Polarized X-rays reveal shape, orientation of extremely hot matter around black hole

Researchers' recent observations of a stellar-mass black hole called Cygnus X-1 reveal new details about the configuration of extremely hot matter in the region immediately surrounding the black hole.

Matter is heated to millions of degrees as it is pulled toward a black hole. This hot matter glows in X-rays. Researchers are using measurements of the polarization of these X-rays to test and refine models that describe how black holes swallow matter, becoming some of the most luminous sources of light -- including X-rays -- in the universe.

The new measurements from Cygnus X-1, published online by the journal Science on Thursday, Nov. 3, represent the first observations of a mass-accreting black hole from the Imaging X-Ray Polarimetry Explorer (IXPE) mission, an international collaboration between NASA and the Italian Space Agency (ASI). Cygnus X-1 is one of the brightest X-ray sources in our galaxy, consisting of a 21 solar mass black hole in orbit with a 41 solar mass companion star.

"Previous X-ray observations of black holes only measured the arrival direction, arrival time and energy of the X-rays from hot plasma spiraling toward the black holes," said lead author Henric Krawczynski, the Wayman Crow Professor of Physics in Arts & Sciences at Washington University in St. Louis and a faculty fellow in the university's McDonnell Center for the Space Sciences. "IXPE also measures their linear polarization, which carries information about how the X-rays were emitted -- and if, and where, they scatter off material close to the black hole."

No light, not even light from X-rays, can escape from inside the event horizon of a black hole. The X-rays detected with IXPE are emitted by the hot matter, or plasma, in a 2,000-km diameter region surrounding the 60-km diameter event horizon of the black hole.

Combining the IXPE data with concurrent observations from NASA's NICER and NuSTAR X-ray observatories in May and June 2022 allowed the authors to constrain the geometry -- i.e., shape and location -- of the plasma.

The researchers found that the plasma extends perpendicular to a two-sided, pencil-shaped plasma outflow, or jet, imaged in earlier radio observations. The alignment of the direction of the X-ray polarization and the jet lends strong support to the hypothesis that the processes in the X-ray bright region close to the black hole play a crucial role in launching the jet.

The observations match models predicting that the corona of hot plasma either sandwiches the disk of matter spiraling toward the black hole or replaces the inner portion of that disk. The new polarization data rule out models in which the black hole's corona is a narrow plasma column or cone along the jet axis.

The scientists noted that a better understanding of the geometry of the plasma around a black hole can reveal much about the inner workings of black holes and how they accrete mass.

"These new insights will enable improved X-ray studies of how gravity curves space and time close to black holes," Krawczynski said.

Related to the Cygnus X-1 black hole specifically, "IXPE observations reveal that the accretion flow is seen more edge-on than previously thought," explained co-author Michal Dovčiak at the Astronomical Institute of the Czech Academy of Sciences.

"This may be a signature of a misalignment of the equatorial plane of the black hole and the orbital plane of the binary," or the paired duo of the black hole and its companion star, clarified co-author Alexandra Veledina from the University of Turku. "The system may have acquired that misalignment when the black hole progenitor star exploded."

"The IXPE mission uses X-ray mirrors fabricated at NASA's Marshall Space Flight Center and focal plane instrumentation provided by a collaboration of ASI, the National Institute for Astrophysics (INAF) and the National Institute for Nuclear Physics," said co-author Fabio Muleri of INAF-IAPS. "Beyond Cygnus X-1, IXPE is being used to study a wide range of extreme X-ray sources, including mass accreting neutron stars, pulsars and pulsar wind nebulae, supernova remnants, our galactic center and active galactic nuclei. We've found a lot of surprises, and we're having a lot of fun."

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Organoids reveal how SARS-CoV-2 damages brain cells -- and a potential treatment

Using human brain organoids, an international team of researchers, led by scientists at University of California San Diego School of Medicine and Sanford Consortium, has shown how the SARS-CoV-2 virus that causes COVID-19 infects cortical neurons and specifically destroys their synapses -- the connections between brain cells that allow them to communicate with each other.

The findings, published in the November 3, 2022 issue of PLOS Biology, also report that the antiviral drug sofosbuvir, already an approved treatment for hepatitis C, effectively inhibited SARS-CoV-2 replication and reversed neuronal alterations in infected brain organoids.

"Vaccines and emerging treatments have reduced the health consequences of COVID-19 in most patients," said senior study author Alysson R. Muotri, PhD, professor in departments of Pediatrics and Cellular and Molecular at UC San Diego School of Medicine. "But the phenomenon of Long COVID, characterized by persisting symptoms that include neurological impairment, remains poorly understood and without any specific remedy.

"This work helps explain some of the neurological symptoms of COVID-19 and, more importantly, it suggests that an FDA-approved antiviral drug might be repurposed to restore infected brain cells to health and address long-term neurological outcomes of COVID-19."

Though primarily considered to be a respiratory disease, COVID-19 can cause temporary or long-lasting neurological symptoms in some patients, ranging from loss of taste and smell, impaired concentration (brain fog), and psychological effects such as depression to stroke, epilepsy, and encephalopathy (a change in brain function or structure).

With evidence accumulating that the SARS-CoV-2 virus can infect and alter brain cells (including in developing fetuses), the research team focused on using organoids -- self-organizing, three-dimensional tissues derived from cultured stem cells that can mimic some organ functions.

Researchers exposed the brain organoids to SARS-CoV-2, observed viral infection and replication and noted that the virus rapidly decreased the number of excitatory synapses in neurons within seven days post-infection. Excitatory synapses increase the firing action potential of a neuron, while their counterparts, called inhibitory synapses, decrease that potential.

However, when infected organoids were treated with sofosbuvir, viral replication was inhibited, and observed neurological impairments rescued or restored. The findings echo earlier computational models that suggested sofosbuvir could be a treatment and previous research by Muotri and colleagues that found sofosbuvir effectively protected and rescued neural cells infected by the Zika virus.

"The bottom line is that sofosbuvir appears to have the potential to arrest or prevent the development of neurological symptoms in COVID-19 patients," Muotri said. "And because it has been shown to present no safety concerns in pregnant women, it might also be an option for preventing SARS-CoV-2 transmission to their unborn children.

"Further studies and clinical trials are needed, of course, but these findings offer a path forward for treating a condition (Long COVID) that has so far stymied remedy for millions of people wordwide."

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Astronomers discover closest black hole to earth

Astronomers using the International Gemini Observatory, operated by NSF's NOIRLab, have discovered the closest-known black hole to Earth. This is the first unambiguous detection of a dormant stellar-mass black hole in the Milky Way. Its close proximity to Earth, a mere 1600 light-years away, offers an intriguing target of study to advance our understanding of the evolution of binary systems.

Black holes are the most extreme objects in the Universe. Supermassive versions of these unimaginably dense objects likely reside at the centers of all large galaxies. Stellar-mass black holes -- which weigh approximately five to 100 times the mass of the Sun -- are much more common, with an estimated 100 million in the Milky Way alone. Only a handful have been confirmed to date, however, and nearly all of these are 'active' -- meaning they shine brightly in X-rays as they consume material from a nearby stellar companion, unlike dormant black holes which do not.

Astronomers using the Gemini North telescope on Hawai'i, one of the twin telescopes of the InternationalGemini Observatory, operated by NSF's NOIRLab, have discovered the closest black hole to Earth, which the researchers have dubbed Gaia BH1. This dormant black hole is about 10 times more massive than the Sun and is located about 1600 light-years away in the constellation Ophiuchus, making it three times closer to Earth than the previous record holder, an X-ray binary in the constellation of Monoceros. The new discovery was made possible by making exquisite observations of the motion of the black hole's companion, a Sun-like star that orbits the black hole at about the same distance as the Earth orbits the Sun.

"Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is, and you get this system," explained Kareem El-Badry, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonianand the Max Planck Institute for Astronomy, and the lead author of the paper describing this discovery. "While there have been many claimed detections of systems like this, almost all these discoveries have subsequently been refuted. This is the first unambiguous detection of a Sun-like star in a wide orbit around a stellar-mass black hole in our Galaxy."

Though there are likely millions of stellar-mass black holes roaming the Milky Way Galaxy, those few that have been detected were uncovered by their energetic interactions with a companion star. As material from a nearby star spirals in toward the black hole, it becomes superheated and generates powerful X-rays and jets of material. If a black hole is not actively feeding (i.e., it is dormant) it simply blends in with its surroundings.

"I've been searching for dormant black holes for the last four years using a wide range of datasets and methods," said El-Badry. "My previous attempts -- as well as those of others -- turned up a menagerie of binary systems that masquerade as black holes, but this is the first time the search has borne fruit."

The team originally identified the system as potentially hosting a black hole by analyzing data from the European Space Agency's Gaia spacecraft. Gaia captured the minute irregularities in the star's motion caused by the gravity of an unseen massive object. To explore the system in more detail, El-Badry and his team turned to the Gemini Multi-Object Spectrograph instrument on Gemini North, which measured the velocity of the companion star as it orbited the black hole and provided precise measurement of its orbital period. The Gemini follow-up observations were crucial to constraining the orbital motion and hence masses of the two components in the binary system, allowing the team to identify the central body as a black hole roughly 10 times as massive as our Sun.

"Our Gemini follow-up observations confirmed beyond reasonable doubt that the binary contains a normal star and at least one dormant black hole," elaborated El-Badry. "We could find no plausible astrophysical scenario that can explain the observed orbit of the system that doesn't involve at least one black hole."

The team relied not only on Gemini North's superb observational capabilities but also on Gemini's ability to provide data on a tight deadline, as the team had only a short window in which to perform their follow-up observations.

"When we had the first indications that the system contained a black hole, we only had one week before the two objects were at the closest separation in their orbits. Measurements at this point are essential to make accurate mass estimates in a binary system," said El-Badry. "Gemini's ability to provide observations on a short timescale was critical to the project's success. If we'd missed that narrow window, we would have had to wait another year."

Astronomers' current models of the evolution of binary systems are hard-pressed to explain how the peculiar configuration of Gaia BH1 system could have arisen. Specifically, the progenitor star that later turned into the newly detected black hole would have been at least 20 times as massive as our Sun. This means it would have lived only a few million years. If both stars formed at the same time, this massive star would have quickly turned into a supergiant, puffing up and engulfing the other star before it had time to become a proper, hydrogen-burning, main-sequence star like our Sun.

It is not at all clear how the solar-mass star could have survived that episode, ending up as an apparently normal star, as the observations of the black hole binary indicate. Theoretical models that do allow for survival all predict that the solar-mass star should have ended up on a much tighter orbit than what is actually observed.

This could indicate that there are important gaps in our understanding of how black holes form and evolve in binary systems, and also suggests the existence of an as-yet-unexplored population of dormant black holes in binaries.

"It is interesting that this system is not easily accommodated by standard binary evolution models," concluded El-Badry. "It poses many questions about how this binary system was formed, as well as how many of these dormant black holes there are out there."

"As part of a network of space- and ground-based observatories, Gemini North has not only provided strong evidence for the nearest black hole to date but also the first pristine black hole system, uncluttered by the usual hot gas interacting with the black hole," said NSF Gemini Program Officer Martin Still. "While this potentially augurs future discoveries of the predicted dormant black hole population in our Galaxy, the observations also leave a mystery to be solved -- despite a shared history with its exotic neighbor, why is the companion star in this binary system so normal?"

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Human expansion 1,000 years ago linked to Madagascar's loss of large vertebrates

The island of Madagascar -- one of the last large land masses colonized by humans -- sits about 250 miles (400 kilometers) off the coast of East Africa. While it's still regarded as a place of unique biodiversity, Madagascar long ago lost all its large-bodied vertebrates, including giant lemurs, elephant birds, turtles, and hippopotami. A human genetic study reported in the journal Current Biology on November 4 links these losses in time with the first major expansion of humans on the island, around 1,000 years ago.

"This human demographic expansion was simultaneous with a cultural and ecological transition on the island," says Denis Pierron, French National Centre for Scientific Research (CNRS) researcher in Toulouse, France. "Around the same period, cities appeared in Madagascar and all the vertebrates of more than 10 kilograms disappeared."

The origins of humans in Madagascar has long been an enigma, Pierron explained. Madagascar is home to 25 million people who speak an Asian language despite the island's proximity to East Africa. Other groups who speak similar languages live more than 4,000 miles away. The people that live on Madagascar are known to trace their roots back to two small populations: one Bantu-speaking from Africa and another Austronesian-speaking from Asia. But, beyond that, the history remained rather murky.

To retrace the history and understand more about the origin of Malagasy people, a multi-disciplinary consortium launched in 2007 a project known as Madagascar Genetic and Ethnolinguistic (MAGE). Over a 10-year period, Malagasy and international researchers visited more than 250 villages across the country to sample the cultural and genetic human diversity.

In the new study, Pierron and his colleagues took a close look at the human genetic evidence. More specifically, they closely studied how various segments of human chromosomes were shared together with local ancestry information and computer-simulated genetic data. Together, they've inferred that the Malagasy ancestral Asian population was isolated on the island for more than 1,000 years with an effective population size of just a few hundred individuals.

Their isolation ended about 1,000 years ago when a small group of Bantu-speaking African people came to Madagascar. Afterwards, the population continued to expand rapidly over generations. The growing human population led to extensive changes to the Madagascar landscape and the loss of all large-bodied vertebrates that once lived there, they suggest.

The findings have important implications that may now be applied to studies of other human populations. For instance, it shows it's possible to untangle the demographic history of ancient populations even well after two or more groups have mixed, by using genetic data and computer simulations to test the likelihood of different scenarios. The findings also offer new insights into how past changes in human populations led to changes in whole ecosystems.

"Our study supports the theory that it was not directly the arrival of humans on the island that caused the disappearance of the megafauna, but rather a change in lifestyle that caused both a human population expansion and a reduction in biodiversity in Madagascar," Pierron says.

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Surface melting of glass

In 1842, the famous British researcher Michael Faraday made an amazing observation by chance: A thin layer of water forms on the surface of ice, even though it is well below zero degrees. So the temperature is below the melting point of ice, yet the surface of the ice has melted. This liquid layer on ice crystals is also why snowballs stick together.

It was not until about 140 years later, in 1985, that this "surface melting" could be scientifically confirmed under controlled laboratory conditions. By now, surface melting has been demonstrated in a variety of crystalline materials and is scientifically well understood: Several degrees below the actual melting point, a liquid layer only a few nanometres thick forms on the surface of the otherwise solid material. Because the surface properties of materials play a crucial role in their use as, e.g. catalysts, sensors, battery electrodes and more, surface melting is not only of fundamental importance but also in view of technical applications.

It must be emphasized that this process has absolutely nothing to do with the effect of, say, taking an ice cube out of the freezer and exposing it to ambient temperature. The reason why an ice cube melts on its surface first under such conditions is that the surface is significantly warmer than the ice cube's interior.

Surface melting detected in glass

In crystals with periodically arranged atoms, the thin liquid layer on the surface is typically detected by scattering experiments, which are very sensitive to the presence of atomic order. Since liquids are not arranged in a regular pattern, such techniques can therefore clearly resolve the appearance of a thin liquid film on top of the solid. This approach, however, does not work for glasses (i.e. disordered, amorphous materials) because there is no difference in the atomic order between the solid and the liquid. Therefore, surface melting of glasses has remained rather unexplored with experiments.

To overcome the above-mentioned difficulties, Clemens Bechinger, physics professor at the University of Konstanz, and his colleague Li Tian used a trick: instead of studying an atomic glass, they produced a disordered material made of microscopic glass spheres known as colloids. In contrast to atoms, these particles are about 10,000 times larger and can be observed directly under a microscope.

The researchers were able to demonstrate the process of surface melting in such a colloidal glass because the particles near the surface move much faster compared to the solid below. At first glance, such behaviour is not entirely unexpected, since the particle density at the surface is lower than in the underlying bulk material. Therefore, particles close to the surface have more space to move past each other, which makes them faster.

A surprising discovery

What surprised Clemens Bechinger and Li Tian, however, was the fact that even far below the surface, where the particle density has reached the bulk value, the particle mobility is still significantly higher compared to the bulk material. The microscope images show that this previously unknown layer is up to 30 particle diameters thick and continues from the surface into the deeper regions of the solid in a streak-like pattern. "This layer which reaches far into the material has interesting material properties since it combines liquid and solid features," Bechinger explains.

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How magnetism could help explain Earth's formation

There are several theories about how the Earth and the Moon were formed, most involving a giant impact. They vary from a model where the impacting object strikes the newly formed Earth a glancing blow and then escapes, through to one where the collision is so energetic that both the impactor and the Earth are vaporized.

Now scientists at the University of Leeds and the University of Chicago have analysed the dynamics of fluids and electrically conducting fluids and concluded that the Earth must have been magnetized either before the impact or as a result of it.

They claim this could help to narrow down the theories of the Earth-Moon formation and inform future research into what really happened.

Professor David Hughes, an applied mathematician in the School of Mathematics at the University of Leeds, said: "Our new idea is to point out that our theoretical understanding of the Earth's magnetic field today can actually tell us something about the very formation of the Earth-Moon system.

"At first glance, this seems somewhat surprising, and previous theories had not recognized this potentially important connection."

This new assessment is based on the resilience of Earth's magnetic field, which is maintained by a rotating and electrically conducting fluid in the outer core, known as a geodynamo.

Professor Fausto Cattaneo, an astrophysicist at the University of Chicago, said: "A peculiar property of the Earth's dynamo is that it can maintain a strong magnetic field but not amplify a weak one.

The scientists therefore concluded that if the Earth's field were to get switched off, or even reduced to a very small level, it would not have the capability to kick in again.

"It is this remarkable feature that allows us to make deductions about the history of the early Earth; including, possibly, how the Moon was formed," added Professor Cattaneo.

Professor Hughes added: "And if that is true, then you have to think, where did the Earth's magnetic field come from in the first place?

"Our hypothesis is that it got to this peculiar state way back at the beginning, either pre-impact or as an immediate result of the impact.

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IceCube neutrinos give us first glimpse into the inner depths of an active galaxy

For the first time, an international team of scientists have found evidence of high-energy neutrino emission from NGC 1068, also known as Messier 77, an active galaxy in the constellation Cetus and one of the most familiar and well-studied galaxies to date. First spotted in 1780, this galaxy, located 47 million light-years away from us, can be observed with large binoculars. The results, to be published tomorrow (Nov. 4, 2022) in Science, were shared today in an online scientific webinar that gathered experts, journalists, and scientists from around the globe.

The detection was made at the National Science Foundation-supported IceCube Neutrino Observatory, a massive neutrino telescope encompassing 1 billion tons of instrumented ice at depths of 1.5 to 2.5 kilometers below Antarctica's surface near the South Pole. This unique telescope, which explores the farthest reaches of our universe using neutrinos, reported the first observation of a high-energy astrophysical neutrino source in 2018. The source, TXS 0506+056, is a known blazar located off the left shoulder of the Orion constellation and 4 billion light-years away.

"One neutrino can single out a source. But only an observation with multiple neutrinos will reveal the obscured core of the most energetic cosmic objects," says Francis Halzen, a professor of physics at the University of Wisconsin-Madison and principal investigator of IceCube. He adds, "IceCube has accumulated some 80 neutrinos of teraelectronvolt energy from NGC 1068, which are not yet enough to answer all our questions, but they definitely are the next big step towards the realization of neutrino astronomy."

Unlike light, neutrinos can escape in large numbers from extremely dense environments in the universe and reach Earth largely undisturbed by matter and the electromagnetic fields that permeate extragalactic space. Although scientists envisioned neutrino astronomy more than 60 years ago, the weak interaction of neutrinos with matter and radiation makes their detection extremely difficult. Neutrinos could be key to our queries about the workings of the most extreme objects in the cosmos.

"Answering these far-reaching questions about the universe that we live in is a primary focus of the U.S. National Science Foundation," says Denise Caldwell, director of NSF's Physics Division.

As is the case with our home galaxy, the Milky Way, NGC 1068 is a barred spiral galaxy, with loosely wound arms and a relatively small central bulge. However, unlike the Milky Way, NGC 1068 is an active galaxy where most radiation is not produced by stars but due to material falling into a black hole millions of times more massive than our Sun and even more massive than the inactive black hole in the center of our galaxy.

NGC 1068 is an active galaxy -- a Seyfert II type in particular -- seen from Earth at an angle that obscures its central region where the black hole is located. In a Seyfert II galaxy, a torus of nuclear dust obscures most of the high-energy radiation produced by the dense mass of gas and particles that slowly spiral inward toward the center of the galaxy.

"Recent models of the black hole environments in these objects suggest that gas, dust, and radiation should block the gamma rays that would otherwise accompany the neutrinos," says Hans Niederhausen, a postdoctoral associate at Michigan State University and one of the main analyzers of the paper. "This neutrino detection from the core of NGC 1068 will improve our understanding of the environments around supermassive black holes."

NGC 1068 could become a standard candle for future neutrino telescopes, according to Theo Glauch, a postdoctoral associate at the Technical University of Munich (TUM), in Germany, and another main analyzer.

"It is already a very well-studied object for astronomers, and neutrinos will allow us to see this galaxy in a totally different way. A new view will certainly bring new insights," says Glauch.

These findings represent a significant improvement on a prior study on NGC 1068 published in 2020, according to Ignacio Taboada, a physics professor at the Georgia Institute of Technology and the spokesperson of the IceCube Collaboration.

"Part of this improvement came from enhanced techniques and part from a careful update of the detector calibration," says Taboada. "Work by the detector operations and calibrations teams enabled better neutrino directional reconstructions to precisely pinpoint NGC 1068 and enable this observation. Resolving this source was made possible through enhanced techniques and refined calibrations, an outcome of the IceCube Collaboration's hard work."

The improved analysis points the way toward superior neutrino observatories that are already in the works.

"It is great news for the future of our field," says Marek Kowalski, an IceCube collaborator and senior scientist at Deutsches Elektronen-Synchrotron, in Germany. "It means that with a new generation of more sensitive detectors there will be much to discover. The future IceCube-Gen2 observatory could not only detect many more of these extreme particle accelerators but would also allow their study at even higher energies. It's as if IceCube handed us a map to a treasure trove."

With the neutrino measurements of TXS 0506+056 and NGC 1068, IceCube is one step closer to answering the century-old question of the origin of cosmic rays. Additionally, these results imply that there may be many more similar objects in the universe yet to be identified.

"The unveiling of the obscured universe has just started, and neutrinos are set to lead a new era of discovery in astronomy," says Elisa Resconi, a professor of physics at TUM and another main analyzer.

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Ancient DNA analysis sheds light on the early peopling of South America

The Americas were the last continent to be inhabited by humans. An increasing body of archaeological and genomic evidence has hinted to a complex settlement process. This is especially true for South America, where unexpected ancestral signals have raised perplexing scenarios for the early migrations into different regions of the continent.

Many unanswered questions still persist, such as whether the first humans migrated south along the Pacific coast or by some other route. While there is archaeological evidence for a north-to-south migration during the initial peopling of the Americas by ancient Indigenous peoples, where these ancient humans went after they arrived has remained elusive.

Using DNA from two ancient human individuals unearthed in two different archaeological sites in northeast Brazil -- Pedra do Tubarão and Alcobaça -- and powerful algorithms and genomic analyses, Florida Atlantic University researchers in collaboration with Emory University have unraveled the deep demographic history of South America at the regional level with some unexpected and surprising results.

Not only do researchers provide new genetic evidence supporting existing archaeological data of the north-to-south migration toward South America, they also have discovered migrations in the opposite direction along the Atlantic coast -- for the first time. The work provides the most complete genetic evidence to date for complex ancient Central and South American migration routes.

Among the key findings, researchers also have discovered evidence of Neanderthal ancestry within the genomes of ancient individuals from South America. Neanderthals are an extinct population of archaic humans that ranged across Eurasia during the Lower and Middle Paleolithic.

Results of the study, published in the journal Proceedings of the Royal Society B. (Biological Sciences), suggest that human movements closer to the Atlantic coast eventually linked ancient Uruguay and Panama in a south-to-north migration route -- 5,277 kilometers (3,270 miles) apart. This novel migration pattern is estimated to have occurred approximately 1,000 years ago based on the ages of the ancient individuals.

Findings show a distinct relationship among ancient genomes from northeast Brazil, Lagoa Santa (southeast Brazil), Uruguay and Panama. This new model reveals that the settlement of the Atlantic coast occurred only after the peopling of most of the Pacific coast and Andes.

"Our study provides key genomic evidence for ancient migration events at the regional scale along South America's Atlantic coast," said Michael DeGiorgio, Ph.D., co-corresponding author who specializes in human, evolutionary, and computational genomics and is an associate professor in the Department of Electrical Engineering and Computer Science within FAU's College of Engineering and Computer Science. "These regional events likely derived from migratory waves involving the initial Indigenous peoples of South America near the Pacific coast."

Researchers also found strong Australasian (Australia and Papua New Guinea) genetic signals in an ancient genome from Panama.

"There is an entire Pacific Ocean between Australasia and the Americas, and we still don't know how these ancestral genomic signals appeared in Central and South America without leaving traces in North America," said Andre Luiz Campelo dos Santos, Ph.D., first author, an archaeologist and a postdoctoral fellow in FAU's Department of Electrical Engineering and Computer Science.

To further add to the existing complexity, researchers also detected greater Denisovan than Neanderthal ancestry in ancient Uruguay and Panama individuals. Denisovans are a group of extinct humans first identified from DNA sequences from the tip of finger bone discovered around 2008.

"It's phenomenal that Denisovan ancestry made it all the way to South America," says John Lindo, Ph.D., a co-corresponding author of the article who specializes in ancient DNA analysis and is an assistant professor in the Department of Anthropology at Emory University. "The admixture must have occurred a long time before, perhaps 40,000 years ago. The fact that the Denisovan lineage persisted and its genetic signal made it into an ancient individual from Uruguay that is only 1,500 years old suggests that it was a large admixture event between a population of humans and Denisovans."

Previously at the Federal University of Pernambuco in Recife, Brazil, dos Santos and colleagues uncovered the remains of the two ancient humans from northeast Brazil, which date back to at least 1,000 years before present, and sent them to Lindo for DNA extraction and subsequent genomic sequencing and analyses. Raw data were then sent to FAU for computational analysis of the whole genome sequences from northeast Brazil.

Researchers compared the two newly sequenced ancient whole genomes from northeast Brazil with present-day worldwide genomes and other ancient whole genomes from the Americas. As of the publication date of the article, Lindo says that only a dozen or so ancient whole genomes from South America have been sequenced and published, in contrast to hundreds from Europe.

Apart from the occurrence of mass burials in the sites that yielded the samples from northeast Brazil, Uruguay, southeast Brazil and Panama, there is no other evidence in the archaeological record that indicate shared cultural features among them. Importantly, the analyzed ancient individuals from southeast Brazil are about 9,000 years older than those from northeast Brazil, Uruguay and Panama, enough time for expected and noticeable cultural divergence. Moreover, northeast Brazil, Uruguay and Panama, though more similar in age, are located thousands of kilometers apart from each other.

"This groundbreaking research involved many different fields from archaeology to biological sciences to genomics and data science," said Stella Batalama, Ph.D., dean, FAU College of Engineering and Computer Science. "Our scientists at Florida Atlantic University in collaboration with Emory University have helped to shed light on an important piece of the Americas puzzle, which could not have been solved without powerful genomic and computational tools and analysis."

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Public more likely to support climate action if other countries commit as well

The public is more willing to bear the costs of climate action if other countries contribute as well. This is the result of a study conducted by Professor Dr Michael Bechtel, member of the Cluster of Excellence ECONtribute (University of Cologne), Professor Dr Kenneth Scheve (Yale University), and Dr Elisabeth van Lieshout (Stanford University), which has recently been published in the journal Nature Communications.

In representative surveys, the researchers investigated whether the extent to which the public supports costly climate policies, e.g., the introduction of a domestic carbon tax, depends on whether other countries also pursue climate action. The results suggest that if other countries invest in climate action, the domestic public is more willing to approve introducing a domestic carbon tax because individuals expect these policy efforts to be fairer and more likely to be effective.

The team surveyed a total of 10,000 citizens in Germany, France, the United Kingdom and the United States in early 2019. Respondents were asked to indicate who much they approved or disapproved the introduction of a carbon tax. 60 percent of respondents supported a tax if other countries also introduced one. However, when other countries did not joint these efforts, domestic carbon tax approval dopped to 53 percent. 'We also find that when domestic climate measures are embedded internationally, people are more likely to believe that these reforms will have a positive impact on important social, economic, and environmental sustainability goals, ' says Michael Bechtel.

In a second study, the research team investigated whether the costs of climate action would be more broadly accepted domestically if other countries pursued more ambitious and thus more costly measures. Participants were asked whether they would be willing to support costly climate policy scenarios in which the researchers varied the level of contributions made by other countries. If domestic monthly household costs increased from a low to a higher level, in the case of Germany for example from EUR 39 to 77 per month, support decreased by seven percentage points if the price of carbon dioxide remained low abroad. However, if other industrialized countries decided to introduce high monthly household costs, domestic policy support fell only by about five percentage points in response to a domestic CO2 price increase. 'Even if people generally dislike costs, they are more willing to accept cost increases if other countries also make higher contributions, ' says Michael Bechtel.

Climate change measures in other countries thus play a crucial role in securing mass support for domestic climate policy, according to the study. 'Investing in well-functioning international agreements is worthwhile not only from a natural science perspective, but also for policymakers interested in securing broader public support for costly climate action domestically, ' says Bechtel.

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A stone age child buried with bird feathers, plant fibers and fur

The exceptional excavation of a Stone Age burial site was carried out in Majoonsuo, situated in the municipality of Outokumpu in Eastern Finland. The excavation produced microscopically small fragments of bird feathers, canine and small mammalian hairs, and plant fibres. The findings gained through soil analysis are unique, as organic matter is poorly preserved in Finland's acidic soil. The study, led by Archaeologist Tuija Kirkinen, was aimed at investigating how these highly degraded plant- and animal-based materials could be traced through soil analysis.

During the Stone Age in Finland, the deceased were interred mainly in pits in the ground. Little of the organic matter from human-made objects have been preserved in Stone Age graves in Finland, but it is known, on the basis of burial sites in the surrounding regions, that objects made of bones, teeth and horns as well as furs and feathers were placed in the graves.

Teeth and arrowheads found in the red ochre grave

The Trial Excavation Team of the Finnish Heritage Agency examined the site in 2018, as it was considered to be at risk of destruction. The burial place was located under a gravelly sand road in a forest, with the top of the grave partially exposed. The site was originally given away by the intense colour of its red ochre. Red ochre, or iron-rich clay soil, has been used not only in burials but also in rock art around the world.

In the archaeological dig at the burial site, only a few teeth were found of the deceased, on the basis of which they are known to have been a child between 3 and 10 years of age. In addition, two transverse arrowheads made of quartz and two other possible quartz objects were found in the grave. Based on the shape of the arrowheads and shore-level dating, the burial can be estimated to have taken place in the Mesolithic period of the Stone Age, roughly 6,000 years before the Common Era.

What made the excavation exceptional was the near-complete preservation of the soil originating in the grave. A total of 65 soil sample bags weighing between 0.6 and 3.4 kilograms were collected, also comparison samples were taken from outside the grave. The soil was analyzed in the archaeology laboratory of the University of Helsinki. Organic matter was separated from the samples using water. This way, the exposed fibres and hairs were identified with the help of transmitted-light and electron microscopy.

Oldest feather fragments found in Finland

From the soil samples, a total of 24 microscopic (0.2-1.4 mm) fragments of bird feathers were identified, most of which originated in down. Seven feather fragments were identified as coming from the down of a waterfowl (Anseriformes). These are the oldest feather fragments ever found in Finland. Although the origin of the down is impossible to state with certainty, it may come from clothing made of waterfowl skins, such as a parka or an anorak. It is also possible that the child was laid on a down bed.

In addition to the waterfowl down, one falcon (Falconidae) feather fragment was identified. It may have originally been part of the fletching of the arrows attached to the arrowheads, or, for example, from feathers used to decorate the garment.

Dog or wolf hairs?

Besides the feathers, 24 fragments of mammalian hair were identified, ranging from 0.5 to 9.5 mm in length. Most of the hairs were badly degraded, making identification no longer possible. The finest discoveries were the three hairs of a canine, possibly a predator, found at the bottom of the grave. The hairs may also originate, for example, in footwear made of wolf or dog skin. It is also possible a dog was laid at the child's feet.

"Dogs buried with the deceased have been found in, for example, Skateholm, a famous burial site in southern Sweden dating back some 7,000 years," says Professor Kristiina Mannermaa, University of Helsinki.

"The discovery in Majoonsuo is sensational, even though there is nothing but hairs left of the animal or animals -- not even teeth. We don't even know whether it's a dog or a wolf," she says, adding: "The method used, demonstrates that traces of fur and feathers can be found even in graves several thousands of years old, including in Finland."

"This all gives us a very valuable insight about burial habits in the Stone Age, indicating how people had prepared the child for the journey after death," says Kirkinen.

The soil is full of information

Also found were three fragments of plant fibres, which are preserved particularly poorly in the acidic Finnish soil. The fibres were what are known as bast fibres, meaning that they come from, for example, willows or nettles. At the time, the object they were part of may have been a net used for fishing, a cord used to attach clothes, or a bundle of strings. For the time being, only one other bast fibre discovery dating back to the Mesolithic Stone Age is known in Finland: the famed Antrea Net on display in the National Museum of Finland, laced with willow bast fibres.

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Space probe's collision with asteroid: Study assesses ejecta momentum enhancement

On September 26, NASA's Double Asteroid Redirection Test (DART) spacecraft crashed into Dimorphos, a moonlet of the near-Earth asteroid Didymos, at 14,000 miles per hour. Prior to the impact, Southwest Research Institute engineers and scientists performed an experiment to study the cratering process that produces the mass of ejected materials and measures the subsequent momentum enhancement of the impact. The internally funded experiment, which used a more realistic target than those previously explored, is described in a new paper published in The Planetary Science Journal.

NASA not only tracks near-Earth asteroids (NEAs) that could pose a possible impact threat to our home planet but is also exploring technology to deflect the path of a small NEA. Only a small orbital change would be needed to change an object's trajectory so that it passes safely by Earth, as long as the change is applied sufficiently far in advance of the time of impact. Changing the momentum of an asteroid through a direct collision offers a one-two punch: the direct momentum transfer of the impacting projectile, pushing it forward, and the asteroid's recoil from the debris erupting from the impact crater, also known as crater ejecta. The ejecta transfers momentum, propelling the target away in an "action-reaction" fashion, much like a rocket launches when high-speed gas erupts from the rear of the vehicle.

"One big question we faced was what the asteroid would actually look like and what its composition would be. Whether we can learn something from small-scale laboratory experiments is an issue of major interest to us," said Dr. James D. Walker, director of SwRI's Engineering Dynamics department and the study's lead author.

Walker is a member of the DART Investigation Team alongside his co-authors, Dr. Sidney Chocron, Donald J. Grosch and Dr. Simone Marchi.

The DART mission spacecraft launched from Earth in November 2021. On September 26, it was deliberately crashed into the moonlet Dimorphos to assess whether a spacecraft could deflect an asteroid on a collision course with Earth. Dimorphos orbits the asteroid Didymos, a near-Earth object that has been classified as a potentially hazardous asteroid. DART is designed to nudge the orbit of the moonlet around Didymos.

SwRI's large two-stage light gas gun, which is capable of launching projectiles at speeds up to seven kilometers per second, was used to launch a projectile at an object representing the moonlet. Because Dimorphos was thought to be a "rubble pile" asteroid made up of pieces of rock bound together by gravity, the moonlet was represented by a collection of rocks and stones, in this case held together by cement.

"We fired an aluminum sphere, which represented the DART space probe, using the two-stage light gas gun at the target at 5.44 kilometers per second, which is approaching the expected 6.1 kilometers per second of the DART impact," Walker said. "Our experiment measured a momentum transfer to the target of 3.4 times the incoming momentum of the aluminum sphere projectile. The number 3.4 is referred to by scientists as the Greek letter beta of the impact. Hence the crater ejecta provided an additional 240% of momentum to deflect the body, beyond that provided by the projectile itself."

The experiment aimed to study the cratering process and measure the momentum enhancement that would result from the collision. Crucially, the rubble pile was not held in place but was hung vertically as a pendulum to measure the momentum enhancement, or recoil, created by the impact ejecta.

"It's important to understand the amount of recoil," co-author Dr. Simone Marchi said. "It all boils down to the amount of momentum that has been transferred to the target from the impact, and there was a significant amount of recoil and ejecta material."

By measuring the momentum, the SwRI team could then extract important information that could assess the difficulty of deflecting asteroids in space. In this latest experiment, the momentum enhancement was higher than what was witnessed in the team's prior experiments. A higher recoil suggests it would be easier to deflect the asteroid.

In the weeks following the impact, NASA announced that DART had been successful in nudging the moonlet. Walker is now looking forward to seeing what else can be learned from the mission, including the momentum transfer of the event in space.

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500 million year-old fossils reveal answer to evolutionary riddle

An exceptionally well-preserved collection of fossils discovered in eastern Yunnan Province, China, has enabled scientists to solve a centuries-old riddle in the evolution of life on earth, revealing what the first animals to make skeletons looked like. The results have been published today in Proceedings of the Royal Society B.

The first animals to build hard and robust skeletons appear suddenly in the fossil record in a geological blink of an eye around 550-520 million years ago during an event called the Cambrian Explosion. Many of these early fossils are simple hollow tubes ranging from a few millimetres to many centimetres in length. However, what sort of animals made these skeletons was almost completely unknown, because they lack preservation of the soft parts needed to identify them as belonging to major groups of animals that are still alive today.

The new collection of 514 million year old fossils includes four specimens of Gangtoucunia aspera with soft tissues still intact, including the gut and mouthparts. These reveal that this species had a mouth fringed with a ring of smooth, unbranched tentacles about 5 mm long. It's likely that these were used to sting and capture prey, such as small arthropods. The fossils also show that Gangtoucunia had a blind-ended gut (open only at one end), partitioned into internal cavities, that filled the length of the tube.

These are features found today only in modern jellyfish, anemones and their close relatives (known as cnidarians), organisms whose soft parts are extremely rare in the fossil record. The study shows that these simple animals was among the first to build the hard skeletons that make up much of the known fossil record.

According to the researchers, Gangtoucunia would have looked similar to modern scyphozoan jellyfish polyps, with a hard tubular structure anchored to the underlying substrate. The tentacle mouth would have extended outside the tube, but could have been retracted inside the tube to avoid predators. Unlike living jellyfish polyps however, the tube of Gangtoucunia was made of calcium phosphate, a hard mineral that makes up our own teeth and bones. Use of this material to build skeletons has become more rare among animals over time.

Corresponding author Dr Luke Parry, Department of Earth Sciences, University of Oxford, said: 'This really is a one-in-million discovery. These mysterious tubes are often found in groups of hundreds of individuals, but until now they have been regarded as 'problematic' fossils, because we had no way of classifying them. Thanks to these extraordinary new specimens, a key piece of the evolutionary puzzle has been put firmly in place.'

The new specimens clearly demonstrate that Gangtoucunia was not related to annelid worms (earthworms, polychaetes and their relatives) as had been previously suggested for similar fossils. It is now clear that Gangtoucunia's body had a smooth exterior and a gut partitioned longitudinally, whereas annelids have segmented bodies with transverse partitioning of the body.

The fossil was found at a site in the Gaoloufang section in Kunming, eastern Yunnan Province, China. Here, anaerobic (oxygen-poor) conditions limit the presence of bacteria that normally degrade soft tissues in fossils.

PhD student Guangxu Zhang, who collected and discovered the specimens, said: 'The first time I discovered the pink soft tissue on top of a Gangtoucunia tube, I was surprised and confused about what they were. In the following month, I found three more specimens with soft tissue preservation, which was very exciting and made me rethink the affinity of Gangtoucunia. The soft tissue of Gangtoucunia, particularly the tentacles, reveals that it is certainly not a priapulid-like worm as previous studies suggested, but more like a coral, and then I realised that it is a cnidarian.'

Although the fossil clearly shows that Gangtoucunia was a primitive jellyfish, this doesn't rule out the possibility that other early tube-fossil species looked very different. From Cambrian rocks in Yunnan province, the research team have previously found well-preserved tube fossils that could be identified as priapulids (marine worms), lobopodians (worms with paired legs, closely related to arthropods today) and annelids.

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Why fish look down when they swim

Just as you might look down at the sidewalk as you walk, fish look downward when they swim, a new study by a Northwestern University-led international collaboration has confirmed.

The study is the first to combine simulations of zebrafish's brain, native environment and spatially-varying swimming behavior into one computational model. By analyzing this model, the researchers concluded that this quirk -- looking down while swimming forward -- is an adaptive behavior that evolved to help the fish self-stabilize, as when swimming against a current.

As water moves, fish are constantly trying to self-stabilize in order to stay in place -- rather than getting swept away in a moving stream. Focusing on other fish, plants or debris might give the fish a false sensation that it's moving. The stable riverbed below them, however, gives fish more reliable information about their swimming direction and speed.

"It's similar to sitting on a train car that isn't moving. If the train next to yours starts to pull to away from the station, it can trick you into thinking you are moving too," said Northwestern's Emma Alexander, who led the study. "The visual cue from the other train is so strong that it overrides the fact that all of your other senses are telling you that you are sitting still. That's exactly the same phenomenon that we are studying in fish. There are many misleading motion cues above them, but the most abundant and reliable signals are from the bottom of the river."

The study will be published Nov. 2 in the journal Current Biology.

Alexander is an assistant professor of computer science in Northwestern's McCormick School of Engineering, where she runs the Bio Inspired Vision Lab.

Going 'back to the source'

To conduct the research, Alexander and her collaborators focused on zebrafish, a well-studied model organism. But, although many laboratories have tanks full of zebrafish, the team wanted to focus on the fish's native environment in India.

"It was recently discovered that fish respond to motion below them more strongly than motion above them. We wanted to dig into that mystery and understand why," Alexander explained. "Many zebrafish that we study grow up in lab tanks, but their native habitats shaped the evolution of their brains and behaviors, so we needed to go back to the source to investigate the context for where the organism developed."

Armed with camera equipment, the team visited seven sites across India to gather video data of shallow rivers, where zebrafish naturally live. The field team encased a 360-degree camera inside a waterproof diving case and attached it to a remotely-controlled robotic arm. Then, they used the robotic arm to plunge the camera into the water and move it around.

"It allowed us to put our eyes where the fish eyes would be, so it's seeing what the fish see," Alexander said. "From the video data, we were able to model hypothetical scenarios where a simulated fish moved arbitrarily through a realistic environment."

'Wait for me!'

Back in the lab, the team also tracked zebrafish's motions inside a ball of LEDs. Because fish have a large field of view, they do not have to move their eyes to look around like people do. So, the researchers played motion stimuli across the lights and watched the fishes' responses. When patterns appeared on the bottom of the tank, the fish swam along with the moving patterns -- more evidence that the fish were taking their visual cues from looking downward.

"If you play a video with moving stripes, the fish will move along with the stripes," Alexander said. "It's like they are saying 'wait for me!' In the behavioral experiment, we counted their tail beats. The more they wagged their tails, the more they wanted to keep up with the moving stripes."

The team then abstracted data from its videos and combined it with data from how motion signals get encoded into the fish's brain. They fed the datasets into two pre-existing algorithms used for studying optic flow (or the movement of the world across our eyes or camera lenses).

Ultimately, they discovered that in both scenarios -- in the wild and in the lab -- zebrafish look down when swimming forward. The researchers concluded that fish look down to understand their environment's motion and then swim to counteract it -- to avoid being swept away.

"We tied everything together into a simulation that showed that, in fact, this is an adaptive behavior," said Alexander, who led the computational part of the study. "The water surface is constantly moving, and other fish and plants are moving by. Fish are better off omitting that information and focusing on the information below them. Riverbeds have a lot of texture, so fish are seeing strong features they can track."

Building better robots

Not only does this information gives some insight into fishes' behavior, it could also inform designs for artificial vision systems and sophisticated bio-inspired robots.

"If you were making a fish-inspired robot and you just looked at its anatomy, you might think 'the eyes are pointing sideways, so I'm going to point my cameras sideways,'" Alexander said. "But it turns out that the eyes are pointing sideways because they are balancing several tasks. We think they point sideways because it's a compromise -- they look upward to hunt and downward to swim."

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Climate change could trigger the Congo peatlands to release billions of tons of carbon

New research published in Nature today (Wed, Nov 2) reveals that the world's largest tropical peatland turned from being a major store of carbon to a source of damaging carbon dioxide emissions as a result of climate change thousands of years ago.

Around the time that Stonehenge was built, 5,000 years ago, the climate of central Congo began to dry leading to the peatlands emitting carbon dioxide. The peatlands only stopped releasing carbon and reverted back to taking carbon out of the atmosphere when the climate got wetter again in the past 2,000 years, according to a major international study co-coordinated by the University of Leeds.

Scientists involved in the study are warning that if modern-day global heating produces droughts in the Congo region, history could repeat itself, dangerously accelerating climate change.

If that were to happen, up to 30 billion tonnes of carbon could be released from the peatlands into the atmosphere as carbon dioxide, a potent greenhouse gas. That is equivalent to the global emissions from fossil fuel burning over a three-year period.

Professor Simon Lewis, from the University of Leeds and University College London, a senior author of the study, said: "Our study brings a brutal warning from the past. If the peatlands dry beyond a certain threshold they will release colossal quantities of carbon to the atmosphere, further accelerating climate change.

"There is some evidence that dry seasons are lengthening in the Congo Basin, but it is unclear if these will continue. But evidence from our study shows that drier conditions have existed in the past and did trigger a breakdown of the peatlands as a store of carbon.

"This is an important message for world leaders gathering at the COP27 climate talks next week. If greenhouse gas emissions drive the central Congo peatlands to become too dry, then the peatlands will contribute to the climate crisis rather than protect us."

Warnings from the past

The Congo peatlands in central Africa are the world's largest tropical peatlands complex, occupying an area of 16.7 million hectares, bigger than England and Wales combined.

Congolese and European scientists took peat samples from beneath the remote swamp forests of central Congo. By analysing plant remains, the researchers were able to build a record of the vegetation and rainfall in the central Congo basin over the last 17,500 years when the peat began to form.

Waxes from plant leaves, which were preserved in the peat, were used to calculate rainfall levels at the time the plant was living.

The findings -- Hydroclimatic vulnerability of peat carbon in the central Congo Basin -- paint a picture of a drier climate developing in central Africa, which began around 5,000 years ago.

At the most intense period of drought, rainfall was reduced by at least 800 mm a year. This caused the water table in the Congo peatlands to drop, exposing older layers of peat to the air, causing oxidation and release of carbon dioxide.

Ghost interval in the peat record

Between 7,500 and 2,000 years ago, the peat layers either decomposed or never accumulated. The researchers described this as the "ghost interval." This same ghost interval was found in peat samples from hundreds of kilometres away in the Democratic Republic of the Congo (DRC) indicating it happened across the whole peatland region.

Dr Yannick Garcin, from the National Research Institute for Sustainable Development of France and lead author of the study, said: "The peat samples show us that there was a period of around 5,000 years when there was almost no build-up of peat, less than 0.1 mm per year.

"The samples also reveal what the rainfall and vegetation was like when the peat was formed. Together they give a picture of a drying climate that got progressively drier until about 2,000 years ago.

"This drought led to a huge loss of peat, at least 2 metres. The drought flipped the peatland to a huge carbon source as the peat decomposed. This decomposition only stopped when the drought stopped allowing peat to start accumulating again."

Peatlands are 'vulnerable'

The scientists warn that while the peatlands are currently largely intact and managed sustainably by local people, they are vulnerable.

Apart from the threat of the peatlands getting drier from climate change, the region is subject to additional pressures which could cause damage to the fragile peatland ecosystem, from draining the peatland for industrial-scale agriculture, logging, and oil exploration.

Professor Corneille Ewango, from the University of Kisangani in the Democratic Republic of the Congo and who led the expeditions to collect the peat samples from the DRC, said: "This is another astonishing finding about the peatlands. They are more vulnerable than we thought, and everyone must play their role in protecting them.

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ESO captures the ghost of a giant star

A spooky spider web, magical dragons or wispy trails of ghosts? A beautiful tapestry of colours shows the ghostly remains of a gigantic star, and was captured here in incredible detail with the VLT Survey Telescope, hosted at the European Southern Observatory's (ESO's) Paranal site in Chile.

The wispy structure of pink and orange clouds is all that remains of a massive star that ended its life in a powerful explosion around 11,000 years ago. When the most massive stars reach the end of their life, they often go out with a bang, in an outburst called a supernova. These explosions cause shock waves that move through the surrounding gas, compressing it and creating intricate thread-like structures. The energy released heats the gaseous tendrils, making them shine brightly, as seen in this image.

In this 554-million-pixel image, we get an extremely detailed view of the Vela supernova remnant, named after the southern constellation Vela (The Sails). You could fit nine full Moons in this entire image, and the whole cloud is even larger. At only 800 light-years away from Earth, this dramatic supernova remnant is one of the closest known to us.

As it exploded, the outermost layers of the progenitor star were ejected into the surrounding gas, producing the spectacular filaments that we observe here. What remains of the star is an ultra-dense ball in which the protons and electrons are forced together into neutrons -- a neutron star. The neutron star in the Vela remnant, placed slightly outside of this image to the upper left, happens to be a pulsar that spins on its own axis at an incredible speed of more than 10 times per second.

This image is a mosaic of observations taken with the wide-field camera OmegaCAM at the VLT Survey Telescope (VST), hosted at ESO's Paranal Observatory in Chile. The 268-million-pixel camera can take images through several filters that let through light of different colours. In this particular image of the Vela remnant, four different filters were used, represented here by a combination of magenta, blue, green and red.

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Learning to better understand the language of algae

Communication is everything -- and that applies for algae, too. However, their chemical language and its significance in aquatic ecosystems remain largely unknown. A research duo from the Helmholtz Centre for Environmental research (UFZ) and the Plymouth Marine Laboratory (PML) have published a corresponding review in Biological Reviews. This summarizes the current state of knowledge and identifies new approaches for future research in the language of algae and their ecological relationships.

Can algae talk? "Well, although they don't have any mouth or ears, algae still communicate with their own kind and with other organisms in their surroundings. They do this with volatile organic substances they release into the water," says Dr. Patrick Fink, a water ecologist at the UFZ's Magdeburg site. These chemical signals are known as BVOCs (biogenic volatile organic compounds) and are the equivalent of odours in the air with which flowering plants communicate and attract their pollinators. When under attack by parasites, some plant species release odours that attract the parasites' natural enemies to them. "Algae also employ such interactions and protective mechanisms," says Fink. "After all, they are among the oldest organisms on Earth, and chemical communication is the most original form of exchanging information in evolutionary history. However, our knowledge in this area still remains very fragmentary."

Patrick Fink is the corresponding author of the article recently appearing in Biological Reviews, where he has summarized the current status of research in the chemical communication of algae. "For example, we know from laboratory investigations that some species of cyanobacteria keep water fleas at bay by releasing BVOCs in the water. This signal apparently acts as a repellent and has a true added value for the algae, namely that of effective grazing protection," says Fink. In contrast, it is not yet understood why some freshwater algae growing as biofilms on rocks or shellfish shells, for example, release BVOCS on grazing by pond snails. Because: These chemical signals attract more snails. "The pond snails very clearly use the BVOCs to their advantage -- but it remains unknown what function they actually serve for the algae," says Fink. An example from the ocean: A diatom bloom represents a true feast for copepods. This rich offering of nutrients should ensure that their population subsequently grows. However, this is not the case. "Although the copepods are well nourished, their spawn that they carry with them in their egg sack is at serious risk. Because the BVOCS from the diatoms impede cell division and thus disrupt embryonic development," Fink explains "In this way, the diatoms prevent excessive predation on their descendants -- thereby ensuring the preservation of their kind."

The language of algae was first detected in investigations of macroalgae in the early 1970s. "Macroalgae -- such as the bladder wrack also known from the coasts of Germany -- reproduce by releasing gametes into the water. The male and female gametes each release pheromones so that they can also find each other in the vastness of the ocean," explains Dr. Mahasweta Saha, marine chemical ecologist at the Plymouth Marine Laboratory (PML) in Great Britain. "This was the first indication that algae communicate via chemical signals, and that they fulfil important ecological functions."

In their publication, the author duo references the presumably significant effect of BVOCS within aquatic ecosystems, identifies gaps in knowledge and indicates possible future research areas such as coevolutionary processes between signal senders and receivers or the consequences of changes in the environment caused by humans on aquatic ecosystems. "As the primary producers, algae form the basis of life of all aquatic food webs," says Fink. "It is therefore important that we learn to better understand the chemical communication of algae and their basic functional relationships in aquatic ecosystems."

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Ancient genomes reveal hidden history of human adaptation

The use of ancient DNA, including samples of human remains around 45,000 years old, has shed light on a previously unknown aspect of human evolution.

Dr Yassine Souilmi, Group Leader at the University of Adelaide's Australian Centre for Ancient DNA, co-led the new study published in Nature Ecology and Evolution.

"It was widely believed the genetics of our human ancestors didn't change due to environmental pressures as much as other animals, due to our enhanced communication skills and ability to make and use tools," Dr Souilmi said.

"However, by comparing modern genomes with ancient DNA, we discovered more than 50 cases of an initially rare beneficial genetic variant becoming prevalent across all members of ancient human groups.

"In contrast to many other species, evidence for this type of adaptive genetic change has been inconsistent in humans. This discovery consequently challenges the prevailing view of human adaptation, and gives us a new and exciting insight into how humans have adapted to the novel environmental pressures they encountered as we spread across the planet."

Co-lead author Dr Ray Tobler -- an Adjunct Fellow at the University of Adelaide and a DECRA fellow at the Australian National University -- said examining ancient DNA has been critical in unlocking the secrets of human evolution.

"We believed historical mixing events between human groups might have hidden signs of genetic changes in modern human genomes," Dr Tobler said.

"We examined DNA from more than 1,000 ancient genomes, the oldest which was around 45,000 years old, to see if certain types of genetic adaptation had been more common in our history than studies of modern genomes had suggested."

Professor Christian Huber, a senior author of the research paper, is an Adjunct Fellow at the University of Adelaide and an Assistant Professor at Penn State University.

"The use of ancient genomes was crucial because they preceded major historical mixing events that have radically reshaped modern European genetic ancestry," Professor Huber said.

"This allowed the recovery of historical signs of adaptation that are invisible to standard analysis of modern genomes."

Established in 2005, the Australian Centre for Ancient DNA is a world leader in the research and development of advanced ancient DNA approaches for evolutionary, environmental and conservation applications.

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Mathematicians explain how some fireflies flash in sync

Stake out in Pennsylvania's Cook State Forest at the right time of year and you can see one of nature's great light shows: swarms of fireflies that synchronize their flashes like strings of Christmas lights in the dark.

A new study by Pitt mathematicians shows that math borrowed from neuroscience can describe how swarms of these unique insects coordinate their light show, capturing key details about how they behave in the wild.

"This firefly has a quick sequence of flashes, and then a big pause before the next burst," said Jonathan Rubin, professor and chair of the Department of Mathematics in the Kenneth P. Dietrich School of Arts and Sciences. "We knew a good framework for modeling this that could capture a lot of the features, and we were curious how far we could push it."

Male fireflies produce a glow from their abdomens to call out to potential mates, sending out blinking patterns in the dark to woo females of their own species. Synchronous fireflies of the species Photinus carolinus take it a step further, coordinating their blinking throughout entire swarms. It's a rare trait -- there are only a handful of such species in North America -- and the striking lights they produce draw crowds to locations where the insects are known to gather.

They've also attracted the interest of mathematicians seeking to understand how they synchronize their blinks. It's just one example of how synchronization can evolve from randomness, a process that has intrigued mathematicians for centuries. One famous example from the 1600s showed that pendulum clocks hung next to one another synchronize through vibrations that travel through the wall, and the same branch of math can be used to describe everything from the action of intestines to audience members clapping.

"Synchrony is important for a lot of things, good and bad," said co-author Bard Ermentrout, distinguished professor of mathematics in the Dietrich School. "Physicists, mathematicians, we're all interested in synchronization."

To crack the fireflies' light show, the Pitt team used a more complex model called an "elliptic burster" that's used to describe the behavior of brain cells. The duo, along with then-undergrad Madeline McCrea (A&S '22) published details of their model Oct. 26 in the Journal of the Royal Society Interface.

The first step was to simulate the blinks of a single firefly, then expand to a pair to see how they matched their flashing rates to one another. Next, the team moved to a bigger swarm of simulated insects to see how number, distance and flying speed affect the resulting blinks.

Varying the distances each firefly could "see" each other and respond to one another changed the insects' light show, they found: By tweaking the parameters, they could produce patterns of blinks that looked like either ripples or spirals.

The results line up with several recently published observations about real-life synchronous fireflies -- for instance, that individual fireflies are inconsistent while groups flash more regularly, and that when new fireflies join the swarm, they're already perfectly in time.

"It captured a lot of the finer details that they saw in the biology, which was cool," said Ermentrout. "We didn't expect that."

The math also makes some predictions that could inform firefly research -- for instance, light pollution and the time of day both may alter the patterns produced by fireflies by changing how well they can see one another's blinks.

McCrea worked on the research as an undergraduate supported by the department's Painter Fellowship, which gave her funding to work on the project through the summer. "She was awesome working on this project, and really persistent," said Rubin.

The team is the first to use this particular brain-cell framework to model fireflies, which several different research teams are trying to understand using different types of math. "It's more of a wild west research topic," said Ermentrout. "It's early days, and who knows where things are going to go from here?"

Ermentrout and Rubin also hopeful that the math will capture the imagination of those inspired by the glow of fireflies. In the midst of this project, Rubin himself decided to head up to Cook State Forest to see if he could spot his research subjects firsthand.

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Largest potentially hazardous asteroid detected in eight years

Twilight observations with the US Department of Energy-fabricated Dark Energy Camera at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF's NOIRLab, have enabled astronomers to spot three near-Earth asteroids (NEA) hiding in the glare of the Sun. These NEAs are part of an elusive population that lurks inside the orbits of Earth and Venus. One of the asteroids is the largest object that is potentially hazardous to Earth to be discovered in the last eight years.

An international team using the Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF's NOIRLab, has discovered three new near-Earth asteroids (NEAs) hiding in the inner Solar System, the region interior to the orbits of Earth and Venus. This is a notoriously challenging region for observations because asteroid hunters have to contend with the glare of the Sun.

By taking advantage of the brief yet favorable observing conditions during twilight, however, the astronomers found an elusive trio of NEAs. One is a 1.5-kilometer-wide asteroid called 2022 AP7, which has an orbit that may someday place it in Earth's path. The other asteroids, called 2021 LJ4 and 2021 PH27, have orbits that safely remain completely interior to Earth's orbit. Also of special interest to astronomers and astrophysicists, 2021 PH27 is the closest known asteroid to the Sun. As such, it has the largest general-relativity effects of any object in our Solar System and during its orbit its surface gets hot enough to melt lead.

"Our twilight survey is scouring the area within the orbits of Earth and Venus for asteroids," said Scott S. Sheppard, an astronomer at the Earth and Planets Laboratory of the Carnegie Institution for Science and the lead author of the paper describing this work. "So far we have found two large near-Earth asteroids that are about 1 kilometer across, a size that we call planet killers."

"There are likely only a few NEAs with similar sizes left to find, and these large undiscovered asteroids likely have orbits that keep them interior to the orbits of Earth and Venus most of the time," said Sheppard. "Only about 25 asteroids with orbits completely within Earth's orbit have been discovered to date because of the difficulty of observing near the glare of the Sun."

Finding asteroids in the inner Solar System is a daunting observational challenge. Astronomers have only two brief 10-minute windows each night to survey this area and have to contend with a bright background sky resulting from the Sun's glare. Additionally, such observations are very near to the horizon, meaning that astronomers have to observe through a thick layer of Earth's atmosphere, which can blur and distort their observations.

Discovering these three new asteroids despite these challenges was possible thanks to the unique observing capabilities of DECam. The state-of-the-art instrument is one of the highest-performance, wide-field CCD imagers in the world, giving astronomers the ability to capture large areas of sky with great sensitivity. Astronomers refer to observations as 'deep' if they capture faint objects. When hunting for asteroids inside Earth's orbit, the capability to capture both deep and wide-field observations is indispensable. DECam was funded by the US Department of Energy (DOE) and was built and tested at DOE's Fermilab. "Large areas of sky are required because the inner asteroids are rare, and deep images are needed because asteroids are faint and you are fighting the bright twilight sky near the Sun as well as the distorting effect of Earth's atmosphere," said Sheppard. "DECam can cover large areas of sky to depths not achievable on smaller telescopes, allowing us to go deeper, cover more sky, and probe the inner Solar System in ways never done before."

As well as detecting asteroids that could potentially pose a threat to Earth, this research is an important step toward understanding the distribution of small bodies in our Solar System. Asteroids that are further from the Sun than Earth are easiest to detect. Because of that these more-distant asteroids tend to dominate current theoretical models of the asteroid population.

Detecting these objects also allows astronomers to understand how asteroids are transported throughout the inner Solar System and how gravitational interactions and the heat of the Sun can contribute to their fragmentation.

"Our DECam survey is one of the largest and most sensitive searches ever performed for objects within Earth's orbit and near to Venus's orbit," said Sheppard. "This is a unique chance to understand what types of objects are lurking in the inner Solar System."

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Uncovering the massive quantum mysteries of black holes

Bizarre quantum properties of black holes -- including their mind-bending ability to have different masses simultaneously -- have been confirmed by University of Queensland physicists.

A UQ-led team of theoretical physicists, headed by PhD candidate Joshua Foo, ran calculations that reveal surprising black hole quantum phenomena.

"Black holes are an incredibly unique and fascinating feature of our universe," Mr Foo said.

"They're created when gravity squeezes a vast amount of matter incredibly densely into a tiny space, creating so much gravitational pull that even light cannot escape.

"It's a phenomenon that can be triggered by a dying star.

"But, until now, we haven't deeply investigated whether black holes display some of the weird and wonderful behaviours of quantum physics.

"One such behaviour is superposition, where particles on a quantum scale can exist in multiple states at the same time.

"This is most commonly illustrated by Schrödinger's cat, which can be both dead and alive simultaneously.

"But, for black holes, we wanted to see whether they could have wildly different masses at the same time, and it turns out they do.

"Imagine you're both broad and tall, as well as short and skinny at the same time -- it's a situation which is intuitively confusing since we're anchored in the world of traditional physics.

"But this is reality for quantum black holes."

To reveal this, the team developed a mathematical framework allowing us to "place" a particle outside a theoretical mass-superposed black hole.

Mass was looked at specifically, as it is a defining feature of a black hole, and as it is plausible that quantum black holes would naturally have mass superposition.

Research co-supervisor, Dr Magdalena Zych, said that the research in fact reinforces conjectures raised by pioneers of quantum physics.

"Our work shows that the very early theories of Jacob Bekenstein -- an American and Israeli theoretical physicist who made fundamental contributions to the foundation of black hole thermodynamics -- were on the money," she said.

"He postulated that black holes can only have masses that are of certain values, that is, they must fall within certain bands or ratios -- this is how energy levels of an atom works, for example.

"Our modelling showed that these superposed masses were, in fact, in certain determined bands or ratios -- as predicted by Bekenstein.

"We didn't assume any such pattern going in, so the fact we found this evidence was quite surprising.

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Climate change to produce more rainbows

Climate change will increase opportunities to see rainbows, according to a new study led by researchers at the University of Hawai'i (UH) at Manoa. The study's authors estimate that by 2100, the average land location on Earth will experience about 5% more days with rainbows than at the beginning of the 21st century. Northern latitudes and very high elevations, where warming is predicted to lead to less snow and more rain, will experience the greatest gains in rainbow occurrence. However, places with reduced rainfall under climate change -- such as the Mediterranean -- are projected to lose rainbow days.

Rainbows are produced when water droplets refract sunlight. Sunlight and rainfall are therefore essential ingredients for rainbows. Human activities such as burning fossil fuels are warming the atmosphere, which changes patterns and amounts of rainfall and cloud cover.

"Living in Hawai'i, I felt grateful that stunning, ephemeral rainbows were a part of my daily life," said the lead author of the study, Kimberly Carlson, who is now at New York University's Department of Environmental Studies. "I wondered how climate change might affect such rainbow viewing opportunities."

Camilo Mora, at the UH Manoa Geography and Environment department, was intrigued by the question and pitched it as the focus of a project for one of his graduate courses.

According to Mora, "We often study how climate change directly affects people's health and livelihoods, for instance via the occurrence of heat stroke during climate change-enhanced heat waves."

However, few researchers have examined how climate change might affect the aesthetic qualities of our environment, and no one had bothered to map rainbow occurrences, much less under climate change.

To answer this question, a team including students at UH Manoa looked at photographs uploaded to Flickr, a social media platform where people share photographs. They sorted through tens of thousands of photos taken around the world, labeled with the word "rainbow," to identify rainbows generated from the refraction of light by rain droplets.

Amanda Wong, then an undergraduate student in Global Environmental Science in the UH Manoa School of Ocean and Earth Science and Technology (SOEST) and a co-author on the paper, noted, "We had to sort through photos of rainbow artwork, rainbow flags, rainbow trout, rainbow eucalyptus, and rainbow foods to find the real rainbows."

Then, the scientists trained a rainbow prediction model based on rainbow photo locations and maps of precipitation, cloud cover, and sun angle. Finally, they applied their model to predict present day and future rainbow occurrences over global land areas. The model suggests that islands are rainbow hotspots.

"Islands are the best places to view rainbows," according to Steven Businger, professor of Atmospheric Sciences in SOEST. "This is because island terrain lifts the air during daily sea breezes, producing localized showers surrounded by clear skies that let the sun in to produce majestic rainbows."

The Hawaiian Islands, recently dubbed the "rainbow capital of the world," are predicted to experience a few more days with rainbows per year. The authors stopped short of discussing how changes in rainbow occurrence might affect human wellbeing. However, rainbows are an important part of human culture throughout history and around the world and are aesthetically pleasing.

"Climate change will generate pervasive changes across all aspects of the human experience on Earth. Shifts in intangible parts of our environment -- such as sound and light -- are part of these changes and deserve more attention from researchers," said Carlson.

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New computational method builds detailed maps of human tissues

Weill Cornell Medicine researchers have developed a computational method to map the architecture of human tissues in unprecedented detail. Their approach promises to accelerate studies on organ-scale cellular interactions and could enable powerful new diagnostic strategies for a wide range of diseases.

The method, published Oct. 31 in Nature Methods, grew out of the scientists' frustration with the gap between classical microscopy and modern single-cell molecular analysis. "Looking at tissues under the microscope, you see a bunch of cells that are grouped together spatially -- you see that organization in images almost immediately," said lead author Junbum Kim, a graduate student in physiology and biophysics at Weill Cornell Medicine. "Now, cell biologists have gained the ability to examine individual cells in tremendous detail, down to which genes each cell is expressing, so they're focused on the cells instead of focusing on the tissue structure," he said.

However, "it's crucial for researchers to learn more about the details of tissue structure; fundamental changes in the relationships between cells within a tissue drive both healthy and diseased organ function," said senior author Dr. Olivier Elemento, director of the Englander Institute for Precision Medicine and a professor of physiology and biophysics and of computational genomics in computational biomedicine at Weill Cornell Medicine.

Manually combining single cell data with maps of tissue structure is slow and tedious, though. Machine learning algorithms have shown some potential for automating the process, but they're limited by the data used to train them. To address that, Kim and his colleagues developed an unsupervised computational strategy, using a combination of single-cell gene expression profiles and cells' locations to define structural regions within a tissue.

Co-senior author Dr. André Rendeiro, a postdoctoral fellow at Weill Cornell Medicine during the study and currently a principal investigator at the Research Center for Molecular Medicine of the Austrian Academy of Sciences in Vienna, Austria, compares the new method to mapping a city such as New York: "One way to go about it would be to go to every intersection and count each kind of building: is it residential, is it commercial … is it a shop or restaurant?" Putting all of those data into one matrix, and the buildings' locations into another, one could then combine the two matrices and look for patterns.

"Essentially, we could start to make a general statement about where the different neighborhoods are and where their borders are based on the abundance of, say, residential versus commercial buildings -- just as anyone walking through the Upper East Side, Midtown or Downtown would do based on their observations," said Dr. Rendeiro.

The researchers used the new method to generate detailed maps of several types of tissues, identifying and quantifying new aspects of microanatomy -- the patterns that emerge at small scale when cells interact and that determine the ultimate function of tissue. Collaborating with a colleague at the University of North Carolina at Chapel Hill who studies lung disease, they also demonstrated that their technique could draw fine shades of distinction between different disease states in a tissue.

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Just like humans, more intelligent jays have greater self-control

A study has found that Eurasian jays can pass a version of the 'marshmallow test' -- and those with the greatest self-control also score the highest on intelligence tests.

This is the first evidence of a link between self-control and intelligence in birds.

Self-control -- the ability to resist temptation in favour of a better but delayed reward -- is a vital skill that underpins effective decision-making and future planning.

Jays are members of the corvid family, often nicknamed the 'feathered apes' because they rival non-human primates in their cognitive abilities. Corvids hide, or 'cache', their food to save it for later. In other words, they need to delay immediate gratification to plan for future meals. The researchers think this may have driven the evolution of self-control in these birds.

Self-control has been previously shown to be linked to intelligence in humans, chimpanzees and -- in an earlier study by these researchers -- in cuttlefish. The greater the intelligence, the greater the self-control.

The new results show that the link between intelligence and self-control exists across distantly related animal groups, suggesting it has evolved independently several times.

Of all the corvids, jays in particular are vulnerable to having their caches stolen by other birds. Self-control also enables them to wait for the right moment to hide their food without being seen or heard.

The results are published today in the journal Philosophical Transactions of the Royal Society B.

To test the self-control of ten Eurasian jays, Garrulus glandarius, researchers designed an experiment inspired by the 1972 Stanford Marshmallow test -- in which children were offered a choice between one marshmallow immediately, or two if they waited for a period of time.

Instead of marshmallows, the jays were presented with mealworms, bread and cheese. Mealworms are a common favourite; bread and cheese come second but individuals vary in their preference for one over the other.

The birds had to choose between bread or cheese -- available immediately, and mealworm that they could see but could only get to after a delay, when a Perspex screen was raised. Could they delay immediate gratification and wait for their favourite food?

A range of delay times was tested, from five seconds to five and a half minutes, before the mealworm was made available if the bird had resisted the temptation to eat the bread or cheese.

All the birds in the experiment managed to wait for the worm, but some could wait much longer than others. Top of the class was 'JayLo', who ignored a piece of cheese and waited five and a half minutes for a mealworm. The worst performers, 'Dolci' and 'Homer', could only wait a maximum of 20 seconds.

"It's just mind-boggling that some jays can wait so long for their favourite food. In multiple trials, I sat there watching JayLo ignore a piece of cheese for over five minutes -- I was getting bored, but she was just patiently waiting for the worm," said Dr Alex Schnell at the University of Cambridge's Department of Psychology, first author of the report.

The jays looked away from the bread or cheese when it was presented to them, as if to distract themselves from temptation. Similar behaviour has been seen in chimpanzees and children.

The researchers also presented the jays with five cognitive tasks that are commonly used to measure general intelligence. The birds that performed better in these tasks also managed to wait longer for the mealworm reward. This suggests that self-control is linked with intelligence in jays.

"The birds' performance varied across individuals -- some did really well in all the tasks and others were mediocre. What was most interesting was that if a bird was good at one of the tasks, it was good at all of them -- which suggests that a general intelligence factor underlies their performance," said Schnell.

The jays also adjusted their self-control behaviour according to the circumstances: in another experiment where the worm was visible but always out of reach, the jays always ate the immediately available bread or cheese. And the length of time they were willing to wait for the worm fell if it was pitted against their second most preferred food as the immediate treat, compared to their third. This flexibility shows that jays only delay gratification when it is warranted.

Research by other scientists has found that children taking the Stanford marshmallow test vary greatly in their self-control, and this ability is linked to their general intelligence. Children that can resist temptation for longer also get higher scores in a range of academic tasks.

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Scientists use deep planetary scan to confirm Martian core

Seismologists from The Australian National University (ANU) have developed a new method to scan the deep interior of planets in our solar system to confirm whether they have a core at the heart of their existence.  

The scanning method, which works in a similar way to an ultrasound scan using sound waves to generate images of a patient's body, requires only a single seismometer on a planet's surface in order to work. It can also be used to confirm the size of a planet's core. The research is published in Nature Astronomy.  

Using the ANU model to scan the entirety of Mars' interior, the researchers confirmed the Red Planet has a large core at its centre -- a theory first confirmed by a team of scientists in 2021.

Study co-author Professor Hrvoje Tkalčić, from ANU, said based on data collected using the ANU technique, the researchers determined that the Martian core, which is smaller than Earth's, is about 3,620 kilometres in diameter. 

"Our research presents an innovative method using a single instrument to scan the interior of any planet in a way that's never been done before," he said.   

Confirming the existence of a planetary core, which the researchers refer to as the "engine room" of all planets, can help scientists learn more about a planet's past and evolution. It can also help scientists determine at what point in a planet's history a magnetic field formed and ceased to exist.

The core plays an active role in sustaining a planet's magnetic field. In the case of Mars, it could help explain why, unlike Earth, the Red Planet no longer has a magnetic field -- something that is critical to sustaining all life forms.   

"Modelling suggests that the Martian core is liquid and while it is made up of mostly iron and nickel, it could also contain traces of lighter elements such as hydrogen and sulphur. These elements can alter the ability of the core to transport heat," lead author Dr Sheng Wang, who is also from ANU, said. 

"A magnetic field is important because it shields us from cosmic radiation, which is why life on Earth is possible."

Using a single seismometer on Mars' surface, the ANU team measured specific types of seismic waves. The seismic waves, which were triggered by marsquakes, give off a spectrum of signals, or "echoes," that change over time as they reverberate throughout the Martian interior.  

These seismic waves pierce through and bounce off the Martian core. 

Professor Tkalčić said researchers are interested in the "late" and "weaker" signals that can survive hours after they are emitted from quakes, meteoroid impacts and other sources.  

"Although these late signals appear to be noisy and not useful, the similarity between these weak signals recorded at various locations on Mars manifests itself as a new signal that reveals the presence of a large core in the Red Planet's heart," Professor Tkalčić said. 

"We can determine how far these seismic waves travel to reach the Martian core but also the speed at which they travel through Mars' interior. This data helps us make estimations about the size of Mars' core." 

The researchers say their method of using a single seismometer to confirm the presence of a planetary core is also a "cost-effective solution."

"There is a single seismic station on Mars. There were four of them on the Moon in 1970s. The situation of having a limited number of instruments is unlikely to change in the coming decades or even this century due to high cost," Dr Wang said.

"We need an approach right now to use only a single seismometer to study planetary interiors."

The researchers hope this new ANU-developed technique involving a single seismometer could be used to help scientists learn more about our other planetary neighbours, including the moon. 

"The US and China plan to send seismometers to the moon, and Australia also has ambitions to participate in future missions, so there's potential for further studies using new and more sophisticated instruments," Professor Tkalčić said.  

Dr Wang said: "Although there are many studies on planetary cores, the images we have of planetary interiors are still very blurry. But with new instruments and methods like ours we'll be able to get sharper images which will help us answer questions such as how big the cores are and whether they take a solid or liquid form. 

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