Sunday, December 16, 2018

Researchers Use Jiggly Jell-O To Make Powerful New Hydrogen Fuel Catalyst

The inexpensive new material can split water just as efficiently as costly platinum.

A cheap and effective new catalyst developed by researchers at the University of California, Berkeley, can generate hydrogen fuel from water just as efficiently as platinum, currently the best -- but also most expensive -- water-splitting catalyst out there.

The catalyst, which is composed of nanometer-thin sheets of metal carbide, is manufactured using a self-assembly process that relies on a surprising ingredient: gelatin, the material that gives Jell-O its jiggle.

Two-dimensional metal carbides spark a reaction that splits water into oxygen and valuable hydrogen gas. Berkeley researchers have discovered an easy new recipe for cooking up these nanometer-thin sheets that is nearly as simple as making Jell-O from a box.
An illustration shows hydrogen gas bubbling off of a sheet of metal carbide
Credit : Xining Zang graphic, copyright Wiley

"Platinum is expensive, so it would be desirable to find other alternative materials to replace it," said senior author Liwei Lin, professor of mechanical engineering at UC Berkeley. "We are actually using something similar to the Jell-O that you can eat as the foundation, and mixing it with some of the abundant earth elements to create an inexpensive new material for important catalytic reactions."

This study was made available online in Oct. 2018 in the journal Advanced Materials ahead of final publication in print on Dec. 13.

A zap of electricity can break apart the strong bonds that tie water molecules together, creating oxygen and hydrogen gas, the latter of which is an extremely valuable source of energy for powering hydrogen fuel cells. Hydrogen gas can also be used to help store energy from renewable yet intermittent energy sources like solar and wind power, which produce excess electricity when the sun shines or when the wind blows, but which go dormant on rainy or calm days.

But simply sticking an electrode in a glass of water is an extremely inefficient method of generating hydrogen gas. For the past 20 years, scientists have been searching for catalysts that can speed up this reaction, making it practical for large-scale use.

When magnified, the two-dimensional metal carbides resemble sheets of cellphane.
A black and white image of metal carbide under high magnification.
Credit : Xining Zang photo, copyright Wiley

"The traditional way of using water gas to generate hydrogen still dominates in industry. However, this method produces carbon dioxide as byproduct," said first author Xining Zang, who conducted the research as a graduate student in mechanical engineering at UC Berkeley. "Electrocatalytic hydrogen generation is growing in the past decade, following the global demand to lower emissions. Developing a highly efficient and low-cost catalyst for electrohydrolysis will bring profound technical, economical and societal benefit."

To create the catalyst, the researchers followed a recipe nearly as simple as making Jell-O from a box. They mixed gelatin and a metal ion -- either molybdenum, tungsten or cobalt -- with water, and then let the mixture dry.

"We believe that as gelatin dries, it self-assembles layer by layer," Lin said. "The metal ion is carried by the gelatin, so when the gelatin self-assembles, your metal ion is also arranged into these flat layers, and these flat sheets are what give Jell-O its characteristic mirror-like surface."

Heating the mixture to 600 degrees Celsius triggers the metal ion to react with the carbon atoms in the gelatin, forming large, nanometer-thin sheets of metal carbide. The unreacted gelatin burns away.

The researchers tested the efficiency of the catalysts by placing them in water and running an electric current through them. When stacked up against each other, molybdenum carbide split water the most efficiently, followed by tungsten carbide and then cobalt carbide, which didn't form thin layers as well as the other two. Mixing molybdenum ions with a small amount of cobalt boosted the performance even more.

Molecules in gelatin naturally self-assemble in flat sheets, carrying the metal ions with them (left). Heating the mixture to 600 degrees Celsius burns off the gelatin, leaving nanometer-thin sheets of metal carbide.


Credit : Xining Zang graphic, copyright Wiley

"It is possible that other forms of carbide may provide even better performance," Lin said.

The two-dimensional shape of the catalyst is one of the reasons why it is so successful. That is because the water has to be in contact with the surface of the catalyst in order to do its job, and the large surface area of the sheets mean that the metal carbides are extremely efficient for their weight.

Because the recipe is so simple, it could easily be scaled up to produce large quantities of the catalyst, the researchers say.

"We found that the performance is very close to the best catalyst made of platinum and carbon, which is the gold standard in this area," Lin said. "This means that we can replace the very expensive platinum with our material, which is made in a very scalable manufacturing process."



Contacts and sources:
Kara Manke
University of California, Berkeley

Citation: Self‐Assembly of Large‐Area 2D Polycrystalline Transition Metal Carbides for Hydrogen Electrocatalysis Xining Zang Wenshu Chen Xiaolong Zou J. Nathan Hohman Lujie Yang Buxuan Li Minsong Wei Chenhui Zhu Jiaming Liang Mohan Sanghadasa Jiajun Gu Liwei Lin http://dx.doi.org/10.1002/adma.201805188




Saturday, December 15, 2018

Organic Food Worse for the Climate

​Organically farmed food has a bigger climate impact than conventionally farmed food, due to the greater areas of land required. This is the finding of a new international study involving Chalmers University of Technology, Sweden, published in the journal Nature. 

​The researchers developed a new method for assessing the climate impact from land-use, and used this, along with other methods, to compare organic and conventional food production. The results show that organic food can result in much greater emissions. 

The crops per hectare are lower in organic farming, which leads to greater indirect carbon dioxide emissions from deforestation.
Illustration

“Our study shows that organic peas, farmed in Sweden, have around a 50 percent bigger climate impact than conventionally farmed peas. For some foodstuffs, there is an even bigger difference – for example, with organic Swedish winter wheat the difference is closer to 70 percent,” says Stefan Wirsenius, an associate professor from Chalmers, and one of those responsible for the study.

The reason why organic food is so much worse for the climate is that the yields per hectare are much lower, primarily because fertilisers are not used. To produce the same amount of organic food, you therefore need a much bigger area of land.

Credit:: Yen Strandqvist

The ground-breaking aspect of the new study is the conclusion that this difference in land usage results in organic food causing a much larger climate impact.

“The greater land-use in organic farming leads indirectly to higher carbon dioxide emissions, thanks to deforestation,” explains Stefan Wirsenius. “The world’s food production is governed by international trade, so how we farm in Sweden influences deforestation in the tropics. If we use more land for the same amount of food, we contribute indirectly to bigger deforestation elsewhere in the world.”

Even organic meat and dairy products are – from a climate point of view – worse than their conventionally produced equivalents, claims Stefan Wirsenius.

“Because organic meat and milk production uses organic feed-stocks, it also requires more land than conventional production. This means that the findings on organic wheat and peas in principle also apply to meat and milk products. We have not done any specific calculations on meat and milk, however, and have no concrete examples of this in the article,” he explains.

A new metric: Carbon Opportunity Cost
The researchers used a new metric, which they call “Carbon Opportunity Cost”, to evaluate the effect of greater land-use contributing to higher carbon dioxide emissions from deforestation. This metric takes into account the amount of carbon that is stored in forests, and thus released as carbon dioxide as an effect of deforestation. The study is among the first in the world to make use of this metric.

Stefan Wirsenius, Associate Professor at the Department of Space, Earth and Environment.
Stefan Wirsenius
Credit:   Johan Bodell


“The fact that more land use leads to greater climate impact has not often been taken into account in earlier comparisons between organic and conventional food,” says Stefan Wirsenius. “This is a big oversight, because, as our study shows, this effect can be many times bigger than the greenhouse gas effects, which are normally included. It is also serious because today in Sweden, we have politicians whoseal goals is to increase production of organic food. If thoseat goals isare implemented, the climate influence from Swedish food production will probably increase a lot.”


So why have earlier studies not taken into account land-use and its relationship to carbon dioxide emissions? 

“There are surely many reasons. An important explanation, I think, is simply an earlier lack of good, easily applicable methods for measuring the effect. Our new method of measurement allows us to make broad environmental comparisons, with relative ease,” says Stefan Wirsenius.



Contacts and sources:
Johanna Wilde / Stefan Wirsenius
Chalmers University of Technology

Citation: Journal Reference: Assessing the efficiency of changes in land use for mitigating climate change.Timothy D. Searchinger, Stefan Wirsenius, Tim Beringer, Patrice Dumas. Nature, 2018; 564 (7735): 249 DOI: 10.1038/s41586-018-0757-z










Young Star Caught Forming Like A Planet



Astronomers have captured one of the most detailed views of a young star taken to date, and revealed an unexpected companion in orbit around it.

While observing the young star, astronomers led by Dr John Ilee from the University of Leeds discovered it was not in fact one star, but two.

The main object, referred to as MM 1a, is a young massive star surrounded by a rotating disc of gas and dust that was the focus of the scientists' original investigation.

This is an artists impression of the disc of dust and gas surrounding the massive protostar MM 1a, with its companion MM 1b forming in the outer regions.

Credit: J. D. Ilee / University of Leeds

A faint object, MM 1b, was detected just beyond the disc in orbit around MM 1a. The team believe this is one of the first examples of a "fragmented" disc to be detected around a massive young star.

"Stars form within large clouds of gas and dust in interstellar space," said Dr Ilee, from the School of Physics and Astronomy at Leeds.

"When these clouds collapse under gravity, they begin to rotate faster, forming a disc around them. In low mass stars like our Sun, it is in these discs that planets can form."

"In this case, the star and disc we have observed is so massive that, rather than witnessing a planet forming in the disc, we are seeing another star being born."

By measuring the amount of radiation emitted by the dust, and subtle shifts in the frequency of light emitted by the gas, the researchers were able to calculate the mass of MM 1a and MM 1b.

Their work, published today in the Astrophysical Journal Letters, found MM 1a weighs 40 times the mass of our Sun. The smaller orbiting star MM 1b was calculated to weigh less than half the mass of our Sun.



Observation of the dust emission (green) and the cool gas around MM1a (red is receding gas, blue is approaching gas), indicating that the outflow cavity rotates in the same sense as the central accretion disc. MM1b is seen orbiting in the lower left.

Credit: J. D. Ilee / University of Leeds

"Many older massive stars are found with nearby companions," added Dr Ilee. "But binary stars are often very equal in mass, and so likely formed together as siblings. Finding a young binary system with a mass ratio of 80:1 is very unusual, and suggests an entirely different formation process for both objects."

The favoured formation process for MM 1b occurs in the outer regions of cold, massive discs. These "gravitationally unstable" discs are unable to hold themselves up against the pull of their own gravity, collapsing into one - or more - fragments.

Dr Duncan Forgan, a co-author from the Centre for Exoplanet Science at the University of St Andrews, added: "I've spent most of my career simulating this process to form giant planets around stars like our Sun. To actually see it forming something as large as a star is really exciting."

The researchers note that newly-discovered young star MM 1b could also be surrounded by its own circumstellar disc, which may have the potential to form planets of its own - but it will need to be quick.

Observation of the dust emission (green) and hot gas rotating in the disc around MM 1a (red is receding gas, blue is approaching gas). MM 1b is seen the lower left.

Credit: J. D. Ilee / University of Leeds

Dr Ilee added: "Stars as massive as MM 1a only live for around a million years before exploding as powerful supernovae, so while MM 1b may have the potential to form its own planetary system in the future, it won't be around for long."

The astronomers made this surprising discovery by using a unique new instrument situated high in the Chilean desert - the Atacama Large Millimetre/submillimetre Array (ALMA).

Using the 66 individual dishes of ALMA together in a process called interferometry, the astronomers were able to simulate the power of a single telescope nearly 4km across, allowing them to image the material surrounding the young stars for the first time.

The team have been granted additional observing time with ALMA to further characterise these exciting stellar systems in 2019. The upcoming observations will simulate a telescope that is 16km across - comparable to the area inside of the ring-road surrounding Leeds.




Contacts and sources:
 Anna Harrison
University of Leeds

Citation:  G11.92-0.61 MM1: A Fragmented Keplerian Disk Surrounding a Proto-O Star is published in the Astrophysical Journal Letters 14 December 2018.





Death Near the Shoreline, Not Life on Land


Our understanding of when the very first animals started living on land is helped by identifying trace fossils—the tracks and trails left by ancient animals—in sedimentary rocks that were deposited on the continents.

Diplopodichnus highlighted: Close-up of a looping millipede death-trail.

Photo by Anthony Shillito.

Geoscientists Anthony P. Shillito and Neil S. Davies of the University of Cambridge studied the site of what has widely been accepted as the earliest set of non-marine trackways, in Ordovician (ca. 455 million-year-old) strata from the Lake District, England.

Tracks showing evidence that the animals went briefly out of the water.

' Photo by Neil Davies.


"What they discovered is that the trackways occur within volcanic ash that settled under water, and not within freshwater lake and sub-aerial sands (as previously thought). This means that the site is not the oldest evidence for animal communities on land, but instead "is actually a remarkable example of a 'prehistoric Pompeii'," says Shillito—a suite of rocks that preserve trails made by distressed and dying millipede-like arthropods as they were overcome by ash from volcanic events.

Diplichnites highlighted: Close-up of one of the millipede trackways.

Photo by Anthony Shillito.

Shillito and Davies directed their research at this site in particular because it seemed unusual—at every other known trackway site in the world the evidence for when animals came onto land dates to the latest Silurian (ca. 420 million years ago), so something about the Borrowdale site didn't seem right. Further investigation proved that this was the case. In the course of their study, they found 121 new millipede trackways, all within volcanic ash with evidence for underwater or shoreline deposition.

Trackways.

 Photo by Anthony Shillito.


Volcanic ash is known to cause mass death in some modern arthropod communities, particularly in water, because ash is so tiny it can get inside arthropod exoskeletons and stick to their breathing and digestive apparatus. Shilllito and Davies noticed that most of the trails were extremely tightly looping—a feature which is commonly associated with "death dances" in modern and ancient arthropods.

This study, published in Geology, overturns what is known about the earliest life on land and casts new light onto one of the key evolutionary events in the history of life on Earth. Shillito notes, "It reveals how even surprising events can be preserved in the ancient rock record, but—by removing the 'earliest' outlier of evidence—suggests that the invasion of the continents happened globally at the same time."

Overview of the rocks where the trails were found.

Photo by Anthony Shillito.

Understanding how life engineered major evolutionary advances within environments, and the rate and impact of these advances on the functioning of the Earth system, provides vital context for understanding global change at the present day, and underlines the inseparable relationship between life and the planet.



Contacts and sources:
Kea Giles
Geological Society of America


Citation: Death near the shoreline, not life on land: Ordovician arthropod trackways in the Borrowdale Volcanic Group, UK
Anthony P. Shillito and Neil S. Davies, University of Cambridge. Contact: as2195@cam.ac.uk. Geology, https://pubs.geoscienceworld.org/gsa/geology/article/567352/death-near-the-shoreline-not-life-on-land.



New Approach Monitors the Environment with Artificial Intelligence


UNIGE researchers have developed an approach that combines genomics and machine learning tools to explore the microbial biodiversity of ecosystems.

Microorganisms perform key functions in ecosystems and their diversity reflects the health of their environment. However, they are still largely under-exploited in current biomonitoring programs because they are difficult to identify. Researchers from the University of Geneva (UNIGE), Switzerland, have recently developed an approach combining two cutting edge technologies to fill this gap. They use genomic tools to sequence the DNA of microorganisms in samples, and then exploit this considerable amount of data with artificial intelligence. They build predictive models capable of establishing a diagnosis of the health of ecosystems on a large scale and identify species that perform important functions. 

Bioindication of the health status of ecosystems by micro-organisms
Credit: © Yvain Coudert

This new approach, published in the journal Trends in Microbiology, will significantly increase the observation capacity of large ecosystems and reduce the time of analysis for very efficient routine biomonitoring programs.

Monitoring the health status of ecosystems is of crucial importance in a context of sustainable development and increasing human pressure on the environment. Different species of micro-organisms sensitive to changes in their surroundings are used as bio-indicators for monitoring environmental quality. However, their morphological identification requires a lot of time and expertise. 

“A year ago, we were able to establish a water quality index based solely on the DNA sequences of unicellular algae present in the samples, without needing to visually identify each species”, explains Jan Pawlowski, Professor at the Department of Genetics and Evolution of the UNIGE Faculty of Science.

Use DNA sequences without having to identify them

Genomic tools make it possible to quickly and very accurately describe the biological communities inhabiting an environment. However, a large proportion of the data cannot be used to conduct environmental health diagnoses because many DNA sequences are not referenced in existing databases. The species that possess these sequences are therefore unknown, as well as their ecological role.

“In order to exploit all environmental genomics data, namely all the biodiversity of the samples, we used a machine learning algorithm”, notes Tristan Cordier, a member of the Geneva group and first author of the study.

The biologists used samples of different known ecological quality status, ranging from good to bad, from which they sequenced the DNA. The combination of this information allowed them to build a reference system with the data from each sample. “A predictive model was then developed with this algorithm, based on our training data. These include data from reference diagnoses and data from the sequencing of unknown species”, says Jan Pawlowski. This model is refined and validated over time by including new reference samples to the existing training dataset.

Discover new bio-indicators

The combination of these two cutting edge technologies makes it possible to obtain ecological values for DNA sequences without having to identify them. Species of microorganisms, already described or not, performing important functions can be discovered through this approach, as well as new bio-indicators. “Our research shares some similarities with the research on the human microbiome. Both aim to unravel microbial communities and identify biomarkers that can be used as powerful diagnostic tools to detect environmental pollution or human disease”, concludes Tristan Cordier.


Contacts and sources:
 Jan Pawlowski / Tristan Cordier
University of Geneva (UNIGE)



Being Yelled at Puts Our Brain on Alert in a Flash


Researchers from the University of Geneva studied the way our attention focuses on different sounds in our environment and observed how the brain is alerted when it perceives anger.

Sight and hearing are the two main sensory modalities allowing us to interact with our environment. But what happens within the brain when it perceives a threatening signal, such as an aggressive voice? How does it distinguish a threatening voice from the surrounding noise? How does it process this information? To answers these questions, researchers from the University of Geneva (UNIGE), Switzerland, studied brain activity during the processing of various emotional voices. They discovered that we notice a voice much faster when it is considered threatening than when it is perceived as normal or happy. Our attention is more focused on threatening voices to enable us to clearly recognize the location of the potential threat.

Credit: © UNIGE

This study, published in the journal Social, Cognitive and Affective Neuroscience, demonstrates the resources leveraged by our brain when we sense danger to allow for adequate survival behavior.

Sight and hearing are the two senses that allow human beings to detect threatening situations. Although sight is critical, it does not allow for a 360-degree coverage of the surrounding space - unlike hearing. “That’s why we are interested in how fast our attention responds to the different intonations of the voices around us and how our brain deals with potentially threatening situations,” explains Nicolas Burra, a researcher in the psychology section of the Faculty of Psychology and Education Sciences (FPSE) at UNIGE.

To examine the brain’s response to threats in the auditory environment, the researchers presented 22 short human voice sounds (600 milliseconds) that were neutral utterances or expressed either anger or joy. Using two loudspeakers, these sounds were presented to 35 participants while an electroencephalogram (EEG) measured electrical activity in the brain down to the millisecond. More specifically, the researchers focused on the electrophysiological components related to auditory attentional processing. 

“Each participant heard two sounds simultaneously: two neutral voices, one neutral and one angry voice, or one neutral and one happy voice. When they perceived anger or joy, they had to respond by pressing a key on a keyboard as accurately and quickly as possible,” explains Leonardo Ceravolo, researcher at UNIGE’s Swiss Centre for Affective Sciences. “We then measured the intensity of brain activity when attention is focused on the different sounds, as well as the duration of this focus before a return to the basic state,” he adds.

Our brain quickly differentiates angry from happy voices

Using data from the EEG, the researchers examined the appearance of a cerebral marker of auditory attention called N2ac. As Nicolas Burra explains, “When the brain perceives an emotional target sound, N2ac activity is triggered after 200 milliseconds. However, when it perceives anger, the N2ac is amplified and lasts longer, which is not the case for joy!”

Subsequently, after 400 milliseconds, our attention must disengage from the emotional vocal stimulus. At this moment, a cerebral marker of auditory attention, called LPCpc, intervenes. Interestingly enough, LPCpc activity is also stronger for angry than for happy voices. Why? “Anger can signal a potential threat, which is why the brain analyzes these kinds of stimuli for a longer time. In an auditory environment, this mechanism allows us to not become alarmed at the slightest potentially threatening noise or, conversely, to adopt the most appropriate behavior in case of danger. These extra milliseconds of attention are, therefore, crucial to the accurate interpretation of a threat in a complex auditory environment,” says Ceravolo.

This additional temporal cost was also evident in the participants’ response times. When they had to indicate that they perceived anger, it took them longer than when they did so for joy. In contrast, brain activity was enhanced in the case of angry stimuli. Does it sound conflicting? “No. The explanation is logical. As attention in the brain remains focused on the threatening sound, the motor response via the keyboard is delayed,” says Nicolas Burra.

In summary, this study demonstrated for the first time that in a few hundred milliseconds, our brain is sensitive to the presence of angry voices. This rapid detection of the source of a potential threat in a complex environment is essential, as it is “critical in crisis situations and a great advantage for our survival,” concludes Ceravolo.

Contacts and sources:
Nicolas Burra / Leonardo Ceravolo
Université de Genève





Hot Neptunes Transform into Super-Earths by Evaporation

Astronomers from the UNIGE explain the rarity of the hot Neptunes by their evaporation which transforms them into super-Earths.

This artist’s illustration shows a giant cloud of hydrogen streaming off a warm, Neptune-sized planet just 97 light-years from Earth. The exoplanet is tiny compared to its star, a red dwarf named GJ 3470. The star’s intense radiation is heating the hydrogen in the planet’s upper atmosphere to a point where it escapes into space. The alien world is losing hydrogen at a rate 100 times faster than a previously observed warm Neptune whose atmosphere is also evaporating away. 
page_garde_Bourrier.png
© Crédit NASA, ESA, and D. Player (STScI)

“But where did the hot Neptunes go?” This is the question astronomers have been asking for a long time, faced with the mysterious absence of planets the size of Neptunes very close to their star. A team of researchers, led by astronomers from the University of Geneva (UNIGE), Switzerland, has just discovered that one of these planets is losing its atmosphere at a frantic pace. This observation strengthens the theory that hot Neptunes have lost much of their atmosphere and turned into smaller planets called super-Earths, which are much more numerous. Results to read in the journal Astronomy & Astrophysics.

Fishermen would be puzzled if they netted only big and little fish, but few medium-sized fish. This is similar to what happens to astronomers hunting exoplanets. They found a large number of hot planets the size of Jupiter and numerous others a little larger than the Earth (called super-Earths whose diameter does not exceed 1.5 times that of the Earth), but no planets close to their star the size of Neptune. This mysterious “desert” of hot Neptunes suggests two explanations: either such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.

A few years ago, UNIGE astronomers using NASA’s Hubble Space Telescope discovered that a warm Neptune on the edge of the desert, GJ 436b, was losing hydrogen from its atmosphere. This loss is not enough to threaten the atmosphere of GJ 436b, but suggested that Neptunes receiving more energy from their star could evolve more dramatically. This has just been confirmed by the same astronomers, members of the national research center PlanetS*. They observed with Hubble that another warm Neptune at the edge of the desert, named GJ 3470b, is losing its hydrogen 100 times faster than GJ 436b. The two planets reside about 3.7 million kilometres from their star, one-tenth the distance between Mercury and the Sun, but the star hosting GJ 3470b is much younger and energetic.

“This is the first time that a planet has been observed to lose its atmosphere so quickly that it can impact its evolution,” says Vincent Bourrier, researcher in the Astronomy Department of the Faculty of Science of the UNIGE, member of the European project FOUR ACES** and first author of the study. The team estimates that GJ 3470b has already lost more than a third of its mass.

“Until now we were not sure of the role played by the evaporation of atmospheres in the formation of the desert”, states Vincent Bourrier. The discovery of several warm Neptunes at the edge of the desert losing their atmosphere supports the idea that the hotter version of these planets is short-lived. Hot Neptunes would have shrunk to become mini-Neptunes, or would have eroded completely to leave only their rocky core. “This could explain the abundance of hot super-Earths that have been discovered,” says David Ehrenreich, associate professor in the astronomy department of the science faculty at UNIGE and co-author of the study.


The evolution of the hot Neptun hunt

Observing the evaporation of two warm Neptunes is encouraging, but team members know they need to study more of them to confirm their predictions. Unfortunately, the hydrogen that escapes from these planets cannot be detected if they are more than 150 light-years from Earth (GJ 3470b is 97 light-years away), because hydrogen is then hidden by interstellar gas. Researchers thus plan to use Hubble to look for other traces of atmospheric escape, because hydrogen could drag upward heavier elements such as carbon. The solution could also come from helium, whose infrared radiation isn’t blocked by interstellar medium. 

“Helium will expand the range of our surveys,” said Vincent Bourrier, “the high sensitivity of the James Webb space telescope should allow us to detect helium escaping small planets, such as mini-Neptunes, and complete our observations of the edge of the desert.”

*Planets is a National Research Centre, a research instrument of the Swiss National Science Foundation dedicated to research on exoplanets.

**FOUR ACES, Future of Upper Atmospheric Characterisation of Exoplanets with Spectroscopy, is a project funded by a European Research Council (ERC) Consolidator Grant under the European Commission’s Research and Innovation Programme Horizon 2020 (Grant No 724427).





Contacts and sources:
Vincent Bourrier
Université de Genève

Citation: Hubble PanCET: an extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470b.
V. Bourrier, A. Lecavelier des Etangs, D. Ehrenreich, J. Sanz-Forcada, R. Allart, G. E. Ballester, L. A. Buchhave, O. Cohen, D. Deming, T. M. Evans, A. García Muñoz, G. W. Henry, T. Kataria, P. Lavvas, N. Lewis, M. López-Morales, M. Marley, D. K. Sing, H. R. Wakeford. Astronomy & Astrophysics, 2018; 620: A147 DOI: 10.1051/0004-6361/201833675



Electronic Pill Can Relay Diagnostic Information Wirelessly or Release Drugs in Response to Smartphone Commands.

An electronic pill can relay diagnostic information or release drugs in response to smartphone commands.

MIT researchers have designed an ingestible sensor that can lodge in the stomach for a few weeks and communicate wirelessly with an external device.
MIT researchers have designed an ingestible sensor that can lodge in the stomach for a few weeks and communicate wirelessly with an external device.
Image courtesy of the researchers

Researchers at MIT, Draper, and Brigham and Women’s Hospital have designed an ingestible capsule that can be controlled using Bluetooth wireless technology. The capsule, which can be customized to deliver drugs, sense environmental conditions, or both, can reside in the stomach for at least a month, transmitting information and responding to instructions from a user’s smartphone.

The capsules, manufactured using 3-D-printing technology, could be deployed to deliver drugs to treat a variety of diseases, particularly in cases where drugs must be taken over a long period of time. They could also be designed to sense infections, allergic reactions, or other events, and then release a drug in response.

“Our system could provide closed-loop monitoring and treatment, whereby a signal can help guide the delivery of a drug or tuning the dose of a drug,” says Giovanni Traverso, a visiting scientist in MIT’s Department of Mechanical Engineering, where he will be joining the faculty in 2019.

These devices could also be used to communicate with other wearable and implantable medical devices, which could pool information to be communicated to the patient’s or doctor’s smartphone.

“We are excited about this demonstration of 3-D printing and of how ingestible technologies can help people through novel devices that facilitate mobile health applications,” says Robert Langer, the David H. Koch Institute Professor and a member of MIT’s Koch Institute for Integrative Cancer Research.

Langer and Traverso are the senior authors of the study, which appears in the Dec. 13 issue of Advanced Materials Technologies. Yong Lin Kong, a former MIT postdoc who is now an assistant professor at the University of Utah, is the paper’s lead author.

Wireless communication

For the past several years, Langer, Traverso, and their colleagues have been working on a variety of ingestible sensors and drug delivery capsules, which they believe would be useful for long-term delivery of drugs that currently have to be injected. They could also help patients to maintain the strict dosing regimens required for patients with HIV or malaria.

In their latest study, the researchers set out to combine many of the features they had previously developed. In 2016, the researchers designed a star-shaped capsule with six arms that fold up before being encased in a smooth capsule. After being swallowed, the capsule dissolves and the arms expand, allowing the device to lodge in the stomach. Similarly, the new device unfolds into a Y-shape after being swallowed. This enables the device to remain the stomach for about a month, before it breaks into smaller pieces and passes through the digestive tract.

One of these arms includes four small compartments that can be loaded with a variety of drugs. These drugs can be packaged within polymers that allow them to be released gradually over several days. The researchers also anticipate that they could design the compartments to be opened remotely through wireless Bluetooth communication.

The device can also carry sensors that monitor the gastric environment and relay information via a wireless signal. In previous work, the researchers designed sensors that can detect vital signs such as heart rate and breathing rate. In this paper, they demonstrated that the capsule could be used to monitor temperature and relay that information directly to a smartphone within arm’s length.

“The limited connection range is a desirable security enhancement,” Kong says. “The self-isolation of wireless signal strength within the user’s physical space could shield the device from unwanted connections, providing a physical isolation for additional security and privacy protection.”

To enable the manufacturing of all of these complex elements, the researchers decided to 3-D print the capsules. This approach allowed them to easily incorporate all of the various components carried by the capsules, and to build the capsule from alternating layers of stiff and flexible polymers, which helps it to withstand the acidic environment of the stomach.

“Multimaterials 3-D printing is a highly versatile manufacturing technology that can create unique multicomponent architectures and functional devices, which cannot be fabricated with conventional manufacturing techniques,” Kong says. “We can potentially create customized ingestible electronics where the gastric residence period can be tailored based on a specific medical application, which could lead to a personalized diagnostic and treatment that is widely accessible.”

Early response

The researchers envision that this type of sensor could be used to diagnose early signs of disease and then respond with the appropriate medication. For example, it could be used to monitor certain people at high risk for infection, such as patients who are receiving chemotherapy or immunosuppressive drugs. If infection is detected, the capsule could begin releasing antibiotics. Or, the device could be designed to release antihistamines when it detects an allergic reaction.

“We’re really excited about the potential for gastric resident electronics to serve as platforms for mobile health to help patients remotely,” Traverso says.

The current version of the device is powered by a small silver oxide battery. However, the researchers are exploring the possibility of replacing the battery with alternative power sources, such as an external antenna or stomach acid.

The researchers are also working on developing other kinds of sensors that could be incorporated into the capsules. In this paper, they tested the temperature sensor in pigs, and they estimate that within about two years, they may be able to start testing ingestible sensors in human patients. They have launched a company that is working on developing the technology for human use.

The research was funded by the Bill and Melinda Gates Foundation and the National Institutes of Health through Draper.

Other authors of the paper include Xingyu Zou, Caitlin McCandler, Ameya Kirtane, Shen Ning, Jianlin Zhou, Abubakar Abid, Mousa Jafari, Jaimie Rogner, Daniel Minahan, Joy Collins, Shane McDonnell, Cody Cleveland, Taylor Bensel, Siid Tamang, Graham Arrick, Alla Gimbel, Tiffany Hua, Udayan Ghosh, Vance Soares, Nancy Wang, Aniket Wahane, Alison Hayward, Shiyi Zhang, and Brian Smith.




Contacts and sources:
Anne Trafton
Massachusetts Institute of Technology

Citation: 3D‐Printed Gastric Resident Electronics.
Yong Lin Kong, Xingyu Zou, Caitlin A. McCandler, Ameya R. Kirtane, Shen Ning, Jianlin Zhou, Abubakar Abid, Mousa Jafari, Jaimie Rogner, Daniel Minahan, Joy E. Collins, Shane McDonnell, Cody Cleveland, Taylor Bensel, Siid Tamang, Graham Arrick, Alla Gimbel, Tiffany Hua, Udayan Ghosh, Vance Soares, Nancy Wang, Aniket Wahane, Alison Hayward, Shiyi Zhang, Brian R. Smith, Robert Langer, Giovanni Traverso.Advanced Materials Technologies, 2018; 1800490 DOI: 10.1002/admt.201800490


Virus Made to Spy on Communicating Bacteria and Kill It on Command

Princeton molecular biologist Bonnie Bassler and graduate student Justin Silpe have identified a virus, VP882, that can listen in on bacterial conversations — and then, in a twist like something out of a spy novel, they found a way to use that to make it attack bacterial diseases like E. coli and cholera.

“The idea that a virus is detecting a molecule that bacteria use for communication — that is brand-new,” said Bassler, the Squibb Professor of Molecular Biology. “Justin found this first naturally occurring case, and then he re-engineered that virus so that he can provide any sensory input he chooses, rather than the communication molecule, and then the virus kills on demand.” Their paper will appear in the Jan. 10 issue of the journal Cell.

A virus can only ever make one decision, Bassler said: Stay in the host or kill the host. That is, either remain under the radar inside its host or activate the kill sequence that creates hundreds or thousands of offspring that burst out, killing the current host and launching themselves toward new hosts.

There’s an inherent risk in choosing the kill option: “If there are no other hosts nearby, then the virus and all its kin just died,” she said. VP882 has found a way to take the risk out of the decision. It listens for the bacteria to announce that they are in a crowd, upping the chances that when the virus kills, the released viruses immediately encounter new hosts. “It’s brilliant and insidious!” said Bassler.

These E. coli bacteria harbor proteins from the eavesdropping virus. One of the viral proteins has been tagged with a red marker. When the virus is in the “stay” mode (left), the bacteria grow and the red protein is spread throughout each cell. When the virus overhears that its hosts have achieved a quorum (right), the kill-stay decision protein is flipped to “kill” mode. A second viral protein binds the red protein and sends it to the cell poles (yellow dots). All the cells in the right panel will soon die.

Images courtesy of Bonnie Bassler and Justin Silpe, Department of Molecular Biology, Princeton University

“This paper provides an entirely new perspective on the dynamic relationship between viruses and their hosts,” said Graham Hatfull, the Eberly Family Professor of Biotechnology at the University of Pittsburgh, who was not involved in this research. “This study tells us for the first time … that when a phage is in the lysogenic [stay] state, it is not ‘fast asleep’, but rather catnapping, with one eye open and ears alert, ready to respond when it ‘hears’ signals that cells are getting ready to respond to changes in their environment.”

Bassler, who is also the chair of molecular biology and a Howard Hughes Medical Institute Investigator, had discovered years before that bacteria can communicate and sense one another’s presence and that they wait to establish a quorum before they act in concert. But she had never imagined that a virus could eavesdrop on this quorum-sensing communication.

“The bugs are getting bugged,” she said with a laugh. “Plus, Justin’s work shows that these quorum-sensing molecules are conveying information across kingdom boundaries.” Viruses are not in the same kingdom as bacteria — in fact, they are not in any kingdom, because they are not technically alive. But for such radically different organisms to be able to detect and interpret each other’s signals is simply mind-boggling, she said. It’s not like enemy nations spying on each other, or even like a human communicating with a dog — those at least are members of the same kingdom (animal) and phylum (vertebrate).

After finding the first evidence of this cross-kingdom eavesdropping, Silpe started looking for more — and found it.

“He just started a brand-new field,” Bassler said. “The idea that there’s only one example of this cross-domain communication made no sense to us. Justin discovered the first case, and then, with his discovery in hand, he went looking more deeply and he found a whole set of viruses that harbor similar capabilities. They may not all be listening in to this quorum-sensing information, but it is clear that these viruses can listen in to their hosts’ information and then use that information to kill them.”

Professor Bonnie Bassler and graduate student Justin Silpe discovered a bacteria-killing virus that can eavesdrop on bacterial conversations. They re-engineered it to attack diseases including salmonella, E. coli and cholera.
Bonnie Bassler and Justin Silpe sit at a computer station and a microscope, looking at bacteria
Photo by Denise Applewhite, Office of Communications

Silpe said he was drawn to work in Bassler’s lab because of her research on bacterial communication. “Communication seems like such an evolved trait,” he said. “To hear that bacteria can do it — her discovery — it was just mind-blowing that organisms you think of as so primitive could actually be capable of communication. And viruses are even simpler than bacteria. The one I studied, for example, only has about 70 genes. It’s really remarkable that it devotes one of those genes to quorum sensing. Communication is clearly not something higher organisms created.”

Once Silpe demonstrated that VP882 was eavesdropping, he began experimenting with feeding it misinformation to trick the virus into killing on command — to turn the predator into an assassin.

VP882 is not the first virus used as an antimicrobial treatment. Viruses that prey on bacteria are called “phages,” and “phage therapy” — targeting a bacterial disease with a phage — is a known medical strategy. But VP882 is the first phage that uses eavesdropping to know when it is optimal to kill its targets, making Silpe’s experiments with salmonella and other disease-causing bacteria the first time that phage therapy has used trans-kingdom communication.

In addition, this virus holds enormous promise as a therapeutic tool because it does not act like a typical virus, Bassler said. Most viruses can only infect a very specific type of cell. Flu viruses, for example, only infect lung cells; HIV only targets specific immune-system cells. But the virus VP882 has an “exceptionally broad host range,” Bassler said. So far, Silpe has only performed “proof of principle” tests with three unrelated bacteria: Vibrio cholerae (cholera), salmonella and E. coli. Those diseases have evolved separately for hundreds of millions of years, so the fact that they are all susceptible to this bacterial assassin suggests that many, many more are as well.

Hatfull is also optimistic about the utility of this re-engineered virus for antibiotic-resistant bacteria. “Antibiotic resistance is clearly a major global health threat, and there is a clear and evident demand for new strategies and approaches to this problem,” he said. “Although we have admittedly found it tricky even to reach ‘first base’ with basic therapeutic use of naturally occurring phages, we can envisage the possibility of a ‘home run’ if we can engineer phages for therapeutic use that have very specific targeting.” These viral assassins might even slow down the emergence of antibiotic resistant strains, he said.

Bassler gives all credit for the discovery to Silpe. After identifying a new quorum-sensing gene in V. cholerae, he made the choice to search genome databases for that gene. It showed up in some cholera-related strains and exactly one virus. Bassler wondered if that could be a meaningless data artifact, but Silpe wanted to get a specimen of the virus and run experiments.

“He was gung-ho, and I thought, ‘What the heck, give this kid a little rope. If this isn’t working soon, we can always move on,’” she said. “His was a crazy idea, because there’s never, ever been evidence of a virus listening in on bacterial host information to decide whether to stay put or kill. But this lab was built on crazy ideas, like bacteria talking to each other, and we’ve kind of made a living out of it. … Of course, that’s the beauty of science, and science at Princeton, that you have enough resources to play those hunches out, and see if there’s a ‘there’ there. And this time, there was a big ‘there’ there.”

A Host-Produced Quorum-Sensing Autoinducer Controls a Phage Lysis-Lysogeny Decision,” by Justin Silpe and Bonnie Bassler, will be published in the Jan. 10 issue of Cell and was released online Dec. 13 (DOI: 10.1016/j.cell.2018.10.059). It was supported by the Howard Hughes Medical Institute, NIH Grant 2R37GM065859, National Science Foundation Grant MCB-1713731, the Max Planck Society-Alexander von Humboldt, and the Department of Defense through the National Defense Science & Engineering Graduate Fellowship.




Contacts and sources:
Liz Fuller-Wright
Princeton University

Citation: A Host-Produced Quorum-Sensing Autoinducer Controls a Phage Lysis-Lysogeny Decision.
Justin E. Silpe, Bonnie L. Bassler. Cell, 2018; DOI: 10.1016/j.cell.2018.10.059


Origins of Pain: Researchers Identify Pathway That Drives Sustained Pain Following Injury

Researchers have identified the nerve-signaling pathway behind the deep, sustained pain that sets in following injury.
painful shoulder
Credit: Harvard Medical School

A toddler puts her hand on a hot stove and swiftly withdraws it. Alas, it’s too late—the child’s finger has sustained a minor burn. To soothe the pain, she puts the burned finger in her mouth.

Withdrawing one’s hand to avoid injury and soothing the pain of that injury are two distinct evolutionary responses, but their molecular origins and signaling pathways have eluded scientists thus far.

Now research led by investigators at Harvard Medical School, published Dec. 10 in Nature, identifies the nerve-signaling pathway behind the deep, sustained pain that sets in immediately following injury. The findings also shed light on the different pathways that drive reflexive withdrawal to avoid injury and the subsequent pain-coping responses.

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Clinical observations of patients with neurological damage together with past research have outlined the distinct brain regions that differentiate between the reflexive withdrawal from a skin prick, for example, and the long-lasting pain arising from tissue injury caused by the pinprick.

The new study, however, is the first one to map out how these responses arise outside the brain.

The findings, based on experiments in mice, put into question the validity of current experimental approaches for assessing the efficacy of candidate pain-relief compounds. Most current methods rely on measuring the initial, reflexive response that serves to avert tissue injury, rather than on measuring the lasting pain that arises from actual tissue damage, the researchers said. As a result, they said, some drug compounds that might have been successful in assuaging the sustained pain—the lasting sensation of pain that immediately follows injury—could have been dismissed as ineffective because they were assessed against the wrong outcome.

“The ongoing opioid crisis has created an acute and pressing need to develop new pain treatments, and our findings suggest that a more tailored approach to assessing pain response would be to focus on sustained pain response rather than reflexive protective withdrawal,” said study senior author Qiufu Ma, professor of neurobiology in the Blavatnik Institute at Harvard Medical School and a researcher at Dana-Farber Cancer Institute.

“All these years, researchers may have been measuring the wrong response,” Ma added. “Indeed, our results could explain, at least in part, the poor translation of candidate treatments from preclinical studies into effective pain therapies.”

Previous work by Ma and colleagues, as well as others, points to the existence of two sets of peripheral neurons—the nerve cells located outside the brain and spinal cord. One set of peripheral nerve cells send and receive signals exclusively to and from the superficial layers of the skin. As a first-line of defense against external threats, these peripheral nerve cells are geared toward preventing injury by triggering reflexive withdrawal—think pulling your hand after a pinprick or to avoid the hot tip of a flame. Another set of neurons are dispersed throughout the body and thought to drive the lasting pain that sets in after initial injury and induces pain-coping behaviors such as pressing a banged finger or licking a cut in the skin to sooth the damaged area.

Yet the existence of these neurons could not fully explain how the pain signal travels throughout the body and to the brain. So, Ma and colleagues proposed the existence of another critical player in this relay.

The team focused on a set of neurons called Tac1 emanating from the so-called dorsal horn, a cluster of nerves located at the lower end of the spinal cord that transmit signals between the brain and the rest of the body. The precise function of Tac1 had remained poorly understood so Ma and colleagues wanted to know whether and how these neurons were involved in the sensation of sustained pain.

In a series of experiments, the team assessed pain response in two groups of mice—one with intact Tac1 neurons and another with chemically disabled Tac1 neurons.

Mice with inactivated Tac1 neurons had normal withdrawal reflexes when exposed to a painful stimulus. They showed no notable differences in their withdrawal from pricking or exposure to heat and cold. However, when the researchers injected the animals with burn-inducing mustard oil, they did not engage in the typical paw licking that animals perform immediately following injury. By contrast, mice with intact Tac1 neurons engaged in vigorous and prolonged paw licking to assuage the pain.

Similarly, mice with disabled Tac1 neurons showed no pain-coping responses when their hind paws were pinched—something that induces sustained pain in humans. These animals did not engage in any paw licking as a result of the pinch. Such loss of sensitivity to a specific type of pain mimics the loss of sensation seen in people with strokes or tumors in a particular area of the brain’s pain-processing center—the thalamus—that renders them incapable of sensing lasting pain.

These observations confirm that Tac1 neurons are critical for pain-coping behaviors stemming from sustained irritation or injury but that they play no role in reflexive-defensive reactions to external threats.

Next, researchers wanted to know whether Tac1 neurons shared a common connection with another class of neurons, called Trpv1, present throughout the body and already known to drive the sensation of lasting pain induced by injury. Mice that had functional Tac1 but nonfunctioning Trpv1 neurons responded weakly to pinch-induced pain, showing minimal paw licking. The finding suggests that pain-sensing Trvp1 neurons connect to Tac1 neurons in the dorsal horn of the spinal cord to transmit their signals.

“We believe that Tac1 neurons act as a relay station that dispatches pain signals from the tissue, through Trpv1 nerve fibers all the way to the brain,” Ma said.

Taken together, the results of the study affirm the presence of two lines of defense in response to injury, each controlled by separate nerve-signaling pathways. The rapid withdrawal reflex is nature’s first line of defense, an escape attempt designed to avoid injury. By contrast, the secondary, pain coping response helps reduce suffering and avert widespread tissue damage as a result of the injury.

“We believe it’s an evolutionary mechanism conserved across multiple species to maximize survival,” Ma said.

Additional investigators included Tianwen Huang, Shing-Hong Lin, Yan Zhang and Ying Zhang of Dana-Farber Cancer Institute; Nathalie M. Malewicz and Robert H. LaMotte of Yale University; and Martyn Goulding of the Salk Institute for Biological Studies.

The work was supported by National Institutes of Health grants (R01 DE018025 and R01 NS086372), a Wellcome Trust grant (200183/Z/15/Z), and a Research Fellowship (326726541) from the German Research Foundation.



Contacts and sources:
Ekaterina Pesheva 
Harvard Medical School

Citation: Identifying the pathways required for coping behaviours associated with sustained pain
Tianwen Huang, Shing-Hong Lin, Nathalie M. Malewicz, Yan Zhang, Ying Zhang, Martyn Goulding, Robert H. LaMotte, Qiufu Ma. . Nature, 2018; DOI: 10.1038/s41586-018-0793-8


Human Brain Suppresses Obvious Ideas Reaching for More Creative Ones

The human brain needs to suppress obvious ideas in order to reach the most creative ones, according to scientists at Queen Mary University of London and Goldsmiths, University of London.

Creativity requires us to break away from more common and easily reached ideas but we know little about how this happens in our brain.

A new study, published in the Proceedings of the National Academy of Sciences of the USA, shows that brainwaves play a crucial role in inhibiting habitual thinking modes to pave the way to access more remote ideas.

The researchers found that these brainwaves, or alpha oscillations in the right temporal area of the brain, increase when individuals need to suppress misleading associations in creative tasks.

These obvious associations are present in both convergent thinking (finding an ‘out-of-the-box’ solution) and also in divergent thinking (when individuals have to come up with several creative ideas). 

EEG AND tACS in use
Credit: Queen Mary University of London

Higher levels of alpha brainwaves enable people to come up with ideas which are further away from the obvious or well-known uses.

Stimulating creative thinking

The researchers show that stimulating the right temporal part of the brain in the alpha frequency increases the capability of inhibiting obvious links in both types of creative thinking.

This was demonstrated by applying an electrical current to the brain through a non-invasive technique called transcranial alternating current brain stimulation (tACS) which causes minimal to no side effects or sensations.

The findings have implications for how we understand creativity and opens up potential ways of affecting the creative process including by using tACS.

Lead researcher Dr Caroline Di Bernardi Luft, from Queen Mary University of London, said: “Obvious associations are like walls which prevent you from reaching novel ideas. For example, if we need to generate alternative uses of a glass, first we must break away from our past experience which leads us to think of a glass as a container. Our study’s novelty is to demonstrate that right temporal alpha oscillations is a key neural mechanism for overriding these obvious associations; they help us by actively breaking those walls”.
Monitoring the brain

The researchers demonstrated the neural mechanism responsible for creativity by monitoring the brain’s electrical activity through an electroencephalogram (EEG) which picks up electrical signals through small sensors placed on the head. Using tACS also enabled them to probe the waves’ causal role.

The experiments they conducted looked at how the brain tackles a series of creative tasks such as finding words that link to one another. For example, every time we search for concepts associated with a word we start from stronger associations to move progressively towards weaker or more remote ones (e.g. cat > dog > animal > pet > human > people > family).

Previous studies show that some people are more creative than others because they are able to avoid strong associations in order to reach more remote ones and this study demonstrates that the alpha brainwaves are crucially involved in this process.

'The one less travelled'

Goldsmiths, University of London’s Professor Joydeep Bhattacharya, a co-author of this study, added: “Two roads diverged in a wood, I took the one less travelled by. And that has made all the difference,’ wrote Robert Frost in his famous poem.”

“Taking a less travelled route is needed for thinking creatively, and our findings provide some evidence on how this is done in our brain.”

The researchers hope to understand how neural processes are integrated when solving creative problems out of the laboratory settings and whether it is possible to build stimulation devices which can monitor the brain and stimulate creativity whenever needed.

The research was supported by a European Commission project, CREAM (Creativity enhancement through advanced brain mapping and stimulation).


  Contacts and sources:
Queen Mary University of London


Citation: Right temporal alpha oscillations as a neural mechanism for inhibiting obvious associations.
Caroline Di Bernardi Luft, Ioanna Zioga, Nicholas M. Thompson, Michael J. Banissy, Joydeep Bhattacharya. Proceedings of the National Academy of Sciences, 2018; 201811465 DOI: 10.1073/pnas.1811465115


Thursday, December 13, 2018

Tornadoes from the Ground Up Not in the Clouds As Once Thought

Historically, scientists assumed tornado rotation began in storm clouds, creating a funnel that travels downwards. This theory matches what storm chasers commonly observe visually in the field. Viewers often report seeing funnel clouds gradually descending until they make contact with the ground.

But new research combining a new type of Doppler radar with photos and videos of tornadoes formed by supercell thunderstorms shows the opposite is true: Tornadoes materialize from the ground up.

Weather forecasters typically issue tornado warnings based on radar observations of strong rotation above the ground, but the new findings suggest forecasters must re-evaluate their warning procedure, according to the researchers.

A tornado in Galatia, Kansas on 25 May 2012 as it was decaying.

Credit: Jana Houser.

“We need to reconsider the paradigms that we have to explain tornado formation, and we especially need to communicate this to forecasters who are trying to make warnings and issue warnings,” said Jana Houser, a meteorologist at Ohio University in Athens who will present the new findings here today at the American Geophysical Union’s Fall Meeting. “You are not going to really ever be finding strong evidence of a tornado descending, so we need to stop making that a priority in our forecasting strategies.”

Research conducted in the 1970s suggested tornadoes form from rotation that starts several kilometers above Earth’s surface. The theory was that this funnel gradually sucked in air from below, descending until it touched the ground.

Most meteorologists have accepted this theory of tornado formation, but a series of new observations from rapidly scanning radars has started to change that.

One of the pivotal cases contributing to the new understanding of tornado formation occurred on May 31, 2013. On this day, the El Reno tornado formed in central Oklahoma and shattered previous tornado records. It was the widest tornado ever recorded, peaking at 4.2 kilometers (2.6 miles) wide, and had wind speeds of more than 480 kilometers per hour (300 miles per hour), the second-highest wind speeds recorded on Earth.

Shot of the El Reno, Oklahoma EF-3 tornado near maximum width and peak intensity on 31 May 2013.

Credit: Nick Nolte, CC-BY-3.0.

Houser and a team of researchers from the University of Oklahoma happened to be monitoring the storm with a new type of mobile Doppler radar system that collected tornado wind speeds every 30 seconds. Afterwards, Anton Seimon, a geographer at Appalachian State University in Boone, North Carolina who had chased the El Reno storm, collected hundreds of still photos and videos of the epic twister from citizens and fellow storm chasers.

When Houser compared her radar data with images collected by Seimon, she noticed something odd. The images clearly showed a visible tornado at the ground several minutes before her radar picked it up.

Puzzled, Houser went back through her radar data and analyzed the data taken at the ground. It is typically difficult to get good radar measurements at or near the ground, but Houser and her team had deployed their instrument on a slight rise and there were no obstructions between them and the tornado, so this time, they had data good enough to work with.

Jana Houser standing next to the Rapid X-Pol radar instrument, a new type of rapidly-scanning mobile radar system, during a storm chase on 8 May 2012.

Credit: Jana Houser.

She found clear evidence of rotation at the ground before there was rotation at higher altitudes. Houser then examined other sets of tornado data and found that in many cases, tornado-strength rotation develops at or near the ground first, rather than starting in the cloud itself. In all four datasets she analyzed, none of the tornadoes formed following the classical “top-down” process.

“It emphasizes the fact that we need to have strong, low-level, basically near-ground level rotation, located in the right spot, at the right time, with respect to the larger parent storm circulations in order to form a tornado,” Houser said.



Contacts and sources:
Jana Houser / Lauren Lipuma
The American Geophysical Union 





Hubble Finds a Fast Evaporating Exoplanet


Fishermen would be puzzled if they netted only big and little fish, but few medium-sized fish. Astronomers likewise have been perplexed in conducting a census of star-hugging extrasolar planets. They have found hot Jupiter-sized planets and hot super-Earths (planets no more than 1.5 times Earth's diameter). These planets are scorching hot because they orbit very close to their star. But so-called "hot Neptunes," whose atmospheres are heated to more than 1,700 degrees Fahrenheit, have been much harder to find. In fact, only about a handful of hot Neptunes have been found so far.

In fact, most of the known Neptune-sized exoplanets are merely "warm," because they orbit farther away from their star than those in the region where astronomers would expect to find hot Neptunes. The mysterious hot-Neptune deficit suggests that such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.

This artist's illustration shows a giant cloud of hydrogen streaming off a warm, Neptune-sized planet just 97 light-years from Earth. The exoplanet is tiny compared to its star, a red dwarf named GJ 3470. The star's intense radiation is heating the hydrogen in the planet's upper atmosphere to a point where it escapes into space. The alien world is losing hydrogen at a rate 100 times faster than a previously observed warm Neptune whose atmosphere is also evaporating away.
Artist's Illustration of Gas Streaming from GJ 3470b
Credit:  NASA, ESA, and D. Player (STScI)

A few years ago astronomers using NASA's Hubble Space Telescope found that one of the warmest known Neptunes (GJ 436b) is losing its atmosphere. The planet isn't expected to evaporate away, but hotter Neptunes might not have been so lucky.

Now, astronomers have used Hubble to nab a second "very warm" Neptune (GJ 3470b) that is losing its atmosphere at a rate 100 times faster than that of GJ 436b. Both planets reside about 3.7 million miles from their star. That's one-tenth the distance between our solar system's innermost planet, Mercury, and the Sun.

"I think this is the first case where this is so dramatic in terms of planetary evolution," said lead researcher Vincent Bourrier of the University of Geneva in Sauverny, Switzerland. "It's one of the most extreme examples of a planet undergoing a major mass-loss over its lifetime. This sizable mass loss has major consequences for its evolution, and it impacts our understanding of the origin and fate of the population of exoplanets close to their stars."

As with the previously discovered evaporating planets, the star's intense radiation heats the atmosphere to a point where it escapes the planet's gravitational pull like an untethered hot air balloon. The escaping gas forms a giant cloud around the planet that dissipates into space. One reason why GJ 3470b may be evaporating faster than GJ 436b is that it is not as dense, so it is less able to gravitationally hang on to the heated atmosphere.

What's more, the star hosting GJ 3470b is only 2 billion years old, compared to the 4-billion- to 8-billion-year-old star that planet GJ 436b orbits. The younger star is more energetic, so it bombards the planet with more blistering radiation than GJ 436b receives. Both are red dwarf stars, which are smaller and longer-lived than our Sun.

Uncovering two evaporating warm Neptunes reinforces the idea that the hotter version of these distant worlds may be a class of transitory planet whose ultimate fate is to shrink down to the most common type of known exoplanet, mini-Neptunes — planets with heavy, hydrogen-dominated atmospheres that are larger than Earth but smaller than Neptune. Eventually, these planets may downsize even further to become super-Earths, more massive, rocky versions of Earth.

"The question has been, where have the hot Neptunes gone?" said Bourrier. "If we plot planetary size and distance from the star, there's a desert, a hole, in that distribution. That's been a puzzle. We don't really know how much the evaporation of the atmospheres played in forming this desert. But our Hubble observations, which show a large amount of mass loss from a warm Neptune at the edge of the desert, is a direct confirmation that atmospheric escape plays a major role in forming this desert."

The researchers used Hubble's Space Telescope Imaging Spectrograph to detect the ultraviolet-light signature of hydrogen in a huge cocoon surrounding the planet as it passed in front of its star. The intervening cocoon of hydrogen filters out some of the starlight. These results are interpreted as evidence of the planet's atmosphere bleeding off into space.

The team estimates that the planet has lost as much as 35 percent of its material over its lifetime, because it was probably losing mass at a faster rate when its red-dwarf star was younger and emitting even more radiation. If the planet continues to rapidly lose material, it will shrink down to a mini-Neptune in a few billion years.

Hydrogen probably isn't the only element evaporating away: it may be a tracer for other material streaming off into space. The researchers plan to use Hubble to hunt for elements heavier than hydrogen and helium that have hitched a ride with the hydrogen gas to escape the planet. "We think that the hydrogen gas could be dragging heavy elements such as carbon, which reside deeper in the atmosphere, upward and out into space," Bourrier said.


This graphic plots exoplanets based on their size and distance from their star. Each dot represents an exoplanet. Planets the size of Jupiter (located at the top of the graphic) and planets the size of Earth and so-called super-Earths (at the bottom) are found both close to and far from their star. But planets the size of Neptune (in the middle of the plot) are scarce close to their star. This so-called desert of hot Neptunes shows that such alien worlds are rare, or, they were plentiful at one time, but have since disappeared. The detection that GJ 3470b, a warm Neptune at the border of the desert, is fast losing its atmosphere suggests that hotter Neptunes may have eroded down to smaller, rocky super-Earths.
Exoplanet Radius vs. Distance from Star
Credit: NASA, ESA, and A. Feild (STScI)

The observations are part of the Panchromatic Comparative Exoplanet Treasury (PanCET) survey, a Hubble program to look at 20 exoplanets, mostly hot Jupiters, in the first large-scale ultraviolet, visible, and infrared comparative study of distant worlds.

Observing the evaporation of these two warm Neptunes is encouraging, but team members know they need to study more of them to confirm predictions. Unfortunately, there may be no other planets of this class residing close enough to Earth to observe. The problem is that hydrogen gas cannot be detected in warm Neptunes farther away than 150 light-years from Earth because it is obscured by interstellar gas. GJ 3470b resides 97 light-years away.

However, helium is another tracer for material escaping a warm Neptune's atmosphere. Astronomers could use Hubble and the upcoming NASA James Webb Space Telescope to search in infrared light for helium, because it is not blocked by interstellar material in space.

"Looking for helium could expand our survey range," Bourrier said. "Webb will have incredible sensitivity, so we would be able to detect helium escaping from smaller planets, such as mini-Neptunes."

The researcher's paper will appear in the Dec. 13 issue of Astronomy and Astrophysics.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Contacts and sources:

Citation:



The Epoch of Planet Formation, Unprecedented Views of the Birth of Planets

ALMA's high-resolution images of nearby protoplanetary disks, which are results of the Disk Substructures at High Angular Resolution Project (DSHARP).

Credit: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello

Astronomers have cataloged nearly 4,000 exoplanets in orbit around distant stars. Though the discovery of these newfound worlds has taught us much, there is still a great deal we do not know about the birth of planets and the precise cosmic recipes that spawn the wide array of planetary bodies we have already uncovered, including so-called hot Jupiters, massive rocky worlds, icy dwarf planets, and – hopefully someday soon – distant analogs of Earth.

To help answer these and other intriguing questions, a team of astronomers has conducted ALMA‘s first large-scale, high-resolution survey of protoplanetary disks
, the belts of dust and gas around young stars.

Known as the Disk Substructures at High Angular Resolution Project (DSHARP), this “Large Program” of the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded stunning, high-resolution images of 20 nearby protoplanetary disks and given astronomers new insights into the variety of features they contain and the speed with which planets can emerge.

The results of this survey will appear in a special focus issue of the Astrophysical Journal Letters.

According to the researchers, the most compelling interpretation of these observations is that large planets, likely similar in size and composition to Neptune or Saturn, form quickly, much faster than current theory would allow. Such planets also tend to form in the outer reaches of their solar systems at tremendous distances from their host stars.

Artist's animation of a protoplanetary disk. Newly formed planets can be seen traveling around the central host star, sweeping their orbits clear of dust and gas. These same ring-link structures were observed recently by ALMA around a number of young stars.

Credit: National Science Foundation, A. Khan

Such precocious formation could also help explain how rocky, Earth-size worlds are able to evolve and grow, surviving their presumed self-destructive adolescence.

“The goal of this months-long observing campaign was to search for structural commonalities and differences in protoplanetary disks. ALMA’s remarkably sharp vision has revealed previously unseen structures and unexpectedly complex patterns,” said Sean Andrews, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) and a leader of the ALMA observing campaign along with Andrea Isella of Rice University, Laura Pérez of the University of Chile, and Cornelis Dullemond of Heidelberg University. “We are seeing distinct details around a wide assortment of young stars of various masses. The most compelling interpretation of these highly diverse, small-scale features is that there are unseen planets interacting with the disk material.”

The leading models for planet formation hold that planets are born by the gradual accumulation of dust and gas inside a protoplanetary disk, beginning with grains of icy dust that coalesce to form larger and larger rocks, until asteroids, planetesimals, and planets emerge. This hierarchical process should take many millions of years to unfold, suggesting that its impact on protoplanetary disks would be most prevalent in older, more mature systems. Mounting evidence, however, indicates that is not always the case.

ALMA’s early observations of young protoplanetary disks, some only about one million years old, reveal surprisingly well-defined structures, including prominent rings and gaps, which appear to be the hallmarks of planets. Astronomers were initially cautious to ascribe these features to the actions of planets since other natural process could be at play.

“It was surprising to see possible signatures of planet formation in the very first high-resolution images of young disks. It was important to find out whether these were anomalies or if those signatures were common in disks,” said Jane Huang, a graduate student at CfA and a member of the research team.

ALMA's high-resolution images of nearby protoplanetary disks, which are results of the Disk Substructures at High Angular Resolution Project (DSHARP).
Credit: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello

Since the initial sample of disks that astronomers could study was so small, however, it was impossible to draw any overarching conclusions. It could have been that astronomers were observing atypical systems. More observations on a variety of protoplanetary disks were needed to determine the most likely causes of the features they were seeing.

The DSHARP campaign was designed to do precisely that by studying the relatively small-scale distribution of dust particles around 20 nearby protoplanetary disks. These dust particles naturally glow in millimeter-wavelength light, enabling ALMA to precisely map the density distribution of small, solid particles around young stars.

Depending on the star’s distance from Earth, ALMA was able to distinguish features as small as a few Astronomical Units

An Astronomical Unit is the average distance of the Earth to the Sun – about 150 million kilometers, which is a useful scale for measuring distances on the scale of star systems). Using these observations, the researchers were able to image an entire population of nearby protoplanetary disks and study their AU-scale features.
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The researchers found that many substructures – concentric gaps, narrow rings – are common to nearly all the disks, while large-scale spiral patterns and arc-like features are also present in some of the cases. Also, the disks and gaps are present at a wide range of distances from their host stars, from a few AU to more than 100 AU, which is more than three times the distance of Neptune from our Sun.

These features, which could be the imprint of large planets, may explain how rocky Earth-like planets are able to form and grow. For decades, astronomers have puzzled over a major hurdle in planet-formation theory: Once dusty bodies grow to a certain size – about one centimeter in diameter – the dynamics of a smooth protoplanetary disk would induce them to fall in on their host star, never acquiring the mass necessary to form planets like Mars, Venus, and Earth.

The dense rings of dust we now see with ALMA would produce a safe haven for rocky worlds to fully mature. Their higher densities and the concentration of dust particles would create perturbations in the disk, forming zones where planetesimals would have more time to grow into fully fledged planets.

Labeled version of four of the twenty disks that comprise ALMA's highest resolution survey of nearby protoplanetary disks. - AS 209 is a star hosting a disk that is 1 million years old and located about 400 light-years from Earth. The ALMA image shows a tightly packed series of dusty rings in its inner disk and two additional thin bands of dust very far from the central star. - HD 143006 is about 5 million years old and resides 540 light-years from Earth. This star hosts a disk that shows wide gaps between dusty lanes that demarcate the inner and outer portions of the disk. A dense arc-shaped region, possibly heralding a concentration of material where comets or other icy bodies are forming, can be seen on the lower left portion of the outer ring. - ALMA reveals sweeping spiral arms in the dust disk orbiting IM Lup, a young star located about 515 light-years from Earth. These patterns may be the result of an unseen planetary companion perturbing the disk, or a global instability in the disk structure similar to those seen in spiral galaxies like the Milky Way. - AS 205 is a multiple star system, with each star sporting its own dusty disk. Since most stars in the Milky Way are multiples, this observation provides clues to the potential for planets in such systems. This system is located about 420 light-years from Earth.

Credit: ALMA (ESO/NAOJ/NRAO) S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello

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“When ALMA truly revealed its capabilities with its iconic image of HL Tau, we had to wonder if that was an outlier since the disk was comparatively massive and young,” noted Laura Perez with the University of Chile and a member of the research team. “These latest observations show that, though striking, HL Tau is far from unusual and may actually represent the normal evolution of planets around young stars.”

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 Blue
National Radio Astronomy Observatory

Citation:

This research is presented in the following papers accepted to the Astrophysical Journal Letters.
“The Disk Substructures at High Angular Resolution Project (DSHARP): I. Motivation, Sample, Calibration, and Overview: S. Andrews, et al. [https://arxiv.org/abs/1812.04040]
“The Disk Substructures at High Angular Resolution Project (DSHARP): II. Characteristics of Annular Substructures,” J. Huang, et al. [https://arxiv.org/abs/1812.04041]
“The Disk Substructures at High Angular Resolution Project (DSHARP): III. Spiral Structures in the Millimeter Continuum of the Elias 27, IM Lup, and WaOph 6 Disks,” J. Huang, et al. [https://arxiv.org/abs/1812.04193]
“The Disk Substructures at High Angular Resolution Project (DSHARP): IV. Characterizing Substructures and Interactions in Disks around Multiple Star Systems,” N. Kurtovic, et al. [https://arxiv.org/abs/1812.04536]
“The Disk Substructures at High Angular Resolution Project (DSHARP): V. Interpreting ALMA Maps of Protoplanetary Disks in Terms of a Dust Model” T. Birnstiel, et al. [https://arxiv.org/abs/1812.04043]
“The Disk Substructures at High Angular Resolution Project (DSHARP): VI. Dust Trapping in Thin-Ringed Protoplanetary Disks,” C. Dullemond, et al. [https://arxiv.org/abs/1812.04044]
“The Disk Substructures at High Angular Resolution Project (DSHARP): VII. The Planet-Disk Interactions Interpretation” S. Zhang, et al. [https://arxiv.org/abs/1812.04045]
“The Disk Substructures at High Angular Resolution Project (DSHARP): VIII. The Rich Ringed Substructures in the AS 209 Disk,” V, Guzmán, et al. [https://arxiv.org/abs/1812.04046]
“The Disk Substructures at High Angular Resolution Project (DSHARP): IX. A High Definition Study of the HD 163296 Planet Forming Disk” A. Isella, et al. [https://arxiv.org/abs/1812.04047]
“The Disk Substructures at High Angular Resolution Project (DSHARP): X. Multiple Rings, a Misaligned Inner Disk, and a Bright Arc in the Disk around the T Tauri Star HD 143006,” L. Pérez, et al. [https://arxiv.org/abs/1812.04049]





Tuesday, December 11, 2018

Solar Activity Research Provides Insight into Sun’s Past and Future



Andrés Muñoz-Jaramillo of Southwest Research Institute and José Manuel Vaquero of University of Extremadura have developed a new technique for looking at historic solar data to distinguish trustworthy observations from those that should be used with care. This work is critical to understanding the Sun’s past and future as well as whether solar activity plays a role in climate change.

“Scientists have been monitoring solar activity since Galileo made the first drawings in 1612 by counting sunspots and groups of sunspots,” said SwRI’s Muñoz-Jaramillo, a senior research scientist who is first author of a paper in Nature Astronomy outlining the research. “However, putting all observations in perspective is quite challenging due to wide-ranging observation techniques and telescope magnifications used. We see much more now and our understanding of what we see changes the way we count spots.”

A team led by SwRI integrated a sunspot drawing made by Hevelius in 1644 (top) with images from NASA's Solar Dynamics Observatory to illustrate how widely varying telescopes and observation techniques can affect data. The team integrated data from 700 observations to assess the reliability of historical data, to better understand the history of solar activity.
Credit: NASA/SDO/SwRI

The team created a technique that takes all historic data gathered and digitized thus far and combines them visually, to provide a complete picture of the data we have and where are we missing information. Roughly every 11 years, the magnetic structure and activity of the Sun cycle between periods known as solar minimum and solar maximum. During solar maximum, the Sun emits high levels of solar radiation, ejects large amounts solar material and displays large numbers of intense sunspots, flares and other phenomena. During solar minimum, this activity is muted. Changes on the Sun cause effects in space, in the atmosphere and on Earth’s surface.

The Sun also experiences century-long variations, including periods of abnormally low solar activity called grand minima. Maunder Minimum refers to a 70-year period between 1645 and 1715 when observations revealed thousands of days without sunspots. The term was the title of a 1976 paper that first identified these longer cycles, named for a husband-wife team of solar astronomers from the late 17th century. In contrast, modern observations typically record hundreds of days without sunspots over similar periods of time.

“Scientists are investigating whether Maunder Minimum could serve as archetype of a grand minimum in magnetic activity for the Sun and other stars,” Muñoz said. However, data prior to, during and after the Maunder Minimum, is less reliable and lacks the precision and coverage of today’s measurements. Recent reevaluations of sunspot observations have yielded a conflicted view on the evolution of solar activity over the last 400 years.

“Due to our lack coverage we don’t know if the Sun took decades to recover from the Maunder Minimum to the levels of solar activity we see today, or if it was quick as if a switch had been turned on,” Munoz said. “There is currently a team of experts from all over the world working hard to find the best way of combining these data. In the meantime, one has to be very careful when using historic sunspot data to study potential links between the Sun and changes in terrestrial climate, given that these effects would be complex and subtle. Our work uses historical data to provide context to users of these estimates that may not be aware of their limitations.”

“Visualization of the challenges and limitations of the long-term sunspot number record” was published Dec. 10 in Nature Astronomy. This work is part of an international effort to reconstruct solar activity levels during the last 400 years, led by the SILSO World Data Center and funded by the NASA Grand Challenge and Living with a Star programs, and other Spanish institutions.


Contacts and sources:
Joanna Carver
Southwest Research Institute

Citation: Visualization of the challenges and limitations of the long-term sunspot number record.
Andrés Muñoz-Jaramillo, José M. Vaquero. Nature Astronomy, 2018; DOI: 10.1038/s41550-018-0638-2



Did Supernovae Kill Off Megalodon and Other Large Ocean Animals at Dawn of Pleistocene?

About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light years away from Earth. Within a few hundred years, long after the strange light in the sky had dwindled, a tsunami of cosmic energy from that same shattering star explosion could have reached our planet and pummeled the atmosphere, touching off climate change and triggering mass extinctions of large ocean animals, including a shark species that was the size of a school bus.

 A nearby supernova remnant.

 Credit: NASA
 

The effects of such a supernova — and possibly more than one — on large ocean life are detailed in a paper just published in Astrobiology.

“I’ve been doing research like this for about 15 years, and always in the past it’s been based on what we know generally about the universe — that these supernovae should have affected Earth at some time or another,” said lead author Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas. “This time, it’s different. We have evidence of nearby events at a specific time. We know about how far away they were, so we can actually compute how that would have affected the Earth and compare it to what we know about what happened at that time — it’s much more specific.”

Melott said recent papers revealing ancient seabed deposits of iron-60 isotopes provided the “slam-dunk” evidence of the timing and distance of supernovae.

Muons showering Earth may have spelled curtains for Megalodon, a school-bus-sized shark, 2.6 million years ago.
Credit: Wikimedia Commons.

“As far back as the mid-1990s, people said, ‘Hey, look for iron-60. It’s a telltale because there’s no other way for it to get to Earth but from a supernova.’ Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us. There’s some debate about whether there was only one supernova really nearby or a whole chain of them. I kind of favor a combo of the two — a big chain with one that was unusually powerful and close. If you look at iron-60 residue, there’s a huge spike 2.6 million years ago, but there’s excess scattered clear back 10 million years.”

Melott’s co-authors were Franciole Marinho of Universidade Federal de São Carlos in Brazil and Laura Paulucci of Universidade Federal do ABC, also in Brazil.

According to the team, other evidence for a series of supernovae is found in the very architecture of the local universe.

“We have the Local Bubble in the interstellar medium,” Melott said. “We’re right on its edge. It’s a giant region about 300 light years long. It’s basically very hot, very low-density gas — nearly all the gas clouds have been swept out of it. The best way to manufacture a bubble like that is a whole bunch of supernovae blows it bigger and bigger, and that seems to fit well with idea of a chain. When we do calculations, they’re based on the idea that one supernova that goes off, and its energy sweeps by Earth, and it’s over. But with the Local Bubble, the cosmic rays kind of bounce off the sides, and the cosmic-ray bath would last 10,000 to 100,000 years. This way, you could imagine a whole series of these things feeding more and more cosmic rays into the Local Bubble and giving us cosmic rays for millions of years.”

Whether or not there was one supernova or a series of them, the supernova energy that spread layers of iron-60 all over the world also caused penetrating particles called muons to shower Earth, causing cancers and mutations — especially to larger animals.

“The best description of a muon would be a very heavy electron — but a muon is a couple hundred times more massive than an electron,” Melott said. “They’re very penetrating. Even normally, there are lots of them passing through us. Nearly all of them pass through harmlessly, yet about one-fifth of our radiation dose comes by muons. But when this wave of cosmic rays hits, multiply those muons by a few hundred. Only a small faction of them will interact in any way, but when the number is so large and their energy so high, you get increased mutations and cancer — these would be the main biological effects. We estimated the cancer rate would go up about 50 percent for something the size of a human — and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up.”

 Adrian Melott
Credit:  University of Kansas

A supernova 2.6 million years ago may be related to a marine megafaunal extinction at the Pliocene-Pleistocene boundary where 36 percent of the genera were estimated to become extinct. The extinction was concentrated in coastal waters, where larger organisms would catch a greater radiation dose from the muons.

According to the authors of the new paper, damage from muons would extend down hundreds of yards into ocean waters, becoming less severe at greater depths: “High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases,” they write.

Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation.

“One of the extinctions that happened 2.6 million years ago was Megalodon,” Melott said. “Imagine the Great White Shark in ‘Jaws,’ which was enormous — and that’s Megalodon, but it was about the size of a school bus. They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been.”

The KU researcher said the evidence of a supernova, or series of them, is “another puzzle piece” to clarify the possible reasons for the Pliocene-Pleistocene boundary extinction.

“There really hasn’t been any good explanation for the marine megafaunal extinction,” Melott said. “This could be one. It’s this paradigm change — we know something happened and when it happened, so for the first time we can really dig in and look for things in a definite way. We now can get really definite about what the effects of radiation would be in a way that wasn’t possible before.”





Contacts and sources:
Brendan M. Lynch
University of Kansas


Citation: Hypothesis: Muon Radiation Dose and Marine Megafaunal Extinction at the End-Pliocene Supernova
Adrian L. Melott, Franciole Marinho, Laura Paulucci.. Astrobiology, 2018; DOI: 10.1089/ast.2018.1902