Aug 24, 2016

Arctic gives clues on worst mass extinction of life

After an extreme global warming 252 million years ago, a severe mass extinction of life took place on Earth. A new study in the Arctic has been seeking clues as to what limited return of life to world´s oceans after this event.
Extreme global warming 252 million years ago caused a severe mass extinction of life on Earth. It took life up to 9 million years to recover. New study finds clues in the Arctic as to why this recovery took so long.

96 percent of marine species, and 70 percent of terrestrial life died off in the Permian-Triassic extinction event, as geologists know it. It is also known as The Great Dying Event for obvious reasons.

"The mass extinction was likely triggered by a explosive event of volcanic eruptions in what is now Siberia. These eruptions lasted for a million years and emitted enormous amounts of volatiles, such as carbon dioxide and methane, which made our planet unbearably hot." says Jochen Knies, researcher at Centre for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Tromsø.

Life took an extraordinary amount of time to recover from this extinction, from 5 to 9 million years. Why recovery was so delayed, has remained a mystery.

Clues are in the Arctic

Knies is the co-author of a study in Geology that took to the Arctic to look for clues as to what limited return of life to world´s oceans. The results of the study illustrate potential long-term impacts on marine ecosystems in response to global warming.

"What used to be the northwestern continental margin of the supercontinent Pangaea is now Canadian High Arctic. There we found evidence in geological records for a significant nutrient gap during this period. This means that global oceans were severely poor in nutrients such as nitrogen," says Knies.

This nutrient gap is most likely the result of extremely high ocean surface temperatures in the aftermath of the extinction.

Be cool -- stay alive

Our oceans are not a single body of water. They are comprised of layers and boundaries based on temperature (thermocline) and nutrients (nutricline) among others.

"The high temperatures caused deepening of the thermocline and nutricline in the ocean so that upwelling of nutrients from the bottom to the surface of ocean ceased. With that the marine algae productivity was stalled," according to Knies.

And without algae, which are the base of the food chain, the life in the ocean did not thrive.

Once oceans finally started cooling 6-7 million years after the extinction, nutrient rich waters returned.

"The boundaries that kept the nutrients from reaching the surface were weakened and the ocean waters were mixed. This caused the upwelling of nutrients, resuscitating the oceans, and leading to an explosion of life. The ecosystem voids created by the worst mass extinction in Earth history were finally filled." states Jochen Knies.

Read more at Science Daily

Humans Have Caused Climate Change For 180 Years

Humans have been changing Earth's climate for 180 years, earlier than scientists had previously believed, a new study reports.

The research, published in the journal Nature, involved 25 scientists from Australia, the United States, Europe and Asia, working together as part of the Past Global Changes 2000 Year (PAGES 2K) Consortium. Lead author Nerilie Abram, an associate professor at Australian National University, and colleagues examined detailed climate reconstructions spanning the past 500 years to determine when the current warming trend truly began, and analyzed thousands of years of climate models to confirm its cause.

After poring through climate histories preserved in the likes of corals, cave decorations, tree rings and ice cores, Abram and her team established that the first signals of climate change could be observed as early as the 1830s.

That industrial age is generally considered to have begun in Britain in the mid-to-late 1700s; the development of mass production transformed the country and ultimately the world, but the use of coal to power the steam engines and factories that made it possible released carbon dioxide, a greenhouse gas, levels of which have been increasing in the atmosphere ever since. During ice ages, CO2 levels were around 200 parts per million (ppm), and prior to the Industrial Revolution, they were around 280 ppm; in 2013, CO2 levels surpassed 400 ppm.

Interestingly, the study found that warming's footprints spread gradually across the globe. The Arctic began warming first, and continues to show the greatest extent of warming on the planet. Tropical oceans show signs of climate change at around the same time, followed in short order by Europe, Asia and North America, with sustained warming beginning about 50 years later in Australasia and South America. There are localized variations within such regional changes, however: Sea surface temperature in the eastern tropical Pacific may have undergone sustained warming "markedly later" than other tropical ocean regions.

The authors note that the point at which they say warming began was immediately preceded by some cooling in the tropical oceans and over Northern Hemisphere landmasses, largely caused by increased volcanic activity, such as the 1815 Tambora eruption. However, their reconstructions found that, even after accounting for a recovery from such conditions, the evidence was unambiguous: even the relatively small amount of greenhouse gases that had been released to that point were enough to stimulate warming.

"It was an extraordinary finding," said Abram. "It was one of those moments where science really surprised us. But the results were clear. The climate warming we are witnessing today started about 180 years ago."

From Discovery News

Rare Endangered Primate Spotted in Vietnam

A new group of critically endangered primates has been spotted in Vietnam, raising hopes the rare creatures may not be wiped out in the next decade as scientists had feared.

The Delacour's langur, black and white with a full face of whiskers, is indigenous to Vietnam, but their numbers have dwindled in recent years because of poaching and mining activity in the country's northern forests.

A team of scientists from Fauna and Flora International spotted a group of about 40 of the primates, mostly juveniles and infants, bringing their total population to less than 250.

"It's great news for this particular species because had we not found this new population, they were in grave danger of being wiped out within a decade," spokeswoman for FFI in Vietnam, Akofa Wallace, told AFP Tuesday.

"The fact that they are breeding is brilliant news," she added.

FFI did not say where scientists spotted the langurs, whose habitat is threatened by mining activity in the area, including charcoal production.

They are also targeted by poachers who hunt them for meat, with their bones used for traditional medicine and their pelts for decoration.

The primate was discovered in northern Vietnam in the 1930s by French scientist Jean Theodore Delacour, and are only found in Vietnam.

FFI country director Benjamin Rawson said urgent interventions were needed to protect the species, which numbered about 300 in the early 1990s.

"We continue to work alongside officials and local communities to ensure the Delacour's langur doesn't become this century's first primate extinction," Rawson said in a statement.

Read more at Discovery News

NASA Regains Contact With 'Dead' Solar Mission

NASA has finally re-established contact with a sun-watching probe that was thought to be lost in space after it abruptly went silent in 2014.

A signal from the long-lost spacecraft, called STEREO-B, was detected Sunday evening (Aug. 21) by NASA's Deep Space Network, a collection of space tracking stations that follows the agency's space missions across the solar system and beyond. NASA scientists had kept vigil for STEREO-B, making monthly searches for the probe until it phoned home Sunday at 6:57 p.m. EDT (2257 GMT).

Right now, it's unclear how healthy the spacecraft is after drifting in space for nearly two years. NASA lost contact with it on Oct. 1, 2014, after commanding a reset from Earth. The spacecraft's twin, STEREO-A, is still working normally.

"The STEREO Missions Operations team plans further recovery processes to assess observatory health, re-establish attitude control, and evaluate all subsystems and instruments," NASA officials wrote in a statement.

The STEREO spacecraft twins (their name is short for Solar and Terrestrial Relations Observatory) were launched in October 2006 and were originally supposed to last until 2008. With an extended mission, however, came challenges. For example, the orbits of both STEREO spacecraft went behind the sun in 2015, for three months each.

 STEREO-B was initially lost when NASA was testing a command loss timer, which is a reset triggered during solar conjunction. Conjunction was expected to happen between January and March 2015, when STEREO-B's orbit took it behind the sun, putting it out of contact with Earth.Both STEREO spacecraft have a command loss timer that resets the spacecraft every 72 hours when it is not communicating with Earth. In 2014, controllers deliberately stopped communicating with STEREO-A to test this process, and it worked perfectly after reorienting itself with respect to certain guide stars, and sending a signal to Earth.

With STEREO-B, however, the test did not play out as planned. The hard reset did occur, and STEREO-B sent a weak signal to Earth. But the spacecraft quickly faded into silence.

Only a few packets of data made it to Earth, but from that, the team concluded in December 2015 that the inertial measurement unit (which tells the spacecraft if it is rotating, and how fast) gave incorrect information into STEREO-B's guidance computer. At the time, NASA concluded that this set the spacecraft into a spin that left its solar panels out of sunlight most of the time, making it difficult to recharge the battery.

Read more at Discovery News

Aug 23, 2016

Immune breakthrough: Unscratching poison ivy's rash

Stylised image: Urushiol (in green), the 'active ingredient' in poison ivy, entrapped by CD1a molecule (in pink), which mediates the inflammatory response.
We all know that a brush with poison ivy leaves us with an itchy painful rash. Now, Monash University and Harvard researchers have discovered the molecular cause of this irritation. The finding brings us a step closer to designing agents to block this mechanism and sheds light on other serious skin conditions, such as psoriasis.

The international team of scientists have shown, for the first time, a connection between an immune molecule found in the skin and skin sensitisers -- the research was published overnight in Nature Immunology.

Professor Jamie Rossjohn, co-lead author with Dr Florian Winau, Harvard Medical School, confirmed the body's immune molecule, CD1a, plays a crucial role in mediating skin inflammation and irritation after contact with urushiol -- the 'active ingredient' found in plants endemic to Northern America and parts of Europe and Australia.

"A complex set of experiments, coupled with imaging techniques at the Australian Synchrotron revealed the molecular interplay between CD1a and urushiol. This highlights CDIa's role in sudden and uncomfortable skin reactions," Professor Rossjohn says.

Dr Tang Yongqing and Dr Jerome Le Nours say the research team needed a combination of scientific creativity and ingenuity to crack the CD1a-urushiol code.

"For over 35 years we have known CD1a is abundant in the skin," says Dr Le Nours. "Its role in inflammatory skin disorders has been difficult to investigate and until now has been really unclear. Our work, which included imaging the CD1a-urushiol connection, represents clear evidence that CD1a is instrumental in skin-related diseases."

"Our results were strengthened by in vivo and clinical studies at Harvard Medical School, in the United States," Dr Yongqing says.

The studies in Boston also showed that blocking the function of CD1a prevents the triggering of this skin-based allergic reaction, giving the researchers further evidence of just how important CD1a is.

"Future research could lead to the development of new treatments to combat minor skin irritations as well as chronic inflammatory skin diseases like psoriasis, eczema and rosacea," says Dr Yongqing.

"We now have a target to further investigate. Our basic discovery may make a big difference in the future treatment and prevention of inflammatory skin diseases," Dr Le Nours concludes.

Read more at Science Daily

Nanofiber scaffolds demonstrate new features in the behavior of stem and cancer cells

A discovery in the field of biomaterials may open new frontiers in stem and cancer cell manipulation and associated advanced therapy development. Novel scaffolds are shown enabling cells to behave in a different but controlled way in vitro due to the presence of aligned, self-assembled ceramic nanofibers of an ultra-high anisotropy ratio augmented into graphene shells.

"This unique hybrid nano-network allows for an exceptional combination of selective guidance stimuli for stem cell development, variations in immune reactions, and behavior of cancer cells," says Professor Michael Gasik from Aalto University.

These scaffolds, for example, were shown to be able to direct the preferential orientation of human mesenchymal stem cells, similarly to neurogenic lineage, to suppress of major inflammatory factors expression and to immobilize cancer cells.

The selective downregulation of specific inflammatory cytokines may be anticipated as a new tool for understanding the human immune system and ways of treating associated diseases. The effects observed are self-regulated by cells only, without the side effects usually arising from the use of external factors.

New scaffolds may help to control the fate of stem cells, such as development towards axons and neurites formation. This is important, for instance, in the development of Alzheimer's disease therapy. The discovery may also be very useful in developing new cancer tumour models, understanding how cancer develops, and developing new cancer therapies.

From Science Daily

Fossilized rivers suggest warm, wet ancient Mars

Extensive systems of fossilised riverbeds have been discovered on an ancient region of the Martian surface, supporting the idea that the now cold and dry Red Planet had a warm and wet climate about 4 billion years ago, according to UCL-led research.

The study, published in Geology and funded by the Science & Technology Facilities Council and the UK Space Agency, identified over 17,000km of former river channels on a northern plain called Arabia Terra, providing further evidence of water once flowing on Mars.

"Climate models of early Mars predict rain in Arabia Terra and until now there was little geological evidence on the surface to support this theory. This led some to believe that Mars was never warm and wet but was a largely frozen planet, covered in ice-sheets and glaciers. We've now found evidence of extensive river systems in the area which supports the idea that Mars was warm and wet, providing a more favourable environment for life than a cold, dry planet," explained lead author, Joel Davis (UCL Earth Sciences).

Since the 1970s, scientists have identified valleys and channels on Mars which they think were carved out and eroded by rain and surface runoff, just like on Earth. Similar structures had not been seen on Arabia Terra until the team analysed high resolution imagery from NASA's Mars Reconnaissance Orbiter (MRO) spacecraft.

The new study examined images covering an area roughly the size of Brazil at a much higher resolution than was previously possible -- 6 metres per pixel compared to 100 metres per pixel. While a few valleys were identified, the team revealed the existence of many systems of fossilised riverbeds which are visible as inverted channels spread across the Arabia Terra plain.

The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low -- in most other environments, the channels are worn away before they can become inverted.

"The networks of inverted channels in Arabia Terra are about 30m high and up to 1-2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9-3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present," added Joel Davis.

"These ancient Martian flood plains would be great places to explore to search for evidence of past life. In fact, one of these inverted channels called Aram Dorsum is a candidate landing site for the European Space Agency's ExoMars Rover mission, which will launch in 2020," said Dr Matthew Balme, Senior Lecturer at The Open University and co-author of the study.

The researchers now plan on studying the inverted channels in greater detail, using higher-resolution data from MRO's HiRISE camera.

From Science Daily

'Alien Megastructure' Star Is Still Really Weird

In September 2015, a team led by Yale University astronomer Tabetha Boyajian announced that a star about 1,500 light-years from Earth called KIC 8462852 had dimmed oddly and dramatically several times over the past few years.

These dimming events, which were detected by NASA's planet-hunting Kepler space telescope, were far too substantial to be caused by an orbiting planet, scientists said. (In one case, 22 percent of the star's light was blocked. For comparison, when huge Jupiter crosses the sun's face, the result is a dimming of just 1 percent or so.)

Boyajian and her colleagues suggested that a cloud of fragmented comets or planetary building blocks might be responsible, but other researchers noted that the signal was also consistent with a possible "alien megastructure" — perhaps a giant swarm of energy-collecting solar panels known as a Dyson sphere.

Astronomers around the world soon began studying Tabby's star with a variety of instruments, and reanalyzing old observations of the object, in an attempt to figure out what, exactly, is going on. But they have yet to solve the puzzle.

"I'd say we have no good explanation right now for what's going on with Tabby's star," Jason Wright, an astronomer at Pennsylvania State University, said earlier this month during a talk at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California. "For now, it's still a mystery."

More Surprises


In fact, that mystery may have deepened over the past 12 months.

For example, in January, Bradley Schaefer, a professor of physics and astronomy at Louisiana State University, determined that, in addition to the weird short-term dimming events, the brightness of Tabby's star had dropped by about 20 percent overall between 1890 and 1989. That pattern is very difficult for known natural phenomena to explain, he said.

Schaefer came to this conclusion after poring over old photographic plates of the night sky that captured Tabby's star. Other researchers suggested that the trend Schaefer saw could have been caused by changes in the instruments used to take those photos over the century-long timespan. However, a new study bolsters Schaefer's interpretation.

In the new work, Benjamin Montet (of the California Institute of Technology and the Harvard-Smithsonian Center for Astrophysics) and Joshua Simon (of the Observatories of the Carnegie Institution of Washington) reanalyzed Kepler observations of Tabby's star from 2009 through 2013. They found that the object dimmed by 3 percent over that span, with a rapid 2-percent brightness dip over one 200-day period.

"Of a sample of 193 nearby comparison stars and 355 stars with similar stellar parameters, 0.6 percent change brightness at a rate as fast as 0.341 percent [per year], and none exhibit either the rapid decline by > 2 percent or the cumulative fading by 3 percent of KIC 8462852," Montet and Simon wrote in the new study, which they uploaded to the online preprint site ArXiv on Aug. 5. "No known or proposed stellar phenomena can fully explain all aspects of the observed light curve."

Schaefer's results, combined with those of Montet and Simon, make the comet hypothesis look less and less likely, Wright said in his SETI talk.

"Why would comets, over a century, make the star dimmer?" he said. "What's going on?"

Alien Megastructure?

The sustained dimming of Tabby's star is still consistent with at least some variants of the "alien megastructure" hypothesis, Wright said.

"Some people have sort of facetiously offered that perhaps this is a Dyson sphere under construction: You're seeing lots of material getting built," he said. "In just 100 years, they've blotted out 20 percent of the starlight. That seems kind of fast to me — but, you know, aliens, right?"

It's also possible that the alien megastructure — if it exists — is fully constructed, and some parts are just denser than others, Wright added.

"That would naturally make the star get brighter and dimmer, as dense parts of the swarm came around," he said. "So if I had to invoke megastructures to explain it, that seems consistent. You've got lots of panels of different shapes, different sizes, and the big ones make big dips and the little ones make little dips, and the whole swarm is sort of like a translucent screen that makes the whole thing dimmer."

But Wright and others have always stressed that the "E.T. did it" scenario is very unlikely, and that a more prosaic explanation will probably rise to the top eventually. And indeed, other recent observations throw some cold water on the alien-megastructure idea — and any other hypothesis that invokes some object or phenomenon near Tabby's star.

Any structure surrounding the star, be it alien-made or naturally occurring, would heat up and give off infrared radiation, Wright said. But he and his colleagues saw no signatures of such "waste heat" in data gathered by NASA'sWide-field Infrared Survey Explorer spacecraft. And another research team — which analyzed observations by the Submillimeter Array telescope and the Submillimeter Common-User Bolometer Array-2 instrument, both of which are in Hawaii — also came up empty.

Whatever is blocking the starlight from Tabby's star is "not surrounding the whole star — it must be along our line of sight," Wright said. "So you can do that if it's in a disk of some kind. And that hopefully will help constrain what the heck is going on."

Wright has a hunch that the answer lies far away from Tabby's star, out in the dark depths of space.

"I think I've all but abandoned circumstellar explanations, and I think now we're going to have to talk about [some] bizarre structure in the interstellar medium, and stuff like that," he said.

Read more at Discovery News

Stellar 'Time Bomb' Proves Cosmic Crime Doesn't Pay

This beautiful Hubble image shows the ghostly remains of a star, which detonated 160,000 light-years away, blasting hot gases through interstellar space. But this explosion wasn't caused by a massive star running out of hydrogen, it was a different type of supernova that started with a thieving white dwarf and ended with a boom.

The stellar remains, called DEM L71, were spied by Hubble's Wide Field Camera 3 in the Large Magellanic Cloud (a satellite galaxy that orbits the Milky Way) and was formed by a type of supernova seeded by a binary star system that consists of a white dwarf and another star.

White dwarfs are the leftover husks of stars that once resembled our sun. Rather than exploding when they reach the ends of their lives, they run out of hydrogen and puff up into spectacular red giants. Once expanded, violent stellar winds strip away their outer layers, creating a planetary nebula. In the center, a dense, tiny star remains that can persist for many billions of years long after its parent star becomes a distant memory. In around 4 billion years time, our own sun will experience this fate.

But things get interesting should a white dwarf be paired up with another star; it will steal the other star's gas, causing the white dwarf to form a new outer layer. As this stellar thievery unfolds, the white dwarf seals its own fate by inadvertently starting the timer on a bomb.

When the gas reaches a certain threshold around the white dwarf, swelling to around one and a half times the size of our sun, it becomes critically unstable and explodes as a special kind of supernova -- a Type 1a. (Aside: Type 1a supernovae are used as cosmic "standard candles" by astronomers to precisely measure cosmic distances as they explode with the same amount of gas, and therefore with the same luminosity, every time.) In the case of DEM L71, we're seeing the aftermath of what happens when the hot debris from the supernova ripped into the cool interstellar gases, creating this beautiful nebulous remnant.

In other words, if you're a greedy white dwarf, crime doesn't pay and, if you steal your neighbor's gas, you'll explode. Also, the binary partners of exploding stars have been found to survive, amazingly. Although the cosmos is often cruel and unforgiving, in this case, justice can be served.

From Discovery News

Aug 22, 2016

In the ocean, clever camouflage beats super sight

In a matchup of animal superpowers, a clever form of camouflage might beat super sight -- at least in the ocean.

There's nowhere to hide in the open ocean, far from the shore or the seafloor. But some fish have a clever disappearing trick. The silvery skin of fish like herring, sardines, mackerel and tuna act like mirrors, reflecting their watery surroundings to better blend in. The effect serves as a kind of underwater invisibility cloak that helps them hide in plain sight.

Researchers have long assumed that some animals could see through this silvery disguise, thanks to a superpower of their own: the ability to detect a property of light -- called polarization -- that humans can't see.

Octopuses and squid, shrimp and other crustaceans, and some fish such as trout and salmon all have the gift, called polarization vision.

"It's kind of like wearing polarized sunglasses," said Sonke Johnsen, biology professor at Duke University and the first author on a new study of how well animals see reflective camouflage in the ocean.

The polarization state of light changes when it bounces off a silvery fish's shiny scales. Scientists long presumed that this makes it easier for animals with polarization vision to make silvery fish out against the background, to eat them or avoid them.

But the newly released findings suggest otherwise.

In a study published Aug. 22 in the journal Current Biology, researchers went scuba diving in the waters around Australia's Great Barrier Reef and took hundreds of pictures of silvery fish, including tuna, amberjack, barracuda and queenfish.

The fish were photographed from six to 10 feet away using a custom-built underwater camera with tiny polarizing filters built into the sensor.

The researchers used the images to measure the polarization state and brightness of the light reflected from the fish and the background water. By combining this information with a mathematical model of visual perception, they were able to calculate the maximum distance from which silvery fish can be detected using polarization vision versus a "regular" light cue like brightness.

The fish did reflect a slightly contrasting polarization pattern with respect to the background water, which could theoretically betray their presence, the researchers found.

But surprisingly, the data showed that polarization vision doesn't help animals spot silvery fish from any farther away than they could without this special sensitivity.

"Sighting distance is important, because hunting and avoiding being eaten in the open ocean is about seeing other animals before they see you," Johnsen said. "Once you're seen, you're dead. It's over."

If animals with this superpower aren't better equipped to spot a hungry tuna approaching from afar, then why do so many marine animals have polarization vision, and how do they use it? On land, this "sixth sense" is known to help insects and other animals find food, mates and suitable sites to lay their eggs. But in the ocean, now its function is less clear, Johnsen said.

Read more at Science Daily