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Thursday, December 31, 2015

Tens of Millions of Trees in Danger from California Drought

 California's forests are home to the planet's oldest, tallest and most-massive trees. New research from Carnegie's Greg Asner and his team reveals that up to 58 million large trees in California experienced severe canopy water loss between 2011 and today due to the state's historic drought. Their results are published in Proceedings of the National Academy of Sciences.

In addition to the persistently low rainfall, high temperatures and outbreaks of the destructive bark beetle increased forest mortality risk. But gaining a large-scale understanding a forest's responses to the drought, as well as to ongoing changes in climate, required more than just a picture of trees that have already died.

This image shows progressive water stress on California's forests.

Courtesy of Greg Asner.

A higher-tech approach was necessary; so Asner and his team used the laser-guided imaging spectroscopy tools mounted on the Carnegie Airborne Observatory (CAO) to measure the full impact of the drought on California's forests for the first time. They combined the CAO data with more-traditional satellite data going back to 2011.

Their new approach revealed a progressive loss of water in California's forest canopies over the four-year span. Mapping changes in canopy water content tells scientists when trees are under drought stress and greatly aids in predicting which trees are at greatest death and fire risk.

"California relies on its forests for water provisioning and carbon storage, as well as timber products, tourism, and recreation, so they are tremendously important ecologically, economically, and culturally," Asner explained. "The drought put the forests in tremendous peril, a situation that may cause long-term changes in ecosystems that could impact animal habitats and biodiversity."

The team's advanced tools showed that about 41,000 square miles (10.6 million hectares) of forest containing up to 888 million large trees experienced measurable losses of canopy water between 2011 and 2015. Of this group, up to 58 million large trees reached water loss thresholds that the scientists deemed extremely threatening to long-term forest health. Given the severity of the situation, even with increased precipitation due to El Nino, if drought conditions reoccur in the near future, the team predicts that there would be substantial changes to already significantly weakened forest structures and systems.

This image shows mixed levels of drought stress in a forested landscape in California.
 Courtesy of Greg Asner.

"The Carnegie Airborne Observatory's research provides invaluable insight into the severity of drought impacts in California's iconic forests. It will be important to bring their cutting-edge data and expertise to bear as the state seeks to address the effects of this epidemic of dying trees and aid in the recovery of our forests," said Ashley Conrad-Saydah, deputy secretary for climate policy at the California Environmental Protection Agency.

Since day one of CAO flight operations, Asner has been engaged with forest managers and officials from the California EPA and Department of Forestry and Fire Protection to inform decision-makers on the severity of forest water losses from the drought and beetle outbreaks. The team's results also helped motivate the California governor's recent proclamation of a state of emergency for dead and dying trees across the state. The latest CAO maps of forest vulnerability were recently transmitted to both state and federal partners.

"Our high-resolution mapping approach identifies vulnerable trees and changing landscapes," Asner added. "Continued airborne and satellite monitoring will enable actions on the ground to mitigate a cascade of negative impacts from forest losses due to drought, as well as aid in monitoring forest recovery if and when the drought subsides."

Contacts and sources: 
Courtesy of Greg Asner.
The Carnegie Institution for Science

Description of Mechanism That Halts Solar Eruptions

Among the most feared events in space physics are solar eruptions, massive explosions that hurl millions of tons of plasma gas and radiation into space. These outbursts can be deadly: if the first moon-landing mission had encountered one, the intense radiation could have been fatal to the astronauts. And when eruptions reach the magnetic field that surrounds the Earth, the contact can create geomagnetic storms that disrupt cell phone service, damage satellites and knock out power grids.

NASA is eager to know when an eruption is coming and when what looks like the start of an outburst is just a false alarm. Knowing the difference could affect the timing of future space missions such as journeys to Mars, and show when steps to protect satellites, power systems and other equipment need to be taken.

This solar flare occurred at the peak of the solar cycle in October 2014 with no observed eruptions. PPPL researchers say this is a promising candidate for studying the effect of guide magnetic fields.
Credit: NASA

At the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), researchers led by physicist Clayton Myers have identified a mechanism that may halt eruptions before they leave the sun. The finding, reported in the December 24-31 issue of Nature magazine, provides a potentially important way to distinguish the start of explosions from buildups that will fail. This work was supported by the DOE office of Science.

The violent eruptions, called "coronal mass ejections," stem from a sudden release of magnetic energy that is stored in the sun's corona, the outermost layer of the star. This energy is often found in what are called "magnetic flux ropes," massive arched structures that can twist and turn like earthly twine. When these long-lived structures twist and destabilize, they can either erupt out into the solar system or fail and collapse back toward the sun.

The researchers found in laboratory experiments that such failures occur when the guide magnetic field -- a force that runs along the flux rope -- is strong enough to keep the rope from twisting and destabilizing. Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic force that halts the eruptions. PPPL has discovered the importance of this force, called the "toroidal field tension force," which is missing from existing models of solar eruptions.

The researchers discovered this importance using the Laboratory's Magnetic Reconnection Experiment (MRX), the world's leading device for studying how magnetic fields in plasma converge and violently snap apart. The scientists modified the device to produce both a flux rope, which stores a significant amount of energy that seeks to drive the rope outward, and a "potential magnetic field" like the ones that enclose the rope in the solar corona.

This potential magnetic field is composed of magnetic "strapping" and "guide" fields, each of which provides restraining forces. Eruptions burst forth when the restraining forces in the strapping field become too weak to hold the rope down, creating what is called a "torus instability" that shoots plasma into space. The guide field, which reduces the twist in the flux rope, had long been thought to be of secondary importance.

But the researchers found that the guide field can play an important role in halting eruptions. When the flux rope starts to move outward in the presence of a sufficiently powerful guide field, the plasma undergoes an internal reconfiguration -- or "self-organization" -- that causes the eruption to lose energy and collapse. "The presence of a substantial guide field should therefore indicate a reduced probability of eruption," said Myers.

Solar physicists should thus be on the lookout for guide fields, which can be found in relatively simple reconstructions of the sun's potential magnetic field. One promising candidate for study is the largest active region in the peak solar cycle that took place in October 2014, which produced many large flares but no observed eruptions. Preliminary analysis of this region shows that a number of these flares were associated with failed eruptions that could have been caused by the mechanism the MRX experiments found.

Contacts and sources:
 John Greenwald
U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL)


A Clue to Generate Electric Current without Energy Consumption at Room Temperature

A group of researchers in Japan and China identified the requirements for the development of new types of extremely low power consumption electric devices by studying Cr-doped (Sb, Bi)2Te3 thin films. This study has been reported in Nature Communications.

At extremely low temperatures, an electric current flows around the edge of the film without energy loss, and under no external magnetic field. This attractive phenomenon is due to the material's ferromagnetic properties; however, so far, it has been unclear how the material gains this property. For the first time, researchers have revealed the mechanism by which this occurs. "Hopefully, this achievement will lead to the creation of novel materials that operate at room temperature in the future," said Akio Kimura, a professor at Hiroshima University and a member of the research group.

Sb atoms and Te atoms serve as the glue to fix the N-S orientations of Cr atoms in Cr-doped (Sb, Bi)2Te3. This makes the material ferromagnetic.

Credit: Hiroshima University

Their achievement can be traced back to the discovery of the quantum Hall effect in the 1980's, where an electric current flows along an edge (or interface) without energy loss. However, this requires both a large external magnetic field and an extremely low temperature. This is why practical applications have not been possible. Researchers believed that this problem could be overcome with new materials called topological insulators that have ferromagnetic properties such as those found in Cr-doped (Sb, Bi)2Te3.

A topological insulator, predicted in 2005 and first observed in 2007, is neither a metal nor an insulator, and has exotic properties. For example, an electric current is generated only at the surface or the edge of the material, while no electric current is generated inside it. It looks as if only the surface or the edge of the material has metallic properties, while on the inside it is an insulator.

At extremely low temperatures, a thin film made of Cr-doped (Sb, Bi)2Te3 shows a peculiar phenomenon. As the film itself is ferromagnetic, an electric current is spontaneously generated without an external magnetic field and electric current flows only around the edge of the film without energy loss. However, it was previously unknown as to why Cr-doped (Sb, Bi)2Te3 had such ferromagnetic properties that allowed it to generate electric current.

"That's why we selected the material as the object of our study," said Professor Kimura.

Because Cr is a magnetic element, a Cr atom is equivalent to an atomic-sized magnet. The N-S orientations of such atomic-sized magnets tend to be aligned in parallel by the interactions between the Cr atoms. When the N-S orientations of Cr atoms in Cr-doped (Sb, Bi)2Te3 are aligned in parallel, the material exhibits ferromagnetism. However, the interatomic distances between the Cr atoms in the material are, in fact, too long to interact sufficiently to make the material ferromagnetic.

The group found that the non-magnetic element atoms, such as the Sb and Te atoms, mediate the magnetic interactions between Cr atoms and serve as the glue to fix the N-S orientations of Cr atoms that face one direction. In addition, the group expects that its finding will provide a way to increase the critical temperature for relevant device applications.

The experiments for this research were mainly conducted at SPring-8. "We would not have achieved perfect results without the facilities and the staff there. They devoted themselves to detecting the extremely subtle magnetism that the atoms of non-magnetic elements exhibit with extremely high precision. I greatly appreciate their efforts," Kimura said.

Contacts and sources:
Norifumi Miyokawa
Hiroshima University

Citation: Ye, M. et al. Carrier-mediated ferromagnetism in the magnetic topological insulator Cr-doped (Sb,Bi)2Te3. Nat. Commun. 6:8913 doi: 10.1038/ncomms9913 (2015). http://www.nature.com/ncomms/2015/151119/ncomms9913/full/ncomms9913.html

Thursday, December 24, 2015

'Forbidden' Substances on Super-Earths

Scientists say 'forbidden' substances may increase heat transfer rates and strengthen magnetic fields on super-Earths.

Using mathematical models, scientists have 'looked' into the interior of super-Earths and discovered that they may contain compounds that are forbidden by the classical rules of chemistry -- these substances may increase the heat transfer rate and strengthen the magnetic field on these planets. The findings have been presented in a paper published in the journal Scientific Reports.

Illustration of the inferred size of the super-Earth COROT-7b (center) in comparison with Earth and Neptune

Credit: NASA
The authors of the paper are a group of researchers from MIPT led by Artem Oganov, a professor of the Skolkovo Institute of Science and Technology and the head of the MIPT Laboratory of Computer Design. In a previous study, Oganov and his colleagues used an algorithm created by Oganov called USPEX to identify new compounds of sodium and chlorine, as well as other exotic substances.

In their latest paper, the researchers attempted to find out which compounds may be formed by silicon, oxygen, and magnesium at high pressures. These particular elements were not chosen by chance.

"Earth-like planets consist of a thin silicate crust, a silicate-oxide mantle -- which makes up approximately 7/8 of the Earth's volume and consists more than 90% of silicates and magnesium oxide -- and an iron core. We can say that magnesium, oxygen, and silicon form the basis of chemistry on Earth and on Earth-like planets," says Oganov.

Using the USPEX algorithm, the researchers investigated various structural compositions of Mg-Si-O that may occur at pressures ranging from 5 to 30 million atmospheres. Such pressures may exist in the interior of super-Earths -- planets with a solid surface mass several times greater than the mass of the Earth. There are no planets like this in the solar system, but astronomers know of planets orbiting other stars that are not as heavy as the gas giants, but are considerably heavier than the Earth. They are called super-Earths. These planets include the recently discovered Gliese 832c, which is five times heavier than the Earth, or the mega-Earth Kepler-10c, which is 17 times heavier than the Earth.

The results of the computer modelling show that the interior of these planets may contain the "exotic" compounds MgSi3O12 and MgSiO6. They have many more oxygen atoms than the MgSiO3 on Earth.

Sizes of Kepler Planet Candidates - based on 2,740 candidates orbiting 2,036 stars as of November 4, 2013 
File:Size of Kepler Planet Candidates.jpg
Credit: NASA

In addition, MgSi3O12 is a metal oxide and a conductor, whereas other substances consisting of Mg-Si-O atoms are dielectrics or semiconductors. "Their properties are very different to normal compounds of magnesium, oxygen, and silicon - many of them are metals or semiconductors. This is important for generating magnetic fields on these planets. As magnetic fields produce electrical currents in the interiors of a planet, high conductivity could mean a significantly more powerful magnetic field," explains Oganov.

A more powerful magnetic field means more powerful protection from cosmic radiation, and consequently more favourable conditions for living organisms. The researchers also predicted new magnesium and silicon oxides that do not fit in with the rules of classical chemistry -- SiO, SiO3, and MgO3, in addition to the oxides MgO2 and Mg3O2 previously predicted by Oganov at lower pressures.

The computer model also enabled the researchers to determine the decomposition reactions that MgSiO3 undergoes at the ultra-high pressures on super-Earths -- post-perovskite.

"This affects the boundaries of the layers in the mantle and their dynamics. For example, an exothermic phase change speeds up the convection of the mantle and the heat transfer within the planet, and an endothermic phase change slows them down. This means that the speed of motion of lithospheric plates on the planet may be higher," says Oganov.

Convection, which determines plate tectonics and the mixing of the mantle, can either be faster (speeding up the mixing of the mantle and heat transfer) or slower. In endothermic change, a possible scenario could be the disintegration of a planet into several independently convecting layers, he noted.

The fact that the Earth's continents are in constant motion, "floating" on the surface of the mantle, is what gives volcanism and a breathable atmosphere. If continental drift were to stop, it could have disastrous consequences for the climate.

Contacts and sources:
Valerii Roizen
Moscow Institute of Physics and Technology  

Wednesday, December 23, 2015

Volcanic Event Caused Ice Age during Jurassic Period, New Research Suggests

Pioneering new research has shed new light on the causes behind an ‘ice-age’ that took place on Earth around 170 million years ago.

An international team of experts, including researchers from the Camborne School of Mines, have found evidence of a large and abrupt cooling of the Earth’s temperature during the Jurassic Period, which lasted millions of years.

Four fairly regular glacial-interglacial cycles occurred during the past 450,000 years. The shorter interglacial cycles (10,000 to 30,000 years) were about as warm as present and alternated with much longer (70,000 to 90,000 years) glacial cycles substantially colder than present. Notice the longer time with jagged cooling events dropping into the colder glacials followed by the faster abrupt temperature swings to the warmer interglacials. This graph combines several ice-core records from Antarctica and is modified from several sources including Evidence for Warmer Interglacials in East Antarctic Ice Cores, 2009, L.C. Sime and others. Note the shorter time scale of 450,000 years compared to the previous figure, as well as the colder temperatures, which are latitude-specific (e.g., Antartica, Alaska, Greenland) temperature changes inferred from the Antarctic ice cores (and not global averages).

Credit: Utah Geological Survey

The scientists found that the cooling coincided with a large-scale volcanic event – called the North Sea Dome – which restricted the flow of ocean water and the associated heat that it carried from the equator towards the North Pole region.

The team suggest that it is this volcanic event, preventing the ocean flow, rather than a change in CO2 in the atmosphere (which causes today’s climate change), that led to an extended Ice age in a period more synonymous with very warm conditions.

The research appears in respected scientific journal, Nature Communications, on Friday, December 11 2015.

Geology experts Professor Stephen Hesselbo and Dr Clemens Ullmann, both from the Camborne School of Mines, based at Exeter’s Penryn Campus in Cornwall, took part in the study.

Credit: Utah Geological Survey

Professor Hesselbo said: “We tend to think of the Jurassic as a warm ‘greenhouse’ world where high temperatures were governed by high atmospheric carbon dioxide contents. This new study suggests that re-organization of oceanic current patterns may also have triggered large scale climate changes.”

Rather than the seven continents that cover Earth’s surface today, during the Jurassic Period there was one single ‘supercontinent’, called Pangaea. This supercontinent had a broad seaway across it that connected a north polar sea to a warm equatorial ocean, called Tethys.

The team of scientists spent 10 years constructing a record of seawater temperature change using fossil mollusc shells. They found that during the same period that the North Sea Dome event occurred, the Earth experienced a significant and fast cooling in temperature. The team have hypothesized that this volcanic event restricted the poleward flow of ocean water and associated heat, flipping the northern hemisphere from a very warm climate to a cold climate state. The evidence indicates that this cold period lasted many millions of years, until the North Sea Dome subsided.

Professor Hesselbo added: “Although we have known about the occurrence of cold periods during greenhouse times for a while, their origins have remained mysterious. This work suggests a mechanism at play that may also have been important for driving other climate change events in the Jurassic and at other times in Earth history.”

The research, called "Jurassic climate mode governed by ocean gateway” is published online by Nature Communications.

Contacts and sources:
Duncan Sandes
University of Exeter

Crows Caught on Camera Fashioning Special Hook Tools

Scientists have been given an extraordinary glimpse into how wild New Caledonian crows make and use ‘hooked stick tools’ to hunt for insect prey.

Dr Jolyon Troscianko, from the University of Exeter, and Dr Christian Rutz, from the University of St Andrews, have captured first video recordings documenting how these tropical corvids fashion these particularly complex tools in the wild.

The pair developed tiny video ‘spy-cameras’ which were attached to the crows, to observe their natural foraging behaviour.

They discovered two instances of hooked stick tool making on the footage they recorded, with one crow spending a minute making the tool, before using it to probe for food in tree crevices and even in leaf litter on the ground.
The findings are reported in the Royal Society’s journal Biology Letters on Wednesday, December 23.

Dr Troscianko is a Postdoctoral Research Fellow in Exeter’s Biosciences Department based at the Penryn Campus in Cornwall, who worked on the project while at the University of Birmingham.

He said: “While fieldworkers had previously obtained brief glimpses of hooked stick tool manufacture, the only video footage to date came from baited feeding sites, where tool raw materials and probing tasks had been provided to crows by scientists. We were keen to get close-up video of birds making these tools under completely natural conditions.”

“New Caledonian crows are notoriously difficult to observe, not just because of the challenging terrain of their tropical habitats, but also because they can be quite sensitive to disturbance. By documenting their fascinating behaviour with this new camera technology, we obtained valuable insights into the importance of tools in their daily search for food.”

To obtain a ‘crow’s-eye view’ of this elusive behaviour, the two researchers developed video cameras that are attached to the crows’ tail feathers. The cameras are about the weight of a British 2-pound coin, and a tiny integrated radio beacon let the scientists recover the devices once they had safely detached after a few days. Dr Christian Rutz, Reader in the School of Biology in St Andrews, explains: “These cameras store video footage on a micro-SD card, using technology similar to that found in people’s smart phones. This produced video recordings of stunning quality.”

The team deployed 19 cameras on crows at their chosen dry forest study site, where in hundreds of hours of fieldwork, despite two brief glimpses with binoculars, they had never managed to film crows manufacturing hooked stick tools.

The team were excited to record two instances of this behaviour on footage recovered from ten birds in their latest study.

Troscianko noted: “The behaviour is easy to miss – the first time I watched the footage, I didn’t see anything particularly interesting. Only when I went through it again frame-by-frame, I discovered this fascinating behaviour. Not once, but twice!”

“In one scene, a crow drops its tool, and then recovers it from the ground shortly afterwards, suggesting they value their tools and don’t simply discard them after a single use.” According to Rutz, this observation agrees with recent aviary experiments conducted by his group: “Crows really hate losing their tools, and will use all sorts of tricks to keep them safe. We even observed them storing tools temporarily in tree holes, the same way a human would put a treasured pen into a pen holder.”

New Caledonian crows (Corvus moneduloides) are found on the South Pacific island of New Caledonia.

They can use their bills to whittle twigs and leaves into bug-grabbing implements; some believe their tool-use is so advanced that it rivals that of some primates.

Contacts and sources:
Dr Jolyon Troscianko
University of Exeter

'Virtual Fossil' Reveals Common Ancestor of Humans Last and Neanderthals

We know we share a common ancestor with Neanderthals, the extinct species that were our closest prehistoric relatives. But what this ancient ancestral population looked like remains a mystery, as fossils from the Middle Pleistocene period, during which the lineage split, are extremely scarce and fragmentary.

This is the 'virtual fossil' of last common ancestor of humans and Neanderthals as hypothesized in the new study.

Credit: Dr. Aurélien Mounier

Now, researchers have applied digital 'morphometrics' and statistical algorithms to cranial fossils from across the evolutionary story of both species, and recreated in 3D the skull of the last common ancestor of Homo sapiens and Neanderthals for the first time.

New digital techniques have allowed researchers to predict structural evolution of the skull in the lineage of Homo sapiens and Neanderthals, in an effort to fill in blanks in the fossil record, and provide the first 3D rendering of their last common ancestor. Here, lead researcher Dr. Aurélien Mounier from Cambridge's Leverhulme Centre for Human Evolutionary Studies describes part of the research that led to this 'virtual fossil'.

The 'virtual fossil' has been simulated by plotting a total of 797 'landmarks' on the cranium of fossilised skulls stretching over almost two million years of Homo history -- including a 1.6 million-year-old Homo erectus fossil, Neanderthal crania found in Europe and even 19th century skulls from the Duckworth collection in Cambridge.

The landmarks on these samples provided an evolutionary framework from which researchers could predict a timeline for the skull structure, or 'morphology', of our ancient ancestors. They then fed a digitally-scanned modern skull into the timeline, warping the skull to fit the landmarks as they shifted through history.

This allowed researchers to work out how the morphology of both species may have converged in the last common ancestor's skull during the Middle Pleistocene -- an era dating from approximately 800 to 100 thousand years ago.

The team generated three possible ancestral skull shapes that corresponded to three different predicted split times between the two lineages. They digitally rendered complete skulls and then compared them to the few original fossils and bone fragments of the Pleistocene age.

This enabled the researchers to narrow down which virtual skull was the best fit for the ancestor we share with Neanderthals, and which timeframe was most likely for that last common ancestor to have existed.

Previous estimates based on ancient DNA have predicted the last common ancestor lived around 400,000 years ago. However, results from the 'virtual fossil' show the ancestral skull morphology closest to fossil fragments from the Middle Pleistocene suggests a lineage split of around 700,000 years ago, and that -- while this ancestral population was also present across Eurasia -- the last common ancestor most likely originated in Africa.

The results of the study are published in the Journal of Human Evolution.

"We know we share a common ancestor with Neanderthals, but what did it look like? And how do we know the rare fragments of fossil we find are truly from this past ancestral population? Many controversies in human evolution arise from these uncertainties," said the study's lead author Dr Aurélien Mounier, a researcher at Cambridge University's Leverhulme Centre for Human Evolutionary Studies (LCHES).

Top: Modern human skull from 19th century South Africa. Now part of the Duckworth Collection at the Leverhulme Centre for Human Evolutionary Studies, University of Cambridge. Middle: 'Virtual fossil' of Last Common Ancestor Bottom: Neanderthal skull found in La Ferrassie, France, and dating from 53 to 66 thousand years ago. Now curated in the Musée de l'Homme in Paris.

Credit: Dr. Aurélien Mounier

"We wanted to try an innovative solution to deal with the imperfections of the fossil record: a combination of 3D digital methods and statistical estimation techniques. This allowed us to predict mathematically and then recreate virtually skull fossils of the last common ancestor of modern humans and Neanderthals, using a simple and consensual 'tree of life' for the genusHomo," he said.

The virtual 3D ancestral skull bears early hallmarks of both species. For example, it shows the initial budding of what in Neanderthals would become the 'occipital bun': the prominent bulge at the back of the skull that contributed to elongated shape of a Neanderthal head.

However, the face of the virtual ancestor shows hints of the strong indention that modern humans have under the cheekbones, contributing to our more delicate facial features. In Neanderthals, this area -- the maxillia -- is 'pneumatized', meaning it was thicker bone due to more air pockets, so that the face of a Neanderthal would have protruded.

Research from New York University published last week showed that bone deposits continued to build on the faces of Neanderthal children during the first years of their life.

The heavy, thickset brow of the virtual ancestor is characteristic of the hominin lineage, very similar to early Homo as well as Neanderthal, but lost in modern humans. Mounier says the virtual fossil is more reminiscent of Neanderthals overall, but that this is unsurprising as taking the timeline as a whole it is Homo sapiens who deviate from the ancestral trajectory in terms of skull structure.

"The possibility of a higher rate of morphological change in the modern human lineage suggested by our results would be consistent with periods of major demographic change and genetic drift, which is part of the history of a species that went from being a small population in Africa to more than seven billion people today," said co-author Dr Marta Mirazón Lahr, also from Cambridge's LCHES.

The population of last common ancestors was probably part of the species Homo heidelbergensis in its broadest sense, says Mounier. This was a species of Homo that lived in Africa, Europe and western Asia between 700 and 300 thousand years ago.

For their next project, Mounier and colleagues have started working on a model of the last common ancestor of Homo and chimpanzees. "Our models are not the exact truth, but in the absence of fossils these new methods can be used to test hypotheses for any palaeontological question, whether it is horses or dinosaurs," he said.

Contacts and sources:
Fred Lewsey
University of Cambridge

Engineers Demo First Processor That Uses Light For Ultrafast Communications

Engineers have successfully married electrons and photons within a single-chip microprocessor, a landmark development that opens the door to ultrafast, low-power data crunching.

The researchers packed two processor cores with more than 70 million transistors and 850 photonic components onto a 3-by-6-millimeter chip. They fabricated the microprocessor in a foundry that mass-produces high-performance computer chips, proving that their design can be easily and quickly scaled up for commercial production.

This packaged electronic-photonic processor microchip under illumination reveals the chip's primary features. The light rays emanating from the chip are drawn to show that the processor talks to the outside world using light.
Image by Glenn J. Asakawa, University of Colorado, 

The new chip, described in a paper to be published Dec. 24 in the print issue of the journal Nature, marks the next step in the evolution of fiber optic communication technology by integrating into a microprocessor the photonic interconnects, or inputs and outputs (I/O), needed to talk to other chips.

"This is a milestone. It's the first processor that can use light to communicate with the external world," said Vladimir Stojanović, an associate professor of electrical engineering and computer sciences at the University of California, Berkeley, who led the development of the chip. "No other processor has the photonic I/O in the chip."

Stojanović and fellow UC Berkeley professor Krste Asanović teamed up with Rajeev Ram at the Massachusetts Institute of Technology and Milos Popović at the University of Colorado, Boulder, to develop the new microprocessor.

"This is the first time we've put a system together at such scale, and have it actually do something useful, like run a program," said Asanović, who helped develop the free and open architecture called RISC-V (reduced instruction set computer), used by the processor.

Greater bandwidth with less power

Compared with electrical wires, fiber optics support greater bandwidth, carrying more data at higher speeds over greater distances with less energy. While advances in optical communication technology have dramatically improved data transfers between computers, bringing photonics into the computer chips themselves had been difficult.

This is a raw, high-resolution photo of the chip, with all chip electrical and photonic features clearly visible. Photo taken under microscope at the UC Berkeley Marvell Nanofabrication Laboratory.
Image by Chen Sun, sunchen@eecs.berkeley.edu, with help from Sangyoon Han

That's because no one until now had figured out how to integrate photonic devices into the same complex and expensive fabrication processes used to produce computer chips without changing the process itself. Doing so is key since it does not further increase the cost of the manufacturing or risk failure of the fabricated transistors.

The researchers verified the functionality of the chip with the photonic interconnects by using it to run various computer programs, requiring it to send and receive instructions and data to and from memory. They showed that the chip had a bandwidth density of 300 gigabits per second per square millimeter, about 10 to 50 times greater than packaged electrical-only microprocessors currently on the market.

The photonic I/O on the chip is also energy-efficient, using only 1.3 picojoules per bit, equivalent to consuming 1.3 watts of power to transmit a terabit of data per second. In the experiments, the data was sent to a receiver 10 meters away and back.

The electronic-photonic processor chip communicates to the outside world directly using light. This photo shows the chip naturally illuminated by red and green bands of light.

Image by Glenn J. Asakawa, University of Colorado,

"The advantage with optical is that with the same amount of power, you can go a few centimeters, a few meters or a few kilometers," said study co-lead author Chen Sun, a recent UC Berkeley Ph.D. graduate from Stojanović's lab at the Berkeley Wireless Research Center. "For high-speed electrical links, 1 meter is about the limit before you need repeaters to regenerate the electrical signal, and that quickly increases the amount of power needed. For an electrical signal to travel 1 kilometer, you'd need thousands of picojoules for each bit."

The achievement opens the door to a new era of bandwidth-hungry applications. One near-term application for this technology is to make data centers more green. According to the Natural Resources Defense Council, data centers consumed about 91 billion kilowatt-hours of electricity in 2013, about 2 percent of the total electricity consumed in the United States, and the appetite for power is growing exponentially.

This research has already spun off two startups this year with applications in data centers in mind. SiFive is commercializing the RISC-V processors, while Ayar Labs is focusing on photonic interconnects. Earlier this year, Ayar Labs - under its previous company name of OptiBit - was awarded the MIT Clean Energy Prize. Ayar Labs is getting further traction through the CITRIS Foundry startup incubator at UC Berkeley.

The advance is timely, coming as world leaders emerge from the COP21 United Nations climate talks with new pledges to limit global warming.

Further down the road, this research could be used in applications such as LIDAR, the light radar technology used to guide self-driving vehicles and the eyes of a robot; brain ultrasound imaging; and new environmental biosensors.

'Fiat lux' on a chip

The researchers came up with a number of key innovations to harness the power of light within the chip.

Each of the key photonic I/O components - such as a ring modulator, photodetector and a vertical grating coupler - serves to control and guide the light waves on the chip, but the design had to conform to the constraints of a process originally thought to be hostile to photonic components. To enable light to move through the chip with minimal loss, for instance, the researchers used the silicon body of the transistor as a waveguide for the light. They did this by using available masks in the fabrication process to manipulate doping, the process used to form different parts of transistors.

After getting the light onto the chip, the researchers needed to find a way to control it so that it can carry bits of data. They designed a silicon ring with p-n doped junction spokes next to the silicon waveguide to enable fast and low-energy modulation of light.

Using the silicon-germanium parts of a modern transistor - an existing part of the semiconductor manufacturing process - to build a photodetector took advantage of germanium's ability to absorb light and convert it into electricity.

A vertical grating coupler that leverages existing poly-silicon and silicon layers in innovative ways was used to connect the chip to the external world, directing the light in the waveguide up and off the chip. The researchers integrated electronic components tightly with these photonic devices to enable stable operation in a hostile chip environment.

The authors emphasized that these adaptations all worked within the parameters of existing microprocessor manufacturing systems, and that it will not be difficult to optimize the components to further improve their chip's performance.

Contacts and sources:
Sarah Yang
University of California, Berkeley

New Research Shows Same Growth Rate for Farming, Non-Farming Prehistoric People

Prehistoric human populations of hunter-gatherers in a region of North America grew at the same rate as farming societies in Europe, according to a new radiocarbon analysis involving researchers from the University of Wyoming and the Harvard-Smithsonian Center for Astrophysics.

The findings challenge the commonly held view that the advent of agriculture 10,000-12,000 years ago accelerated human population growth. The research is reported this week in the Proceedings of the National Academy of Sciences, a major scientific journal.

University of Wyoming students excavate a prehistoric rock shelter in the Big Horn Mountains of northern Wyoming during the summer of 2015. Hearths excavated at sites such as this provided many of the radiocarbon dates for new research showing that hunter-gatherers in the region that is now Wyoming and Colorado grew at the same rate as farming societies in Europe.

Credit: UW Photo

"Our analysis shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies," says Robert Kelly, University of Wyoming professor of anthropology and co-author of the PNAS paper. "The same rate of growth measured for populations dwelling in a range of environments, and practicing a variety of subsistence strategies, suggests that the global climate and/or other biological factors -- not adaptability to local environment or subsistence practices -- regulated long-term growth of the human population for most of the past 12,000 years."

The lead author of the paper is Jabran Zahid of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Erick Robinson, post-doctoral researcher in the University of Wyoming's Department of Anthropology, also participated in the research.

While the world's human population currently grows at an average rate of 1 percent per year, earlier research has shown that long-term growth of the prehistoric human population beginning at the end of the Ice Age was just 0.04 percent annually. That held true until about 200 years ago, when a number of factors led to higher growth rates.

For their research, the UW and Harvard-Smithsonian scientists analyzed radiocarbon dates from Wyoming and Colorado that were recovered predominantly from charcoal hearths, which provide a direct record of prehistoric human activity.

For humans in the region that is now Wyoming and Colorado between 6,000 and 13,000 years ago -- people who foraged on animals and plants to survive -- the analysis showed a long-term annual growth rate of 0.041 percent, consistent with growth that took place throughout North America. During that same period, European societies were farming or transitioning to agriculture, yet the growth rate there was essentially the same.

"The introduction of agriculture cannot be directly linked to an increase in the long-term annual rate of population growth," the researchers wrote.

In general, similar rates of growth -- around 0.04 percent -- were measured for prehistoric human populations across a broad range of geographies and climates, the scientists say. "This similarity in growth rates suggests that prehistoric humans effectively adapted to their surroundings such that region-specific environmental pressure was not the primary mechanism regulating long-term population growth."

Instead, the factors that controlled long-term population growth during that period likely were global in nature, such as climate change or biological factors affecting all humans, such as disease.

While concluding that population growth held steady overall at about 0.04 percent annually for thousands of years, the paper acknowledges that there were short-term fluctuations in human growth rates in certain regions lasting from a few hundred to 1,000 years. The authors suggest further statistical analysis of radiocarbon dates of human remains to study the mechanisms regulating population growth.

Contacts and sources:
Erick Robinson
University of Wyoming 

Burgess Shale Fossil Site Gives Up Oldest Evidence of Brood Care

508 million-year-old Waptia found to have eggs containing preserved embryos.

Long before kangaroos carried their joeys in their pouches and honey bees nurtured their young in hives, there was the 508-million-year-old Waptia. Little is known about the shrimp-like creature first discovered in the renowned Canadian Burgess Shale fossil deposit a century ago, but recent analysis by scientists from the University of Toronto, Royal Ontario Museum, and Centre national de la recherche scientifique has uncovered eggs with embryos preserved within the body of the animal. It is the oldest example of brood care in the fossil record.

Waptia fieldensis (middle Cambrian) is seen with overlay of scanning electron microscope image highlighting location of eggs.

Credit: Copyright: Royal Ontario Museum

"As the oldest direct evidence of a creature caring for its offspring, the discovery adds another piece to our understanding of brood care practices during the Cambrian Explosion, a period of rapid evolutionary development when most major animal groups appear in the fossil record," said Jean-Bernard Caron, curator of invertebrate palaeontology at the Royal Ontario Museum and associate professor in the Departments of Earth Sciences and Ecology & Evolutionary Biology at the University of Toronto.

Caron, along with Jean Vannier at the Centre national de la recherche scientifique in Lyon, France, describe the findings in a study published December 17 in Current Biology.

Waptia fieldensis is an early arthropod, belonging to a group of animals that includes lobsters and crayfish. It had a two-part structure covering the front segment of its body near the head, known as a bivalved carapace. Caron and Vannier believe the carapace played a fundamental role in how the creature practised brood care.

Illustration of Waptia fieldensis (middle Cambrian) shows eggs brooded between the inner surface of the carapace and the body.

Illustration: Danielle Dufault, Copyright: Royal Ontario Museum

"Clusters of egg-shaped objects are evident in five of the many specimens we observed, all located on the underside of the carapace and alongside the anterior third of the body," said Caron.

The clusters are grouped in a single layer on each side of the body with no or limited overlapping among the eggs. In some specimens, eggs are equidistant from each other, while in others, some are are closer together, probably reflecting variations in the angle of burial and movement during burial. The maximum number of eggs preserved per per individuals probably reached 24.

"This creature is expanding our perspective on the diversification of brood care in early arthropods," said Vannier, the co-author of the study. "The relatively large size of the eggs and the small number of them, contrasts with the high number of small eggs found previously in another bivalved arthropod known as Kunmingella douvillei. And though that creature predates Waptia by about seven million years, none of its eggs contained embryos."

Kunmingella douvillei also presented a different method of carrying its young, as its eggs were found lower on the body and attached to its appendages.

The presence of these two different parental strategies suggests an independent and rapid evolution of a variety of methods of parental care of offspring. Together with previously described brooded eggs in ostracods from the Upper Ordovician period 450 million years ago, the discovery supports the theory that the presence of a bivalved carapace played a key role in the early evolution of brood care in arthropods.


The research appears in a study titled "Waptia and the diversification of brood care in early arthropods" published in Current Biology. It was supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant to Jean-Bernard Caron, an ANR (Agence Nationale de la Recherche) Grant to Jean Vannier, and the University of Lyon.

Contacts and sources: 
Sean Bettam
 University of Toronto

Study Finds People Transformed How Species Associated After 300 Million Years

A study published today finds a surprising and very recent shift away from the steady relationship among species that prevailed for more than 300 million years.

The study, published in the journal Nature, offers the first long-term view of how species associated with each other for half of the existence of multicellular life on Earth, says co-author Donald Waller, a professor of botany at the University of Wisconsin-Madison. "We did not expect, or predict, that we would see continuity in the fossil record for such a long time. The fraction of plant and animal species that were positively associated with each other was mostly unchanged for 300 million years. Then that fraction sharply declined over the last 6,000 years," says Waller, a plant ecologist.

Species are 'positively associated' if they are found in the same place and time.

Starting about 6,000 years ago, negatively associated species were preponderant, meaning plants and animals are seldom found in the same place and time, a sign that longstanding relationships have been disturbed.

A Southern Wisconsin woods being strangled by buckthorn, a tree that was sold in nurseries and started to invade the region over the past half-century. As buckthorn excludes all other vegetation, this site that was formerly dominated by oak shows some of the ways that human activity has changed the relationship among species, as described by UW-Madison botany professor Donald Waller and co-authors in a new study in the journal Nature.

Credit: David J Tenenbaum, University of Wisconsin-Madison

In assessing the cause of the dramatic change they found, the researchers first eliminated five possible sources of error. "Senior author Nicholas Gotelli, of the University of Vermont, developed careful methods to guard against false positive results," Waller says. "With a result as unexpected as this, we wanted to be very careful to make sure that the pattern was real and not an artifact of the methods we were using, or the particular datasets we looked at."

The most likely cause for the shift, the researchers state, was rapid human population growth, with ensuing effects from plant and animal agriculture. "The conclusion we reluctantly came to is that there have been systematic changes around the world in ecological conditions, prompting changes in the pattern of species coexistence," Waller says. "This is an aspect of global change that has never been noticed, or documented before."

Although the researchers do not have direct evidence for the cause of any particular species assemblage, patterns of species living together form an intricate ecological web involving predation, symbiosis, disease, nutrition, habitat and evolution, Waller points out.

The situation on continents, often recognized as having more stable species assemblages, is now starting to resemble the situation on islands, Waller says. "In general, island habitats are fragmented, and species are vulnerable and declining. Islands are models for conservation biology because they indicate what happens in the end game" as species go extinct and biodiversity declines.

The study, supported by the National Science Foundation, is more evidence that humans have substantially changed the planet, Waller adds. "The Paris accord on climate signed last week reflects a global recognition that humans have fundamentally changed our planet's climate. Now we present evidence that humans are changing the Earth in another fundamental way: how species are associated with one another. It's fossil evidence that we have entered the 'anthropocene,' a geologic era marked by human dominance of the planet. In fact, the study even provides a way to date the start of the anthropocene."

Contacts and sources: 
Donald Waller
David Tenenbaum
University of Wisconsin-Madison

Chinese Rover Analyzes Moon Rocks: First New 'Ground Truth' In 40 Years

In 2013, Chang'e-3, an unmanned lunar mission, touched down on the northern part of the Imbrium basin, one of the most prominent of the lava-filled impact basins visible from Earth. The rover found volcanic rocks unlike those returned by Apollo and Luna missions, tantalizing clues to the period of lunar volcanism

It was a beautiful landing site, said Bradley L. Jolliff, PhD, the Scott Rudolph Professor of Earth and Planetary Sciences at Washington University in St. Louis, who is a participant in an educational collaboration that helped analyze Chang'e-3 mission data. The lander touched down on a smooth flood basalt plain next to a relatively fresh impact crater (now officially named the Zi Wei crater) that had conveniently excavated bedrock from below the regolith for the Yutu rover to study.

Four views of the Mare Imbrium basin and the Chang'e-3 landing site demonstrate how different the Moon looks to different types of remote sensing, underscoring the need for ground truth to calibrate the orbital observations.

Credit:  NASA/LPI

Since the Apollo program ended, American lunar exploration has been conducted mainly from orbit. But orbital sensors primarily detect the regolith (the ground-up surface layer of fragmented rock) that blankets the Moon, and the regolith is typically mixed and difficult to interpret.

Because Chang'e-3 landed on a comparatively young lava flow, the regolith layer was thin and not mixed with debris from elsewhere. Thus it closely resembled the composition of the underlying volcanic bedrock. This characteristic made the landing site an ideal location to compare in situ analysis with compositional information detected by orbiting satellites.

"We now have 'ground truth' for our remote sensing, a well-characterized sample in a key location," Jolliff said. "We see the same signal from orbit in other places, so we now know that those other places probably have similar basalts."

The basalts at the Chang'e-3 landing site also turned out to be unlike any returned by the Apollo and Luna sample return missions.

"The diversity tells us that the Moon's upper mantle is much less uniform in composition than Earth's," Jolliff said. "And correlating chemistry with age, we can see how the Moon's volcanism changed over time."

Two partnerships were involved in the collection and analysis of this data, published in the journal Nature Communications Dec. 22. Scientists from a number of Chinese institutions involved with the Chang'e-3 mission formed one partnership; the other was a long-standing educational partnership between Shandong University in Weihai, China, and Washington University in St. Louis.

A mineralogical mystery

The Moon, thought to have been created by the collision of a Mars-sized body with the Earth, began as a molten or partially molten body that separated as it cooled into a crust, mantle and core. But the buildup of heat from the decay of radioactive elements in the interior then remelted parts of the mantle, which began to erupt onto the surface some 500 million years after the Moon's formation, pooling in impact craters and basins to form the maria, most of which are on the side of the Moon facing the Earth.

Chang'e-3 landing site is indicated with a white square in this lunar map, a mosaic made with the Lunar Reconnaissance Orbiter's Wide Angle Camera. The landing sites of the Apollo missions are in red.


The American Apollo (1969-1972) and Russian Luna (1970-1976) missions sampled basalts from the period of peak volcanism that occurred between 3 and 4 billion years ago. But the Imbrium basin, where Chang'e-3 landed, contains some of the younger flows -- 3 billion years old or slightly less.

The basalts returned by the Apollo and Luna missions had either a high titanium content or low to very low titanium; intermediate values were missing. But measurements made by an alpha-particle X-ray spectrometer and a near-infrared hyperspectral imager aboard the Yutu rover indicated that the basalts at the Chang'e-3 landing site are intermediate in titanium, as well as rich in iron, said Zongcheng Ling, PhD, associate professor in the School of Space Science and Physics at Shandong University in Weihai, and first author of the paper.

Titanium is especially useful in mapping and understanding volcanism on the Moon because it varies so much in concentration, from less than 1 weight percent TiO2 to over15 percent. This variation reflects significant differences in the mantle source regions that derive from the time when the early magma ocean first solidified.

Minerals crystallize from basaltic magma in a certain order, explained Alian Wang, PhD, research professor in earth and planetary sciences in Arts & Sciences at Washington University. Typically, the first to crystallize are two magnesium- and iron-rich minerals (olivine and pyroxene) that are both a little denser than the magma, and sink down through it, then a mineral (plagioclase feldspar), that is less dense and floats to the surface. This process of separation by crystallization led to the formation of the Moon's mantle and crust as the magma ocean cooled.

The titanium ended up in a mineral called ilmenite (FeTiO3) that typically doesn't crystallize until a very late stage, when perhaps only 5 percent of the original melt remains. When it finally crystallized, the ilmenite-rich material, which is also dense, sank into the mantle, forming areas of Ti enrichment.

"The variable titanium distribution on the lunar surface suggests that the Moon's interior was not homogenized," Jolliff said. "We're still trying to figure out exactly how this happened. Possibly there were big impacts during the magma ocean stage that disrupted the mantle's formation."

Another clue to the Moon's past

The story has another twist that also underscores the importance of checking orbital data against ground truth. The remote sensing data for Chang'e-3's landing site showed that it was rich in olivine as well as titanium.

The Chinese lunar rover, Yutu, photographed by its lander Chang'e-3, after the lander touched down in Mare Imbrium, a giant impact basin that had been filled by successive lava flows.


That doesn't make sense, Wang said, because olivine usually crystallizes early and the titanium-rich ilmenite crystallizes late. Finding a rock that is rich in both is a bit strange.

But Yutu solved this mystery as well. In olivine, silicon is paired with either magnesium or iron but the ratio of those two elements is quite variable in different forms of the mineral. The early-forming olivine would be magnesium rich, while the olivine detected by Yutu has a composition that ranges from intermediate in iron to iron-rich.

"That makes more sense," Jolliff said, "because iron-enriched olivine and ilmenite are more likely to occur together.

"You still have to explain how you get to an olivine-rich and ilmenite-rich rock. One way to do that would be to mix, or hybridize, two different sources," he said.

The scientists infer that late in the magma-ocean crystallization, iron-rich pyroxene and ilmenite, which formed late and at the crust-mantle boundary, might have begun to sink. and early-formed magnesium-rich olivine might have begun to rise. As this occurred, the two minerals might have mixed and hybridized.

"Given these data, that is our interpretation," Jolliff said.

In any case, it is clear that these newly characterized basalts reveal a more diverse Moon than the one that emerged from studies following the Apollo and Luna missions. Remote sensing suggests that there are even younger and even more diverse basalts on the Moon, waiting for future robotic or human explorers to investigate, Jolliff said.

Contacts and sources:
Diana Lutz
Washington University in St. Louis

Tuesday, December 22, 2015

Existing Theory of Auroral Breakup Overthrown

Auroras are dimly present throughout the night in polar regions, but sometimes these lights explode in brightness. Now Japanese scientists have unlocked the mystery behind this spectacle, known as auroral breakup.

A Japanese research team has solved how auroral breakups occur. Hot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the 'surge,' the very bright sparks of light that characterize substorms.

Credit: Yusuke Ebihara/Kyoto University

For years, scientists have contemplated what triggers the formation of auroral substorms and the sudden bursts of brightness. Appearing in the Journal of Geophysical Research, the current study overthrows existing theories about the mechanism behind this phenomenon.

The Kyoto-Kyushu research team has revealed that hot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the "surge", the very bright sparks of light that characterize substorms.

"This isn't like anything that us space physicists had in mind," said study author Yusuke Ebihara of Kyoto University.

Ebihara based the study on a supercomputer simulation program developed by Takashi Tanaka, professor emeritus at Kyushu University.

Auroras originate from plasma from the sun, known as the solar wind. In the 1970s, scientists discovered that when this plasma approaches the Earth together with magnetic fields, it triggers a change in the Earth's magnetic field lines on the dayside, and then on the night side. This information alone couldn't explain how the fluttering lights emerge in the sky, however.

On the left is and aurora oval before the auroral breakup occurs On the right is a supercomputer simulation reveals how auroral breakups develop Hot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the 'surge', the very bright sparks of light that characterize substorms.

Credit: Kyoto University

Scientists had come up with theories for separate parts of the process. Some suggested that acceleration of plasma from the reconnection of magnetic field lines caused auroral breakup. Others argued that the electrical current running near the Earth diverts a part of the electrical current into the ionosphere for some unknown reason, triggering the bright bursts of light. This theory was widely accepted because it offered an explanation for why upward-flowing currents emerged out of our planet. But the pieces of the puzzle didn't quite fit well together.

Tanaka's supercomputer simulation program, on the other hand, offers a logical explanation from start to finish.

"Previous theories tried to explain individual mechanisms like the reconnection of the magnetic field lines and the diversion of electrical currents, but there were contradictions when trying to explain the phenomena in its entirety," said Ebihara. "What we needed all along was to look at the bigger picture."

The current paper builds on earlier work by Ebihara and Tanaka about how the bursts emerge. This explores the succeeding processes, namely how the process expands into a large scale breakup.

The research also has the potential to alleviate hazardous problems associated with auroral breakups that can seriously disrupt satellites and power grids.

Contacts and sources:
Anna Ikarashi
 Kyoto University
Citation:  "Substorm simulation: Formation of westward traveling surge" will appear 21 December 2015 in the Journal of Geophysical Research, with doi: 10.1002/2015JA021697

Monday, December 21, 2015

Twisted Magnetic Fields Give New Insights on Star Formation

Using new images that show unprecedented detail, scientists have found that material rotating around a very young protostar probably has dragged in and twisted magnetic fields from the larger area surrounding the star. The discovery, made with the National Science Foundation's Karl G. Jansky Very Large Array (VLA) radio telescope, has important implications for how dusty disks -- the raw material for planet formation -- grow around young stars.

The scientists studied a young protostar about 750 light-years from Earth in the constellation Perseus. Their observations, made in 2013 and 2014, measured the alignment, or polarization, of radio waves emitted by material, mostly dust, falling into a burgeoning disk orbiting the young star. The polarization information revealed the configuration of magnetic fields in this region near the star.

Magnetic field lines (purple) are twisted as they are dragged inward toward a swirling, dusty disk surrounding a young star in this artist's conception.

Credit: Bill Saxton, NRAO/AUI/NSF.

"The alignment of magnetic fields in this region near young stars is very important to the development of the disks that orbit them. Depending on its alignment, the magnetic field can either hinder the growth of the disk or help funnel material onto the disk, allowing it to grow," said Leslie Looney, of the University of Illinois at Urbana-Champaign.

As material from the envelope of dust and gas surrounding the young star falls inward toward the rotating disk, it is likely to drag magnetic field lines with it. Because of this, the structure of the magnetic field near the star will become different from the field's structure farther away.

"Our VLA observations are showing us this region, where the change in shape of the magnetic field is taking place," said Erin Cox, also of the University of Illinois Urbana-Champaign. The observations, she added, produced the first images at wavelengths of 8 and 10 millimeters to show the polarization near a protostar.

The observations also indicated that millimeter- to centimeter-sized particles are numerous in the disk surrounding the young star. Since the protostar is only about 10,000 years old -- very short in astronomical timescales -- this may mean that such grains form and grow quickly in the environment of a still-forming star.

The star, dubbed NGC1333 IRAS 4A, is one of two young stars forming within a common envelope of dust and gas. The disk around it contains material with a total mass more than twice that of our Sun.

Cox and Looney are part of an international team of astronomers studying the protostar. The scientists are reporting their results in the Astrophysical Journal Letters.

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

Contacts and sources:
Dave Finley
The National Radio Astronomy Observatory 

Giant Planets Carving Paths around Four Young Stars, ALMA Observations Suggest

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest evidence yet that giant planets have recently formed around four young stars. These new worlds, each presumably several times more massive than Jupiter, were inferred by the telltale structures they produced in the disks of gas and dust that surround the stars.

This ALMA image combines a view of the dust around the young star DoAr 44 (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disk. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU). 

Though planets appear remarkably plentiful in our Galaxy, astronomers still don’t fully understand how and under what conditions they form. To help answer these questions, scientists study the structure and composition of the planet-forming disks of dust and gas around young stars. 

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in disks around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these disks.
Credit: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser

Certain disks, called transitional disks, have a surprising absence of dust at their centers, in the region around the star. Two main ideas have been put forward to explain these mysterious cavities. First, the strong stellar winds and intense radiation from the star could have blown away or simply destroyed the encircling gas and dust. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star. Previous observations lacked the sensitivity and resolution to determine the most likely explanation.

With ALMA, however, the team of astronomers, led by Nienke van der Marel of Leiden Observatory, the Netherlands, was able to map the distribution of gas and dust in four of these transitional disks better than ever before.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in disks around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these disks. This schematic diagram shows how the dust (brown) and gas (blue) is distributed around the star, and how a young planet is clearing the central gap. 
Credit: ESO/M. Kornmesser

The new ALMA images confirm that the dust-free zones of these disks are not empty, but instead contain significant amounts of gas. These gas-filled regions, the researchers discovered, also contain cavities that are up to three times smaller than the gaps observed in the dust. Such structures are best explained by the scenario in which newly formed massive planets have cleared the gas as they traveled around their orbits.

“Previous observations already hinted at the presence of gas inside the dust cavities,” explains Nienke van der Marel. “But as ALMA can image the material in the entire disk with much greater sharpness and depth than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disk.”

Remarkably, these observations were conducted utilizing just one tenth of the current resolving power of ALMA, as they were performed while half of the array was still under construction on Chajnantor Plateau in northern Chile. 

This ALMA image combines a view of the dust around the young star HD 135344B (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disk. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU). 

Further studies are now needed to determine whether more transitional disks also point toward this planet-clearing scenario, though ALMA’s observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.

“We can now take these exquisite ALMA data and better understand the step-by-step process of planet formation in these disks of gas and dust,” says team member Sean Andrews with the Harvard-Smithsonian Center for Astrophysics. “I and other astronomers are excited to take an even better look at these regions with the full power of ALMA.”

The formal names of the specific stars studied by ALMA are: SR 21, HD 135344B (SAO206462), DoAr 44, and Oph IRS 48.

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

Potatoes on Mars: Crop Harvested Under Red Planet Conditions Will Set Course for Martian Farming

A team of world-class scientists will grow potatoes under Martian conditions in a bid to save millions of lives.

The experiment, led by the International Potato Center (CIP) and NASA, is a major step towards building a controlled dome on Mars capable of farming the invaluable crop in order to demonstrate that potatoes can be grown in the most inhospitable environments.

The goal is to raise awareness of the incredible resilience of potatoes, and fund further research and farming in devastated areas across the globe where malnutrition and poverty are rife and climbing.

Conserving the genetic resources of potato and sweetpotato has been a major priority of CIP since its founding in 1971. CIP maintains the largest collections of potato (more than 4,000 varieties) and sweetpotato (more than 8,000 varieties) in the world. The genebank holds over 80% of the world's native potato and sweetpotato cultivars and over 80% of the known species of wild potato. It also maintains more than 1,500 accessions of native Andean root and tuber crops (ARTCs). CIP conserves and preserves the genetic diversity of these valuable crops so that future generations can benefit from the amazing benefits of these treasured crops -- much of which is yet to be discovered. By maintaining these collections, CIP conserves this diversity in perpetuity so new discoveries can be made.

Credit: International Potato Center/Memac Ogilvy

"How better to learn about climate change than by growing crops on a planet that died two billion years ago?" said Joel Ranck, CIP Head of Communications. "We need people to understand that if we can grow potatoes in extreme conditions like those on Mars, we can save lives on Earth."

Currently, famine affects 842 million people around the world. Global warming creates poor soil conditions and increases the prevalence of pests and disease which have the combined effect of limiting harvests globally but particularly in vulnerable areas where poverty, malnutrition and food insecurity already exist.

For years, Peru-based global research and development organization, CIP, has been testing the robustness of potatoes in the most unlikely places. Beyond the ability to thrive in such challenging conditions, they are also highly nutritious. An excellent source of vitamin C, iron, and zinc, they contain critical micronutrients missing in vulnerable communities globally. CIP's scientists use research and development innovations to fight malnutrition, lift people out of poverty and increase food security around the world.

The potato's center of diversity is in the Andean region. It was domesticated roughly 3800 years ago along the shores of Lake Titicaca in Peru. Farmers today use the traditional knowledge of their ancestors to grow this Andean treasure. Still the potato has its vulnerabilities, climate change being one of the most severe challenges. In Potato Park in Pisac, Peru near Cusco, farmers use ancient methods and modern research to learn more about how climate change will affect potato as the Earth's temperature increases. 

These Quechua-speaking farmers demonstrate one of several test plots planted one hundred meters apart ascending up the slope of a mountain. They monitor temperature, rainfall, and pests and diseases to see which potato varieties perform best under the conditions at each level of altitude. In general Potato requires a period of cold weather to perform best. Slowly that critical temperature required is moving up the hillside, requiring farmers to cultivate fields at higher and higher elevations as pests and diseases thrive in the warmer conditions at elevations in which they had not previously existed.

Credit: International Potato Center/Memac Ogilvy

Understanding atmospheric changes on the surface of Mars will help build more dynamic and accurate simulation centers on Earth, providing further research for both CIP and NASA, who are looking to pioneer space farming for future manned missions to other planets and moons in our solar system.

"I am excited to put potatoes on Mars and even more so that we can use a simulated Martian terrain so close to the area where potatoes originated." said Julio E. Valdivia-Silva, SETI Researcher Associate of NASA, who is leading the project's science team.

The project is led by Will Rust, Creative Director of Memac Ogilvy Dubai. He conceived the idea while working closely with CIP to spread the word of how the potato could be the answer to global hunger. Will connected the CIP and NASA teams to initiate this project to support life on Mars and to bring direct benefit to smallholder farmers on Earth who deserve more food secure futures as well.

By using soils almost identical to those found on Mars, sourced from the Pampas de La Joya Desert in Peru, the teams will replicate Martian atmospheric conditions in a laboratory and grow potatoes. The increased levels of carbon dioxide will benefit the crop, whose yield is two to four times that of a regular grain crop under normal Earth conditions. The Martian atmosphere is near 95 per cent carbon dioxide.

Potatoes are clonally propagated, meaning that potatoes leftover and chosen from the recent harvest are saved for the next planting season. The potatoes saved are genetically identical to the potatoes planted the season before. This is an important aspect of the potato as a food security crop because if disease free and high quality planting material is used it can be reused in subsequent seasons if cared for properly.

Credit: International Potato Center/Memac Ogilvy

"The extraordinary efforts of the team have set the bar for extraterrestrial farming. The idea of growing food for human colonies in space could be a reality very soon." said Chris McKay, planetary scientist of the NASA Ames research centre.

Melissa Guzman, Astrobiologist at NASA Ames, stated, "The image of students building plant growth payloads and communicating virtually from labs in California, Lima, and Dubai is exciting for the future of planetary exploration and astrobiology.

"We see the science, educational, and humanitarian goals as being intertwined. In the process of working together toward establishing a community on Mars, our students will also be establishing a community on Earth," she added.

Contacts and sources:
Joel Ranck
The International Potato Center

Life Exploded On Earth Following Slow Rise of Oxygen

It took 100 million years for oxygen levels in the oceans and atmosphere to increase to the level that allowed the explosion of animal life on Earth about 600 million years ago, according to a UCL-led study funded by the Natural Environment Research Council.

Fictional Snowball Earth
Credit:  Neethis via Wikimedia Commons

Before now it was not known how quickly Earth’s oceans and atmosphere became oxygenated and if animal life expanded before or after oxygen levels rose. The new study, published today in Nature Communications, shows the increase began significantly earlier than previously thought and occurred in fits and starts spread over a vast period. It is therefore likely that early animal evolution was kick-started by increased amounts of oxygen, rather than a change in animal behaviour leading to oxygenation.

Lead researcher, Dr Philip Pogge von Strandmann (UCL Earth Sciences), said: “We want to find out how the evolution of life links to the evolution of our climate. The question on how strongly life has actively modified Earth’s climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place.”

Researchers from UCL, Birkbeck, Bristol University, University of Washington, University of Leeds, Utah State University and University of Southern Denmark tracked what was happening with oxygen levels globally 770 – 520 million years ago (Ma) using new tracers in rocks across the US, Canada and China.

Samples of rocks that were laid down under the sea at different times were taken from different locations to piece together the global picture of the oxygen levels of Earth’s oceans and atmosphere. By measuring selenium isotopes in the rocks, the team revealed that it took 100 million years for the amount of oxygen in the atmosphere to climb from less than 1% to over 10% of today's current level. This was arguably the most significant oxygenation event in Earth history because it ushered in an age of animal life that continues to this day.

Dr Pogge von Strandmann, said: "We took a new approach by using selenium isotope tracers to analyse marine shales which gave us more information about the gradual changes in oxygen levels than is possible using the more conventional techniques used previously. We were surprised to see how long it took Earth to produce oxygen and our findings dispel theories that it was a quick process caused by a change in animal behaviour."

During the period studied, three big glaciations –the ‘snowball Earth’ Sturtian (~716Ma), and Marinoan (~635Ma) glaciations and the smaller Gaskiers glaciation (~580Ma) - occurred whereby the Earth's land was covered in ice and most of the oceans were frozen from the poles to the tropics. During these periods, temperatures plummeted and rose again, causing glacial melting and an influx of nutrients into the ocean, which researchers think caused oxygen levels to rise deep in the oceans.

Increased nutrients means more ocean plankton, which will bury organic carbon in seafloor sediments when they die. Burying carbon results in oxygen increasing, dramatically changing conditions on Earth. Until now, oxygenation was thought to have occurred after the relatively small Gaskiers glaciation melted. The findings from this study pushes it much earlier, to the Marinoan glaciation, after which animals began to flourish in the improved conditions, leading to the first big expansion of animal life.

Co-author Professor David Catling (University of Washington Earth and Space Sciences), added: “Oxygen was like a slow fuse to the explosion of animal life. Around 635 Ma, enough oxygen probably existed to support tiny sponges. Then, after 580 Ma, strange creatures, as thin as crêpes, lived on a lightly oxygenated seafloor. Fifty million years later, vertebrate ancestors were gliding through oxygen-rich seawater. Tracking how oxygen increased is the first step towards understanding why it took so long. Ultimately, a grasp of geologic controls on oxygen levels can help us understand whether animal-like life might exist or not on Earth-like planets elsewhere.”

Contacts and sources: 
Bex Caygill
University College London

Mammal Diversity Exploded Immediately After Dinosaur Extinction

The diversity of mammals on Earth exploded straight after the dinosaur extinction event, according to University College London (UCL) researchers. New analysis of the fossil record shows that placental mammals, the group that today includes nearly 5000 species including humans, became more varied in anatomy during the Paleocene epoch - the 10 million years immediately following the event.

Senior author, Dr Anjali Goswami (UCL Genetics, Evolution & Environment), said: "When dinosaurs went extinct, a lot of competitors and predators of mammals disappeared, meaning that a great deal of the pressure limiting what mammals could do ecologically was removed. They clearly took advantage of that opportunity, as we can see by their rapid increases in body size and ecological diversity. Mammals evolved a greater variety of forms in the first few million years after the dinosaurs went extinct than in the previous 160 million years of mammal evolution under the rule of dinosaurs."

The Natural Environment Research Council-funded research, published today in the Biological Journal of the Linnean Society, studied the early evolution of placental mammals, the group including elephants, sloths, cats, dolphins and humans. The scientists gained a deeper understanding of how the diversity of the mammals that roamed the Earth before and after the dinosaur extinction changed as a result of that event.

Placental mammal fossils from this period have been previously overlooked as they were hard to place in the mammal tree of life because they lack many features that help to classify the living groups of placental mammals. Through recent work by the same team at UCL, this issue was resolved by creating a new tree of life for placental mammals, including these early forms, which was described in a study published in Biological Reviews yesterday.

First author of both papers, Dr Thomas Halliday (UCL Earth Sciences and Genetics, Evolution & Environment), said: "The mass extinction that wiped out the dinosaurs 66 million years ago is traditionally acknowledged as the start of the 'Age of Mammals' because several types of mammal appear for the first time immediately afterwards.

Reconstructions of Oligocene mammals.

Credit:  American Museum of Natural History'

"Many recent studies suggest that little changed in mammal evolution during the Paleocene but these analyses don't include fossils from that time. When we look at the mammals that were present, we find a burst of evolution into new forms, followed by specialisation that finally resulted in the groups of mammals we see today. The earliest placental mammal fossils appear only a few hundred thousand years after the mass extinction, suggesting the event played a key role in diversification of the mammal group to which we belong."

The team studied the bones and teeth of 904 placental fossils to measure the anatomical differences between species. This information was used to build an updated tree of life containing 177 species within Eutheria (the group of mammals including all species more closely related to us than to kangaroos) including 94 from the Paleocene - making it the tree with the largest representation from Paleocene mammals to date. The new tree was analysed in time sections from 140 million years ago to present day, revealing the change in the variety of species.

Animals of the Miocene (Chalicotherium, Hyenadon, Entelodont...). Mammals are the dominant terrestrial vertebrates of the Cenozoic.

Credit: Wikipedia

Three different methods were used by the team to investigate the range and variation of the mammals present and all showed an explosion in mammal diversity after the dinosaur extinction. This is consistent with theories that mammals flourished when dinosaurs were no longer hunting them or competing with them for resources.

Dr Anjali Goswami (UCL Genetics, Evolution & Environment), added: "Extinctions are obviously terrible for the groups that go extinct, non-avian dinosaurs in this case, but they can create great opportunities for the species that survive, such as placental mammals, and the descendants of dinosaurs: birds."

Professor Paul Upchurch (UCL Earth Sciences), co-author of the Biological Reviews study, added: "Several previous methodological studies have shown that it is important to include as many species in an evolutionary tree as possible: this generally improves the accuracy of the tree. By producing such a large data set, we hope that our evolutionary tree for Paleocene mammals is more robust and reliable than any of the previous ones. Moreover, such large trees are very useful for future studies of large-scale evolutionary patterns, such as how early placental mammals dispersed across the continents via land bridges that no longer exist today."

The team are now investigating rates of evolution in these mammals, as well as looking at body size more specifically. Further work will involve building data from DNA into these analyses, to extend these studies to modern mammals.

Contacts and sources:
Rebecca Caygill
University College London