millimeter/submillimeter interferometers.

For their demonstration observations, the team chose R Leporis, a star in the final stage of stellar evolution, located approximately 1,535 light-years away from Earth. The team succeeded in observing R Leporis with the best resolution ever, 5 milli-arcsec, which is the equivalent of being able to see a single human hair two and a half miles away. The observations show the surface of the star and a ring of gas around the star. The team also confirmed that gas from the star is escaping to the surrounding space.

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Temperature variability reduces nesting success

Many songbirds are nesting earlier in spring because of warmer temperatures brought about by climate change. But the shift brings another danger that is especially deadly for nestlings: greater exposure to temperature variability in the form of cold snaps and heat waves. Such extremes result in more nest failures. These findings come from a Cornell Lab of Ornithology study just published in the journal Nature Communications.

"When we talk about temperature changes, the focus is mostly on averages," said co-lead author Conor Taff, a researcher in Cornell University's Ecology and Evolutionary Biology Department. "But all creatures, including humans, interact with weather conditions right in the moment, not with long-term averages. Even a one or two-day period when it's really cold or really hot can be incredibly challenging even if the average temperature hasn't changed. Changing temperature averages and temperature variability are two different components of climate change."

To understand how temperature variability might affect nesting success, the researchers analyzed 300,000 breeding bird records submitted to the Cornell Lab's NestWatch project between 1995 and 2020. They pinpointed the coldest three-day day period and the hottest three-day period for each one of the nests and then looked at whether those values predicted lower nesting success. Success was measured by how many nestlings survived to fledge.

"We found that 16 of the 24 species we studied had reduced reproductive success when a cold snap occurred during the incubation or nestling stages," Taff said. "Eleven of 24 had reduced success when a heat wave occurred during the breeding season. Aerial insectivores were the most sensitive to temperature extremes, especially cold."

The vast majority of birds feed insects to their young, regardless of their final diet, and cold snaps reduce insect availability. If these episodes occur when nestlings are most vulnerable, they can trigger a mass die-off. During a cold snap, adult birds may move away to find survivable conditions which leaves eggs and nestlings exposed to cold and lack of food.

"It's the nestlings that really get hit hard because they can't regulate their own body temperature yet," said co-author Ryan Shipley, a Cornell University Ph.D. student at the time of the research. "Nestlings also grow at an exponential rate during the first week or two of life and if insect activity drops because of a cold snap, the young birds likely won't survive."

Taff and Shipley also examined 100 years of weather data to see if there have been changes in the timing of cold snaps and heat waves during the March through August breeding season in the United States and Canada. Although they found no clear pattern in the timing of temperature extremes, they do note that it's getting warmer everywhere.

"Even if nestlings somehow manage to survive a cold snap or heat wave, there may still be long-term consequences affecting the overall health of the birds," notes Shipley. "We're only looking at a brief snapshot during early life and cannot measure long-term health in an unbanded wild population."

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Plants that survived dinosaur extinction pulled nitrogen from air

Once a favored food of grazing dinosaurs, an ancient lineage of plants called cycads helped sustain these and other prehistoric animals during the Mesozoic Era, starting 252 million years ago, by being plentiful in the forest understory. Today, just a few species of the palm-like plants survive in tropical and subtropical habitats.

Like their lumbering grazers, most cycads have gone extinct. Their disappearance from their prior habitats began during the late Mesozoic and continued into the early Cenozoic Era, punctuated by the cataclysmic asteroid impact and volcanic activity that mark the K-Pg boundary 66 million years ago. However, unlike the dinosaurs, somehow a few groups of cycads survived to the present.

A new study appearing Nov. 16 in the journal Nature Ecology & Evolution has concluded that the cycad species that survived relied on symbiotic bacteria in their roots, which provide them with nitrogen to grow. Just like modern legumes and other plants that use nitrogen fixation, these cycads trade their sugars with bacteria in their roots in exchange for nitrogen plucked from the atmosphere.

What originally interested lead author Michael Kipp is that the tissues of nitrogen-fixing plants can provide a record of the composition of the atmosphere they grew up in. He combines geochemistry with the fossil record to try to understand the Earth's climate history.

Knowing already that modern cycads are nitrogen-fixers, Kipp began analyzing some very old plant fossils during his Ph.D. work at the University of Washington to see if he could get a different look at ancient atmospheres. Most of the old cycads revealed that they weren't nitrogen-fixers, but these also turned out to be the extinct lineages.

"Instead of being a story about the atmosphere, we realized this was a story about the ecology of these plants that changed through time," said Kipp, who spent nearly a decade on this finding, first at UW and then as a postdoctoral researcher at CalTech.

Kipp is joining the Duke faculty this year as an assistant professor of Earth and Climate Sciences in the Nicholas School of the Environment to continue using the fossil record to understand Earth's climate history so that we can understand its possible future.

Much of what we know about ancient atmospheres comes from chemical studies of ancient sea life and sediments, Kipp said. Applying some of those methods to terrestrial plants is a new wrinkle.

"Going into the project, there were no published nitrogen isotope data from fossilized plant foliage," Kipp said. It took a while for him to fine-tune the method and to secure samples of precious plant fossils that museum curators were reluctant to see vaporized to get the data.

"In the few fossil samples that are of surviving (cycad) lineages, and that are not so old -- 20, 30 million years -- we see the same nitrogen signature as we see today," Kipp said. That means their nitrogen came from symbiotic bacteria. But in the older and extinct cycad fossils, that nitrogen signature was absent.

What is less clear is how nitrogen fixation helped the surviving cycads. It may have helped them weather the dramatic shift in climate or it may have allowed them to compete better with the faster-growing angiosperm plants that flourished after the extinction, "or it could be both."

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No scientific evidence for cognitively advanced behaviors and symbolism by Homo naledi

A new study has cast doubt on claims that Homo naledi, a small-brained hominin dating to between 335-241,000 years ago, deliberately buried their dead and produced rock art in Rising Star Cave, South Africa.

Three pre-print articles published this year in eLife suggested the recent excavations at the Rising Star Cave system provided evidence of at least three burial features, two in the Dinaledi Chamber and a third in the Hill Antechamber cavity.

The articles claimed the features represented the earliest evidence of deliberate burial by a hominin species, and that Homo naledi lit up dark passageways using fire and intentionally carried the bodies of at least three individuals deep inside the Rising Star Cave system, dug pits, deposited corpses inside the pits, and covered the bodies with sediments.

It was also claimed that the Hill Antechamber feature contained a stone tool in close proximity to the hominin hand.

However, a group of  experts with specialisations in biological anthropology, archaeology, geochronology, and rock art, have now called for a deeper dig into the science behind the findings in a first, peer-reviewed critique published in the Journal of Human Evolution (JHE).

Professor Michael Petraglia from Griffith University's Australian Research Centre for Human Evolution, Professor Andy Herries from La Trobe University, María Martinón-Torres from the National Research Center on Human Evolution in Spain and Diego Garate from the University of Cantabria in Spain co-authored the peer-reviewed article.

The research team conclude the evidence presented so far was not compelling enough to support the deliberate burial of the dead by Homo naledi, nor that they made the purported engravings.

"We really need substantial additional documentation and scientific analyses before we can rule out that natural agents and post-depositional processes were responsible for the accumulation of bodies/body parts and to prove the intentional excavation and filling of pits by Homo naledi," Professor Martinón-Torres said.

Moreover, Professor Petraglia added: "Unfortunately, there is a distinct possibility that the so-called stone artifact next to the hominin hand is a geofact, and not a product of stone tool flaking by Homo naledi."

Professor Herries said: "There is no evidence that Homo naledi lit fires in the cave, purported buring locations could just be from manganese staining and charcoal within the cave remains to be dated. Charcoal from natural fires is not uncommon in caves."

"Detailed analyses are also needed to demonstrate that the so-called 'engravings' are indeed human-made marks, as marks like these can be produced as a product of natural weathering or animal claws," said Dr Garate.

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With unprecedented flares, stellar corpse shows signs of life

After a distant star's explosive death, an active stellar corpse was the likely source of repeated energetic flares observed over several months -- a phenomenon astronomers had never seen before, a Cornell-led team reports in new research published Nov. 15 in Nature.

The bright, brief flashes -- as short as a few minutes in duration, and as powerful as the original explosion 100 days later -- appeared in the aftermath of a rare type of stellar cataclysm that the researchers had set out to find, known as a luminous fast blue optical transient, or LFBOT.

Since their discovery in 2018, astronomers have speculated about what might drive such extreme explosions, which are far brighter than the violent ends massive stars typically experience, but fade in days instead of weeks. The research team believes the previously unknown flare activity, which was studied by 15 telescopes around the world, confirms the engine must be a stellar corpse: a black hole or neutron star.

"We don't think anything else can make these kinds of flares," said Anna Y. Q. Ho, assistant professor of astronomy in the College of Arts and Sciences. "This settles years of debate about what powers this type of explosion, and reveals an unusually direct method of studying the activity of stellar corpses."

Ho is the first author of "Minutes-duration Optical Flares with Supernova Luminosities," published with more than 70 co-authors who helped characterize the LFBOT officially labeled AT2022tsd and nicknamed "the Tasmanian devil," and the ensuing pulses of light seen roughly a billion light years from Earth.

Ho wrote the software that flagged the event in September 2022, while sifting through a half-million changes, or transients, detected daily in an all-sky survey conducted by the Califrnia-based Zwicky Transient Facility.

Then in December 2022, while routinely monitoring the fading explosion, Ho and collaborators Daniel Perley of Liverpool John Moores University in England, and Ping Chen of the Weizmann Institute of Science in Israel, met to review new observations conducted and analyzed by Ping -- a set of five images, each spanning several minutes. The first showed nothing, as expected, but the second picked up light, followed by an intensely bright spike in the middle frame that quickly vanished.

"No one really knew what to say," Ho recalled. "We had never seen anything like that before -- something so fast, and the brightness as strong as the original explosion months later -- in any supernova or FBOT. We'd never seen that, period, in astronomy."

To further investigate the abrupt rebrightening, the researchers engaged partners who contributed observations from more than a dozen other telescopes, including one equipped with a high-speed camera. The team combed through earlier data and worked to rule out other possible light sources. Their analysis ultimately confirmed at least 14 irregular light pulses over a 120-day period, likely only a fraction of the total number, Ho said.

"Amazingly, instead of fading steadily as one would expect, the source briefly brightened again -- and again, and again," she said. "LFBOTs are already a kind of weird, exotic event, so this was even weirder."

Exactly what processes were at work -- perhaps a black hole funneling jets of stellar material outward at close to the speed of light -- continues to be studied. Ho hopes the research advances longstanding goals to map how stars' properties in life may predict the way they'll die, and the type of corpse they produce.

In the case of LFBOTs, rapid rotation or a strong magnetic field likely are key components of their launching mechanisms, Ho said. It's also possible that they aren't conventional supernovas at all, instead triggered by a star's merger with a black hole.

"We might be seeing a completely different channel for cosmic cataclysms," she said.

The unusual explosions promise to provide new insight into stellar lifecycles typically only seen in snapshots of different stages -- star, explosion, remnants -- and not as part of a single system, Ho said. LFBOTs may present an opportunity to observe a star in the act of transitioning to its afterlife.

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Not so silver lining: Microplastics found in clouds could affect the weather

From the depths of the seas to snow on mountains and even the air above cities, microplastics are turning up increasingly often. Now, in ACS' Environmental Science & Technology Letters, researchers have analyzed microplastics in clouds above mountains. They suggest that these tiny particles could play a role in cloud formation and, in turn, affect weather.

Microplastics -- plastic fragments smaller than five millimeters -- originate from a myriad of items used daily, such as clothing, packaging and car tires. As research in the field evolves, scientists are not only detecting microplastics in the atmosphere but also investigating how they may play a role in cloud formation. For example, a group of researchers recently detected plastic granules, which had water-attracting surfaces, in Japanese mountaintop clouds. So, to learn more, Yan Wang and colleagues set out to look for microplastics in mountain clouds, used computer models to figure out how they could have gotten there, and tested how the particles could have impacted -- and been impacted by -- the clouds.

Wang and the team first collected 28 samples of liquid from clouds at the top of Mount Tai in eastern China. Then they analyzed the samples and found:

• Low-altitude and denser clouds contained greater amounts of microplastics.
• Particles were made of common polymers, including polyethylene terephthalate, polypropylene, polyethylene, polystyrene and polyamide.
• The microplastics tended to be smaller than 100 micrometers in length, although some were as long as 1,500 micrometers.
• Older, rougher particles had more lead, mercury and oxygen attached to their surfaces, which the researchers suggest could facilitate cloud development.

To investigate where the plastic particles in the clouds originated, Wang and the team developed computer models that approximated how the particles traveled to Mount Tai. These models suggested that airflow from highly populated inland areas, rather than from over the ocean or other nearby mountains, served as the major source of the fragments. In laboratory experiments, the researchers demonstrated that microplastics exposed to cloud-like conditions -- ultraviolet light and filtered cloud-sourced water -- had smaller sizes and rougher surfaces than those exposed to pure water or air. Additionally, particles impacted by the cloud-like conditions had more lead, mercury and oxygen-containing groups. These results suggest that clouds modify microplastics in ways that could enable the particles to affect cloud formation and the fate of airborne metals. The researchers conclude that more work is needed to fully understand how microplastics affect clouds and the weather.

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When we see what others do, our brain sees not what we see, but what we expect

When we engage in social interactions, like shaking hands or having a conversation, our observation of other people's actions is crucial. But what exactly happens in our brain during this process: how do the different brain regions talk to each other? Researchers at the Netherlands Institute for Neuroscience provide an intriguing answer: our perception of what others do depends more on what we expect to happen than previously believed.

For some time, researchers have been trying to understand how our brains process other people's actions. It is known, for example, that watching someone perform an action activates similar brain areas compared to when we perform that action ourselves. People assumed these brain regions become activated in a particular order: seeing what others do first activates visual brain regions, then later, parietal and premotor regions we normally use to perform similar actions. Scientists thought that this flow of information, from our eyes to our own actions, is what makes us understand what others do. This belief is based on measurements of brain activity in humans and monkeys while they watched simple actions, such as picking up a knife, presented in isolation in the lab. In reality, actions don't usually happen in isolation, out of the blue: they follow a predictable sequence with an end-goal in mind, like making breakfast. How does our brain deal with this?

Chaoyi Qin, Frederic Michon and their colleagues, led by Christian Keysers and Valeria Gazzola provide us with an intriguing answer: if we observe actions in such meaningful sequences, our brains increasingly ignore what comes into our eyes, and depend more on predictions of what should happen next, derived from our own motor system. "What we would do next, becomes what our brain sees," summarizes Christian Keysers, a senior author of the study and director of the social brain lab in the institute. To arrive at that counterintuitive conclusion, the team, in collaboration with the Jichi Medical University in Japan, had the unique opportunity to measure brain activity directly from the brain of epilepsy patients who participated in intracranial eeg-research for medical purposes. Such an examination involves measuring the brain's electrical activity using electrodes that are not on the skull, but under it.

Unique opportunity

The advantage of this technique is that it is the only technique that allows to directly measure the electrical activity the brain uses to work. Clinically, it is used as a final step for medication-resistant epilepsy patients, as it can determine the exact source of epilepsy. But while the medical team waits for epileptic seizures to occur, these patients have a period in which they have to stay in their hospital bed and have nothing to do but wait -- researchers used this period as an opportunity to peak into the working of the brain with unprecedented temporal and spatial accuracy.

During the experiment, participants performed a simple task: they watched a video in which someone performed various daily actions, such as preparing breakfast or folding a shirt. During that time, their electrical brain activity could be measures through the implanted electrodes across the brain regions involved in action observation to examine how they talk to each other. Two different conditions were tested, resulting in differing brain activity while watching. In one, the video was shown -- as we would normally see the action unfold every morning -- in its natural sequence: you see someone pick a bread-roll, then a knife, then cut open the roll, then scoop some butter etc.; in the other, these individual acts were re-shuffled into a random order. People saw the exact same actions in the two conditions, but only in the natural order, can their brain utilize its knowledge of how it would butter a bread-roll to predict what action comes next.

Different flow of information

Using sophisticated analyses in collaboration with Pascal Fries of the Ernst Strüngmann Institute (ESI) in Germany, what the team could reveal is that when participants viewed the reshuffled, unpredictable sequence, the brain indeed had an information flow going from visual brain regions, thought to describe what the eye is seeing, to parietal and premotor regions, that also controls our own actions -- just as the classical model predicted. But when participants could view the natural sequences, the activity changed dramatically. "Now, information was actually flowing from the premotor regions, that know how we prepare breakfast ourselves, down to the parietal cortex, and suppressed activity in the visual cortex," explains Valeria Gazzola. "It is as if they stopped to see with their eyes, and started to see what they would have done themselves."

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Scientists 3D-print hair follicles in lab-grown skin

A team led by scientists at Rensselaer Polytechnic Institute has 3D-printed hair follicles in human skin tissue cultured in the lab. This marks the first time researchers have used the technology to generate hair follicles, which play an important role in skin healing and function.

The finding, published in the journal Science Advances, has potential applications in regenerative medicine and drug testing, though engineering skin grafts that grow hair are still several years away.

"Our work is a proof-of-concept that hair follicle structures can be created in a highly precise, reproducible way using 3D-bioprinting. This kind of automated process is needed to make future biomanufacturing of skin possible," said Pankaj Karande, Ph.D., an associate professor of chemical and biological engineering and a member of Rensselaer's Shirley Ann Jackson, Ph.D. Center for Biotechnology and Interdisciplinary Studies, who led the study.

"The reconstruction of hair follicles using human-derived cells has historically been a challenge. Some studies have shown that if these cells are cultured in a three-dimensional environment, they can potentially originate new hair follicles or hair shafts, and our study builds on this work," Karande said.

When it comes to engineering human skin, hair may at first seem superfluous. However, hair follicles are quite important: They produce sweat, helping regulate body temperature, and they contain stem cells that help skin heal.

Hair follicles are also an entry point for topical drugs and cosmetics, making them an important part of dermatological testing. But today, initial safety testing is done on engineered skin tissues that lack hair follicles.

"Right now, contemporary skin models -- the engineered structures that mimic human skin -- are quite simple. Increasing their complexity by adding hair follicles would give us even more information about how skin interacts with topical products," said Carolina Catarino, Ph.D., first author of the study, who earned her doctorate at Rensselaer and is now a researcher developing new skin testing methods at Grupo Boticário, a cosmetics company in her home country of Brazil.

"Dr. Karande's lab is at the forefront of skin tissue engineering. This team has already successfully printed skin with working blood vessels, and this latest research is an exciting next step in developing and testing better treatments for burns and other skin conditions," said Deepak Vashishth, Ph.D., director of the Shirley Ann Jackson, Ph.D. Center for Biotechnology and Interdisciplinary Studies.

"Dr. Karande's work is a great example of advances being made by RPI researchers at the interface of engineering and life sciences with impact on human health," said Shekhar Garde, Ph.D., dean of Rensselaer's School of Engineering. "Bringing multichannel 3-D printing to biological realm is opening exciting opportunities that would have been hard to imagine in the past."

The researchers created their follicle-bearing skin with 3D-printing techniques adapted for printing at the cellular level.

The scientists begin by allowing samples of skin and follicle cells to divide and multiply in the lab until there are enough printable cells. Next, the researchers mix each type of cell with proteins and other materials to create the "bio-ink" used by the printer. Using an extremely thin needle to deposit the bio-ink, the printer builds the skin layer by layer, while also creating channels for depositing the hair cells. Over time, the skin cells migrate to these channels surrounding the hair cells, mirroring the follicle structures present in real skin.

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James Webb Space Telescope detects water vapor, sulfur dioxide and sand clouds in the atmosphere of a nearby exoplanet

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European astronomers, co-led by researchers from the Institute of Astronomy, KU Leuven, used recent observations made with the James Webb Space Telescope to study the atmosphere of the nearby exoplanet WASP-107b. Peering deep into the fluffy atmosphere of WASP-107b they discovered not only water vapour and sulfur dioxide, but even silicate sand clouds. These particles reside within a dynamic atmosphere that exhibits vigorous transport of material.

Astronomers worldwide are harnessing the advanced capabilities of the Mid-Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST) to conduct groundbreaking observations of exoplanets – planets orbiting stars other than our own Sun. One of these fascinating worlds is WASP-107b, a unique gaseous exoplanet that orbits a star slightly cooler and less massive than our Sun. The mass of the planet is similar to that of Neptune but its size is much larger than that of Neptune, almost approaching the size of Jupiter. This characteristic renders WASP-107b rather ‘fluffy’ when compared to the gas giant planets within our solar system. The fluffiness of this exoplanet enables astronomers to look roughly 50 times deeper into its atmosphere compared to the depth of exploration achieved for a solar-system giant like Jupiter.

The team of European astronomers took full advantage of the remarkable fluffiness of this exoplanet, enabling them to look deep into its atmosphere. This opportunity opened a window into unravelling the complex chemical composition of its atmosphere. The reason behind this is quite straightforward: the signals, or spectral features, are far more prominent in a less dense atmosphere compared to a more compact one. Their recent study, now published in Nature, reveals the presence of water vapour, sulfur dioxide (SO2), and silicate clouds, but notably, there is no trace of the greenhouse gas methane (CH4).

A dynamic atmosphere

These detections provide crucial insights into the dynamics and chemistry of this captivating exoplanet. First, the absence of methane hints at a potentially warm interior, offering a tantalising glimpse into the movement of heat energy in the planet’s atmosphere. Secondly, the discovery of sulfur dioxide (known for the odour of burnt matches), was a major surprise. Previous models had predicted its absence, but novel climate models of WASP-107b’s atmosphere now show that the very fluffiness of WASP-107b accommodates the formation of sulfur dioxide in its atmosphere. Even though its host star emits a relatively small fraction of high-energy photons due to its cooler nature, these photons can reach deep into the planet’s atmosphere thanks to its fluffy nature. This enables the chemical reactions required to produce sulfur dioxide to occur.

But that's not all they've observed. Both the spectral features of sulfur dioxide and water vapour are significantly diminished compared to what they would be in a cloudless scenario. High-altitude clouds partially obscure the water vapour and sulfur dioxide in the atmosphere. While clouds have been inferred on other exoplanets, this marks the first instance where astronomers can definitively identify the chemical composition of these clouds. In this case, the clouds consist of small silicate particles, a familiar substance for humans found in many parts of the world as the primary constituent of sand.

"JWST is revolutionising exoplanet characterisation, providing unprecedented insights at remarkable speed," says lead author Prof. Leen Decin of KU Leuven. "The discovery of clouds of sand, water, and sulfur dioxide on this fluffy exoplanet by JWST's MIRI instrument is a pivotal milestone. It reshapes our understanding of planetary formation and evolution, shedding new light on our own Solar System."

In contrast to Earth’s atmosphere, where water freezes at low temperatures, in gaseous planets reaching temperatures around 1000 degrees Celsius, silicate particles can freeze out to form clouds. However, in the case of WASP-107b, with a temperature of around 500 degrees Celsius in the outer atmosphere, traditional models predicted that these silicate clouds should be forming deeper within the atmosphere, where temperatures are substantially higher. In addition, sand clouds high up in the atmosphere rain out. How is it then possible that these sand clouds exist at high altitudes and continue to endure?

According to lead author Dr. Michiel Min: "The fact that we see these sand clouds high up in the atmosphere must mean that the sand rain droplets evaporate in deeper, very hot layers and the resulting silicate vapour is efficiently moved back up, where they recondense to form silicate clouds once more. This is very similar to the water vapour and cloud cycle on our own Earth but with droplets made of sand." This continuous cycle of sublimation and condensation through vertical transport is responsible for the enduring presence of sand clouds in WASP-107b's atmosphere.

This pioneering research not only sheds light on the exotic world of WASP-107b but also pushes the boundaries of our understanding of exoplanetary atmospheres. It marks a significant milestone in exoplanetary exploration, revealing the intricate interplay of chemicals and climatic conditions on these distant worlds.

“JWST enables a deep atmospheric characterisation of an exoplanet that does not have any counterpart in our Solar System, we are unravelling new worlds!”, says lead author Dr. Achrène Dyrek at CEA Paris.

Design and development of the MIRI instrument

Thanks to funding by the Belgian federal science policy office BELSPO via the ESA PRODEX programme, Belgian engineers and scientists played a key role in the design and development of the MIRI instrument, including the Centre Spatial de Liege (CSL), Thales Alenia Space (Charleroi) and OIP Sensor Systems (Oudenaarde). At the Institute of Astronomy at KU Leuven, instrument scientists tested the MIRI instrument extensively in special test chambers simulating the space environment in laboratories in the UK, at NASA Goddard and NASA Johnson Space centres.

“With colleagues across Europe and the United States we have been building and testing the MIRI instrument for almost 20 years. It is rewarding to see our instrument unravel the atmosphere of this intriguing exoplanet,” says instrument specialist Dr. Bart Vandenbussche of KU Leuven.

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Climate engineering could slow Antarctic ice loss

Scattering sunlight-reflecting particles in the atmosphere could slow rapid melting in West Antarctica and reduce the risk of catastrophic sea-level rise, according to a study led by Indiana University researchers.

The study, one of the first to look at how climate engineering might impact Antarctica, comes as scientists sound the alarm over the increasing likelihood of accelerated ice loss in West Antarctica this century. The work appears in the Journal of Geophysical Research: Atmospheres.

"Even if the world meets the ambitious target of limiting global warming to 1.5 degrees Celsius above pre-industrial levels -- which we are not on track to do -- we are going to see significant sea-level rise," said Paul Goddard, an assistant research scientist in the IU College of Arts and Sciences' Department of Earth and Atmospheric Sciences and the lead author of the study. "Exploring ways to reflect sunlight into space before it is absorbed into Earth's climate system could help buy us more time to address climate change and avoid or delay climate tipping points, such as collapse of the West Antarctic Ice Sheet."

In addition to Goddard, co-authors on the paper include IU earth and atmospheric sciences assistant professor Ben Kravitz; Douglas MacMartin and Daniele Visioni of Cornell University; Ewa Bednarz with the National Oceanic and Atmospheric Administration; and Walker Lee of the National Center for Atmospheric Research.

The study explored a form of climate engineering called stratospheric aerosol injection, in which large amounts of tiny sulfur droplets are released into the stratosphere by a fleet of airplanes as a proposed method for keeping global temperatures in check.

The approach mimics what happens when a large volcano spews vast amounts of particles into the upper atmosphere and precipitates a cooling effect that can last months to years. It was recently discussed in a White House report outlining a potential research program on stratospheric aerosol injection and marine cloud brightening, another proposed strategy for cooling the planet.

Ten of the hottest years on record have occurred in the last 14 years. That's including 2023, which is on track to supplant 2016 as the hottest year ever recorded. The spike in global temperatures has coincided with unprecedented heat waves, wildfires, flash flooding, and other climate-related impacts around the world.

In their study, IU researchers and collaborators used high-performance computers and global climate models to simulate different stratospheric aerosol injection scenarios, identifying the cooling strategy with the most potential to slow Antarctic ice loss. A portion of the data analysis conducted for the study took place on IU University Information Technology Services' large-memory computer cluster, Carbonate.

"Where you release the aerosols matters a lot and can affect the climate differently," Goddard said. "In this case, we found that releasing stratospheric aerosols at multiple latitudes within the tropics and sub-tropics, with a greater proportion in the Southern Hemisphere, is the best strategy for preserving land ice in Antarctica because it helps keep warm ocean waters away from the ice shelves."

Researchers simulated 11 different stratospheric aerosol injection scenarios. Three cases spanned multiple latitudes -- considered the most likely approach for how stratospheric aerosols injection might be implemented -- with temperature targets of 1.5, 1 and 0.5 degrees Celsius above pre-industrial levels. The simulations, which started in 2035 and ran through 2070, included a moderate emissions scenario with no stratospheric aerosol injection that served as a key point of comparison.

Though simulated scenarios with stratospheric aerosol injection at multiple latitudes showed benefits in terms of Antarctic ice loss, further study is needed to quantify the change in melt rates, Goddard said.

Notably, several single-latitude injection scenarios actually accelerated Antarctic ice loss due to a southward shift of prevailing winds drawing warm ocean waters toward the ice shelves.

"If we're ever going to engineer the climate, how we do it really matters," Goddard said.

Some of the risks related to stratospheric aerosol injection, for example, include changes in regional precipitation patterns and the possibility of "termination shock," a rapid rebound of global temperatures to pre-stratospheric aerosols injection levels should the decades-long treatment be interrupted.

The study adds to an expanding body of knowledge about the benefits and drawbacks of deliberately cooling the planet, a concept that is being discussed more widely as the effects of climate change become more prominent, Kravitz said.

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Evolution of taste: Early sharks were able to perceive bitter substances

A research team from the University of Cologne, in collaboration with colleagues from the Leibniz Institute for Food Systems Biology in Freising, has discovered a receptor for bitter taste in twelve different cartilaginous fish (sharks and rays). The receptor belongs to the so-called taste receptors type 2 (T2R), which also make humans perceive bitter and potentially toxic foods. Until now, it was assumed that such receptors only occur in bony vertebrates. The work was published under the title 'A singular shark bitter taste receptor provides insights into the evolution of bitter taste perception' in the journal Proceedings of the National Academy of Sciences (PNAS).

In the past, molecular research has had limited information on sharks, as their genomes are often relatively large. Therefore, sequencing is often more complex and takes longer than with many other animals. However, the techniques are more advanced nowadays, providing ever more information on the gene sequences of many cartilaginous fishes. This enabled the neurobiologists lecturer (Privatdozent) Dr Maik Behrens and Tatjana Lang from the Leibniz Institute for Food Systems Biology and Professor Dr Sigrun Korsching at the Institute of Genetics of the University of Cologne to specifically search for bitter taste receptors in cartilaginous fish.

Twelve out of seventeen cartilaginous fish genomes studied contained genes for the taste receptors type 2, with only one T2R gene present in each species. The researchers named this single gene T2R1. The fact that only a single T2R gene was found suggests that it is the original form of these bitter taste receptors, which was not altered by gene duplication and subsequent different specialization of the resulting receptors.

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Printed robots with bones, ligaments, and tendons

3D printing is advancing rapidly, and the range of materials that can be used has expanded considerably. While the technology was previously limited to fast-curing plastics, it has now been made suitable for slow-curing plastics as well. These have decisive advantages as they have enhanced elastic properties and are more durable and robust.

The use of such polymers is made possible by a new technology developed by researchers at ETH Zurich and a US start-up. As a result, researchers can now 3D print complex, more durable robots from a variety of high-quality materials in one go. This new technology also makes it easy to combine soft, elastic, and rigid materials. The researchers can also use it to create delicate structures and parts with cavities as desired.

Materials that return to their original state

Using the new technology, researchers at ETH Zurich have succeeded for the first time in printing a robotic hand with bones, ligaments and tendons made of different polymers in one go. "We wouldn't have been able to make this hand with the fast-curing polyacrylates we've been using in 3D printing so far," explains Thomas Buchner, a doctoral student in the group of ETH Zurich robotics professor Robert Katzschmann and first author of the study. "We're now using slow-curing thiolene polymers. These have very good elastic properties and return to their original state much faster after bending than polyacrylates." This makes thiolene polymers ideal for producing the elastic ligaments of the robotic hand.

In addition, the stiffness of thiolenes can be fine-tuned very well to meet the requirements of soft robots. "Robots made of soft materials, such as the hand we developed, have advantages over conventional robots made of metal. Because they're soft, there is less risk of injury when they work with humans, and they are better suited to handling fragile goods," Katzschmann explains.

Scanning instead of scraping

3D printers typically produce objects layer by layer: nozzles deposit a given material in viscous form at each point; a UV lamp then cures each layer immediately. Previous methods involved a device that scraped off surface irregularities after each curing step. This works only with fast-curing polyacrylates. Slow-curing polymers such as thiolenes and epoxies would gum up the scraper.

To accommodate the use of slow-curing polymers, the researchers developed 3D printing further by adding a 3D laser scanner that immediately checks each printed layer for any surface irregularities. "A feedback mechanism compensates for these irregularities when printing the next layer by calculating any necessary adjustments to the amount of material to be printed in real time and with pinpoint accuracy," explains Wojciech Matusik, a professor at the Massachusetts Institute of Technology (MIT) in the US and co-author of the study. This means that instead of smoothing out uneven layers, the new technology simply takes the unevenness into account when printing the next layer.

Inkbit, an MIT spin-off, was responsible for developing the new printing technology. The ETH Zurich researchers developed several robotic applications and helped optimise the printing technology for use with slow-curing polymers. The researchers from Switzerland and the US have now jointly published the technology and their sample applications in the journal Nature.

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Tracking down quantum flickering of the vacuum

Absolutely empty -- that is how most of us envision the vacuum. Yet, in reality, it is filled with an energetic flickering: the quantum fluctuations. Experts are currently preparing a laser experiment intended to verify these vacuum fluctuations in a novel way, which could potentially provide clues to new laws in physics. A research team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has developed a series of proposals designed to help conduct the experiment more effectively -- thus increasing the chances of success. The team presents its findings in the scientific journal Physical Review D.

The physics world has long been aware that the vacuum is not entirely void but is filled with vacuum fluctuations -- an ominous quantum flickering in time and space. Although it cannot be captured directly, its influence can be indirectly observed, for example, through changes in the electromagnetic fields of tiny particles.

However, it has not yet been possible to verify vacuum fluctuations without the presence of any particles. If this could be accomplished, one of the fundamental theories of physics, namely quantum electrodynamics (QED), would be proven in a hitherto untested area. Should such an experiment reveal deviations from the theory, however, it would suggest the existence of new, previously undiscovered particles.

The experiment intended to accomplish this is planned as part of the Helmholtz International Beamline for Extreme Fields (HIBEF), a research consortium led by the HZDR at the HED experimental station of the European XFEL in Hamburg, the largest X-ray laser in the world. The underlying principle is that an ultra-powerful laser fires short, intense flashes of light into an evacuated stainless steel chamber. The aim is to manipulate the vacuum fluctuations so that they, seemingly magically, change the polarization of an X-ray flash from the European XFEL, i.e., rotate its direction of oscillation.

"It would be like sliding a transparent plastic ruler between two polarizing filters and bending it back and forth," explains HZDR theorist Prof. Ralf Schützhold. "The filters are originally set up so that no light passes through them. Bending the ruler would now change the direction of the light's oscillation in such a way that something could be seen as a result." In this analogy, the ruler corresponds to the vacuum fluctuations while the ultra-powerful laser flash bends them.

Two flashes instead of just one

The original concept involved shooting just one optical laser flash into the chamber and using specialized measurement techniques to register whether it changes the X-ray flash's polarization. But there is a problem: "The signal is likely to be extremely weak," explains Schützhold. "It is possible that only one in a trillion X-ray photons will change its polarization."

But this might be below the current measurement limit -- the event could simply fall through the cracks undetected. Therefore, Schützhold and his team are relying on a variant: instead of just one, they intend to shoot two optical laser pulses simultaneously into the evacuated chamber.

Both flashes will strike there and literally collide. The X-ray pulse of the European XFEL is set to fire precisely into their collision point. The decisive factor: The colliding laser flashes affect the X-ray pulse like a type of crystal. Just as X-rays are diffracted, i.e., deflected, when passing through a natural crystal, the XFEL X-ray pulse should also be deflected by the briefly existing "light crystal" of the two colliding laser flashes.

"That would not only change the polarization of the X-ray pulse but also slightly deflect it at the same time," explains Ralf Schützhold. This combination could increase the chances of actually being able to measure the effect -- so the researchers hope. The team has calculated various options for the striking angle of the two laser flashes colliding in the chamber. Experiments will show which variant proves to be most suitable.

Targeting ultra-light ghost particles?

The prospects could even be improved further if the two laser flashes shot into the chamber were not of the same color but of two different wavelengths. This would also allow the energy of the X-ray flash to change slightly, which would, likewise, help to measure the effect. "But this is technically quite challenging and may only be implemented at a later date," says Schützhold.

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How climate change could be affecting your brain

A new element of the catastrophic impacts of climate change is emerging -- how global warming is impacting the human brain.

In a paper published today in Nature Climate Change, an international team of academics explore the ways in which research has shown that a changing environment affects how our brains work, and how climate change could impact our brain function in the future. The paper is led by the University of Vienna with input from the universities of Geneva, New York, Chicago, Washington, Stanford, Exeter in the UK and the Max Plank Institute in Berlin. It also explores the role that neuroscientists can play in further understanding and addressing these challenges.

Lead author Dr Kimberly C. Doell, of the University of Vienna, said: "We've long known that factors in our environment can lead to changes in the brain. Yet we're only just beginning to look at how climate change, the greatest global threat of our time, might change our brains. Given the increasingly frequent extreme weather events we're already experiencing, alongside factors such as air pollution, the way we access nature and the stress and anxiety people experience around climate change, it's crucial that we understand the impact this could all have on our brains. Only then can we start to find ways to mitigate these changes."

Since the 1940s, scientists have known from mouse studies that changing environmental factors can profoundly change the development and plasticity of the brain. This effect as also been seen in humans in research looking at the effects of growing up in poverty, which found disturbances to brain systems, including lack of cognitive stimulation, exposure to toxins, poor nutrition, and heightened childhood stress. While not entirely surprising, this research highlights the profound impact that one's environment can have on their brain.

Now, the authors are calling for research to explore the impact on the human brain of being exposed to more extreme weather events, such as heatwaves, droughts, and hurricanes, and associated forest fires and floods. They believe such events may change brain structure, function, and overall health, and also call for more research to evaluate how this may explain changes in well-being and behaviour.

The paper also explores the role that neuroscience can play in influencing the way we think about climate change, our judgments and how we respond.

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Earth's surface water dives deep, transforming core's outer layer

A few decades ago, seismologists imaging the deep planet identified a thin layer, just over a few hundred kilometers thick. The origin of this layer, known as the E prime layer, has been a mystery -- until now.

An international team of researchers, including Arizona State University scientists Dan Shim, Taehyun Kim and Joseph O'Rourke of the School of Earth and Space Exploration, has revealed that water from the Earth's surface can penetrate deep into the planet, altering the composition of the outermost region of the metallic liquid core and creating a distinct, thin layer. Illustration of silica crystals coming out from the liquid metal of the Earth's outer core due to a water-induced chemical reaction.

Their research was recently published in Nature Geoscience.

Research indicates that over billions of years, surface water has been transported deep into the Earth by descending, or subducted, tectonic plates. Upon reaching the core-mantle boundary, about 1,800 miles below the surface, this water triggers a profound chemical interaction, altering the core's structure.

Along with Yong Jae Lee of Yonsei University in South Korea, Shim and his team have demonstrated through high-pressure experiments that subducted water chemically reacts with core materials. This reaction forms a hydrogen-rich, silicon-depleted layer, altering the topmost outer core region into a film-like structure. Additionally, the reaction generates silica crystals that rise and integrate into the mantle. This modified liquid metallic layer is predicted to be less dense, with reduced seismic velocities, in alignment with anomalous characteristics mapped by seismologists.

Illustration of Earth's interior revealing subducting water and a rising plume of magma. At the interface where subducting water meets the core, a chemical exchange occurs to form a hydrogen-rich layer in the topmost outer core and dense silica in the bottom of the mantle. Image courtesy Yonsei University

"For years, it has been believed that material exchange between Earth's core and mantle is small. Yet, our recent high-pressure experiments reveal a different story. We found that when water reaches the core-mantle boundary, it reacts with silicon in the core, forming silica," said Shim. "This discovery, along with our previous observation of diamonds forming from water reacting with carbon in iron liquid under extreme pressure, points to a far more dynamic core-mantle interaction, suggesting substantial material exchange."

This finding advances our understanding of Earth's internal processes, suggesting a more extensive global water cycle than previously recognized. The altered "film" of the core has profound implications for the geochemical cycles that connect the surface-water cycle with the deep metallic core.

This study was conducted by an international team of geoscientists using advanced experimental techniques at the Advanced Photon Source of Argonne National Lab and PETRA III of Deutsches Elektronen-Synchrotron in Germany to replicate the extreme conditions at the core-mantle boundary.

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AI faces look more real than actual human face

White faces generated by artificial intelligence (AI) now appear more real than human faces, according to new research led by experts at The Australian National University (ANU).

In the study, more people thought AI-generated white faces were human than the faces of real people. The same wasn't true for images of people of colour.

The reason for the discrepancy is that AI algorithms are trained disproportionately on white faces, Dr Amy Dawel, the senior author of the paper, said.

"If white AI faces are consistently perceived as more realistic, this technology could have serious implications for people of colour by ultimately reinforcing racial biases online," Dr Dawel said.

"This problem is already apparent in current AI technologies that are being used to create professional-looking headshots. When used for people of colour, the AI is altering their skin and eye colour to those of white people."

One of the issues with AI 'hyper-realism' is that people often don't realise they're being fooled, the researchers found.

"Concerningly, people who thought that the AI faces were real most often were paradoxically the most confident their judgements were correct," Elizabeth Miller, study co-author and PhD candidate at ANU, said.

"This means people who are mistaking AI imposters for real people don't know they are being tricked."

The researchers were also able to discover why AI faces are fooling people.

"It turns out that there are still physical differences between AI and human faces, but people tend to misinterpret them. For example, white AI faces tend to be more in-proportion and people mistake this as a sign of humanness," Dr Dawel said.

"However, we can't rely on these physical cues for long. AI technology is advancing so quickly that the differences between AI and human faces will probably disappear soon."

The researchers argue this trend could have serious implications for the proliferation of misinformation and identity theft, and that action needs to be taken.

"AI technology can't become sectioned off so only tech companies know what's going on behind the scenes. There needs to be greater transparency around AI so researchers and civil society can identify issues before they become a major problem," Dr Dawel said.

Raising public awareness can also play a significant role in reducing the risks posed by the technology, the researchers argue.

"Given that humans can no longer detect AI faces, society needs tools that can accurately identify AI imposters," Dr Dawel said.

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Second-most distant galaxy discovered using James Webb Space Telescope

The second- and fourth-most distant galaxies ever observed have been discovered in a region of space known as Pandora's Cluster, or Abell 2744, using data from NASA's James Webb Space Telescope (JWST). Following up on a deep field image of the area, an international team led by Penn State researchers confirmed the distance of these ancient galaxies and inferred their properties using new spectroscopic data -- information about light emitted across the electromagnetic spectrum -- from JWST. At nearly 33 billion light years away, these incredibly distant galaxies offer insights into how the earliest galaxies might have formed.

Unlike other galaxies confirmed at this distance that appear in images as red dots, the new galaxies are larger and appear like a peanut and a fluffy ball, according to the researchers. A paper describing the galaxies appears today (Nov 13) in the journal Astrophysical Journal Letters.

"Very little is known about the early universe, and the only way to learn about that time and to test our theories of early galaxy formation and growth is with these very distant galaxies," said first-author Bingjie Wang, postdoctoral scholar in the Penn State Eberly College of Science and a member of the JWST UNCOVER (Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization) team that conducted the research. "Prior to our analysis, we knew of only three galaxies confirmed at around this extreme distance. Studying these new galaxies and their properties has revealed the diversity of galaxies in the early universe and how much there is to be learned from them."

Because the light from these galaxies had to travel for so long to reach Earth, it provides a window into the past. The research team estimates that the light detected by JWST was emitted by the two galaxies when the universe was about 330 million years old and traveled for about 13.4 billion light years to reach the JWST. But, the researchers said, the galaxies are currently closer to 33 billion light years away from Earth due to the expansion of the universe over this time.

"The light from these galaxies is ancient, about three times older than the Earth," said Joel Leja, assistant professor of astronomy and astrophysics at Penn State and a member of UNCOVER. "These early galaxies are like beacons, with light bursting through the very thin hydrogen gas that made up the early universe. It is only by their light that we can begin to understand the exotic physics that governed the galaxy near the cosmic dawn."

Notably, the two galaxies are considerably larger than the three galaxies previously located at these extreme distances. One is at least six times larger at about 2,000 light years across. For comparison, the Milky Way is approximately 100,000 light years across, but, Wang said, the early universe is thought to have been very compressed, so it's surprising that the galaxy is as large as it is.

"Previously discovered galaxies at these distances are point sources -- they appear as a dot in our images," Wang said. "But one of ours appears elongated, almost like a peanut, and the other looks like a fluffy ball. It is unclear if the difference in size is due to how the stars formed or what happened to them after they formed, but the diversity in the galaxy properties is really interesting. These early galaxies are expected to have formed out of similar materials, but already they are showing signs of being very different than one another."

The two galaxies were among 60,000 sources of light in Pandora's Cluster detected in one of JWST's first deep field images taken during 2022, its first year of science operations. This region of space was selected in part because it is located behind several galaxy clusters that create a natural magnification effect called gravitational lensing. The gravitational pull of the clusters' combined mass warps the space around it, focusing and magnifying any light that passes nearby and providing a magnified view behind the clusters.

In a matter of months, the UNCOVER team narrowed down the 60,000 light sources to 700 candidates for follow up study, eight of which they thought could potentially be among the first galaxies. Then, JWST again pointed at Pandora's Cluster, recording the candidates' spectra -- a sort of fingerprint detailing the amount of light given off at each wavelength.

"Several different teams are using different approaches to look for these ancient galaxies, and each have their strengths and weaknesses," Leja said. "The fact that we're pointing at this giant magnifying lens in space gives us an incredibly deep window, but it's a very small window so we were rolling the dice. Several of the candidates were inconclusive, and at least one was a case of mistaken identity -- it was something much closer that mimics a distant galaxy. But we were lucky, and two turned out to be these ancient galaxies. It's incredible."

The researchers also used detailed models to infer the properties of these early galaxies when they emitted the light detected by JWST. As the researchers expected, the two galaxies were young, had few metals in their composition, and were growing rapidly and actively forming stars.

"The first elements were forged in the cores of early stars through the process of fusion," Leja said. "It makes sense that these early galaxies don't have heavy elements like metals because they were some of the first factories to build those heavy elements. And, of course, they would have to be young and star-forming to be the first galaxies, but confirming these properties is an important basic test of our models and helps confirm the whole paradigm of the Big Bang theory."

The researchers noted that, alongside the gravitational lens, JWST's powerful infrared instruments should be able to detect galaxies at an even further distance, if they exist.

"We had a very tiny window into this region, and we didn't observe anything beyond these two galaxies, even though JWST has the capability," Leja said. "That could mean that galaxies just didn't form before that time and that we're not going to find anything further away. Or it could mean we didn't get lucky enough with our small window."

This work was the result of a successful proposal submitted to NASA suggesting how to use JWST during its first year of science operations. In the first three cycles of submissions, NASA received four to ten times more proposals than available observing time on the telescope would allow and had to select only a fraction of those proposals.

"Our team was very excited and a little surprised when our proposal was accepted," Leja said. "It involved coordination, quick human action and the telescope pointing at the same thing twice, which is a lot to ask of a telescope in its first year. There was a lot of pressure because we only had a few months to determine the objects for follow up. But JWST was built for finding these first galaxies, and it's so exciting to be doing that now."

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Diverse forests hold huge carbon potential, as long as we cut emissions

Research results published in the journal, Nature, show that realistic global forest carbon potential is approximately 226 Gigatonnes (Gt) of carbon. The study, which involved hundreds of scientists around the world, highlights the critical importance of forest conservation, restoration, and sustainable management in moving towards international climate and biodiversity targets. The researchers stress that this potential can be achieved by incentivizing community-driven efforts to promote biodiversity.

The forest carbon potential has been a highly controversial topic. Four years ago, a study published in the journal Science found that the restoration of forests could capture over 200 Gt of carbon -- which could draw down approximately 30 percent of excess anthropogenic carbon. While this study elevated a discussion about the role of nature in fighting climate change, it also raised concerns around the adverse environmental impacts of mass tree plantations, carbon offsetting schemes, and greenwashing. While some scientific studies have supported the scale of this finding, others argued that this forest carbon estimate could be up to 4 or 5 times too high.

To address this controversial topic an international team of hundreds of researchers led by the Crowther Lab at ETH Zurich joined forces to build an integrated assessment using a comprehensive range of approaches, including vast ground-sourced data and satellite datasets.

Achieving forest carbon potential

Due to ongoing deforestation, the total amount of carbon stored in forests is ~328 Gt below its natural state. Of course, much of this land is used for extensive human development including urban and agricultural land. However, outside of those areas, researchers found that forests could capture approximately 226 Gt C in regions with a low human footprint if they were allowed to recover. Approximately 61 percent of this potential can be achieved by protecting existing forests, so that they can recover to maturity. The remaining 39 percent can be achieved by reconnecting fragmented forest landscapes through sustainable ecosystem management and restoration.

"Most of the world's forests are highly degraded. In fact, many people have never been in one of the few old growth forests that remain on Earth," said Lidong Mo, a lead author of the study. "To restore global biodiversity, ending deforestation must be a top priority."

The dataset revealed that biodiversity accounts for approximately half of the global forest productivity. As such, the researchers highlighted that, to achieve the full carbon potential, restoration efforts should include a natural diversity of species. In addition, sustainable agricultural, forestry, and restoration practices that promote biodiversity have the greatest potential for carbon capture.

Redefining restoration

The authors stress that responsible restoration is a fundamentally social endeavour. It includes countless actions such as conservation, natural regeneration, rewilding, silviculture, agroforestry, and all other community-driven efforts to promote biodiversity. It requires equitable development, driven by policies that prioritize the rights of local communities and Indigenous people.

"We need to redefine what restoration means to many people," said Thomas Crowther, the senior author of the paper and a professor at ETH Zurich. "Restoration is not about mass tree plantations to offset carbon emissions. Restoration means directing the flow of wealth towards millions of local communities, Indigenous populations, and farmers that promote biodiversity across the globe. Only when healthy biodiversity is the preferred choice for local communities will we get long-term carbon capture as a biproduct."

The researchers conclude that ecologically responsible forest restoration does not include the conversion of other ecosystems that would not naturally contain forests. "Global restoration is not only about trees," said Constantin Zohner, a senior researcher at ETH Zurich. "We have to protect natural biodiversity in all ecosystems including grasslands, peatlands, and wetlands that are equally essential for life on Earth."

Nature for climate

This study brings to light the critical importance of natural, diverse forests in contributing to 30 percent of carbon drawdown potential. However, forests cannot be a substitute for cutting fossil fuel emissions. If emissions continue to rise, the study warns, then on-going droughts, fires, and warming will threaten forests and limit their ability to absorb carbon.

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Solar-powered device produces clean water and clean fuel at the same time

A floating, solar-powered device that can turn contaminated water or seawater into clean hydrogen fuel and purified water, anywhere in the world, has been developed by researchers.

The device, developed by researchers at the University of Cambridge, could be useful in resource-limited or off-grid environments, since it works with any open water source and does not require any outside power.

It takes its inspiration from photosynthesis, the process by which plants convert sunlight into food. However, unlike earlier versions of the 'artificial leaf', which could produce green hydrogen fuel from clean water sources, this new device operates from polluted or seawater sources and can produce clean drinking water at the same time.

Tests of the device showed it was able to produce clean water from highly polluted water, seawater, and even from the River Cam in central Cambridge. The results are reported in the journal Nature Water.

"Bringing together solar fuels production and water purification in a single device is tricky," said Dr Chanon Pornrungroj from Cambridge's Yusuf Hamied Department of Chemistry, the paper's co-lead author. "Solar-driven water splitting, where water molecules are broken down into hydrogen and oxygen, need to start with totally pure water because any contaminants can poison the catalyst or cause unwanted chemical side-reactions."

"In remote or developing regions, where clean water is relatively scarce and the infrastructure necessary for water purification is not readily available, water splitting is extremely difficult," said co-lead author Ariffin Mohamad Annuar. "A device that could work using contaminated water could solve two problems at once: it could split water to make clean fuel, and it could make clean drinking water."

Pornrungroj and Mohamad Annuar, who are both members of Professor Erwin Reisner's research group, came up with a design that did just that. They deposited a photocatalyst on a nanostructured carbon mesh that is a good absorber of both light and heat, generating the water vapour used by the photocatalyst to create hydrogen. The porous carbon mesh, treated to repel water, served both to help the photocatalyst float and to keep it away from the water below, so that contaminants do not interfere with its functionality.

In addition, the new device uses more of the Sun's energy. "The light-driven process for making solar fuels only uses a small portion of the solar spectrum -- there's a whole lot of the spectrum that goes unused," said Mohamad Annuar.

The team used a white, UV-absorbing layer on top of the floating device for hydrogen production via water splitting. The rest of the light in the solar spectrum is transmitted to the bottom of the device, which vaporises the water.

"This way, we're making better use of the light -- we get the vapour for hydrogen production, and the rest is water vapour," said Pornrungroj. "This way, we're truly mimicking a real leaf, since we've now been able to incorporate the process of transpiration."

A device that can make clean fuel and clean water at once using solar power alone could help address the energy and the water crises facing so many parts of the world. For example, the indoor air pollution caused by cooking with 'dirty' fuels, such as kerosene, is responsible for more than three million deaths annually, according to the World Health Organization. Cooking with green hydrogen instead could help reduce that number significantly. And 1.8 billion people worldwide still lack safe drinking water at home.

"It's such a simple design as well: in just a few steps, we can build a device that works well on water from a wide variety of sources," said Mohamad Annuar.

"It's so tolerant of pollutants, and the floating design allows the substrate to work in very cloudy or muddy water," said Pornrungroj. "It's a highly versatile system."

"Our device is still a proof of principle, but these are the sorts of solutions we will need if we're going to develop a truly circular economy and sustainable future," said Reisner, who led the research. "The climate crisis and issues around pollution and health are closely related, and developing an approach that could help address both would be a game-changer for so many people."

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New drug-like molecule extends lifespan, ameliorates pathology in worms and boosts function in mammalian muscle cells

Having healthy mitochondria, the organelles that produce energy in all our cells, usually portends a long healthy life whether in humans or in C. elegans, a tiny, short-lived nematode worm often used to study the aging process. Researchers at the Buck Institute have identified a new drug-like molecule that keeps mitochondria healthy via mitophagy, a process that removes and recycles damaged mitochondria in multicellular organisms. The compound, dubbed MIC, is a natural compound that extended lifespan in C. elegans, ameliorated pathology in neurodegenerative disease models of C. elegans, and improved mitochondrial function in mouse muscle cells. Results are published in the November 13, 2023, edition of Nature Aging.

The impact of mitochondrial dysfunction in age-related disease

Defective mitophagy is implicated in many age-related diseases. It's tied to neurodegenerative disorders such as Parkinson's and Alzheimer's; it plays a role in cardiovascular diseases including heart failure; it influences metabolic disorders including obesity and type 2 diabetes; it is implicated in muscle wasting and sarcopenia and has a complex relationship with cancer progression. Even though interventions that restore mitophagy and facilitate the elimination of damaged mitochondria hold great promise for addressing these conditions, not one treatment has been approved for human use despite advances in the field.

What's MIC?

MIC (Mitophagy-Inducing Compound) is a coumarin, which are naturally bioactive compounds that have anticoagulant, antibacterial, antifungal, antiviral, anticancer, and antihyperglycemic properties (among others) as well as being an antioxidant with neuroprotective effects. Coumarin is found in many plants and is found in high concentrations in certain types of cinnamon, which is one of the most frequent sources for human exposure to the substance.

A new mechanism of action in mitophagy

The project started in a mouse model of Parkinson's disease where researchers in the laboratory of Julie Andersen, PhD, a senior author of the paper, were looking at known enhancers of mitophagy, including rapamycin. "Co-author Shankar Chinta, PhD, started screening natural compounds in neuronal cells and MIC came up as a major hit," she said. "Rather than taking MIC immediately into a mouse model we wanted to understand its impact on overall aging and identify its mechanism of action, so we took the work into the worm where we found that MIC is in a different class of molecules that enhance the expression of a key protein, TFEB."

In an effort spearheaded by Andersen and research scientist Manish Chamoli, PhD, lead author of the study, researchers found that MIC enhanced the activity of transcription factor TFEB, which is a master regulator of genes involved in autophagy and lysosomal functions. Autophagy is the intracellular recycling process whereby cells clean up damaged proteins; it derives its abilities from the lysosome. Researchers found that MIC robustly increased the lifespan of C. elegans while also preventing mitochondrial dysfunction in mammalian cells.

"This paper helps support the overall notion of TFEB being a key autophagy regulator that extends lifespan, "said Buck professor and Chief Scientific Officer Malene Hansen, PhD, who collaborated on the paper. She added, "Mitophagy is a selective and very significant form of autophagy. The field has recognized TFEB as a player when it comes to quality control in mitochondria. This study provides a possible translational route to induce mitophagy in a TFEB-dependent fashion."

A link to the brain/gut connection

Mechanistically MIC works upstream of TFEB by inhibiting ligand-induced activation of the nuclear hormone receptor DAF-12 (in worms)/FXR (in humans), which in turn induces mitophagy and extends lifespan. FXR is best known for its ability to act in the liver and gut to maintain lipid homeostasis, where it acts to regulate levels of TFEB as part of a feed-fast cycle, but recently TFEB was shown to also be present in brain neurons. This provided Andersen with the clue needed to piece together MIC's potential mechanism of action in the latter. "This study provides another piece of the puzzle when it comes to understanding the brain/gut connection in terms of health and disease," said Andersen.

FXR is regulated by bile salts which are formed in the gut microbiome. "The gut microbiome impacts the body's use of bile acids. Aging impacts our microbiome," said Chamoli. "If levels of bile acids aren't correct it hinders mitophagy. That's how FXR can impact neuronal health. Neurons have a lot of mitochondria which makes mitophagy important in terms of neurodegeneration," he said, noting that experiments are underway to explore neuronal FXR as a therapeutic target for Alzheimer's disease as part of a jointly funded grant shared by the Andersen and Lithgow labs.

MIC as a general geroprotective therapeutic

"There's a bottleneck in efforts to develop potential therapeutics in the field of geroscience, and the bottleneck is that we don't have enough molecules in the pipeline," said Gordon Lithgow, PhD, Buck Professor and Vice President of Academic Affairs and senior co-author. "MIC is a great candidate to bring forward given its therapeutic effect across multiple models and the fact that it is a naturally occurring molecule."

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Milky Way-like galaxy found in the early universe

Using the James Webb Space Telescope, an international team, including astronomer Alexander de la Vega of the University of California, Riverside, has discovered the most distant barred spiral galaxy similar to the Milky Way that has been observed to date.

Until now it was believed that barred spiral galaxies like the Milky Way could not be observed before the universe, estimated to be 13.8 billion years old, reached half of its current age.

The research, published in Nature this week, was led by scientists at the Centro de Astrobiología in Spain.

"This galaxy, named ceers-2112, formed soon after the Big Bang," said coauthor de la Vega, a postdoctoral researcher in the Department of Physics and Astronomy. "Finding ceers-2112 shows that galaxies in the early universe could be as ordered as the Milky Way. This is surprising because galaxies were much more chaotic in the early universe and very few had similar structures to the Milky Way."

Ceers-2112 has a bar in its center. De la Vega explained that a galactic bar is a structure, made of stars, within galaxies. Galactic bars resemble bars in our everyday lives, such as a candy bar. It is possible to find bars in non-spiral galaxies, he said, but they are very rare.

"Nearly all bars are found in spiral galaxies," said de la Vega, who joined UCR last year after receiving his doctoral degree in astronomy at Johns Hopkins University. "The bar in ceers-2112 suggests that galaxies matured and became ordered much faster than we previously thought, which means some aspects of our theories of galaxy formation and evolution need revision."

Astronomers' previous understanding of galaxy evolution was that it took several billion years for galaxies to become ordered enough to develop bars.

"The discovery of ceers-2112 shows that it can happen in only a fraction of that time, in about one billion years or less," de la Vega said.

According to him, galactic bars are thought to form in spiral galaxies with stars that rotate in an ordered fashion, the way they do in the Milky Way.

"In such galaxies, bars can form spontaneously due to instabilities in the spiral structure or gravitational effects from a neighboring galaxy," de la Vega said. "In the past, when the universe was very young, galaxies were unstable and chaotic. It was thought that bars could not form or last long in galaxies in the early universe."

The discovery of ceers-2112 is expected to change at least two aspects of astronomy.

"First, theoretical models of galaxy formation and evolution will need to account for some galaxies becoming stable enough to host bars very early in the universe's history," de la Vega said. "These models may need to adjust how much dark matter makes up galaxies in the early universe, as dark matter is believed to affect the rate at which bars form. Second, the discovery of ceers-2112 demonstrates that structures like bars can be detected when the universe was very young. This is important because galaxies in the distant past were smaller than they are now, which makes finding bars harder. The discovery of ceers-2112 paves the way for more bars to be discovered in the young universe."

De la Vega helped the research team by estimating the redshift and properties of ceers-2112. He also contributed to the interpretation of the measurements.

"Redshift is an observable property of a galaxy that indicates how far away it is and how far back in time the galaxy is seen, which is a consequence of the finite speed of light," he said.

What surprised de la Vega most about the discovery of ceers-2112 is how well the properties of its bar could be constrained.

"Initially, I thought detecting and estimating properties of bars in galaxies like ceers-2112 would be fraught with measurement uncertainties," he said. "But the power of the James Webb Space Telescope and the expertise of our research team helped us place strong constraints on the size and shape of the bar."

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Southern Alaska's national forests key to meeting climate, conservation goals

Analyses of U.S. national forests led by Oregon State University scientists shows that increased protections for two Alaskan forests is a key to meeting climate and biodiversity goals.

In a paper published in AGU Advances, OSU College of Forestry researchers make the case that greater conservation efforts in the Tongass and Chugach national forests in southern Alaska are crucial because of their landscape integrity, high carbon stocks and wildlife habitat extent.

"More thoroughly safeguarding those forests from industrial development would contribute significantly to climate change mitigation and species adaptation in the face of the severe ecological disruption that's expected to occur over the next few decades as the climate rapidly gets warmer," said Oregon State's Bev Law, who co-led the study.

At 16.7 million acres, the Tongass is America's largest national forest. The Chugach is the second-largest at just under 7 million acres.

Not only are they the biggest national forests, they are the most intact, Law said, and provide habitat for iconic, keystone species such as the bald eagle, brown bear and gray wolf.

"Those forests are also cool and wet, with carbon stocks that are only minimally affected by wildfire, stocks that are likely to increase as the climate changes," she said. "Protecting the Tongass and Chugach is a high priority if we want to have a chance to attain global goals relating to climate and diversity of species."

Law and collaborators in the College of Forestry teamed up with researchers at Southern Oregon University, the Woodwell Climate Research Center and EcoSpatial Services L.L.C. to look at 152 national forests and compare them in terms of carbon density and accumulation, total biomass carbon stocks, habitat for eagles, bears and wolves, and landscape integrity -- defined as degree of modification by humans.

The authors report that almost 31% of all high-landscape-integrity area found in national forests -- areas with minimal or no human modification -- is in the Tongass and Chugach, at 25.3% and 5.6%, respectively.

Those forests also combine to account for nearly half of all bald eagle habitat available in national forests, 37% of brown bear habitat and 18% of gray wolf habitat -- no other location has more than 4% of the total wolf habitat found in the U.S. inventory of national forests. All three species were once widespread and abundant across much of North America.

"Forests play an incredibly important part in trying to mitigate climate change and support biodiversity," Law said. "For six decades, ecosystems on land have annually been removing roughly 30% of all the carbon dioxide humans have been putting into the atmosphere, and forests do most of that work. But intact forests with high carbon density and high biodiversity are disappearing at a frightening pace, lost to agriculture, logging and other industries, and development."

In addition to sequestering carbon and providing wildlife habitat, intact forests provide a range of ecosystem services, including helping to keep water clean, the authors note. And in the quest to establish nature-based climate solutions, public lands have outsized importance because they are more likely than private lands to afford more stable carbon storage.

Still, at present, federal forest lands are caught up in a numbers game, and conservation has some ground to make up on the scoreboard, Law said.

"National forests account for 76% of all federal forest land, but logging and other industrial activities are allowed throughout most of that, with only about 19% classified as reserved in one way or another from timber production," she said. "That means there is a substantial gap between current preservation and the preservation targets for protecting biodiversity and carbon stocks."

Ramping up protection in the Alaskan forests offers a big opportunity for closing that gap, the authors point out. Right now, 35% of the Tongass is protected at the two highest levels as categorized by the U.S. Geological Survey and the International Union for Conservation of Nature, and 57.6% of the Chugach.

"Those two forests have historically been wetter and cooler than most national forests, and over the next 100 years they are projected to have much larger increases in precipitation and much lower increases in maximum temperatures," Law said. "Combined with a relatively low occurrence of wildfire, that makes preserving these forests in their intact state highly possible -- if there is the political will to take bold action."

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