Wednesday, September 18, 2019

Aquaculture in Neolithic China Dates Back 8,000 Years

By using age-mortality and species-selection profiles from prehistoric East Asia, researchers identified carp aquaculture in Henan Province, China, thousands of years earlier than previously reported.

In a recent study, an international team of researchers analyzed fish bones excavated from the Early Neolithic Jiahu site in Henan Province, China. By comparing the body-length distributions and species-composition ratios of the bones with findings from East Asian sites with present aquaculture, the researchers provide evidence of managed carp aquaculture at Jiahu dating back to 6200-5700 BC.

Preparing to drain the field at Matsukawa village, Japan

 Credit: © Mark Hudson

Despite the growing importance of farmed fish for economies and diets around the world, the origins of aquaculture remain unknown. The Shijing, the oldest surviving collection of ancient Chinese poetry, mentions carp being reared in a pond circa 1140 BC, and historical records describe carp being raised in artificial ponds and paddy fields in East Asia by the first millennium BC. But considering rice paddy fields in China date all the way back to the fifth millennium BC, researchers from Lake Biwa Museum in Kusatu, Japan, the Max Planck Institute for the Science of Human History in Jena, Germany, the Sainsbury Institute for the Study of Japanese Arts and Cultures in Norwich, U.K., and an international team of colleagues set out to discover whether carp aquaculture in China was practiced earlier than previously thought.

Carp farming goes way back in Early Neolithic Jiahu

Jiahu, located in Henan, China, is known for the early domestication of rice and pigs, as well the early development of fermented beverages, bone flutes, and possibly writing. This history of early development, combined with archaeological findings suggesting the presence of large expanses of water, made Jiahu an ideal location for the present study.

Researchers measured 588 pharyngeal carp teeth extracted from fish remains in Jiahu corresponding with three separate Neolithic periods, and compared the body-length distributions with findings from other sites and a modern sample of carp raised in Matsukawa Village, Japan. While the remains from the first two periods revealed unimodal patterns of body-length distribution peaking at or near carp maturity, the remains of Period III (6200-5700 BC) displayed bimodal distribution, with one peak at 350-400 mm corresponding with sexual maturity, and another at 150-200 mm.

Co-author Junzo Uchiyama preparing to measure common carp removed from the paddy field

Credit: © Mark Hudson

This bimodal distribution identified by researchers was similar to that documented at the Iron Age Asahi site in Japan (circa 400 BC – AD 100), and is indicative of a managed system of carp aquaculture that until now was unidentified in Neolithic China. “In such fisheries,” the study notes, “a large number of cyprinids were caught during the spawning season and processed as preserved food. At the same time, some carp were kept alive and released into confined, human regulated waters where they spawned naturally and their offspring grew by feeding on available resources. In autumn, water was drained from the ponds and the fish harvested, with body-length distributions showing two peaks due to the presence of both immature and mature individuals.”

Species-composition ratios support findings, indicate cultural preferences

The size of the fish wasn’t the only piece of evidence researchers found supporting carp management at Jiahu. In East Asian lakes and rivers, crucian carp are typically more abundant than common carp, but common carp comprised roughly 75% of cyprinid remains found at Jiahu. This high proportion of less-prevalent fish indicates a cultural preference for common carp and the presence of aquaculture sophisticated enough to provide it.

Based on the analysis of carp remains from Jiahu and data from previous studies, researchers hypothesize three stages of aquaculture development in prehistoric East Asia. In Stage 1, humans fished the marshy areas where carp gather during spawning season. In Stage 2, these marshy ecotones were managed by digging channels and controlling water levels and circulation so the carp could spawn and the juveniles later harvested. Stage 3 involved constant human management, including using spawning beds to control reproduction and fish ponds or paddy fields to manage adolescents.

Although rice paddy fields have not yet been identified at Jiahu, the evolution of carp aquaculture with wet rice agriculture seems to be connected, and the coevolution of the two is an important topic for future research.

Contacts and sources:
Anne Gibson
Max Planck Institute for the Science of Human History
Citation: Common carp aquaculture in Neolithic China dates back 8,000 years. Tsuneo Nakajima, Mark J. Hudson, Junzo Uchiyama, Keisuke Makibayashi, Juzhong Zhang. DOI: 10.1038/s41559-019-0974-3 Nature Ecology & Evolution,

Dust from a Giant Asteroid Crash Caused an Ancient Ice Age

About 466 million years ago, long before the age of the dinosaurs, the Earth froze. The seas began to ice over at the Earth’s poles, and the new range of temperatures around the planet set the stage for a boom of new species evolving. The cause of this ice age was a mystery, until now: a new study in Science Advances argues that the ice age was caused by global cooling, triggered by extra dust in the atmosphere from a giant asteroid collision in outer space.

There’s always a lot of dust from outer space floating down to Earth, little bits of asteroids and comets, but this dust is normally only a tiny fraction of the other dust in our atmosphere such as volcanic ash, dust from deserts and sea salt. But when a 93-mile-wide asteroid between Mars and Jupiter broke apart 466 million years ago, it created way more dust than usual.

Credit: State Farm / Wikimedia Commons / Basilicofresco.

 “Normally, Earth gains about 40,000 tons of extraterrestrial material every year,” says Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and one of the paper’s authors. “Imagine multiplying that by a factor of a thousand or ten thousand.” To contextualize that, in a typical year, one thousand semi trucks’ worth of interplanetary dust fall to Earth. In the couple million years following the collision, it’d be more like ten million semis.

“Our hypothesis is that the large amounts of extraterrestrial dust over a timeframe of at least two million years played an important role in changing the climate on Earth, contributing to cooling,” says Heck.

“Our results show for the first time that such dust, at times, has cooled Earth dramatically,” says Birger Schmitz of Sweden’s Lund University, the study’s lead author and a research associate at the Field Museum. “Our studies can give a more detailed, empirical-based understanding of how this works, and this in turn can be used to evaluate if model simulations are realistic.”

To figure it out, researchers looked for traces of space dust in 466-million-year-old rocks, and compared it to tiny micrometeorites from Antarctica as a reference. “We studied extraterrestrial matter, meteorites and micrometeorites, in the sedimentary record of Earth, meaning rocks that were once sea floor,” says Heck. “And then we extracted the extraterrestrial matter to discover what it was and where it came from.”

Extracting the extraterrestrial matter—the tiny meteorites and bits of dust from outer space—involves taking the ancient rock and treating it with acid that eats away the stone and leaves the space stuff. The team then analyzed the chemical makeup of the remaining dust. The team also analyzed rocks from the ancient seafloor and looked for elements that rarely appear in Earth rocks and for isotopes—different forms of atoms—that show hallmarks of coming from outer space. For instance, helium atoms normally have two protons, two neutrons, and two electrons, but some that are shot out of the Sun and into space are missing a neutron. The presence of these special helium isotopes, along with rare metals often found in asteroids, proves that the dust originated from space.

Other scientists had already established that our planet was undergoing an ice age around this time. The amount of water in the Earth’s oceans influences the way that rocks on the seabed form, and the rocks from this time period show signs of shallower oceans—a hint that some of the Earth’s water was trapped in glaciers and sea ice. Schmitz and his colleagues are the first to show that this ice age syncs up with the extra dust in the atmosphere. “The timing appears to be perfect,” he says. The extra dust in the atmosphere helps explain the ice age—by filtering out sunlight, the dust would have caused global cooling.

Since the dust floated down to Earth over at least two million years, the cooling was gradual enough for life to adapt and even benefit from the changes. An explosion of new species evolved as creatures adapted for survival in regions with different temperatures.

Heck notes that while this period of global cooling proved beneficial to life on Earth, fast-paced climate change can be catastrophic. “In the global cooling we studied, we’re talking about timescales of millions of years. It’s very different from the climate change caused by the meteorite 65 million years ago that killed the dinosaurs, and it’s different from the global warming today—this global cooling was a gentle nudge. There was less stress.”

It’s tempting to think that today’s global warming could be solved by replicating the dust shower that triggered global cooling 466 million years ago. But Heck says he would be cautious: “Geoengineering proposals should be evaluated very critically and very carefully, because if something goes wrong, things could become worse than before.”

While Heck isn’t convinced that we’ve found the solution to climate change, he says it’s a good idea for us to be thinking along these lines.

“We’re experiencing global warming, it’s undeniable,” says Heck. “And we need to think about how we can prevent catastrophic consequences, or minimize them. Any idea that’s reasonable should be explored.”

This study was contributed to by scientists from the Field Museum, the University of Chicago, Lund University (lead), the California Institute of Technology, Vriije Universiteit Brussel, Ohio State University, Université Libre de Bruxelles, Russian Academy of Sciences, Federal University Kazan, Royal Belgian Institute of Natural Sciences, Durham University, Chinese Academy of Sciences, Center for Excellence in Comparative Paleontology China, ETH Zürich, Naturmuseum St. Gallen Switzerland, and Woods Hole Oceanographic Institution.

Contacts and sources:
Field Museum

Citation: An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body. Birger Schmitz, Kenneth A. Farley, Steven Goderis, Philipp R. Heck, Stig M. Bergström, Samuele Boschi, Philippe Claeys, Vinciane Debaille, Andrei Dronov, Matthias Van Ginneken, David A.t. Harper, Faisal Iqbal, Johan Friberg, Shiyong Liao, Ellinor Martin, Matthias M. M. Meier, Bernhard Peucker-Ehrenbrink, Bastien Soens, Rainer Wieler and Fredrik Terfelt. Science Advances, 2019 DOI: 10.1126/sciadv.aax4184

Monday, September 16, 2019

Artificial Intelligence Accurately Diagnoses Post Traumatic Stress Disorder from Blood Test

An artificial intelligence tool - which analyzed 28 physical and molecular measures, all but one from blood samples - confirmed with 77 percent accuracy a diagnosis of posttraumatic stress disorder (PTSD) in male combat veterans, according to a new study.

Led by NYU School of Medicine, Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and the U.S. Army Medical Research and Development Command, the study describes for the first time a blood-based biomarker panel for diagnosis of warzone-related PTSD. Published online in the journal Molecular Psychiatry, the measures included genomic, metabolic, and protein biomarkers.

Credit: GrahamColm / Wikimedia Commons

"While work remains to further validate our panel, it holds tremendous promise as the first blood test that can screen for PTSD with a level of accuracy useful in the clinical setting," says senior study author Charles R. Marmar, the Lucius N. Littauer Professor and chair of the Department of Psychiatry at NYU School of Medicine. "If we are successful, this test would be one of the first of its kind - an objective blood test for a major psychiatric disorder."

There are currently no FDA-approved blood tests, for instance, for depression or bipolar disorder, says Marmar. The new study embodies a longstanding goal in the field of psychiatry: to shift mental health toward standards like those used in cardiology or cancer, for instance, in which lab tests enable accurate diagnoses based on physical measures (biomarkers) instead of on self-reporting or interviews with inherent biases.

Those with PTSD experience strong, persistent distress when reminded of a triggering, traumatic event. According to a World Health Organization survey, more than 70 percent of adults worldwide have experienced a traumatic event at some point in their lives, although not all develop the condition.
Twenty Eight Out of a Million

For the current study, 83 male, warzone-exposed veterans of the Iraq and Afghanistan conflicts with confirmed PTSD, and another 82 warzone-deployed veterans serving as healthy controls, were recruited from the Manhattan, Bronx and Brooklyn Veterans Affairs (VA) Medical Centers, as well as from other regional VA medical centers, veterans' service organizations, and the community.

The researchers tested nearly one million features with current genomic and other molecular tests and narrowed them to 28 markers. By measuring a large number of unbiased quantities, the team sought to determine which of them were associated with an accurate PTSD symptom diagnosis.

Using a combination of statistical techniques, the study authors narrowed the best measures from a million to 343 to 77, and then finally to 28, with the final group outperforming the larger groups in prediction accuracy. Some of this winnowing was accomplished using machine learning, mathematical models trained with data to find patterns.

The team then applied their "PTSD blood test" to an independent group of veterans to see how well their new tool matched the diagnoses made previously using standard clinical questionnaires like the Clinician Administered PTSD Scale (CAPS). This comparison yielded the 77 percent accuracy figure.

"These molecular signatures will continue to be refined and adapted for commercialization," says co-senior study author Marti Jett, chief scientist in Systems Biology for the US Army Medical Research & Development Command (USAMRDC), within the US Army Center for Environmental Health Research (CIV USACEHR). "The Department of Health Affairs within the Department of Defense is considering this approach as a potential screening tool that could identify service members, before and after deployment, with features of unresolved post-traumatic stress."

Those identified would be referred for their specific issues (sleep disruption, anger management, etc.), which is available at most military bases, adds Jett.

The current study did not seek to explain the disease mechanisms related to the final markers, but rather to blindly pick those that did the best job of diagnosing PTSD. That said, the group of best-performing markers included the activity levels of certain genes, amounts of key proteins in the blood, levels of metabolites involved in energy processing, as well as levels of circulating microRNAs (miRNAs), snippets of genetic material known to alter gene activity and tied to heart diseases and features of PTSD. The one indicator not measured by blood test was the heart rate variability.

"These results point toward many biochemical pathways that may guide the future design of new drugs, and support the theory that PTSD is a systemic disease that causes genetic and cellular changes well beyond the brain," says corresponding author Frank Doyle, John A. Paulson Dean and John A. and Elizabeth S. Armstrong Professor of Engineering and Applied Sciences.

Previous studies of genetic predictors of PTSD risk have shown strong performance in younger, active duty populations, says author Kelsey Dean, a member of Doyle's group at Harvard. This suggests that such biomarkers may be able to signal for PTSD at its earliest ages, and so be useful in prevention. For future research, studies of populations beyond male veterans will be needed to better understand the clinical utility of the proposed biomarker panel.

Along with Marmar, study authors from the Department of Psychiatry at NYU School of Medicine were Duna Abu-Amara, Eugene Laska, Jennifer Newman, and Carole Siegel. Along with Doyle and Dean, study authors from the Harvard John A. Paulson School of Engineering and Applied Sciences at Harvard University were Burook Misganaw, Pramod Somvanshi, and Gunjan Thakur.

Contacts and sources:
Jim Mandler, 
NYU Langone

Bones of Strange 2000 Pound Giants Discovered in Australia

Palorchestid marsupials, an extinct group of Australian megafauna, had strange bodies and lifestyles unlike any living species, according to a study released September 13, 2019 in the open-access journal PLOS ONE by Hazel Richards of Monash University, Australia and colleagues.

For most of the last 25 million years, eastern Australia was home to a now-extinct group of marsupials called palorchestids. These animals are well known for their large size, strange tapir-like skulls, and large claws, but so far there has been no detailed study of their limb morphology. In this study, Richards and colleagues examined more than 60 fossil specimens of palorchestids of varying geologic ages to characterize the function and evolution of their arms and legs.

Ancient Australia was home to strange marsupial giants, some weighing over 1,000 kg.

Credit: Hazel Richards (2019)

Over the course of their evolution, palorchestids grew larger and stranger. Using limb proportions as a proxy for body size, these authors estimated that the latest and largest of the palorchestids may have weighed over 1,000kg. Furthermore, their forelimbs were extremely muscular and were likely adapted for grabbing or scraping at leaves and branches. Uniquely among known mammals, the elbow joints of the largest palorchestids appear to have been immobile and fixed at roughly a 100-degree angle, so that the arms served as permanently flexed food-gathering tools.

This study provides the first formal description of limb morphology in palorchestid marsupials and reveals a group of giant herbivores that probably filled a niche no longer occupied in modern Australian ecosystems. Fossil remains are still missing for certain parts of the palorchestid body, such as the shoulders and wrists, but the authors are hopeful that more material may be found in existing museum collections.

The authors add: "This study has allowed us for the first time to appreciate just how huge these mega-marsupial palorchestids were, while also providing the first comprehensive view of a strange limb anatomy unprecedented in the mammalian world. This research reveals yet more about the diversity of unique large marsupials that once roamed Australia not so long ago."

Contacts and sources:
Hazel Richards

Citation: Richards HL, Wells RT, Evans AR, Fitzgerald EMG, Adams JW (2019) The extraordinary osteology and functional morphology of the limbs in Palorchestidae, a family of strange extinct marsupial giants. PLoS ONE 14(9): e0221824.
The article is freely available at

Four Billion Microplastic Particles in Major U.S. Body of Water

A new study from the University of South Florida St. Petersburg and Eckerd College estimates the waters of Tampa Bay contain four billion particles of microplastics, raising new questions about the impact of pollution on marine life in this vital ecosystem.

This is the first measurement of microplastic abundance and distribution in the region. Researchers hope the findings will provide necessary data to inform the debate around policies to reduce plastic in the marine environment.

Microplastics are tiny plastic particles less than 1/8 of an inch, barely or not at all visible to the eye. They come from the breakdown of larger plastics, such as water bottles, fishing gear and plastic bags, or from synthetic clothing and other items that contain elements of plastic. Previous studies have found these particles in every ocean on the planet and even in the Arctic.

"Very little is known about how much microplastics are out there and the full consequences of these particles on marine life," said Kinsley McEachern, the first author of the study and a recent Environmental Science and Policy graduate student at USF St. Petersburg. "But emerging research indicates a wide range of impacts on marine ecosystems from the large accumulation of microplastics."

Microplastic viewed under a microscope.

Credit: Cypress Hansen

Since particles are similar size as plankton, filter feeders such as oysters, clams, many fish and some birds ingest microplastics, allowing them to enter the food chain. Persistent organic pollutants, including toxic pesticides, and metals can stick to their surfaces, making ingestion potentially that much more damaging. Effects include cellular damage, reproductive disruption and even death.

The study revealed that the predominant type of these tiny particles in Tampa Bay - in both water and sediment - are thread-like fibers that are generated by fishing lines, nets and washing clothes. Synthetic fibers are released from clothes while they are being laundered, discharged to wastewater treatment plants and eventually released into the bay.

The next largest source are fragments that come from the breakdown of larger plastics.

"These plastics will remain in the bay, the gulf and ocean for more than a lifetime, while we use most plastic bags and bottles for less than an hour," said David Hastings, Principal Investigator of the study, Courtesy Professor at USF College of Marine Science and a recently retired Professor of Marine Science and Chemistry at Eckerd College. "Although it is tempting to clean up the mess, it is not feasible to remove these particles from the water column or separate them out from sediments."

"Only by removing the sources of plastics and microplastic particles can we successfully decrease the potential risks of plastics in the marine environment," added McEachern.

Researchers found the largest concentrations of microplastics in water occurred after intense and long rainfall events, while in sediments the greatest amount of microplastics were located close to industrial sources.

For more than a decade, Hastings led annual research cruises in Tampa Bay with Eckerd College students to collect water samples and plankton. During these trips, he and his students were also seeing small pieces of plastic.

"We were looking at plankton, which form the base of the marine food web. But when we put the samples underneath the microscope, we were astonished to find many brightly colored pieces of microplastic. We wanted to learn more," said Hastings.

Teaming up with McEachern, who was interested in focusing her graduate research on this issue, USFSP Associate Professor of Chemistry Henry Alegria and the Environmental Protection Commission of Hillsborough County, they set about counting microplastics in the region at 24 stations over a 14-month period. Collecting stations were located at the mouths of major rivers, near industrial facilities and in relatively pristine coastal mangroves. Particles believed to be plastic were probed with a hot dissecting needle. If the material quickly melted or disfigured, the sample was classified as a microplastic.

On average, the study found four pieces of microplastic per gallon of water at all sites, and more than 600 pieces of microplastic per pound of dry sediment. Extrapolating those findings to the entire Tampa Bay estuary, the researchers estimated there are approximately four billion particles in the water and more than 3 trillion pieces in surface sediments.

"This is a very important study in that it is the first for our region and shows the extent of the problem," said Alegria. "It also provides a vital baseline on total numbers and distribution. This is important for management plans moving forward to show whether future actions and policies are effective at reducing these particles in our environment."

Researchers say the findings, though substantial, might also be conservative, since collection in the bay occurred several feet below the water surface, likely missing any buoyant microplastics at the surface.

"We collected only a few pieces of Styrofoam, most likely because we sampled below the surface and foam floats at the surface," explained Hastings.

Plastic pollution in the marine environment has been a concern for decades. However, only recently have scientists started to uncover the widespread abundance of microplastics in the environment. With mounting physical evidence of plastic pollution, there have been greater calls for action in coastal communities around the world. Recently bans on plastic bags and single-use plastics have been enacted by some local governments in Tampa Bay to reduce marine pollution and protect Florida's largest open-water estuary.

The findings of billions of particles of microplastics in Tampa Bay waters could bring even greater calls for action and influence future decisions in the region and beyond. Researchers at USF St. Petersburg and Eckerd College are conducting further research to more fully understand microplastic pollution in the marine environment.

Contacts and sources:
Tina Meketa
 University of South Florida St. Petersburg

At Long Last Mystery of Static Electricity Solved

New model explains why a balloon can make hair stand on end.
marks static hair
Credit: Northwestern University

Most people have experienced the hair-raising effect of rubbing a balloon on their head or the subtle spark caused by dragging socked feet across the carpet. Although these experiences are common, a detailed understanding of how they occur has eluded scientists for more than 2,500 years.

Now a Northwestern University team developed a new model that shows that rubbing two objects together produces static electricity, or triboelectricity, by bending the tiny protrusions on the surface of materials.

This new understanding could have important implications for existing electrostatic applications, such as energy harvesting and printing, as well as for avoiding potential dangers, such as fires started by sparks from static electricity.

The research will be published on Thursday, Sept. 12, in the journal Physical Review LettersLaurence Marks, professor of materials science and engineering in Northwestern’s McCormick School of Engineering, led the study. Christopher Mizzi and Alex Lin, doctoral students in Marks’s laboratory, were co-first authors of the paper.

Greek philosopher Thales of Miletus first reported friction-induced static electricity in 600 B.C. After rubbing amber with fur, he noticed the fur attracted dust.

“Since then, it has become clear that rubbing induces static charging in all insulators — not just fur,” Marks said. “However, this is more or less where the scientific consensus ended.”

At the nanoscale, all materials have rough surfaces with countless tiny protrusions. When two materials come into contact and rub against one another, these protrusions bend and deform.

Laurence Marks
Credit; Northwestern University

Marks’s team found that these deformations give rise to voltages that ultimately cause static charging. This phenomenon is called the “flexoelectric effect,” which occurs when the separation of charge in an insulator arises from deformations such as bending.

Using a simple model, the Northwestern team showed that voltages arising from the bending protrusions during rubbing are, indeed, large enough to cause static electricity. This work explains a number of experimental observations, such as why charges are produced even when two pieces of the same material are rubbed together and predicts experimentally measured charges with remarkable accuracy.

“Our finding suggests that triboelectricity, flexoelectricity and friction are inextricably linked,” Marks said. “This provides much insight into tailoring triboelectric performance for current applications and expanding functionality to new technologies.”

“This is a great example of how fundamental research can explain everyday phenomena which hadn't been understood previously, and of how research in one area — in this case friction and wear — can lead to unexpected advances in another area,” said Andrew Wells, a program director at the National Science Foundation (NSF), which funded the research. “NSF funds research like this in materials science and engineering for new knowledge that can one day open new opportunities.”

The research, “Does flexoelectricity drive triboelectricity,” was supported by the NSF (award number CMMI-1400618) and the U.S. Department of Energy (award number DE-FG02-01ER45945).

Contacts and sources:
Christopher Mizzi
Northwestern University

Citation: Does Flexoelectricity Drive Triboelectricity? Christopher A. Mizzi, Alex Y. W. Lin, Laurence D. Marks. Physical Review Letters,

A Goldilocks Zone for Planet Size

In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter. A saline ocean under the moon’s icy crust best explains shifting in the auroral belts measured by the Hubble telescope. Astronomers have long wondered whether Jupiter’s icy moons would be habitable if radiation from the sun increased. 
Image Credit: NASA/ESA

In The Little Prince, the classic novella by Antoine de Saint-Exupéry, the titular prince lives on a house-sized asteroid so small that he can watch the sunset any time of day by moving his chair a few steps.

Of course, in real life, celestial objects that small can’t support life because they don’t have enough gravity to maintain an atmosphere. But how small is too small for habitability?

An illustration of The Little Prince's home planet by Antoine de Saint-Exupéry

(Image courtesy of Wikicommons)

In a recent paper, Harvard University researchers described a new, lower size limit for planets to maintain surface liquid water for long periods of time, extending the so-called Habitable or "Goldilocks’’ Zone for small, low-gravity planets. This research expands the search area for life in the universe and sheds light on the important process of atmospheric evolution on small planets.

The research was published in The Astrophysical Journal.

“When people think about the inner and outer edges of the habitable zone, they tend to only think about it spatially, meaning how close the planet is to the star,” said Constantin Arnscheidt, A.B. ’18, first author of the paper. “But actually, there are many other variables to habitability, including mass. Setting a lower bound for habitability in terms of planet size gives us an important constraint in our ongoing hunt for habitable exoplanets and exomoons.”

Generally, planets are considered habitable if they can maintain surface liquid water long enough to allow for the evolution of life, conservatively about one billion years. Astronomers hunt for these habitable planets within specific distances of certain types of stars — stars that are smaller, cooler and lower mass than our Sun have a habitable zone much closer than larger, hotter stars.

The inner-edge of the habitable zone is defined by how close a planet can be to a star before a runaway greenhouse effect leads to the evaporation of all the surface water. But, as Arnscheidt and his colleagues demonstrated, this definition doesn’t hold for small, low gravity planets.

The runaway greenhouse effect occurs when the atmosphere absorbs more heat that it can radiate back out into space, preventing the planet from cooling and eventually leading to unstoppable warming until its oceans turn to steam in the atmosphere.

However, something important happens when planets decrease in size: as they warm, their atmospheres expand outward, becoming larger and larger relative to the size of the planet. These large atmospheres increase both the absorption and radiation of heat, allowing the planet to better maintain a stable temperature. The researchers found that atmospheric expansion prevents low-gravity planets from experiencing a runaway greenhouse effect, allowing them to maintain surface liquid water while orbiting in closer proximity to their stars.

When planets get too small, however, they lose their atmospheres altogether and the liquid surface water either freezes or vaporizes. The researchers demonstrated that there is a critical size below which a planet can never be habitable, meaning the habitable zone is bounded not only in space, but also in planet size.

The researchers found that the critical size is about 2.7 percent the mass of Earth. If an object is smaller than 2.7 percent the mass of Earth, its atmosphere will escape before it ever has the chance to develop surface liquid water, similar to what happens to comets in the Solar System today. To put that into context, the Moon is 1.2 percent of Earth mass and Mercury is 5.53 percent.

This illustration shows the a lower bound for habitability in terms of planet mass. If an object is smaller than 2.7 percent the mass of Earth, its atmosphere will escape before it ever has the chance to develop surface liquid water

 Illustration courtesy of Harvard SEAS)\.

The researchers were also able to estimate the habitable zones of these small planets around certain stars. Two scenarios were modeled for two different types of stars: a G-type star like our own Sun and an M-type star modeled after a red dwarf in the constellation Leo.

The researchers solved another long-standing mystery in our own solar system. Astronomers have long wondered whether Jupiter’s icy moons Europa, Ganymede, and Callisto would be habitable if radiation from the sun increased. Based on this research, these moons are too small to maintain surface liquid water, even if they were closer to the Sun.

“Low-mass waterworlds are a fascinating possibility in the search for life, and this paper shows just how different their behaviour is likely to be compared to that of Earth-like planets,” said Robin Wordsworth, Associate Professor of Environmental Science and Engineering at SEAS and senior author of the study. “Once observations for this class of objects become possible, it’s going to be exciting to try to test these predictions directly.”

This paper was co-authored by Feng Ding, a postdoctoral fellow at the Harvard John A. Paulson School of Engineering and Applied Sciences.

Contacts and sources:
Leah BurrowsHarvard University John A Paulson School of Engineering and Applied Sciences

Monster at the Center of the Milky Way's Growing Rapacious Glow Never Seen Before

The enormous black hole at the center of our galaxy is having an unusually large meal of interstellar gas and dust, and researchers don’t yet understand why.

“We have never seen anything like this in the 24 years we have studied the supermassive black hole,” said Andrea Ghez, UCLA professor of physics and astronomy and a co-senior author of the research. “It’s usually a pretty quiet, wimpy black hole on a diet. We don’t know what is driving this big feast.”

Rendering of a star called S0-2 orbiting the supermassive black hole at the center of the Milky Way. It did not fall in, but its close approach could be one reason for the black hole’s growing appetite
Star S0-2 orbits black hole
Credit: Nicolle Fuller/National Science Foundation

A paper about the study, led by the UCLA Galactic Center Group, which Ghez heads, is published today in Astrophysical Journal Letters.

The researchers analyzed more than 13,000 observations of the black hole from 133 nights since 2003. The images were gathered by the W.M. Keck Observatory in Hawaii and the European Southern Observatory’s Very Large Telescope in Chile. The team found that on May 13, the area just outside the black hole’s “point of no return” (so called because once matter enters, it can never escape) was twice as bright as the next-brightest observation.

They also observed large changes on two other nights this year; all three of those changes were “unprecedented,” Ghez said.

The brightness the scientists observed is caused by radiation from gas and dust falling into the black hole; the findings prompted them to ask whether this was an extraordinary singular event or a precursor to significantly increased activity.

“The big question is whether the black hole is entering a new phase — for example if the spigot has been turned up and the rate of gas falling down the black hole ‘drain’ has increased for an extended period — or whether we have just seen the fireworks from a few unusual blobs of gas falling in,” said Mark Morris, UCLA professor of physics and astronomy and the paper’s co-senior author.

The team has continued to observe the area and will try to settle that question based on what they see from new images.

“We want to know how black holes grow and affect the evolution of galaxies and the universe,” said Ghez, UCLA’s Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics. “We want to know why the supermassive hole gets brighter and how it gets brighter.”

► UCLA astronomers discussed the project in a Keck Observatory video

The new findings are based on observations of the black hole — which is called Sagittarius A*, or Sgr A* — during four nights in April and May at the Keck Observatory. The brightness surrounding the black hole always varies somewhat, but the scientists were stunned by the extreme variations in brightness during that timeframe, including their observations on May 13.

“The first image I saw that night, the black hole was so bright I initially mistook it for the star S0-2, because I had never seen Sagittarius A* that bright,” said UCLA research scientist Tuan Do, the study’s lead author. “But it quickly became clear the source had to be the black hole, which was really exciting.”

One hypothesis about the increased activity is that when a star called S0-2 made its closest approach to the black hole during the summer 2018, it launched a large quantity of gas that reached the black hole this year.

Another possibility involves a bizarre object known as G2, which is most likely a pair of binary stars, which made its closest approach to the black hole in 2014. It’s possible the black hole could have stripped off the outer layer of G2, Ghez said, which could help explain the increased brightness just outside the black hole.

Morris said another possibility is that the brightening corresponds to the demise of large asteroids that have been drawn in to the black hole.

No danger to Earth

The black hole is some 26,000 light-years away and poses no danger to our planet. Do said the radiation would have to be 10 billion times as bright as what the astronomers detected to affect life on Earth.

Astrophysical Journal Letters also published a second article by the researchers, describing speckle holography, the technique that enabled them to extract and use very faint information from 24 years of data they recorded from near the black hole.

Ghez’s research team reported July 25 in the journal Science the most comprehensive test of Einstein’s iconic general theory of relativity near the black hole. Their conclusion that Einstein’s theory passed the test and is correct, at least for now, was based on their study of S0-2 as it made a complete orbit around the black hole.

► Watch a four-minute film about Ghez’s research
Credit: UCLA

Ghez’s team studies more than 3,000 stars that orbit the supermassive black hole. Since 2004, the scientists have used a powerful technology that Ghez helped pioneer, called adaptive optics, which corrects the distorting effects of the Earth’s atmosphere in real time. But speckle holography enabled the researchers to improve the data from the decade before adaptive optics came into play. Reanalyzing data from those years helped the team conclude that they had not seen that level of brightness near the black hole in 24 years.

“It was like doing LASIK surgery on our early images,” Ghez said. “We collected the data to answer one question and serendipitously unveiled other exciting scientific discoveries that we didn’t anticipate.”

Co-authors include Gunther Witzel, a former UCLA research scientist currently at Germany’s Max Planck Institute for Radio Astronomy; Mark Morris, UCLA professor of physics and astronomy; Eric Becklin, UCLA professor emeritus of physics and astronomy; Rainer Schoedel, a researcher at Spain’s Instituto de Astrofısica de Andalucıa; and UCLA graduate students Zhuo Chen and Abhimat Gautam.

The research is funded by the National Science Foundation, W.M. Keck Foundation, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, Lauren Leichtman and Arthur Levine, and Howard and Astrid Preston

Contacts and sources:
Stuart Wolpert

Hidden Gigantic Towering Radio Bubbles Discovered Above and Below the Center of the Milky Way

An international team of astronomers has discovered one of the largest features ever observed in the center of the Milky Way – a pair of enormous radio-emitting bubbles that tower hundreds of light-years above and below the central region of our galaxy.

This hourglass-like feature, which dwarfs all other radio structures in the galactic center, is likely the result of a phenomenally energetic burst that erupted near the Milky Way’s supermassive black hole a few million years ago.

Radio image of the central portions of the Milky Way galaxy. The plane of the galaxy is marked by a series of bright features, exploded stars and regions where new stars are being born, and runs horizontally through the image. The black hole at the center of the Milky Way is hidden in the brightest of these extended regions. The radio bubbles discovered by MeerKAT extend vertically above and below the plane of the galaxy. Many magnetized filaments can be seen running parallel to the bubbles. (Adapted from results published in Heywood et al. 2019.)

Credit: Oxford, SARAO

“The center of our galaxy is relatively calm when compared to other galaxies with very active central black holes,” said Ian Heywood of the University of Oxford and lead author of an article appearing in the journal Nature. “Even so, the Milky Way’s central black hole can – from time to time – become uncharacteristically active, flaring up as it periodically devours massive clumps of dust and gas. It’s possible that one such feeding frenzy triggered powerful outbursts that inflated this previously unseen feature.”

Using the South African Radio Astronomy Observatory (SARAO) MeerKAT telescope, Heywood and his colleagues mapped out broad regions in the center of the galaxy, conducting observations at wavelengths near 23 centimeters. Radio emission of this kind is generated in a process known as synchrotron radiation, in which electrons moving at close to the speed of light interact with powerful magnetic fields. This produces a characteristic radio signal that can be used to trace energetic regions in space. This radio light easily penetrates the dense clouds of dust that block visible light from the center of the galaxy.

By examining the nearly identical size and shape of the twin bubbles, the researchers think they have found convincing evidence that these features were formed from a violent eruption that over a short period of time punched through the interstellar medium in opposite directions.

“The shape and symmetry of what we have observed strongly suggests that a staggeringly powerful event happened a few million years ago very near our galaxy’s central black hole,” said William Cotton, an astronomer with the National Radio Astronomy Observatory in Charlottesville, Virginia, and co-author on the paper. “This eruption was possibly triggered by vast amounts of interstellar gas falling in on the black hole, or a massive burst of star formation which sent shockwaves careening through the galactic center. In effect, this inflated bubbles in the hot, ionized gas near the galactic center, energizing it and generating radio waves that we could eventually detect here on Earth.”

Radio image of the center of the Milky Way with a portion of the MeerKAT telescope array in the foreground. The plane of the galaxy is marked by a series of bright features, exploded stars and regions where new stars are being born, and runs diagonally across the image from lower right to top center. The black hole at the center of the Milky Way is hidden in the brightest of these extended regions. The radio bubbles extend from between the two nearest antennas to the upper right corner. Many magnetized filaments can be seen running parallel to the bubbles. In this composite view, the sky to the left of the second nearest antenna is the night sky visible to the unaided eye, and the radio image to the right has been enlarged to highlight its fine features.

Credit: Oxford, SARAO

The environment surrounding the black hole at the center of our galaxy is vastly different than the environment elsewhere in the Milky Way, and is a region of many mysteries. Among those are very long and narrow filaments found nowhere else, the origin of which has remained an unsolved puzzle since their discovery 35 years ago. The filaments appear as radio structures tens of light-years long and approximately a light-year wide.

“The radio bubbles discovered by MeerKAT now shed light on the origin of the filaments,” said Farhad Yusef-Zadeh at Northwestern University in Evanston, Illinois, and a co-author on the paper. “Almost all of the more than one hundred filaments are confined by the radio bubbles.”

The authors suggest that the close association of the filaments with the bubbles implies that the energetic event that created the radio bubbles is also responsible for accelerating the electrons required to produce the radio emission from the magnetized filaments.

“These enormous bubbles have until now been hidden by the glare of extremely bright radio emission from the center of the galaxy,” said Fernando Camilo of SARAO in Cape Town, and co-author on the paper. “Teasing out the bubbles from the background noise was a technical tour de force, only made possible by MeerKAT’s unique characteristics and ideal location,” according to Camilo. “With this unexpected discovery we’re witnessing in the Milky Way a novel manifestation of galaxy-scale outflows of matter and energy, ultimately governed by the central black hole.”

According to the researchers, the discovery of these bubbles relatively nearby in the center of our home galaxy brings us one step closer to understanding spectacular activities that occur in more distant cousins of the Milky Way throughout the universe.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Contacts and sources:
 Charles E. Blue
The National Radio Astronomy Observatory

Citation:  “Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event,” I. Heywood, et al., Nature. []

WFIRST Will Help Uncover Fate of the Universe

Scientists have discovered that a mysterious pressure dubbed "dark energy" makes up about 68% of the total energy content of the cosmos, but so far we don't know much more about it. Exploring the nature of dark energy is one of the primary reasons NASA is building the Wide Field Infrared Survey Telescope (WFIRST), a space telescope whose measurements will help illuminate the dark energy puzzle. With a better understanding of dark energy, we will have a better sense of the past and future evolution of the universe.

An Expanding Cosmos

Until the 20th century, most people believed that the universe was static, remaining essentially unchanged throughout eternity. When Einstein developed his general theory of relativity in 1915, describing how gravity acts across the fabric of space-time, he was puzzled to find that the theory indicated the cosmos must either expand or contract. He made changes to preserve a static universe, adding something he called the "cosmological constant," even though there was no evidence it actually existed. This mysterious force was supposed to counteract gravity to hold everything in place.

An artist's rendering of NASA's Wide Field Infrared Survey Telescope (WFIRST), which will study multiple cosmic phenomena, including dark energy.
An artist's rendering of NASA's Wide Field Infrared Survey Telescope (WFIRST)
 Credit: NASA's Goddard Space Flight Center
However, as the 1920s were coming to a close, astronomer Georges Lemaitre, and then Edwin Hubble, made the startling discovery that with very few exceptions, galaxies are racing away from each other. The universe was far from static - it was ballooning outward. Consequently, if we imagine rewinding this expansion, there must have been a time when everything in the universe was almost impossibly hot and close together.

Scientists have discovered that a mysterious pressure dubbed "dark energy" makes up about 68 percent of the total energy content of the cosmos, but so far we don't know much more about it. Exploring the nature of dark energy is one of the primary reasons NASA is building the Wide Field Infrared Survey Telescope (WFIRST), a space telescope whose measurements will help illuminate the dark energy puzzle. With a better understanding of dark energy, we will have a better sense of the past and future evolution of the universe.

The End of the Universe: Fire or Ice?

The Big Bang theory describes the expansion and evolution of the universe from this initial superhot, superdense state. Scientists theorized that gravity would eventually slow and possibly even completely reverse this expansion. If the universe had enough matter in it, gravity would overcome the expansion, and the universe would collapse in a fiery "Big Crunch."

If not, the expansion would never end - galaxies would grow farther and farther away until they pass the edge of the observable universe. Our distant descendants might have no knowledge of the existence of other galaxies since they would be too far away to be visible. Much of modern astronomy might one day be reduced to mere legend as the universe gradually fades to an icy black.

The Universe Isn't Just Expanding - It's Accelerating

Astronomers have measured the rate of expansion by using ground-based telescopes to study relatively nearby supernova explosions. The mystery escalated in 1998 when Hubble Space Telescope observations of more distant supernovae helped show that the universe actually expanded more slowly in the past than it does today. The expansion of the universe is not slowing down due to gravity, as everyone thought. It's speeding up.

Fast forward to today. While we still don't know what exactly is causing the acceleration, it has been given a name - dark energy. This mysterious pressure remained undiscovered for so long because it is so weak that gravity overpowers it on the scale of humans, planets and even the galaxy. It is present in the room with you as you read, within your very body, but gravity counteracts it so you don't go flying out of your seat. It is only on an intergalactic scale that dark energy becomes noticeable, acting like a sort of weak opposition to gravity.

What Is Dark Energy?

What exactly is dark energy? More is unknown than known, but theorists are chasing down a couple of possible explanations. Cosmic acceleration could be caused by a new energy component, which would require some adjustments to Einstein's theory of gravity - perhaps the cosmological constant, which Einstein called his biggest blunder, is real after all.

The Big Bang and expansion of the universe
Credit: NASA

Alternatively, Einstein's theory of gravity may break down on cosmological scales. If this is the case, the theory will need to be replaced with a new one that incorporates the cosmic acceleration we have observed. Theorists still don't know what the correct explanation is, but WFIRST will help us find out.

WFIRST Will Illuminate Dark Energy

Previous missions have gathered some clues, but so far they haven't yielded results that strongly favor one explanation over another. With the same resolution as Hubble's cameras but a field of view that is 100 times larger, WFIRST will generate never-before-seen big pictures of the universe. The new mission will advance the exploration of the dark energy mystery in ways that other telescopes can't by mapping how matter is structured and distributed throughout the cosmos, and also by measuring large numbers of distant supernovae. The results will indicate how dark energy acts across the universe, and whether and how it has changed over cosmic history.

The mission will use three survey methods to search for an explanation of dark energy. The High Latitude Spectroscopic Survey will measure accurate distances and positions of millions of galaxies using a "standard ruler" technique. Measuring how the distribution of galaxies varies with distance will give us a window into the evolution of dark energy over time. This study will connect the galaxies' distances with the echoes of sound waves just after the Big Bang and will test Einstein's theory of gravity over the age of the universe.

The High Latitude Imaging Survey will measure the shapes and distances of multitudes of galaxies and galaxy clusters. The immense gravity of massive objects warps space-time and causes more distant galaxies to appear distorted. Observing the degree of distortion allows scientists to infer the distribution of mass throughout the cosmos. This includes all of the matter we can see directly, like planets and stars, as well as dark matter - another dark cosmic mystery which is visible only through its gravitational effects on normal matter. This survey will provide an independent measurement of the growth of large-scale structure in the universe and how dark energy has affected the cosmos.

WFIRST will also conduct a survey of one type of exploding star, building on the observations that led to the discovery of accelerated expansion. Type Ia supernovae occur when a white dwarf star explodes. Type Ia supernovae generally have the same absolute brightness at their peak, making them so-called "standard candles." That means astronomers can determine how far away they are by seeing how bright they look from Earth - and the farther they are, the dimmer they appear. Astronomers will also look at the particular wavelengths of light coming from the supernovae to find out how fast the dying stars are moving away from us. By combining distances with brightness measurements, scientists will see how dark energy has evolved over time, providing a cross-check with the two high-latitude surveys.

"The WFIRST mission is unique in combining these three methods. It will lead to a very robust and rich interpretation of the effects of dark energy and will allow us to make a definite statement about the nature of dark energy," said Olivier Doré, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and leader of the team planning the first two survey methods with WFIRST.

Discovering how dark energy has affected the universe's expansion in the past will shed some light on how it will influence the expansion in the future. If it continues to accelerate the universe's expansion, we may be destined to experience a "Big Rip." In this scenario, dark energy would eventually become dominant over the fundamental forces, causing everything that is currently bound together - galaxies, planets, people - to break apart. Exploring dark energy will allow us to investigate, and possibly even foresee, the universe's fate.

For more information about WFIRST, visit:

Contacts and sources:
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.

Written by Ashley Balzer
NASA's Goddard Space Flight Center

Newly Discovered Comet Is Likely Interstellar Visitor

A newly discovered comet has excited the astronomical community this week because it appears to have originated from outside the solar system. The object - designated C/2019 Q4 (Borisov) - was discovered on Aug. 30, 2019, by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. The official confirmation that comet C/2019 Q4 is an interstellar comet has not yet been made, but if it is interstellar, it would be only the second such object detected. The first, 'Oumuamua, was observed and confirmed in October 2017.

The new comet, C/2019 Q4, is still inbound toward the Sun, but it will remain farther than the orbit of Mars and will approach no closer to Earth than about 190 million miles (300 million kilometers).

This illustration depicts Comet C/2019 Q4's trajectory. Deemed a possible interstellar object, it will approach no closer to Earth than about 190 million miles (300 million kilometers)
Animation of interstellar object
 Credit: NASA/JPL-Caltech

After the initial detections of the comet, Scout system, which is located at NASA's Jet Propulsion Laboratory in Pasadena, California, automatically flagged the object as possibly being interstellar. Davide Farnocchia of NASA's Center for Near-Earth Object Studies at JPL worked with astronomers and the European Space Agency's Near-Earth Object Coordination Center in Frascati, Italy, to obtain additional observations. He then worked with the NASA-sponsored Minor Planet Center in Cambridge, Massachusetts, to estimate the comet's precise trajectory and determine whether it originated within our solar system or came from elsewhere in the galaxy.

The comet is currently 260 million miles (420 million kilometers) from the Sun and will reach its closest point, or perihelion, on Dec. 8, 2019, at a distance of about 190 million miles (300 million kilometers).

"The comet's current velocity is high, about 93,000 mph [150,000 kph], which is well above the typical velocities of objects orbiting the Sun at that distance," said Farnocchia. "The high velocity indicates not only that the object likely originated from outside our solar system, but also that it will leave and head back to interstellar space."

Currently on an inbound trajectory, comet C/2019 Q4 is heading toward the inner solar system. On Oct. 26, it will pass through the ecliptic plane - the plane in which Earth and the other planets orbit the Sun - from above at roughly a 40-degree angle.

Comet C/2019 Q4 as imaged by the Canada-France-Hawaii Telescope on Hawaii's Big Island on Sept. 10, 2019. 
Comet C/2019 Q4
Credit: Canada-France-Hawaii Telescope

C/2019 Q4 was established as being cometary due to its fuzzy appearance, which indicates that the object has a central icy body that is producing a surrounding cloud of dust and particles as it approaches the Sun and heats up. Its location in the sky (as seen from Earth) places it near the Sun - an area of sky not usually scanned by the large ground-based asteroid surveys or NASA's asteroid-hunting NEOWISE spacecraft.

C/2019 Q4 can be seen with professional telescopes for months to come. "The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020," said Farnocchia. "After that, it will only be observable with larger professional telescopes through October 2020."

Observations completed by Karen Meech and her team at the University of Hawaii indicate the comet nucleus is somewhere between 1.2 and 10 miles (2 and 16 kilometers) in diameter. Astronomers will continue collect observations to further characterize the comet's physical properties (size, rotation, etc.) and also continue to better identify its trajectory.

The Minor Planet Center is hosted by the Harvard-Smithsonian Center for Astrophysics and is a sub-node of NASA's Planetary Data System Small Bodies Node at the University of Maryland. JPL hosts the Center for Near-Earth Object Studies. All are projects of NASA's Near-Earth Object Observations Program and elements of the agency's Planetary Defense Coordination Office within NASA's Science Mission Directorate.

Contacts and sources:
DC Agle
Jet Propulsion Laboratory

More information about asteroids and near-Earth objects can be found at:

For more information about NASA's Planetary Defense Coordination Office, visit:

Friday, September 13, 2019

Soil Changes and Increased Rainfall Threaten Food Security

Coasts, oceans, ecosystems, weather and human health all face impacts from climate change, and now valuable soils may also be affected.

Climate change may reduce the ability of soils to absorb water in many parts of the world, according to a Rutgers-led study. And that could have serious implications for groundwater supplies, food production and security, stormwater runoff, biodiversity and ecosystems.

Increased irrigation by sprinklers at the Konza Prairie Biological Station in the Flint Hills of northeastern Kansas altered the soil pore system of a prairie soil.

Photo: Edouard Sagues

The study is published in the journal Science Advances.

“Since rainfall patterns and other environmental conditions are shifting globally as a result of climate change, our results suggest that how water interacts with soil could change appreciably in many parts of the world, and do so fairly rapidly,” said co-author Daniel Giménez, a soil scientist and professor in the Department of Environmental Sciences at Rutgers University–New Brunswick. “We propose that the direction, magnitude and rate of the changes should be measured and incorporated into predictions of ecosystem responses to climate change.”

Water in soil is crucial for storing carbon, and soil changes could influence the level of carbon dioxide in the air in an unpredictable way, according to Giménez, of the School of Environmental and Biological Sciences. Carbon dioxide is one of the key greenhouse gases linked to climate change.

Giménez co-authored a study published in the journal Nature last year showing that regional increases in precipitation due to climate change may lead to less water infiltration, more runoff and erosion, and greater risk of flash flooding.

Whether rainfall will infiltrate or run off of soil determines how much water will be available for plants or will evaporate into the air. Studies have shown that water infiltration to soil can change over one to two decades with increased rainfall, and climate change is expected to boost rainfall in many areas of the world.

During a 25-year experiment in Kansas that involved irrigation of prairie soil with sprinklers, a Rutgers-led team of scientists found that a 35 percent increase in rainfall led to a 21 percent to 33 percent reduction in water infiltration rates in soil and only a small increase in water retention.

An irrigation test area at Konza Prairie Biological Station in Kansas. Water infiltrated at slower rates in soils that received increased irrigation for 25 years.

Photo: Alan Knapp

The biggest changes were linked to shifts in relatively large pores, or spaces, in the soil. Large pores capture water that plants and microorganisms can use, and that contributes to enhanced biological activity and nutrient cycling in soil and decreases soil losses through erosion.

With increased rainfall, plant communities had thicker roots that could clog larger pores and there were less intense cycles of soil expansion when water was added or contraction when water was removed.

The next step is to investigate the mechanisms driving the observed changes, in order to extrapolate the findings to other regions of the world and incorporate them into predictions of how ecosystems will respond to climate change. The scientists also want to study a wider array of environmental factors and soil types, and identify other soil changes that may result from shifts in climate.

The lead author is Joshua S. Caplan, a former Rutgers postdoctoral associate now at Temple University. Scientists at the University of California, Riverside, University of Kansas, Kansas State University and Colorado State University contributed to the study.

Contacts and sources:
Todd Bates
Rutgers University

Are Black Holes Made of Dark Energy?

Objects like Powehi, the recently imaged supermassive compact object at the center of galaxy M87, might actually be GEODEs. The Powehi GEODEs, shown to scale, would be approximately 2/3 the radius of the dark region imaged by the Event Horizon Telescope. This is nearly the same size expected for a black hole. The region containing Dark Energy (green) is slightly larger than a black hole of the same mass. The properties of any crust (purple), if present, depend on the particular GEODE model. 
astronomy animation
Photo credit: EHT collaboration; NASA/CXC/Villanova University

Two University of Hawaiʻi at Mānoa researchers have identified and corrected a subtle error that was made when applying Einstein’s equations to model the growth of the universe.

Physicists usually assume that a cosmologically large system, such as the universe, is insensitive to details of the small systems contained within it. Kevin Croker, a postdoctoral research fellow in the Department of Physics and Astronomy, and Joel Weiner, a faculty member in the Department of Mathematics, have shown that this assumption can fail for the compact objects that remain after the collapse and explosion of very large stars.

“For 80 years, we’ve generally operated under the assumption that the universe, in broad strokes, was not affected by the particular details of any small region,” said Croker. “It is now clear that general relativity can observably connect collapsed stars—regions the size of Honolulu—to the behavior of the universe as a whole, over a thousand billion billion times larger.”

Croker and Weiner demonstrated that the growth rate of the universe can become sensitive to the averaged contribution of such compact objects. Likewise, the objects themselves can become linked to the growth of the universe, gaining or losing energy depending on the objects’ compositions. This result is significant since it reveals unexpected connections between cosmological and compact object physics, which in turn leads to many new observational predictions.

One consequence of this study is that the growth rate of the universe provides information about what happens to stars at the end of their lives. Astronomers typically assume that large stars form black holes when they die, but this is not the only possible outcome. In 1966, Erast Gliner, a young physicist at the Ioffe Physico-Technical Institute in Leningrad, proposed an alternative hypothesis that very large stars should collapse into what could now be called Generic Objects of Dark Energy (GEODEs). These appear to be black holes when viewed from the outside but, unlike black holes, they contain Dark Energy instead of a singularity.

In 1998, two independent teams of astronomers discovered that the expansion of the Universe is accelerating, consistent with the presence of a uniform contribution of Dark Energy. It was not recognized, however, that GEODEs could contribute in this way. With the corrected formalism, Croker and Weiner showed that if a fraction of the oldest stars collapsed into GEODEs, instead of black holes, their averaged contribution today would naturally produce the required uniform Dark Energy.

The results of this study also apply to the colliding double star systems observable through gravitational waves by the LIGO-Virgo collaboration. In 2016, LIGO announced the first observation of what appeared to be a colliding double black hole system. Such systems were expected to exist, but the pair of objects was unexpectedly heavy—roughly five times larger than the black hole masses predicted in computer simulations. Using the corrected formalism, Croker and Weiner considered whether LIGO-Virgo is observing double GEODE collisions, instead of double black hole collisions. They found that GEODEs grow together with the universe during the time leading up to such collisions. When the collisions occur, the resulting GEODE masses become four to eight times larger, in rough agreement with the LIGO-Virgo observations.

Croker and Weiner were careful to separate their theoretical result from observational support of a GEODEs scenario, emphasizing that “black holes certainly aren’t dead. What we have shown is that if GEODEs do exist, then they can easily give rise to observed phenomena that presently lack convincing explanations. We anticipate numerous other observational consequences of a GEODEs scenario, including many ways to exclude it. We’ve barely begun to scratch the surface.”

The study, “Implications of Symmetry and Pressure in Friedmann Cosmology: I. Formalism”, is published in the August 28, 2019 issue of The Astrophysical Journal.

Follow-up work that details the specific consequences of these results for Dark Energy surveys and gravitational wave observatories is presently in review.

Contacts and sources:
University of Hawaii at Manoa

Citation: Pressure in Friedmann Cosmology. I. Formalism. The Astrophysical Journal, 2019; 882 (1): 19 DOI: 10.3847/1538-4357/ab32da

Water Identified on an Exoplanet Located in its Star’s Habitable Zone

Ever since the discovery of the first exoplanet in the 1990s, astronomers have made steady progress towards finding and probing planets located in the habitable zone of their stars, where conditions can lead to the formation of liquid water and the proliferation of life.

An international study lead by Université de Montréal astronomer Björn Benneke has detected water vapor on the planet K2-18b; this represents a major discovery in the search of alien life.

Credit: Université de Montréal

Results from the Kepler satellite mission, which discovered nearly 2/3 of all known exoplanets to date, indicate that 5 to 20% of Earths and super-Earths are located in the habitable zone of their stars. However, despite this abundance, probing the conditions and atmospheric properties on any of these habitable zone planets is extremely difficult and has remained elusive… until now.

A new study by Professor Björn Benneke of the Institute for Research on Exoplanets at the Université de Montréal, his doctoral student Caroline Piaulet and several of their collaborators reports the detection of water vapour and perhaps even liquid water clouds in the atmosphere of the planet K2-18b.

"This represents the biggest step yet taken towards our ultimate goal of finding life on other planets, of proving that we are not alone. Thanks to our observations and our climate model of this planet, we have shown that its water vapour can condense into liquid water. This is a first", says Björn Benneke.

This exoplanet is about nine times more massive than our Earth and is found in the habitable zone of the star it orbits. This M-type star is smaller and cooler than our Sun, but due to K2-18b’s close proximity to its star, the planet receives almost the same total amount of energy from its star as our Earth receives from the Sun.

The similarities between the exoplanet K2-18b and the Earth suggest to astronomers that the exoplanet may potentially have a water cycle possibly allowing water to condense into clouds and liquid water rain to fall. This detection was made possible by combining eight transit observations - the moment when an exoplanet passes in front of its star - taken by the Hubble Space Telescope.

The Université de Montréal is no stranger to the K2-18 system located 111 light years away. The existence of K2-18b was first confirmed by Prof. Benneke and his team in a 2016 paper using data from the Spitzer Space Telescope. The mass and radius of the planet were then determined by former Université de Montréal and University of Toronto PhD student Ryan Cloutier. These promising initial results encouraged the iREx team to collect follow-up observations of the intriguing world.”

Scientists currently believe that the thick gaseous envelope of K2-18b likely prevents life as we know it from existing on the planet’s surface. However, the study shows that even these planets of relatively low mass which are therefore more difficult to study can be explored using astronomical instruments developed in recent years. By studying these planets which are in the habitable zone of their star and have the right conditions for liquid water, astronomers are one step closer to directly detecting signs of life beyond our Solar System.

Contacts and sources:
Julie Gazaille
Université de Montréal
Citation: ”Water vapor on the habitable-zone exoplanet K2-18b” . Björn Benneke, Ian Wong, Caroline Piaulet, Heather A. Knutson, Ian J.M. Crossfield, Joshua Lothringer, Caroline V. Morley, Peter Gao, Thomas P. Greene, Courtney Dressing, Diana Dragomir, Andrew W. Howard, Peter R. McCullough, Eliza M.-R. Kempton Jonathan J. Fortney, Jonathan Fraine. Astronomical Journal (submitted), 2019

Missed Severe Mass Extinction Event Brings Earth 's Record of Major Dyings to Six

A team of scientists has concluded that earth experienced a previously underestimated severe mass-extinction event, which occurred about 260 million years ago.

A team of scientists has concluded that earth experienced a previously underestimated severe mass-extinction event, which occurred about 260 million years ago--and at the same time as the Emeishan flood-basalt eruption that produced the Emeishan Traps, an extensive rock formation found today in southern China. 

An Emeishan mountain in Sichuan, China. 

Photo credit: lop5712/Getty Images

A team of scientists has concluded that earth experienced a previously underestimated severe mass-extinction event, which occurred about 260 million years ago, raising the total of major mass extinctions in the geologic record to six.

“It is crucial that we know the number of severe mass extinctions and their timing in order to investigate their causes,” explains Michael Rampino, a professor in New York University’s Department of Biology and a co-author of the analysis, which appears in the journal Historical Biology. “Notably, all six major mass extinctions are correlated with devastating environmental upheavals—specifically, massive flood-basalt eruptions, each covering more than a million square kilometers with thick lava flows.”

This file is an identification of large igneous provinces overlaid on a map produced by United States National Oceanic and Atmosphere Administration's National Geophysical Data Center.
Flood Basalt Map.jpg
Credit: Williamborg / Wikimedia Commons

Scientists had previously determined that there were five major mass-extinction events, wiping out large numbers of species and defining the ends of geological periods: the end of the Ordovician (443 million years ago), the Late Devonian (372 million years ago), the Permian (252 million years ago), the Triassic (201 million years ago), and the Cretaceous (66 million years ago). And, in fact, many researchers have raised concerns about the contemporary, ongoing loss of species diversity—a development that might be labeled a “seventh extinction” because such a modern mass extinction, scientists have predicted, could end up being as severe as these past events.

The Historical Biology work, which also included Nanjing University’s Shu-zhong Shen, focused on the Guadalupian, or Middle Permian period, which lasted from 272 to about 260 million years ago.

Here, the researchers observe, the end-Guadalupian extinction event—which affected life on land and in the seas—occurred at the same time as the Emeishan flood-basalt eruption that produced the Emeishan Traps, an extensive rock formation, found today in southern China. The eruption’s impact was akin to those causing other known severe mass extinctions, Rampino says.

“Massive eruptions such as this one release large amounts of greenhouse gases, specifically carbon dioxide and methane, that cause severe global warming, with warm, oxygen-poor oceans that are not conducive to marine life,” he notes.

“In terms of both losses in the number of species and overall ecological damage, the end-Guadalupian event now ranks as a major mass extinction, similar to the other five,” the authors write.

Contacts and sources:
James Devitt
New York University
Citation: The end-Guadalupian (259.8 Ma) biodiversity crisis: the sixth major mass extinction? Michael R. Rampino, Shu-Zhong Shen. Historical Biology, 2019; 1 DOI: 10.1080/08912963.2019.1658096

New "Blackest Black" Is 10 Times Darker Than Other Very Black Materials

With apologies to “Spinal Tap,” it appears that black can, indeed, get more black.

MIT engineers report today that they have cooked up a material that is 10 times blacker than anything that has previously been reported. The material is made from vertically aligned carbon nanotubes, or CNTs — microscopic filaments of carbon, like a fuzzy forest of tiny trees, that the team grew on a surface of chlorine-etched aluminum foil. The foil captures at least 99.995 percent* of any incoming light, making it the blackest material on record.

The researchers have published their findings today in the journal ACS-Applied Materials and Interfaces. They are also showcasing the cloak-like material as part of a new exhibit today at the New York Stock Exchange, titled “The Redemption of Vanity.”

The artwork, a collaboration between Brian Wardle, professor of aeronautics and astronautics at MIT, and his group, and MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, features a 16.78-carat natural yellow diamond from LJ West Diamonds, estimated to be worth $2 million, which the team coated with the new, ultrablack CNT material. The effect is arresting: The gem, normally brilliantly faceted, appears as a flat, black void.

Wardle says the CNT material, aside from making an artistic statement, may also be of practical use, for instance in optical blinders that reduce unwanted glare, to help space telescopes spot orbiting exoplanets.

“There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance,” Wardle says. “Our material is 10 times blacker than anything that’s ever been reported, but I think the blackest black is a constantly moving target. Someone will find a blacker material, and eventually we’ll understand all the underlying mechanisms, and will be able to properly engineer the ultimate black.”

Wardle’s co-author on the paper is former MIT postdoc Kehang Cui, now a professor at Shanghai Jiao Tong University.

Into the void

Wardle and Cui didn’t intend to engineer an ultrablack material. Instead, they were experimenting with ways to grow carbon nanotubes on electrically conducting materials such as aluminum, to boost their electrical and thermal properties.

But in attempting to grow CNTs on aluminum, Cui ran up against a barrier, literally: an ever-present layer of oxide that coats aluminum when it is exposed to air. This oxide layer acts as an insulator, blocking rather than conducting electricity and heat. As he cast about for ways to remove aluminum’s oxide layer, Cui found a solution in salt, or sodium chloride.

A 16.78-carat natural yellow diamond from LJ West Diamonds (left), is coated with a new carbon nanotube-based material that is the blackest material on record (the covered diamond, shown at right). The diamond is the subject of The Redemption of Vanity, a work of art created by MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, in collaboration with MIT engineer Brian Wardle and his lab, on view at the New York Stock Exchange.
A 16.78-carat natural yellow diamond from LJ West Diamonds (left), is coated with a new carbon nanotube-based material that is the blackest material on record (the covered diamond, shown at right). The diamond is the subject of The Redemption of Vanity, a work of art created by MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, in collaboration with MIT engineer Brian Wardle and his lab, on view at the New York Stock Exchange.
Image: R. Capanna, A. Berlato, and A. Pinato

At the time, Wardle’s group was using salt and other pantry products, such as baking soda and detergent, to grow carbon nanotubes. In their tests with salt, Cui noticed that chloride ions were eating away at aluminum’s surface and dissolving its oxide layer.

“This etching process is common for many metals,” Cui says. “For instance, ships suffer from corrosion of chlorine-based ocean water. Now we’re using this process to our advantage.”

Cui found that if he soaked aluminum foil in saltwater, he could remove the oxide layer. He then transferred the foil to an oxygen-free environment to prevent reoxidation, and finally, placed the etched aluminum in an oven, where the group carried out techniques to grow carbon nanotubes via a process called chemical vapor deposition.

By removing the oxide layer, the researchers were able to grow carbon nanotubes on aluminum, at much lower temperatures than they otherwise would, by about 100 degrees Celsius. They also saw that the combination of CNTs on aluminum significantly enhanced the material’s thermal and electrical properties — a finding that they expected.

What surprised them was the material’s color.

“I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker,” Cui recalls. “So I thought I should measure the optical reflectance of the sample.

“Our group does not usually focus on optical properties of materials, but this work was going on at the same time as our art-science collaborations with Diemut, so art influenced science in this case,” says Wardle.

Wardle and Cui, who have applied for a patent on the technology, are making the new CNT process freely available to any artist to use for a noncommercial art project.

“Built to take abuse”

Cui measured the amount of light reflected by the material, not just from directly overhead, but also from every other possible angle. The results showed that the material absorbed at least 99.995 percent of incoming light, from every angle. In other words, it reflected 10 times less light than all other superblack materials, including Vantablack. If the material contained bumps or ridges, or features of any kind, no matter what angle it was viewed from, these features would be invisible, obscured in a void of black.

The researchers aren’t entirely sure of the mechanism contributing to the material’s opacity, but they suspect that it may have something to do with the combination of etched aluminum, which is somewhat blackened, with the carbon nanotubes. Scientists believe that forests of carbon nanotubes can trap and convert most incoming light to heat, reflecting very little of it back out as light, thereby giving CNTs a particularly black shade.

“CNT forests of different varieties are known to be extremely black, but there is a lack of mechanistic understanding as to why this material is the blackest. That needs further study,” Wardle says.

The material is already gaining interest in the aerospace community. Astrophysicist and Nobel laureate John Mather, who was not involved in the research, is exploring the possibility of using Wardle’s material as the basis for a star shade — a massive black shade that would shield a space telescope from stray light.

“Optical instruments like cameras and telescopes have to get rid of unwanted glare, so you can see what you want to see,” Mather says. “Would you like to see an Earth orbiting another star? We need something very black. … And this black has to be tough to withstand a rocket launch. Old versions were fragile forests of fur, but these are more like pot scrubbers — built to take abuse."

*An earlier version of this story stated that the new material captures more than 99.96 percent of incoming light. That number has been updated to be more precise; the material absorbs at least 99.995 of incoming light.

Contacts and sources:
Jennifer Chu
Massachusetts Institute of Technology (MIT)

Tones in the Ringing of a Newborn Black Hole Detected for the First Time

If Albert Einstein’s theory of general relativity holds true, then a black hole, born from the cosmically quaking collisions of two massive black holes, should itself “ring” in the aftermath, producing gravitational waves much like a struck bell reverbates sound waves. Einstein predicted that the particular pitch and decay of these gravitational waves should be a direct signature of the newly formed black hole’s mass and spin.

Now, physicists from MIT and elsewhere have studied the ringing of an infant black hole, and found that the pattern of this ringing does, in fact, predict the black hole’s mass and spin — more evidence that Einstein was right all along.

MIT scientists have captured the “ringing” of a newly-formed black hole, in the form of gravitational waves, depicted in this artist’s illustration.
MIT scientists have captured the “ringing” of a newly-formed black hole, in the form of gravitational waves, depicted in this artist’s illustration.
Credit: MIT

The findings, published today in Physical Review Letters, also favor the idea that black holes lack any sort of “hair” — a metaphor referring to the idea that black holes, according to Einstein’s theory, should exhibit just three observable properties: mass, spin, and electric charge. All other characteristics, which the physicist John Wheeler termed “hair,” should be swallowed up by the black hole itself, and would therefore be unobservable.

The team’s findings today support the idea that black holes are, in fact, hairless. The researchers were able to identify the pattern of a black hole’s ringing, and, using Einstein’s equations, calculated the mass and spin that the black hole should have, given its ringing pattern. These calculations matched measurements of the black hole’s mass and spin made previously by others.

If the team’s calculations deviated significantly from the measurements, it would have suggested that the black hole’s ringing encodes properties other than mass, spin, and electric charge — tantalizing evidence of physics beyond what Einstein’s theory can explain. But as it turns out, the black hole’s ringing pattern is a direct signature of its mass and spin, giving support to the notion that black holes are bald-faced giants, lacking any extraneous, hair-like properties.

“We all expect general relativity to be correct, but this is the first time we have confirmed it in this way,” says the study’s lead author, Maximiliano Isi, a NASA Einstein Fellow in MIT’s Kavli Institute for Astrophysics and Space Research. “This is the first experimental measurement that succeeds in directly testing the no-hair theorem. It doesn’t mean black holes couldn’t have hair. It means the picture of black holes with no hair lives for one more day.”

A chirp, decoded

On Sept. 14, 2015, scientists made the first-ever detection of gravitational waves — infinitesimal ripples in space-time, emanating from distant, violent cosmic phenomena. The detection, named GW150914, was made by LIGO, the Laser Interferometer Gravitational-wave Observatory. Once scientists cleared away the noise and zoomed in on the signal, they observed a waveform that quickly crescendoed before fading away. When they translated the signal into sound, they heard something resembling a “chirp.”

Scientists determined that the gravitational waves were set off by the rapid inspiraling of two massive black holes. The peak of the signal — the loudest part of the chirp — linked to the very moment when the black holes collided, merging into a single, new black hole. While this infant black hole gave off gravitational waves of its own, its signature ringing, physicists assumed, would be too faint to decipher amid the clamor of the initial collision. Thus, traces of this ringing were only identified some time after the peak, where the signal was too faint to study in detail.

Isi and his colleagues, however, found a way to extract the black hole’s reverberation from the moments immediately after the signal’s peak. In previous work led by Isi’s co-author, Matthew Giesler of Caltech, the team showed through simulations that such a signal, and particularly the portion right after the peak, contains “overtones” — a family of loud, short-lived tones. When they reanalyzed the signal, taking overtones into account, the researchers discovered that they could successfully isolate a ringing pattern that was specific to a newly formed black hole.

In the team’s new paper, the researchers applied this technique to actual data from the GW150914 detection, concentrating on the last few milliseconds of the signal, immediately following the chirp’s peak. Taking into account the signal’s overtones, they were able to discern a ringing coming from the new, infant black hole. Specifically, they identified two distinct tones, each with a pitch and decay rate that they were able to measure.

“We detect an overall gravitational wave signal that’s made up of multiple frequencies, which fade away at different rates, like the different pitches that make up a sound,” Isi says. “Each frequency or tone corresponds to a vibrational frequency of the new black hole.”

Listening beyond Einstein

Einstein’s theory of general relativity predicts that the pitch and decay of a black hole’s gravitational waves should be a direct product of its mass and spin. That is, a black hole of a given mass and spin can only produce tones of a certain pitch and decay. As a test of Einstein’s theory, the team used the equations of general relativity to calculate the newly formed black hole’s mass and spin, given the pitch and decay of the two tones they detected.

They found their calculations matched with measurements of the black hole’s mass and spin previously made by others. Isi says the results demonstrate that researchers can, in fact, use the very loudest, most detectable parts of a gravitational wave signal to discern a new black hole’s ringing, where before, scientists assumed that this ringing could only be detected within the much fainter end of the gravitational wave signal, and identifying many tones would require much more sensitive instruments than what currently exist.

“This is exciting for the community because it shows these kinds of studies are possible now, not in 20 years,” Isi says.

As LIGO improves its resolution, and more sensitive instruments come online in the future, researchers will be able to use the group’s methods to “hear” the ringing of other newly born black holes. And if they happen to pick up tones that don’t quite match up with Einstein’s predictions, that could be an even more exciting prospect.

“In the future, we’ll have better detectors on Earth and in space, and will be able to see not just two, but tens of modes, and pin down their properties precisely,” Isi says. “If these are not black holes as Einstein predicts, if they are more exotic objects like wormholes or boson stars, they may not ring in the same way, and we’ll have a chance of seeing them.”

This research was supported, in part, by NASA, the Sherman Fairchild Foundation, the Simons Foundation, and the National Science Foundation.

Contacts and sources:
Jennifer Chu
Massachusetts Institute of Technology (MIT)

Citation: A hierarchical test of general relativity with gravitational waves. Maximiliano Isi, Katerina Chatziioannou, Will M. Farr. Physical Review Letters, 2019