Bacterial bloom as the Earth thawed: Photosynthetic organisms during the Snowball Earth

Some researchers hypothesize that ice sheets enveloped the earth during the Marinoan glaciation (650-535 million years ago) in what is dubbed the "Snowball Earth." The glaciation also impacted the climate and chemical compositions of the oceans, restraining the evolution of early life. Yet, as the earth warmed, and the Ediacaran period dawned, biotic life began to evolve.

A research team from Tohoku University has unveiled more about the evolutionary process of the Marinoan-Ediacaran transition. Using biomarker evidence, they revealed possible photosynthetic activity during the Marinoan glaciation. This was followed by photosynthetic organisms and bacteria entering a period of low productivity. However, as eukaryotes expanded during the early Ediacaran period, they blossomed.

Dr. Kunio Kaiho, who co-authored a paper with Atena Shizuya, said, "Our findings help clarify the evolution of primitive to complex animals in the aftermath of the Snowball Earth." Their paper online was published in the journal Global and Planetary Change on August 8, 2021.

The late Neoproterozoic era (650-530 million years ago) witnessed one of the most severe ice ages in the Earth's 4.6-billion-year history. Researchers believe that ice sheets covered the entire earth since glaciogenic units, such as ice-rafted debris, are distributed globally. Overlaying these glaciogenic formations are cap carbonates. These precipitate under warm conditions and therefore suggest that the glacial environment changed rapidly into a greenhouse environment.

The Snowball Earth hypothesis purports the atmospheric carbon dioxide concentration controlled the change from a frozen state to an ice-free state. Ice sheet-covered oceans prevented the dissolution of carbon dioxide into seawater during the Marinoan ice age, meaning greenhouse gas concentration, emitted by volcanic activity, increased gradually. Once the extreme greenhouse effect kicked in, glaciers melted and excess carbon dioxide precipitated on glaciogenic sediments as cap carbonates.

Whilst the Snowball Earth theory explains the wide distributions of glacial formations, it fails to shed light on the survival of living organisms. To counteract this, some researchers argue that sedimentary organic molecules, a molecular clock, and fossils from the late Neoproterozoic era are evidence that primitive eukaryotes such as sponges survived this severe ice age. Alternative models also propose that an ice-free open sea existed during the glaciation and acted as an oasis for marine life.

But what is understood is that the Marinoan glaciation and the succeeding extreme climatic transition likely had a marked impact on the biosphere. Shortly after the ice age, the Lantian biota, the earliest-known complex macroscopic multicellular eukaryotes, emerged. The Lantian biota includes macrofossils that are phylogenetically uncertain but morphologically and taxonomically diverse. Meanwhile, pre-Marinoan species have simple body plans with limited taxonomic variety.

Bacteria and eukaryote biomarkers demonstrate that bacteria dominated before the glaciation, whereas steranes/hopanes ratios illustrate that eukaryotes dominated just before it. However, the relationship between the biosphere changes and the Marinoan glaciation is unclear.

In 2011, Kaiho and his team traveled to Three Gorges, China under the guidance of China University of Science's Dr. Jinnan Tong to take sedimentary rock samples from the deeper outcrops of marine sedimentary rocks. From 2015 onwards, Shizuya and Kaiho analyzed the biomarkers of algae, photosynthetic activity, bacteria, and eukaryotes from the rock samples.

They found photosynthetic activity based on n-C17 + n-C19 alkanes for algae and pristane + phytane during the Marinoan glaciation. Hopanes within the early and late carbonate deposition showed photosynthetic organisms and other bacteria entering a state of low productivity before recovering. And steranes from carbonates and mudstones after the cap carbonate deposition from the early Ediacaran period indicated the expansion of eukaryotes. The expansion of eukaryotes corresponded to the Lantian biota being morphologically diverse when compared to pre-Marinoan species.

Kaiho believes we are one step closer to understanding the evolutionary process that occurred before and after Snowball Earth. "The environmental stress of closed ocean environments for the atmosphere followed by high temperatures around 60°C may have produced more complex animals in the aftermath." Their findings show that bacterial recovery preceded eukaryotes' domination.

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How disorderly young galaxies grow up and mature

Using a supercomputer simulation, a research team at Lund University in Sweden has succeeded in following the development of a galaxy over a span of 13.8 billion years. The study shows how, due to interstellar frontal collisions, young and chaotic galaxies over time mature into spiral galaxies such as the Milky Way.

Soon after the Big Bang 13.8 billion years ago, the Universe was an unruly place. Galaxies constantly collided. Stars formed at an enormous rate inside gigantic gas clouds. However, after a few billion years of intergalactic chaos, the unruly, embryonic galaxies became more stable and over time matured into well-ordered spiral galaxies. The exact course of these developments has long been a mystery to the world's astronomers. However, in a new study published in Monthly Notices of the Royal Astronomical Society, researchers have been able to provide some clarity on the matter.

"Using a supercomputer, we have created a high-resolution simulation that provides a detailed picture of a galaxy's development since the Big Bang, and how young chaotic galaxies transition into well-ordered spirals" says Oscar Agertz, astronomy researcher at Lund University.

In the study, the astronomers, led by Oscar Agertz and Florent Renaud, use the Milky Way's stars as a starting point. The stars act as time capsules that divulge secrets about distant epochs and the environment in which they were formed. Their positions, speeds and amounts of various chemical elements can therefore, with the assistance of computer simulations, help us understand how our own galaxy was formed.

"We have discovered that when two large galaxies collide, a new disc can be created around the old one due to the enormous inflows of star-forming gas. Our simulation shows that the old and new discs slowly merged over a period of several billion years. This is something that not only resulted in a stable spiral galaxy, but also in populations of stars that are similar to those in the Milky Way," says Florent Renaud, astronomy researcher at Lund University.

The new findings will help astronomers to interpret current and future mappings of the Milky Way. The study points to a new direction for research in which the main focus will be on the interaction between large galaxy collisions and how spiral galaxies' discs are formed. The research team in Lund has already started new super computer simulations in cooperation with the research infrastructure PRACE (Partnership for Advanced Computing in Europe).

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New fossil species represents ancient forerunner of most modern reptiles

Lizards and snakes are a key component of most terrestrial ecosystems on earth today. Along with the charismatic tuatara of New Zealand (a "living fossil" represented by a single living species), squamates (all lizards and snakes) make up the Lepidosauria -- the largest group of terrestrial vertebrates in the planet today with approximately 11,000 species, and by far the largest modern group of reptiles. Both squamates and tuataras have an extremely long evolutionary history. Their lineages are older than dinosaurs having originated and diverged from each other at some point around 260 million years ago. However, the early phase of lepidosaur evolution 260-150 million years ago, is marked by very fragmented fossils that do not provide much useful data to understand their early evolution, leaving the origins of this vastly diverse group of animals embedded in mystery for decades.

In a study published August 25 in Nature an international team of researchers describe a new species that represents the most primitive member of lepidosaurs, Taytalura alcoberi, found in the Late Triassic deposits of Argentina. Discovered by lead author Dr. Ricardo N. Martínez, Universidad Nacional de San Juan, Argentina, and curator at the Instituto y Museo de Ciencias Naturales, Taytalura is the first three-dimensionally preserved early lepidosaur fossil. It allowed scientists to infer with great confidence it's placement in the evolutionary tree of reptiles and aids in closing the gap of our knowledge of the origin and early evolution of lepidosaurs.

Martínez and co-author Dr. Sebastián Apesteguía, Universidad Maimónides, Buenos Aires, Argentina,conducted high-resolution CT scans of Taytalura which provided confirmation that it was something related to ancient lizards. They then contacted co-author Dr. Tiago R. Simões, postdoctoral fellow in The Department of Organismic and Evolutionary Biology, Harvard University, to help identify and analyze the fossil. Simões specializes in studying these creatures and in 2018 published the largest existing dataset to understand the evolution of the major groups of reptiles (living and extinct) in Nature.

"I knew the age and locality of the fossil and could tell by examining some of its external features that it was closely related to lizards, but it looked more primitive than a true lizard and that is something quite special," said Simões.

The researchers then contacted co-author Dr. Gabriela Sobral, Department of Palaeontology, Staatliches Museum für Naturkunde Stuttgart, Germany, to process the CT scan data. Sobral, a specialist in processing CT data, created a mosaic of colors for each bone of the skull allowing the team to understand the fossil's anatomy in high-detail resolution on a scale of only a few micrometers -- about the same thickness as a human hair.

With Sobral's data, Simões was able to apply a Bayesian evolutionary analysis to determine the proper placement of the fossil in the reptile dataset. Simões had recently applied the Bayesian method -- which was adapted from methods originally developed in epidemiology to study how viruses like COVID-19 evolve -- to precisely estimate the time and rates of anatomical evolution during the rise of tetrapods. The statistical analysis confirmed their suspicions that Taytalura was in fact the most primitive member of the lineage that eventually originated all lizards and snakes. "It's not even a lizard in the evolutionary tree," said Simões, "but it's the very next thing there, between true liizards and tuataras, and all other reptiles."

"This beautifully 3D preserved fossil is really an important finding. It is the most complete fossil representing the early stages of lepidosaur evolution that we have so far. All other known fossils are too incomplete, which makes it difficult to classify them for sure, but the complete and articulated nature of Taytalura makes its relationships much more certain," said Sobral.

Simões agreed, "Taytalura is a major point in the reptile tree of life that was previously missing. Because these fossils are so small they are very difficult to preserve in the fossil record. And what candidate fossils we do have are very fragmented and poorly preserved, so they don't provide as much useful data for analysis."

Taytalura's skull reveals that the first lepidosaurs looked substantially more like the tuataras than squamates, and therefore, that squamates represent a major deviation from this ancestral pattern. Further, it has a unique dentition, differing from the teeth found in any living or extinct group of lepidosaurs. "What our analyses tells us, besides some other anatomical traits that we could see on it, in the skull specifically, is that this sphenodontian body type, at least for the skull, is the ancestral pattern for lepidosaurs. The ancestral pattern seems to be more similar to tuataras," said Simões.

"Taytalura preserves a composition of features that we were not expecting to find in such an early fossil. For instance, it shows some features that we thought were exclusive for the tuatara group. On the other hand, it made us question how truly "primitive" certain lizard features are, and it will make scientists reconsider several points in the evolution of this group," said Sobral.

"The almost perfectly preserved Taytalura skull shows us details of how a very successful group of animals, including more than 10,000 species of snakes, lizards, and tuataras, originated," said Martínez. "But it also highlights the paleontological importance of the paleontological site of Ischigualasto Formation, known for preserving some of the most primitive dinosaurs known in the world. The extraordinary quality of preservation of the fossils at this site allowed something as fragile and tiny as this specimen to be preserved for 231 million years."

"Contrary to almost all fossils of Triassic lepidosaurs found in Europe, this is the first early lepidosaur found in South America, suggesting lepidosaurs were able to migrate across vastly distant geographic regions early in their evolutionary history," agreed Simões.

"We are accustomed to accept that the Mesozoic Era was an age of gigantic reptiles, enormous proto-mammals, and huge trees, and thus we commonly look for fossils that are visible at human height, just walking," said Apesteguía. "However, the largest part of the ancient ecosystem components was small, as today. There was a universe of fauna sneaking among bigger, clawed or hoofy paws. Taytalura teaches us that we were missing important information by looking not only for bigger animals, but for also thinking that the origin of lizards occurred only in the Northern Hemisphere as evidence seemed to support until now."

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Will it be safe for humans to fly to Mars?

Sending human travelers to Mars would require scientists and engineers to overcome a range of technological and safety obstacles. One of them is the grave risk posed by particle radiation from the sun, distant stars and galaxies.

Answering two key questions would go a long way toward overcoming that hurdle: Would particle radiation pose too grave a threat to human life throughout a round trip to the red planet? And, could the very timing of a mission to Mars help shield astronauts and the spacecraft from the radiation?

In a new article published in the peer-reviewed journal Space Weather, an international team of space scientists, including researchers from UCLA, answers those two questions with a "no" and a "yes."

That is, humans should be able to safely travel to and from Mars, provided that the spacecraft has sufficient shielding and the round trip is shorter than approximately four years. And the timing of a human mission to Mars would indeed make a difference: The scientists determined that the best time for a flight to leave Earth would be when solar activity is at its peak, known as the solar maximum.

The scientists' calculations demonstrate that it would be possible to shield a Mars-bound spacecraft from energetic particles from the sun because, during solar maximum, the most dangerous and energetic particles from distant galaxies are deflected by the enhanced solar activity.

A trip of that length would be conceivable. The average flight to Mars takes about nine months, so depending on the timing of launch and available fuel, it is plausible that a human mission could reach the planet and return to Earth in less than two years, according to Yuri Shprits, a UCLA research geophysicist and co-author of the paper.

"This study shows that while space radiation imposes strict limitations on how heavy the spacecraft can be and the time of launch, and it presents technological difficulties for human missions to Mars, such a mission is viable," said Shprits, who also is head of space physics and space weather at GFZ Research Centre for Geosciences in Potsdam, Germany.

The researchers recommend a mission not longer than four years because a longer journey would expose astronauts to a dangerously high amount of radiation during the round trip -- even assuming they went when it was relatively safer than at other times. They also report that the main danger to such a flight would be particles from outside of our solar system.

Shprits and colleagues from UCLA, MIT, Moscow's Skolkovo Institute of Science and Technology and GFZ Potsdam combined geophysical models of particle radiation for a solar cycle with models for how radiation would affect both human passengers -- including its varying effects on different bodily organs -- and a spacecraft. The modeling determined that having a spacecraft's shell built out of a relatively thick material could help protect astronauts from radiation, but that if the shielding is too thick, it could actually increase the amount of secondary radiation to which they are exposed.

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Secrets of COVID-19 transmission revealed in turbulent puffs

Turbulence is everywhere -- in the movement of the wind, the ocean waves and even magnetic fields in space. It can also be seen in more transient phenomena, like smoke billowing from a chimney, or a cough.

Understanding this latter type of turbulence -- called puff turbulence -- is important not only for the advancement of fundamental science, but also for practical health and environmental measures, like calculating how far cough droplets will travel, or how pollutants released from a chimney or cigarette might disperse into the surroundings. But creating a complete model of how turbulent puffs of gases and liquids behave has so far proven elusive.

"The very nature of turbulence is chaotic, so it's hard to predict," said Professor Marco Edoardo Rosti, who leads the Complex Fluids and Flows Unit at Okinawa Institute of Science and Technology Graduate University (OIST). "Puff turbulence, which occurs when the ejection of a gas or liquid into the environment is disrupted, rather than continuous, has more complicated characteristics, so it's even more challenging to study. But it's of vital importance -- especially right now for understanding airborne transmission of viruses like SARS-CoV-2."

Until now, the most recent theory was developed in the 1970s, and focused on the dynamics of a puff only at the scale of the puff itself, like how fast it moved and how wide it spread.

The new model, developed in a collaboration between Prof. Rosti from OIST, Japan and Prof. Andrea Mazzino from the University of Genova in Italy, builds on this theory to include how minute fluctuations within the puff behave, and how both large-scale and small-scale dynamics are impacted by changes in temperature and humidity. Their findings were published in Physical Review Letters on August 25th 2021.

Interestingly, the scientists found that at cooler temperatures (15°C or lower), their model deviated from the classical model for turbulence.

In the classical model, turbulence reigns supreme -- determining how all the little swirls and eddies within the flow behave. But once temperatures dipped, buoyancy started to have a greater impact.

"The effect of buoyancy was initially very unexpected. It's a completely new addition to the theory of turbulent puffs," said Prof. Rosti.

Buoyancy exerts an effect when the gas or liquid puff is much warmer than the temperature of the immediate surroundings it is released into. Warm gas or fluid is much less dense than the cold gas or fluid of the environment, and therefore the puff rises, allowing it to travel further.

"Buoyancy generates a very different kind of turbulence -- not only do you see changes in the large-scale movement of the puff, but also changes in the minute movements within the puff," said Prof. Rosti.

The scientists used a powerful supercomputer, capable of resolving behavior of the puff at the large-scale and the small-scale, to run simulations of turbulent puffs, which confirmed their new theory.

The new model could now allow scientists to better predict the movement of droplets in the air that are released when someone coughs or speaks unmasked.

While larger droplets fall quickly to the ground, reaching distances of around one meter, smaller droplets can remain airborne for much longer and travel further.

"How fast the droplets evaporate -- and therefore how small they are -- depends on turbulence, which in turn is affected by the humidity and temperature of the surroundings," explained Prof. Rosti. "We can now start to take these differences in environmental conditions, and how they affect turbulence, into consideration when studying airborne viral transmission."

Next, the researchers plan to study how puffs behave when made of more complicated non-Newtonian fluids, where how easily the fluid flows can change depending on the forces it is under.

"For COVID, this could be useful for studying sneezes, where non-Newtonian fluids like saliva and mucus are forcefully expelled," said Dr. Rosti.

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From couch to ultra-marathon – mental imagery technique can aid running challenge completion

A motivational intervention known as functional imagery training (FIT) can help self-professed non-runners to complete an ultra-marathon (50km plus), according to new research.

The study, led by the University of Plymouth, started by examining the motivation of 31 non-runners who wanted to get fitter, by giving them a recognised behaviour change technique, often used by counsellors, known as Motivational Interviewing (MI). Participants were then left for five months to do whatever they presumed would benefit their fitness and health. After this period all were contacted and asked if they would consider completing an ultra-marathon.

Fifteen participants went on to express an interest in attempting an ultra-marathon as they continued to improve their fitness. Seven were randomly assigned FIT, while eight continued with just MI.

MI is a technique that sees a counsellor support someone to develop, highlight and verbalise their need or motivation for change, and their reasons for wanting to change. Functional Imagery Training builds on MI, as it teaches clients how to elicit and practice motivational imagery themselves, with participants encouraged to utilise all their senses to visualise how it would feel to achieve their goal.

Of the eight participants in the MI only group, four started the race, and two finished. Meanwhile, all seven of the FIT group started, and six finished -- showing that those assigned to the technique were five times more likely to complete the challenge.

While researchers acknowledge the small population size, the study, published in the Journal of Imagery Research in Sport and Physical Activity, adds to the growing body of evidence that FIT can significantly reinforce a person's motivation to complete a challenging goal.

FIT has also previously been shown to boost weight loss, with another Plymouth-led study showing that overweight people who used it lost an average of five times more weight than those using motivational interviewing alone.

Developed at the University of Plymouth, FIT is a unique approach to behaviour change that uses mental imagery to motivate change.

It teaches people new ways of thinking about their immediate future to help them stay motivated as they achieve each small step towards their goal -- with users describing it as a 'mindset shift', where they exercised because they wanted to, rather than feeling they had to.

For example, at difficult points in the race, a participant in the new study -- a teacher -- pictured the conversation they would have at work on Monday morning: visualising the staff room, holding a coffee in hand, imagining the smell and the taste, talking about the challenges with a peer, then using this self-developed image to imagine the feeling at the finish line, as they go from little exercise to ultra-athlete.

Lead author Dr Jon Rhodes, who has worked with professional athletes to improve their resilience, said: "An ultra-marathon requires a huge amount of mental, as well as physical, strength -- even from people who run regularly. Trialling Functional Imagery Training on historically self-professed non-runners was a real test of its efficacy, and to see that it made a difference was a promising finding.

"It shows that multi-sensory imagery is the key difference between those who reach the starting line and then go on to finish, and those who do not -- showing it is critical to maintaining changes and pushing the boundaries of physical and mental performance."

Melissa King, aged 38 from Newquay in Cornwall, was allocated the FIT intervention as she prepared for the Exmoor Ultra Marathon earlier this year. Completing the event successfully, she said: "My honest reason for starting running in the first place was just to see if I could do it.

"FIT has been a huge mindset shift, and I now use imagery as a way to reset; to ground me and help me to focus on being present, appreciating why I am here while also prompting me to cue my immediate, medium- and long-term goals. Having never run before, my ultimate aim is now a running trip in South America which will take a couple of months. It's in three years' time, so I'm starting training early and really embracing the challenge."

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Diverse DNA signatures linked to heart disease

Risk for heart disease does not look the same on the genetic level for different population groups, report an international team of researchers this month in the journal JAMA Cardiology. The study, led by Texas Biomedical Research Institute (Texas Biomed) and Columbia University Mailman School of Public Health, begins to outline gene activity patterns that could serve as early warning indicators for cardiovascular disease.

"We shouldn't expect it to be same for every population group," said Associate Professor Shelley Cole, Ph.D., senior author and co-lead of the Population Health Program at Texas Biomed. "There are some universal factors affecting risk for heart disease, where you live in the world, your environment, your lifestyle, your access to health care, those all influence disease risk and progression. Advances in querying the entire genome or DNA of an individual, and statistical analyses, coupled with large, long-term studies are enabling us to see those influences on the genetic level for different populations."

External influences that leave a mark on DNA are part of the growing field called epigenetics. Essentially, modifications occur that affect how DNA is expressed, without changing the basic genetic code. Identifying epigenetic patterns associated with particular diseases could one day help screen for illness years or even decades before symptoms develop.

"In this study, we harness the country's best clinical data on heart disease from diverse populations to begin to unlock the specific epigenetic changes involved the complex biology that leads to disease," said Ana Navas-Acien, M.D., Ph.D., the study's first author and professor of environmental health sciences at Columbia University Mailman School of Public Health.

Navas-Acien, Cole and their collaborators compiled data from nearly 9,400 participants in four long-term health studies: the Strong Heart Study, which has studied cardiovascular disease among American Indians since the 1980s; the Women's Health Initiative, which follows African-American, Hispanic and white women across the U.S.; the Framingham Heart Study, which follows men and women in Massachusetts; and Atherosclerosis Risk in Communities Study (ARIC), which follows men and women in four U.S. communities. (For this study, the ARIC data was split into two cohorts: Black and white.)

Researchers analyzed the entire genome of each person for DNA methylation, which causes changes to DNA activity without altering the genetic sequence, and compared that with individuals known to have developed coronary heart disease. Among the Strong Heart Study volunteers, there were about 505 methylation points associated with heart disease.

Those sites were compared with the other cohorts. Only 33 were also found in three additional groups with mixed results -- sometimes a common site was associated with heart disease, while other times, it was actually associated with a lower risk of heart disease.

"This underscores the need to tailor indicators of risk and resilience, as well as interventions and treatments, for subpopulations as we move away from a one-size-fits-all approach and towards precision medicine," said Cole, who chairs the Strong Heart Study Steering Committee and directs the Strong Heart Study Genetics Center.

By incorporating data from the Strong Heart Study, which involves 12 tribes in Arizona, Oklahoma, and North and South Dakota, this paper successfully brings advanced genetic analyses to traditionally underserved, rural populations.

"It can be challenging to do field research with remote population groups that don't have easy access to hospitals and clinics, so they are often left out of research projects like this," Cole said. "The Strong Heart Study is providing extremely valuable insights for the participating tribes as well as for the broader global community about how environmental factors influence our health."

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New class of habitable exoplanets represent a big step forward in the search for life

A new class of exoplanet very different to our own, but which could support life, has been identified by astronomers, which could greatly accelerate the search for life outside our Solar System.

In the search for life elsewhere, astronomers have mostly looked for planets of a similar size, mass, temperature and atmospheric composition to Earth. However, astronomers from the University of Cambridge believe there are more promising possibilities out there.

The researchers have identified a new class of habitable planets, dubbed 'Hycean' planets -- hot, ocean-covered planets with hydrogen-rich atmospheres -- which are more numerous and observable than Earth-like planets.

The researchers say the results, reported in The Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next two or three years is a real possibility.

"Hycean planets open a whole new avenue in our search for life elsewhere," said Dr Nikku Madhusudhan from Cambridge's Institute of Astronomy, who led the research.

Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth's most extreme aquatic environments.

These planets also allow for a far wider habitable zone, or 'Goldilocks zone', compared to Earth-like planets. This means that they could still support life even though they lie outside the range where a planet similar to Earth would need to be in order to be habitable.

Thousands of planets outside our Solar System have been discovered since the first exoplanet was identified nearly 30 years ago. The vast majority are planets between the sizes of Earth and Neptune and are often referred to as 'super-Earths' or 'mini-Neptunes': they can be predominantly rocky or ice giants with hydrogen-rich atmospheres, or something in between.

Most mini-Neptunes are over 1.6 times the size of Earth: smaller than Neptune but too big to have rocky interiors like Earth. Earlier studies of such planets have found that the pressure and temperature beneath their hydrogen-rich atmospheres would be too high to support life.

However, a recent study on the mini-Neptune K2-18b by Madhusudhan's team found that in certain conditions these planets could support life. The result led to a detailed investigation into the full range of planetary and stellar properties for which these conditions are possible, which known exoplanets may satisfy those conditions, and whether their biosignatures may be observable.

The investigation led the researchers to identify a new class of planets, Hycean planets, with massive planet-wide oceans beneath hydrogen-rich atmospheres. Hycean planets can be up to 2.6 times larger than Earth and have atmospheric temperatures up to nearly 200 degrees Celsius, but their oceanic conditions could be similar to those conducive for microbial life in Earth's oceans. Such planets also include tidally locked 'dark' Hycean worlds that may have habitable conditions only on their permanent night sides, and 'cold' Hycean worlds that receive little radiation from their stars.

Planets of this size dominate the known exoplanet population, although they have not been studied in nearly as much detail as super-Earths. Hycean worlds are likely quite common, meaning that the most promising places to look for life elsewhere in the Galaxy may have been hiding in plain sight.

However, size alone is not enough to confirm whether a planet is Hycean: other aspects such as mass, temperature and atmospheric properties are required for confirmation.

When trying to determine what the conditions are like on a planet many light years away, astronomers first need to determine whether the planet lies in the habitable zone of its star, and then look for molecular signatures to infer the planet's atmospheric and internal structure, which govern the surface conditions, presence of oceans and potential for life.

Astronomers also look for certain biosignatures which could indicate the possibility of life. Most often, these are oxygen, ozone, methane and nitrous oxide, which are all present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulphide, that are less abundant on Earth but can be promising indicators of life on planets with hydrogen-rich atmospheres where oxygen or ozone may not be as abundant.

"Essentially, when we've been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start," said Madhusudhan. "But we think Hycean planets offer a better chance of finding several trace biosignatures."

"It's exciting that habitable conditions could exist on planets so different from Earth," said co-author Anjali Piette, also from Cambridge.

Madhusudhan and his team found that a number of trace terrestrial biomarkers expected to be present in Hycean atmospheres would be readily detectable with spectroscopic observations in the near future. The larger sizes, higher temperatures and hydrogen-rich atmospheres of Hycean planets make their atmospheric signatures much more detectable than Earth-like planets.

The Cambridge team identified a sizeable sample of potential Hycean worlds which are prime candidates for detailed study with next-generation telescopes, such as the James Webb Space Telescope (JWST), which is due to be launched later this year. These planets all orbit red dwarf stars between 35-150 light years away: close by astronomical standards. Planned JWST observations of the most promising candidate, K2-18b, could lead to the detection of one or more biosignature molecules.

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Central European prehistory was highly dynamic

Centrally located along trade routes and tightly nestled around the important waterways such as the Elbe River, Bohemia attracted many different archaeological cultures, rendering it a key region in understanding the prehistory of Europe. In addition to the expansions associated with the spread of agriculture and "steppe"-related ancestry previously discovered, this new study identifies at least another three migratory events which shaped central European prehistory.

The genetic profiles of people associated with Funnelbeaker and Globular Amphora cultures show evidence of being recent migrants to the region. This finding shows that the period between arrival of agriculture and "steppe"-related ancestry, hitherto thought of as an uneventful period, was more dynamic than previously hypothesised.

Drastic changes to the genetic landscape

The large sample size of the study, particularly concentrated on the Late Neolithic and Early Bronze Age (~6,000-3,700 years ago), also allowed novel insights into social processes to be made. Individuals associated with the Corded Ware culture expanded from Eastern Europe and then assimilated preferentially central European women into their culture, giving them the same burial ritual as members of the immigrating group. "We were finally able to fill key temporal gaps, especially in the transition period around 5,000 years ago, when we see the genetic landscape changing drastically," says Max Planck researcher Wolfgang Haak, senior author and principal investigator of the study. "Intriguingly, in this early horizon we find individuals with high amounts of 'steppe' ancestry next to others with little or none, all buried according to the same customs."

Once established, individuals of the Corded Ware culture (4,900-4,400 years ago) changed genetically through time. One important change seems to have been the sharp decline in Y-chromosome lineage diversity. Although initially carrying five different Y-lineages, later Corded Ware males carry almost exclusively only a single lineage, essentially being descended from the same man in the recent past. "This pattern may reflect the emergence of a new social structure or regulation of mating in which only a subset of men fathered the majority of offspring," says first author Luka Papac, a researcher at the Max Planck Institute for the Science of Human History.

This social structure seems to have been even stricter in the following Bell Beaker society (4,500-4,200 years ago) where every single male sampled belonged to a single, newly introduced Y-lineage. Remarkably, this Bell Beaker Y-lineage is never seen before in Bohemia, implying that a new clan arrived in the region and almost immediately replaced all pre-existing Y-lineages with not a single lineage from Corded Ware or previous societies found among Bell Beaker males.

Cultural, biological, and social changes

The Early Bronze Age Unetice culture has traditionally been thought of descending from Bell Beaker individuals, with perhaps limited input from the southeast (Carpathian Basin). However, the new genetic data supports yet another genetic turnover originating from regions northeast of Bohemia. Remarkably, also 80 percent of the early Unetice Y-lineages are new to Bohemia, some of which are previously found in individuals from north-eastern Europe, providing clues to where they originated from. "This finding was very surprising to us archaeologists as we did not expect to see such clear patterns, even though the region has played a critical role, e.g. in the emerging trade of amber from the Baltic and became an important trading hub during the Bronze and Iron Ages," adds co-author and co-PI Michal Ernée from the Czech Academy of Sciences.

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Artificial intelligence to help predict Arctic sea ice loss

A new AI (artificial intelligence) tool is set to enable scientists to more accurately forecast Arctic sea ice conditions months into the future. The improved predictions could underpin new early-warning systems that protect Arctic wildlife and coastal communities from the impacts of sea ice loss.

Published this week (Thursday 26 August) in the journal Nature Communications, an international team of researchers led by British Antarctic Survey (BAS) and The Alan Turing Institute describe how the AI system, IceNet, addresses the challenge of producing accurate Arctic sea ice forecasts for the season ahead -- something that has eluded scientists for decades.

Sea ice, a vast layer of frozen sea water that appears at the North and South poles, is notoriously difficult to forecast because of its complex relationship with the atmosphere above and ocean below. The sensitivity of sea ice to increasing temperatures has caused the summer Arctic sea ice area to halve over the past four decades, equivalent to the loss of an area around 25 times the size of Great Britain. These accelerating changes have dramatic consequences for our climate, for Arctic ecosystems, and Indigenous and local communities whose livelihoods are tied to the seasonal sea ice cycle.

IceNet, the AI predictive tool, is almost 95% accurate in predicting whether sea ice will be present two months ahead -- better than the leading physics-based model.

Lead author Tom Andersson, Data Scientist at the BAS AI Lab and funded by The Alan Turing Institute, explains: "The Arctic is a region on the frontline of climate change and has seen substantial warming over the last 40 years. IceNet has the potential to fill an urgent gap in forecasting sea ice for Arctic sustainability efforts and runs thousands of times faster than traditional methods."

Dr Scott Hosking, Principal Investigator, Co-leader of the BAS AI Lab and Senior Research Fellow at The Alan Turing Institute, says: "I'm excited to see how AI is making us rethink how we undertake environmental research. Our new sea ice forecasting framework fuses data from satellite sensors with the output of climate models in ways traditional systems simply couldn't achieve."

Unlike conventional forecasting systems that attempt to model the laws of physics directly, the authors designed IceNet based on a concept called deep learning. Through this approach, the model 'learns' how sea ice changes from thousands of years of climate simulation data, along with decades of observational data to predict the extent of Arctic sea ice months into the future.

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