A 'hot Jupiter’s' dark side is revealed in detail for first time

MIT astronomers have obtained the clearest view yet of the perpetual dark side of an exoplanet that is "tidally locked" to its star. Their observations, combined with measurements of the planet's permanent day side, provide the first detailed view of an exoplanet's global atmosphere.

"We're now moving beyond taking isolated snapshots of specific regions of exoplanet atmospheres, to study them as the 3D systems they truly are," says Thomas Mikal-Evans, who led the study as a postdoc in MIT's Kavli Institute for Astrophysics and Space Research.

The planet at the center of the new study, which appears in Nature Astronomy, is WASP-121b, a massive gas giant nearly twice the size of Jupiter. The planet is an ultrahot Jupiter and was discovered in 2015 orbiting a star about 850 light years from Earth. WASP-121b has one of the shortest orbits detected to date, circling its star in just 30 hours. It is also tidally locked, such that its star-facing "day" side is permanently roasting, while its "night" side is turned forever toward space.

"Hot Jupiters are famous for having very bright day sides, but the night side is a different beast. WASP-121b's night side is about 10 times fainter than its day side," says Tansu Daylan, a TESS postdoc at MIT who co-authored the study.

Astronomers had previously detected water vapor and studied how the atmospheric temperature changes with altitude on the planet's day side.

The new study captures a much more detailed picture. The researchers were able to map the dramatic temperature changes from the day to the night side, and to see how these temperatures change with altitude. They also tracked the presence of water through the atmosphere to show, for the first time, how water circulates between a planet's day and night sides.

While on Earth, water cycles by first evaporating, then condensing into clouds, then raining out, on WASP-121b, the water cycle is far more intense: On the day side, the atoms that make up water are ripped apart at temperatures over 3,000 Kelvin. These atoms are blown around to the night side, where colder temperatures allow hydrogen and oxygen atoms to recombine into water molecules, which then blow back to the day side, where the cycle starts again.

The team calculates that the planet's water cycle is sustained by winds that whip the atoms around the planet at speeds of up to 5 kilometers per second, or more than 11,000 miles per hour.

It also appears that water isn't alone in circulating around the planet. The astronomers found that the night side is cold enough to host exotic clouds of iron and corundum -- a mineral that makes up rubies and sapphires. These clouds, like water vapor, may whip around to the day side, where high temperatures vaporize the metals into gas form. On the way, exotic rain might be produced, such as liquid gems from the corundum clouds.

"With this observation, we're really getting a global view of an exoplanet's meteorology," Mikal-Evans says.

The study's co-authors include collaborators from MIT, Johns Hopkins University, Caltech, and other institutions.

Day and night

The team observed WASP-121b using a spectroscopic camera aboard NASA's Hubble Space Telescope. The instrument observes the light from a planet and its star, and breaks that light down into its constituent wavelengths, the intensities of which give astronomers clues to an atmosphere's temperature and composition.

Through spectroscopic studies, scientists have observed atmospheric details on the day sides of many exoplanets. But doing the same for the night side is far trickier, as it requires watching for tiny changes in the planet's entire spectrum as it circles its star.

For the new study, the team observed WASP-121b throughout two full orbits -- one in 2018, and the other in 2019. For both observations, the researchers looked through the light data for a specific line, or spectral feature, that indicated the presence of water vapor.

"We saw this water feature and mapped how it changed at different parts of the planet's orbit," Mikal-Evans says. "That encodes information about what the temperature of the planet's atmosphere is doing as a function of altitude."

The changing water feature helped the team map the temperature profile of both the day and night side. They found the day side ranges from 2,500 Kelvin at its deepest observable layer, to 3,500 Kelvin in its topmost layers. The night side ranged from 1,800 Kelvin at its deepest layer, to 1,500 Kelvin in its upper atmosphere. Interestingly, temperature profiles appeared to flip-flop, rising with altitude on the day side -- a "thermal inversion," in meteorological terms -- and dropping with altitude on the night side.

The researchers then passed the temperature maps through various models to identify chemicals that are likely to exist in the planet's atmosphere, given specific altitudes and temperatures. This modeling revealed the potential for metal clouds, such as iron, corundum, and titanium on the night side.

From their temperature mapping, the team also observed that the planet's hottest region is shifted to the east of the "substellar" region directly below the star. They deduced that this shift is due to extreme winds.

"The gas gets heated up at the substellar point but is getting blown eastward before it can reradiate to space," Mikal-Evans explains.

From the size of the shift, the team estimates that the wind speeds clock in at around 5 kilometers per second.

"These winds are much faster than our jet stream, and can probably move clouds across the entire planet in about 20 hours," says Daylan, who led previous work on the planet using NASA's MIT-led mission, TESS.

The astronomers have reserved time on the James Webb Space Telescope to observe WASP-121b later this year, and hope to map changes in not just water vapor but also carbon monoxide, which scientists suspect should reside in the atmosphere.

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Balkanatolia: The forgotten continent that sheds light on the evolution of mammals

A team of French, American and Turkish palaeontologists and geologists led by CNRS researchers1 has discovered the existence of a forgotten continent they have dubbed Balkanatolia, which today covers the present-day Balkans and Anatolia. Formerly inhabited by a highly specific fauna, they believe that it enabled mammals from Asia to colonise Europe 34 million years ago. Their findings are published in the March 2022 volume of Earth Science Reviews.

For millions of years during the Eocene Epoch (55 to 34 million years ago), Western Europe and Eastern Asia formed two distinct land masses with very different mammalian faunas: European forests were home to endemic fauna such as Palaeotheres (an extinct group distantly related to present-day horses, but more like today's tapirs), whereas Asia was populated by a more diverse fauna including the mammal families found today on both continents.

We know that, around 34 million years ago, Western Europe was colonised by Asian species, leading to a major renewal of vertebrate fauna and the extinction of its endemic mammals, a sudden event called the 'Grande Coupure'. Surprisingly, fossils found in the Balkans point to the presence of Asian mammals in southern Europe long before the Grande Coupure, suggesting earlier colonisation.

Now, a team led by CNRS researchers has come up with an explanation for this paradox. To do this, they reviewed earlier palaeontological discoveries, some of which date back to the 19th century, sometimes reassessing their dating in the light of current geological data. The review revealed that, for much of the Eocene, the region corresponding to the present-day Balkans and Anatolia was home to a terrestrial fauna that was homogeneous, but distinct from those of Europe and eastern Asia. This exotic fauna included, for example, marsupials of South American affinity and Embrithopoda (large herbivorous mammals resembling hippopotamuses) formerly found in Africa. The region must therefore have made up a single land mass, separated from the neighbouring continents.

The team also discovered a new fossil deposit in Turkey (Büyükteflek) dating from 38 to 35 million years ago, which yielded mammals whose affinity was clearly Asian, and are the earliest discovered in Anatolia until now. They found jaw fragments belonging to Brontotheres, animals resembling large rhinoceroses that died out at the end of the Eocene.

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Sonic advance: How sound waves could help regrow bones

Researchers have used sound waves to turn stem cells into bone cells, in a tissue engineering advance that could one day help patients regrow bone lost to cancer or degenerative disease.

The innovative stem cell treatment from researchers at RMIT University in Melbourne, Australia, offers a smart way forward for overcoming some of the field's biggest challenges, through the precision power of high-frequency sound waves.

Tissue engineering is an emerging field that aims to rebuild bone and muscle by harnessing the human body's natural ability to heal itself.

A key challenge in regrowing bone is the need for large amounts of bone cells that will thrive and flourish once implanted in the target area.

To date, experimental processes to change adult stem cells into bone cells have used complicated and expensive equipment and have struggled with mass production, making widespread clinical application unrealistic.

Additionally, the few clinical trials attempting to regrow bone have largely used stem cells extracted from a patient's bone marrow -- a highly painful procedure.

In a new study published in the journal Small, the RMIT research team showed stem cells treated with high-frequency sound waves turned into bone cells quickly and efficiently.

Importantly, the treatment was effective on multiple types of cells including fat-derived stem cells, which are far less painful to extract from a patient.

Fast and simple

Co-lead researcher Dr Amy Gelmi said the new approach was faster and simpler than other methods.

"The sound waves cut the treatment time usually required to get stem cells to begin to turn into bone cells by several days," said Gelmi, a Vice-Chancellor's Research Fellow at RMIT.

"This method also doesn't require any special 'bone-inducing' drugs and it's very easy to apply to the stem cells.

"Our study found this new approach has strong potential to be used for treating the stem cells, before we either coat them onto an implant or inject them directly into the body for tissue engineering."

The high-frequency sound waves used in the stem cell treatment were generated on a low-cost microchip device developed by RMIT.

Co-lead researcher Distinguished Professor Leslie Yeo and his team have spent over a decade researching the interaction of sound waves at frequencies above 10 MHz with different materials.

The sound wave-generating device they developed can be used to precisely manipulate cells, fluids or materials.

"We can use the sound waves to apply just the right amount of pressure in the right places to the stem cells, to trigger the change process," Yeo said.

"Our device is cheap and simple to use, so could easily be upscaled for treating large numbers of cells simultaneously -- vital for effective tissue engineering."

The next stage in the research is investigating methods to upscale the platform, working towards the development of practical bioreactors to drive efficient stem cell differentiation.

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Genetic mutation may identify women with difficulty producing breast milk

Leading health care organizations recommend exclusive breastfeeding for six months after birth, yet some mothers report stopping due to a perceived lack of milk supply. Penn State College of Medicine researchers found in a recent study that women who stopped breastfeeding because they believed they had inadequate milk supply -- a condition called perceived inadequate milk supply (PIMS) -- are more likely to have a specific mutation in a gene found in mammary tissue. These women were also more likely to have babies who gained less weight. The researchers said that screening for this mutation, when combined with maternal characteristics like age and body mass index, could be useful in identifying mothers at risk for stopping breastfeeding prematurely due to a perceived lack of milk supply.

"The World Health Organization, the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists recommend exclusive breastfeeding for at least six months because it provides developing infants with optimum nutrition and is associated with improved health outcomes," said Dr. Steven Hicks, lead researcher and pediatrician at Penn State Health Children's Hospital. "While 83% of women initiate breastfeeding, only a reported 57% continue to six months. Socioeconomic and environmental factors may contribute to early cessation, but milk supply is also an often-cited reason. Identifying women who are more likely to have low milk supply could help get them resources to continue breastfeeding such as lactation consultation services."

Previous research has linked maternal genetics with nutrients in breast milk, but few studies have explored how genetics may relate to supply. The researchers studied 18 genes highly expressed in mammary, or milk-producing, tissue in women. They looked for mutations in those genes to see whether mutations were associated with mothers' perceived milk supply.

The study team followed 88 women between 19 and 42 years old for the first year of their baby's life. The mothers completed surveys about their infant's feeding habits at one, four, six and twelve months of age that asked questions about perceived milk supply, whether women supplemented their child's diet with formula and reasons why they did so. Decreased or low milk production, signs of allergies from breastfeeding and other personal reasons such as work, day care or time constraints were included as possible reasons for why women began to supplement with formula. Mothers also provided a DNA sample by having saliva collected.

Using responses from the surveys, the researchers classified the mothers as having either PIMS or perceived adequate milk supply (PAMS). They found that the 45 mothers with PIMS were more likely to breastfeed for shorter periods, report lower milk supply and have infants who were not gaining adequate weight.

The researchers analyzed the mothers' DNA samples and looked for mutations among 18 genes that are involved in the secretion of breast milk. Although modifications in 10 of the genes studied were found among some women, the team found that only one, a variant in the milk fat globule EGF and factor V/VIII domain containing gene (MFGE8), occurred more frequently in women with PIMS. Those without the mutation were more likely to have adequate milk supply and report a longer duration of breastfeeding.

Using statistical modeling, the researchers found that maternal characteristics like age, previous breastfeeding duration and body mass index alone could not differentiate between mothers with PIMS and PAMS. However, when adding in MFGE8 mutation status into the model, it strongly predicted which women reported adequate or inadequate milk supplies. The researchers published their results in the journal Breastfeeding Medicine.

"Identifying risk of PIMS at the outset of breastfeeding could provide opportunities for early, targeted interventions such as guidance from a trained lactation support professional," Hicks said. He noted that current assessment of PIMS is guided by subjective reports and that counseling may help identify foods and medications that help or hinder milk production.

Hicks said that the study's findings will need to be validated in a larger study that includes more mothers. He also said that more research is needed to uncover the biological processes that determine how this particular gene affects milk supply in moms in order to better understand its association with PIMS status.

"Moms with this mutation still produce milk, even if it may be less than women without the mutation, but challenges like poor diet, hydration or sleep could be enough to hinder the supply that they do have," Hicks said. "Screening for this variant and combining that with maternal reports and characteristics could help identify moms and babies that may need additional support."

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Astronomers discover widest separation of brown dwarf pair to date

A team of astronomers has discovered a rare pair of brown dwarfs that has the widest separation of any brown dwarf binary system found to date.

"Because of their small size, brown dwarf binary systems are usually very close together," said Emma Softich, an undergraduate astrophysics student at the Arizona State University (ASU) School of Earth and Space Exploration and lead author of the study. "Finding such a widely separated pair is very exciting."

The gravitational force between a pair of brown dwarfs is lower than for a pair of stars with the same separation, so wide brown dwarf binaries are more likely to break up over time, making this pair of brown dwarfs an exceptional find.

The study, which is based on observations the University of California San Diego (UC San Diego) Cool Star Lab conducted with W. M. Keck Observatory on Maunakea, Hawai'i Island, is published in today's issue of The Astrophysical Journal Letters.

Using Keck Observatory's Near-Infrared Echellette Spectrometer, or NIRES instrument, members of the UC San Diego Cool Star Lab, including Physics Professor Adam Burgasser and graduate students Christian Aganze and Dino Hsu, obtained infrared spectra of the brown dwarf binary system, called CWISE J014611.20-050850.0AB. The data revealed the two brown dwarfs are about 12 billion miles apart, or three times the separation of Pluto from the Sun. This distance confirms the unusual brown dwarf couple breaks the record for having the widest separation from each other.

"Keck's exceptional sensitivity in the infrared with this instrument was critical for our measurements," said co-author Burgasser, who leads the Cool Star Lab. "The secondary brown dwarf of this system is exceptionally faint, but with Keck we were able to obtain good enough spectral data to classify both sources and identify them as members of a rare class of blue L dwarfs."

"Wide, low-mass systems like CWISE J014611.20-050850.0AB are usually disrupted early on in their lifetimes, so the fact that this one has survived until now is pretty remarkable," said co-author Adam Schneider of the U.S. Naval Observatory, Flagstaff Station and George Mason University.

Brown dwarfs are celestial objects that are smaller than a normal star. These objects are not massive enough to sustain nuclear fusion and shine like normal stars, but are hot enough to radiate energy.

Many brown dwarfs have been discovered with data from NASA's Wide-field Infrared Survey Explorer (WISE) via the Backyard Worlds: Planet 9 citizen science project, which solicits help from the public to search the WISE image data bank to find brown dwarfs and low-mass stars, some of the Sun's nearest neighbors.

For this study, the researchers inspected images of Backyard Worlds discoveries, where companion brown dwarfs may have been overlooked. In doing so, they discovered the rare CWISE J014611.20 050850.0AB brown dwarf binary system.

Softich went through about 3,000 brown dwarfs from Backyard Worlds one by one and compared the WISE images to other survey images, looking for evidence of a brown dwarf companion to the original target. The team then used data from the Dark Energy Survey (DES) to confirm that it was indeed a brown dwarf pair.

They then used Keck Observatory's NIRES to confirm the brown dwarfs have spectral types L4 and L8, and that they are at an estimated distance of about 40 parsecs, or 130.4 light-years from Earth, with a projected separation of 129 astronomical units, or 129 times the distance between the Sun and the Earth.

The team hopes this discovery will allow astronomers the chance to study brown dwarf binary systems and to develop models and procedures that will help in recognizing more of them in the future.

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How to look thousands of kilometers deep into the Earth

Researchers led by Sergey Lobanov from the GFZ German Research Centre for Geosciences have developed a new method to measure the density of silicon dioxide (SiO2) glass, one of the most important materials in industry and geology, at pressures of up to 110 gigapascals, 1.1 million times higher than normal atmospheric pressure. Instead of employing highly focused X-rays at a synchrotron facility, they used a white laser beam and a diamond anvil cell. The researchers report on their new and simple method in the current issue of Physical Review Letters.

The problem of density measurement under extreme conditions

In geosciences, the density of minerals, rocks, and melts at pressures up to several million atmospheres and temperatures of several thousand degrees is of critical importance because it governs the long-term planetary evolution as well as volcanic processes. But how can the density of a material be measured at such extreme conditions? To answer this question for a crystalline mineral or a rock, scientists use X-ray diffraction with which one measures the spacing between the periodically arranged atoms. There is, however, a problem if the material has a disordered structure, i.e. is non-crystalline, like glasses or molten rocks. In this case, the volume of the sample has to be measured directly -- the density of a material equals its mass divided by volume. However, such measurements are extremely difficult because of the tiny volume of the sample brought to high pressure. Previously, these measurements required large scale X-ray facilities and highly specialized equipment, thus being very expensive. Now, a team led by scientist Sergey Lobanov of the GFZ German Research Centre for Geosciences is introducing a new method in which a laser the size of a shoebox allows them to measure the volume of samples brought to pressures similar to that at the depth of more than 2000 km in the Earth.

Inside the Earth, the rock is under unimaginably high pressure, up to several million times higher than normal atmospheric pressure. However, contrary to widespread belief, the Earth's mantle is not liquid, but solid. The rock behaves in a viscoplastic fashion: It moves centimeter by centimeter per year, but it would burst under a hammer blow. Nevertheless, the slow movements drive the Earth's crustal plates and tectonics, which in turn trigger volcanism. Chemical changes, for example, caused by water squeezed out of subducted crustal plates, can change the melting point of the rock in such a way that suddenly molten magma is formed. When this magma makes its way to the Earth's crust and to the surface, volcanic eruptions occur.

Density of disordered materials

No instrument in the world can penetrate the Earth's mantle to study such processes in detail. Therefore, one must rely on calculations, seismic signals and laboratory experiments to learn more about the Earth's interior. A diamond anvil cell can be used to generate the extremely high pressures and temperatures that prevail there. The samples explored in it are smaller than the tip of a pin. Their volume is in the sub nanoliter range (e.g. at least 10 million times smaller than 1 milliliter). When material is compressed under such high pressures, the internal structure changes. To analyze this precisely, X-rays are used on crystals to generate diffraction patterns. This allows conclusions to be drawn about the volume of the crystal lattice and thus also the density of the material. Non-crystalline materials, such as glasses or molten rocks, have so far kept their innermost secrets to themselves. This is because for disordered materials X-ray diffraction does not provide direct information on their volume and density.

Simple trick: measurement with laser instead of X-ray beam

Using a simple trick, researchers led by Sergey Lobanov have now succeeded in measuring the refractive index and density of silicon dioxide (SiO2) glass, one of the most important materials in industry and geology, at pressures of up to 110 gigapascals. This is a pressure that prevails at a depth of more than 2,000 kilometers in the Earth's interior and is 1.1 million times higher than normal atmospheric pressure. The researchers used a multicolor laser to measure the brightness of its reflection from the pressurized sample. The brightness of the laser reflection contained information on the refractive index, a fundamental material property that describes how light slows down and bends as it travels through the material, but also the path length of the laser inside the sample. Materials with a high refractive index and density, such as diamonds and metals, typically appear bright and shiny to our eye. Instead of looking at the tiny samples with a naked eye, Lobanov and his colleagues used a powerful spectrometer to record changes in brightness at high pressure. These measurements yielded the refractive index of SiO2 glass and provided key information to quantify its density.

Significance of the density measurement of glasses for the geosciences

"Earth was a giant ball of molten rock 4.5 billion years ago. To understand how Earth has cooled and produced a solid mantle and crust, we need to know the physical properties of molten rocks at extreme pressure. However, studying melts at high pressure is extremely challenging and to circumvent some of these challenges geologists choose to study glasses instead of melts. Glasses are produced by quickly cooling hot but viscous melts. As a result, the structure of glasses often represents the structure of melts they were formed from. Previous measurements of glass density at high pressure required large and expensive synchrotron facilities that produce a tightly focused beam of X-rays that can be used to view the tiny sample in a diamond anvil cell. These were challenging experiments and only the densities of very few glasses have been measured to a pressure of 1 million atmospheres. We have now shown that the evolution of the sample volume and density of any transparent glass can be accurately measured up to pressures of at least 110 GPa using optical techniques," Lobanov says. "This can be done outside of synchrotron facilities and is therefore much easier and less costly. Our work thus paves the way to future studies of glasses that approximate Earth's present-day and long-gone melts. These future studies will provide new quantitative answers about the evolution of the early Earth as well as the driving forces behind volcanic eruptions."

New possibilities for the investigation of non-crystalline, initially non-transparent solids

Because the samples are extremely small and therefore ultra-thin, even materials that look like a lump of rock in large pieces become translucent. According to the researchers, these developments open up new possibilities for studying the mechanical and electronic properties of non-crystalline solids that appear nontransparent in larger volumes. According to the authors of the study, their findings have far-reaching implications for materials science and geophysics. In addition, this information could serve as a benchmark for computational studies of the transport properties of glasses and melts under extreme conditions.

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The formation of the West Antarctic Ice Sheet was very different than previously believed

Roughly 35 million years ago, Earth cooled rapidly. At roughly the same time, the Drake Passage formed between South America and the Antarctic, paving the way for the Antarctic Circumpolar Current. Thanks to these two factors, Antarctica was soon completely covered in ice. As a study from the Alfred Wegener Institute now shows, this massive glaciation was delayed in at least one region. This new piece of the puzzle concerning the early history of the West Antarctic Ice Sheet could help to predict its unstable future. The study was just released in the Nature journal Communications Earth & Environment.

For climate researchers, the West Antarctic has been in the spotlight for years. Here, the West Antarctic Ice Sheet lying atop the continent stretches to the adjacent Amundsen Sea. Near the coast, the ice is still in direct contact with the soil; farther toward the open sea, it floats. Because climate change progressively warms the seawater, the latter is increasingly eroding the ice shelf from below. The grounding line -the last point at which the ice still rests on the ground -moves farther and farther inland. Due to meltwater and calving icebergs, the Thwaites Glacier, which flows into the Amundsen Sea, now loses twice as much ice as 30 years ago. If the West Antarctic Ice Sheet were to collapse entirely, global sea levels would rise by more than three metres.

"The stability of the West Antarctic Ice Sheet is critical to the future development of the global sea level," says the study's first author, Gabriele Uenzelmann-Neben from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). "Accordingly, researchers around the world are working to predict the future behaviour of the ice in a warmer world using numerical simulation. The more we know about the history of the West Antarctic Ice Sheet, the more accurate we can make these models. Its more recent history is well-documented, but we still know very little about its earlier years -- particularly the formation phase. Our study delivers an important piece of the puzzle."

In the course of two research cruises on board the Polarstern, the Geophysicist and her team investigated sediments in the vicinity of Pine Island Trough, a channel-like furrow in the seafloor of the shallow part of the Amundsen Sea that stretches from north to south and leads directly toward the western coast of Antarctica. To collect data, the AWI team relied on the tried and proven reflection seismology method: the Polarstern towed a 3,000-metre-long measuring cable -- or streamer -- behind her. The streamer is equipped with hydrophones that utilise a total of 240 measuring channels. During survey cruises, an airgun is used to produce seismic pulses behind the ship. These pulses penetrate the seafloor and are reflected back at geological boundaries -- e.g. between the sediment and hard rock -- which is recorded by the streamer's hydrophones. Based on the different travel times for the waves and the respective positions of the individual channels, the internal structure of the seafloor can be mapped.

The measurement data revealed a large sediment body, a sediment drift, on the eastern flank of Pine Island Trough, one with no counterpart on its western side. "Because of the Coriolis effect produced by Earth's rotation, this asymmetrical deposition of a sediment drift on the trough's eastern side but not the western one can only have been produced by a deep-water current that flowed toward the coast from north to south," says Uenzelmann-Neben. "In order for that to occur, the ocean circulation at the time of the deposition had to be similar to today's conditions, that is, the prevailing westerlies and the Antarctic Circumpolar Current had to have been located far to the south. And similar to today, the deep water upwelled through the trough must have been comparatively warm."

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New fossil birds discovered near China’s Great Wall – one had a movable, sensitive 'chin'

Approximately 80 miles from the westernmost reach of China's Great Wall, paleontologists found relics of an even more ancient world. Over the last two decades, teams of researchers unearthed more than 100 specimens of fossil birds that lived approximately 120 million years ago, during the time of the dinosaurs. However, many of these fossils have proved difficult to identify: they're incomplete and sometimes badly crushed. In a new paper published in the Journal of Systematics and Evolution, researchers examined six of these fossils and identified two new species. And as a fun side note, one of those new species had a movable bony appendage at the tip of its lower jaw that may have helped the bird root for food.

"It was a long, painstaking process teasing out what these things were," says Jingmai O'Connor, the study's lead author and the associate curator of vertebrate paleontology at Chicago's Field Museum. "But these new specimens include two new species that increase our knowledge of Cretaceous bird faunas, and we found combinations of dental features that we've never seen in any other dinosaurs."

"These fossils come from a site in China that has produced fossils of birds that are pretty darned close to modern birds, but all the bird fossils described thus far haven't had skulls preserved with the bodies," says co-author Jerry Harris of Utah Tech University. "These new skull specimens help fill in that gap in our knowledge of the birds from this site and of bird evolution as a whole."

All birds are dinosaurs, but not all dinosaurs are birds; a small group of dinosaurs evolved into birds that coexisted with other dinosaurs for 90 million years. Modern birds are the descendants of the group of birds that survived the extinction that killed the rest of the dinosaurs, but many prehistoric birds went extinct then too. O'Connor's work focuses on studying different groups of early birds to figure out why some survived while others went extinct.

The fossil site in northwestern China, called Changma, is an important place for researchers like O'Connor studying bird evolution. It's the second-richest Mesozoic (time of the dinosaurs) fossil bird site in the world, but more than half of the fossils found there belong to the same species, Gansus yumenensis.Determining which fossils are Gansus and which ones aren't is tricky; the six specimens that O'Connor and her colleagues examined in this study are primarily just skulls and necks, parts not preserved in known specimens of Gansus. The fossils were also somewhat smushed by their time deep in the Earth, which made analyzing them difficult.

"The Changma site is a special place," says study co-author Matt Lamanna of Pittsburgh's Carnegie Museum of Natural History. "The fossil-bearing rocks there tend to split into thin sheets along ancient bedding planes. So, when you're digging, it's like you're literally turning back the pages of history, layer by layer uncovering animals and plants that haven't seen the light of day in roughly 120 million years."

"Because the specimens were pretty flattened, CT-scanning them and fully segmenting them could take years and might not even give you that much information, because these thin bones are flattened into almost the same plane, and then it just becomes almost impossible to figure out where the boundaries of these bones are," says O'Connor. "So we had to kind of work with what was exposed." Through painstaking work, the researchers were able to identify key features in the birds' jaws that showed that two of the six specimens were unknown to science.

The new species (or, more accurately, new genera -- genus is a step above species in the order scientists use to name organisms) are called Meemannavis ductrix and Brevidentavis zhangi. Meemannavis is named for Meemann Chang, a Chinese paleontologist who became the first woman to lead the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. The name Brevidentavis means "short-toothed bird." Like Gansus, both Meemannavis and Brevidentavis are ornithuromorph birds -- the group that contains modern birds. Like today's birds, Meemannavis was toothless. Brevidentavis, on the other hand, had small, peg-like teeth packed close together in its mouth. Along with those teeth came another strange feature.

"Brevidentavis is an ornithuromorph bird with teeth, and in ornithuromorphs with teeth, there's a little bone at the front of the jaw called the predentary, where its chin would be if birds had chins," explains O'Connor. In a previous study on the predentary in another fossil bird, the authors figured out, by CT-scanning the bone and staining it with chemicals, that the predentary bone underwent stress and also found a kind of cartilage that only forms when there's movement.

"In this earlier study, we were able to tell that the predentary was capable of being moved, and that it would have been innervated -- Brevidentavis wouldn't just have been able to move its predentary, it would have been able to feel through it," says O'Connor. "It could have helped them detect prey. We can hypothesize that these toothed birds had little beaks with some kind of movable pincer at the tip of their jaws in front of the teeth."

Brevidentavis isn't the first fossil bird discovered with a predentary that might have been used in this way, but its existence, along with Meemannavis, helps round out our understanding of the diversity of prehistoric birds, especially in the Changma region.

The study also helps shed light on the most common bird from the site, Gansus, since at least four of the other specimens examined probably belong to this species. "Gansus is the first known true Mesozoic bird in the world, as Archaeopteryx is more dinosaur-like, and now we know what its skull looks like after about 40 years," notes Hai-Lu You of the IVPP.

"These amazing fossils are like a lockpick allowing us to open the door to greater knowledge of the evolutionary history of the skull in close relatives of living birds," says Tom Stidham, a co-author from the IVPP. "At a time when giant dinosaurs still roamed the land, these birds were the products of evolution experimenting with different lifestyles in the water, in the air, and on land, and with different diets as we can see in some species having or lacking teeth. Very few fossils of this geological age provide the level of anatomical detail that we can see in these ancient bird skulls."

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Ancient dwarf galaxy reconstructed with MilkyWay@home volunteer computer

Astrophysicists for the first time have calculated the original mass and size of a dwarf galaxy that was shredded in a collision with the Milky Way billions of years ago. Reconstructing the original dwarf galaxy, whose stars today thread through the Milky Way in a stellar "tidal stream," will help scientists understand how galaxies like the Milky Way formed, and could aid in the search for dark matter in our galaxy.

"We've been running simulations that take this big stream of stars, back it up for a couple of billion years, and see what it looked like before it fell into the Milky Way," said Heidi Newberg, a professor of physics, astrophysics, and astronomy at Rensselaer Polytechnic Institute. "Now we have a measurement from data, and it's the first big step toward using the information to find dark matter in the Milky Way."

Billions of years ago, the dwarf galaxy and others like it near the Milky Way were pulled into the larger galaxy. As each dwarf galaxy coalesced with the Milky Way, its stars were pulled by "tidal forces," the same kind of differential forces that make tides on Earth. The tidal forces distorted and eventually ripped the dwarf galaxy apart, stretching its stars into a tidal stream flung across the Milky Way. Such tidal mergers are fairly common, and Newberg estimates that "immigrant" stars absorbed into the Milky Way make up most of the stars in the galactic halo, a roughly spherical cloud of stars that surrounds the spiral arms of the central disk.

Critically, the position and velocities of the tidal stream stars carry information about the Milky Way's gravitational field.

Reconstructing the dwarf galaxy is a research task that combines data from star surveys, physics, and Newberg's MilkyWay@Home distributed supercomputer, which harnesses 1.5 petaflops -a measure of computer processing speed- of home computer power donated by volunteers. This large amount of processing power makes it possible to simulate the destruction of a large number of dwarf galaxies with different shapes and sizes, and identify a model that best matches the tidal stream of stars that we see today.

"It's an enormous problem, and we solve it by running tens of thousands of different simulations until we get one that actually matches. And that takes a lot of computer power, which we get with the help of volunteers all over the world who are part of MilkyWay@Home," Newberg said "We're brute-forcing it, but given how complicated the problem is, I think this method has a lot of merit."

As published today in The Astrophysical Journal, Newberg's team estimates the total mass of the original galaxy whose stars today form the Orphan-Chenab Stream as 2x107 times the mass of our sun.

However, only a little more than 1% of that mass is estimated to be made up of ordinary matter like stars. The remainder is assumed to be a hypothetical substance called dark matter that exerts gravitational force, but that we cannot see because it does not absorb or give off light. The existence of dark matter would explain a discrepancy between the gravitational pull of the mass of the matter we can see, and the far larger pull needed to account for the formation and movement of galaxies. The gravitational pull from dark matter is estimated to make up as much as 85% of the matter in the universe, and tidal streams of stars that fell in with dwarf galaxies could be used to determine where dark matter is located in our galaxy.

"Tidal stream stars are the only stars in our galaxy for which it is possible to know their positions in the past," Dr. Newberg said. "By looking at the current speeds of stars along a tidal stream, and knowing they all used to be in about the same place and moving at the same speed, we can figure out how much the gravity changes along that stream. And that will tell us where the dark matter is in the Milky Way."

The research also finds that the progenitor of the Orphan-Chenab stream has less mass than the galaxies measured in the outskirts of our galaxy today, and if this small mass is confirmed it could change our understanding of how small stellar systems form and then merge together to make larger galaxies like our Milky Way.

Dr. Newberg, an expert in the galactic halo, is a pioneer in identifying stellar tidal streams in the Milky Way. One day, she hopes that MilkyWay@home will help her measure more than the properties of one disintegrated dwarf galaxy. Ideally, she would like to simultaneously fit many dwarf galaxies, their orbits, and the properties of the Milky Way galaxy itself. This goal is complicated by the fact that the properties of our galaxy change over the billions of years that it takes for a small galaxy to fall in and be ripped apart to make these tidal streams.

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Scientists map entire human gut at single cell resolution

If you get nervous, you might feel it in your gut. If you eat chili, your gut might revolt, but your friend can eat anything and feel great. You can pop ibuprofen like candy with no ill effects, but your friend's belly might bleed and might get no pain relief. Why is this? The quick answer is because we're all different. The next questions are how different exactly, and what do these differences mean for health and disease? Answering these is much more difficult, but the UNC School of Medicine lab of Scott Magness, PhD, is revealing some interesting scientific answers.

For the first time, the Magness lab used entire human GI tracts from three organ donors to show how cell types differ across all regions of the intestines, to shed light on cellular functions, and to show gene expression differences between these cells and between individuals.

This work, published in Cellular and Molecular Gastroenterology and Hepatology, opens the door to exploring the many facets of gut health in a much more precise manner at greater resolution than ever before.

"Our lab showed it's possible to learn about each cell type's function in important processes, such as nutrient absorption, protection from parasites, and the production of mucus and hormones that regulate eating behavior and gut motility," said Magness, associate professor in the Joint UNC-NC State Department of Biomedical Engineering and senior author of the paper. "We also learned how the gut lining might interact with the environment through receptors and sensors, and how drugs could interact with different cell types."

The Sensitive Gut

Think of a typical pharmaceutical commercial voiceover when the voice actor pleasantly recites possible side effects, such as diarrhea, vomiting, intestinal bleeding, and other unpleasant collateral damage. Well, the Magness lab is attempting to understand why those side effects happen, down to the level of individual cells, their functions, their locations, and their genes.

For this research, the Magness lab focused on the epithelium: the single-cell thick layer separating the inside of the intestines and colon from everything else. Like other cell populations and the microbiota, the epithelium is incredibly important to human health, and for years scientists have been exploring it. But until now, researchers could only take tiny biopsies the size of grains of rice from a few parts of the digestive tract, usually from the colon or limited regions of the small intestine.

"Such exploration would be like looking at the United States from space but only investigating what's going on in Massachusetts, Oklahoma, and California," Magness said. "To really learn about the country, we'd want to see everything."

Magness leaned on co-first authors, postdoctoral fellow Joseph Burclaff, PhD, and graduate student, Jarrett Bliton, both trainees in the Magness lab.

"Not only do we want to identify where the cells are located, but we want to know exactly which cell types do what, and why," Burclaff said. "So, staying with the map analogy, we don't want to just say, 'oh, there's North Carolina'. We want to know where to get the best barbecue. We want a ground level view to know as much as possible."

In the past, researchers would mash up those rice-sized biopsies to identify all epithelial cell types and learn some general features of these cells. Magness's approach was to sample thousands of individual cells from every part of the lower digestive tract (small intestine and colon) to create an atlas and then study the potential roles of these cells through the genes that each cell expresses. Knowing all of this would deepen scientific knowledge about the gut epithelium and hopefully encourage other scientists to explore each cell's function in biology, in disease, and in the unfortunate scenario of pharmaceutical side effects.

To do such a deep individual cell dive, Magness needed two things: better technology and the entire digestive tracts of humans.

The Biology of Data

UNC-Chapel Hill acquired state-of-the-art RNA sequencing technology several years ago for the creation of the Advanced Analytics Core Facility through the UNC Center for Gastrointestinal Disease and Biology, which developed the scientific and intellectual heft -- research faculty, staff, postdocs, and students -- to use state-of-the-art equipment.

The Magness Group acquired human digestive tracts through a research agreement with organ donor services at HonorBridge. When intestines are harvested for transplant and if they are not claimed by higher-priority groups, HonorBridge staff coordinates with the Magness Group to donate the transplant-grade organs for research.

Six to eight hours after harvest, the Magness lab receives intact intestinal tracts, each about 15 to 30 feet long. They remove the epithelial layer, which is one long connected piece of tissue despite being only one cell thick. Then the researchers use enzymes to break down the epithelium into individual cells. For this study, they repeated this for organs from three separate donors.

Using sequencing technology to characterize gene expression, the Magness group first extracts RNA from each cell while keeping each cell separate, and then they run single-cell sequencing, which takes a snapshot of which genes each intestinal cell is expressing and how much.

"The picture we get from each cell is a mosaic of all the different types of genes the cells make and this complement of genes creates a 'signature' to tell us what kind of cell it is and potentially what it is doing," Magness said. "Is it a stem cell or a mucous cell or a hormone-producing cell or an immune-signaling cell?

Burclaff added, "We were able to see the differences in cell types throughout the entire digestive tracts, and we can see different gene expression levels in the same cell types from three different people. We can see the different sets of genes turned on or off in individual cells. This is how, for instance, we might begin to understand why some people form toxicity to certain foods or drugs and some people don't."

A major problem with this kind of research is the sheer amount of data produced. The single cell sequencing picks up about 11,000 'reads', or individual samples of gene products in just one cell, and in many thousands of individual cells, each with different combinations of the 20,000-plus human genes that are turned on or off. This creates almost 140,000,000 data points for all the 12,590 cells in the study that have to be put into a visualizable format so that scientists can make sense of the vast amount of information.

"The human brain can only comprehend two dimensions, three is challenging," Magness said. "Add time, and it's even trickier to comprehend what a single cell is up to. The amount of data our experiments produced was basically millions of dimensions all at once."

Bliton devised computational techniques to filter the data to produce a manageable data set that included cell populations from all portions of the GI tract. Then, based on what Magness and other researchers had already learned of each cell type, Bliton could computationally identify each cell type from each region. He then plotted these data in a manner that humans can understand and interpret.

Reining in the immense data allowed the scientists to learn a lot about each cell type. Consider the tuft cell, discovered 40 years ago and so named because they look as if they have tufts of hair on their surface. Turns out these tuft cells express similar genes as those on taste buds on the tongue. Other researchers discovered that these tuft cells sensed worm infections and sent signals to the immune system to begin waging war. The Magness lab showed that tuft cells exhibit a set of genes thought to be important for sensing and "tasting" other kinds of intestinal content so it can signal the immune system if need be. This would represent a much broader function than sensing if there's a parasite in your gut or not.

"Not only did we describe every single cell type and every single gene they express individually, but we also looked at potential functions," Burclaff said. "If you look at intestinal mucus, which is a complex mixture that protects the cells, we show which cells express various mucin proteins, how much, and in which regions of the digestive tract. We looked at where specific enzymes that digest food are expressed. We looked at cells with anti-inflammatory gene expression and synapse genes where the gut is probably connected to nerves so it can talk to the rest of the body. We looked at aquaporins, proteins involved in transferring water through the intestinal membrane."

What the Magness group found was a whole new level of variation in potential functions that had not previously been appreciated through mashing up biopsy samples.

The researchers explored all epithelial receptors -- the cell surface proteins used to communicate with other cells and molecules and with the environment of the gut. Magness and colleagues could see which receptors were expressed the most and in which cell types, painting a new picture of how cells might interact with gut contents such as nutrients, microbes, toxins, and drugs.

"As far as we know, we're the first to do this kind of analysis across the length of the human gut from three full donors," Bliton said. "We can look at each cell type and predict which pharmaceuticals might affect which cell type individually."

For instance, there's a class of drugs to treat inflammatory bowel disease; they're designed to hit specific targets, certain immune cells that trigger inflammation. But the Magness lab learned that some epithelial cells express the same genes as those in the immune cells that are intended to be the target. This finding indicates there could be "off-target" effects in epithelial cells that are not intended and could lead to side-effects.

"This was not known," Burclaff said. "Lots of drugs have bad GI side effects. And it could be because the drugs are affecting individual cells along the entire length of the GI tract. We show where these receptors are most expressed and in which cell types."

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