Mar 17, 2017

Human skull evolved along with two-legged walking, study confirms

Comparison of the positioning of the foramen magnum in a bipedal springhare (left) and its closest quadrupedal relative, the scaly-tailed squirrel.
The evolution of bipedalism in fossil humans can be detected using a key feature of the skull -- a claim that was previously contested but now has been further validated by researchers at Stony Brook University and The University of Texas at Austin.

Compared with other primates, the large hole at the base of the human skull where the spinal cord passes through, known as the foramen magnum, is shifted forward. While many scientists generally attribute this shift to the evolution of bipedalism and the need to balance the head directly atop the spine, others have been critical of the proposed link. Validating this connection provides another tool for researchers to determine whether a fossil hominid walked upright on two feet like humans or on four limbs like modern great apes.

Controversy has centered on the association between a forward-shifted foramen magnum and bipedalism since 1925, when Raymond Dart discussed it in his description of "Taung child," a 2.8 million-year-old fossil skull of the extinct South African species Australopithecus africanus. A study published last year by Aidan Ruth and colleagues continued to stir up the controversy when they offered additional criticisms of the idea.

However, in a study published in the Journal of Human Evolution, UT Austin anthropology alumna Gabrielle Russo, now an assistant professor at Stony Brook University, and UT Austin anthropologist Chris Kirk built on their own prior research to show that a forward-shifted foramen magnum is found not just in humans and their bipedal fossil relatives, but is a shared feature of bipedal mammals more generally.

"This question of how bipedalism influences skull anatomy keeps coming up partly because it's difficult to test the various hypotheses if you only focus on primates," Kirk said. "However, when you look at the full range of diversity across mammals, the evidence is compelling that bipedalism and a forward-shifted foramen magnum go hand-in-hand."

In this study, Russo and Kirk expanded on their previous research (published in the same journal in 2013) by using new methods to quantify aspects of foramen magnum anatomy and sampling the largest number of mammal species to date.

To make their case, Russo and Kirk compared the position and orientation of the foramen magnum in 77 mammal species including marsupials, rodents and primates. Their findings indicate that bipedal mammals such as humans, kangaroos, springhares and jerboas have a more forward-positioned foramen magnum than their quadrupedal close relatives.

"We've now shown that the foramen magnum is forward-shifted across multiple bipedal mammalian clades using multiple metrics from the skull, which I think is convincing evidence that we're capturing a real phenomenon," Russo said.

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Eruptions on the sun trigger surprising phenomenon near Earth

In connection with violent solar eruptions, large variations occur in electron density in the ionosphere over Greenland, which interferes with GPH navigation signals as well as flight and satellite communication. For the first time ever, researchers from DTU have demonstrated the phenomenon which cannot yet be explained.
New research from DTU and partners from NASA's Jet Propulsion Laboratory and the University of New Brunswick shows that eruptions on the Sun's surface not only send bursts of energetic particles into Earth's atmosphere causing disturbances in our planet's magnetic field, they can also strangely decrease the number of free electrons over large areas in the polar region of the ionosphere.

Eruptions on the Sun's surface, also called solar storms, trigger geomagnetic storms and this usually causes disturbances globally in the ionosphere and the magnetosphere, which is the region of the atmosphere governed primarily by Earth's magnetic field.

Now new research shows that these eruptions on the sun's surface not only send bursts of energetic particles into Earth's atmosphere causing disturbances in the magnetic field, but they may also significantly decrease the number of free electrons over large areas in the polar region of the ionosphere -- the ionized part of the upper atmosphere.

"We have conducted extensive measurements associated with a specific geomagnetic storm over the Arctic in 2014, and here we have found that electrons in large quantities were almost vacuumed out from areas that extend over 500 to 1000 kilometres. It happens just south of an area with strong increases in electron density, called patches," said Professor Per Høeg from DTU Space.

The new research has been carried out by the National Space Research Institute at the Technical University of Denmark (DTU Space) and collaborating international partners from NASA's Jet Propulsion Laboratory (JPL) and the University of New Brunswick (UNB).

A surprising mechanism at play

The research indicates that there is a surprising and previously unknown mechanism at play in the geomagnetic storms.

Solar activity usually tends to increase the rate of ionization in the atmosphere and thus the density of free electrons in the ionosphere or to move electrons to the polar caps. The research show that the opposite, a depletion of electrons, can take place.

"It is a surprising discovery; one we had not expected. But now we can see it happening in other data sets from Canada, which indirectly support our new observations," said Per Høeg.

The new research also provides a host of other insights that increases the understanding of how such geomagnetic storms affect Earth's atmosphere and could possibly lead to improved radio communication and navigation throughout the Arctic.

The results of the research have been published in the American Geophysical Union's scientific journal Radio Science and featured on its cover.

The discovery is an important piece of the puzzle in understanding geomagnetic storms and their impact on Earth's ionosphere. Major geomagnetic storms can put astronauts on the International Space Station and those on future interplanetary space missions in danger, damage satellites, cause failing radio communications, and harm electricity grids and pipelines and so have extensive and costly consequences for society. Studying and understanding geomagnetic storms are hence fundamental for global public and financial safety.

Magnetic fields from Sun and Earth connect

The known phenomenon of adding electrons to the ionosphere also occurs at high latitudes.

It happens because the sun's magnetic field, carried along with the stream of particles following a solar eruption, interferes with Earth's own magnetic field, fundamentally connecting with it. Particles, including electrons, in the solar outburst can penetrate the ionosphere, following Earth's magnetic field lines, which converge at the poles.

The explanation for this phenomenon lies presumably in the processes taking place in Earth's magnetic field in the direction away from the sun. Massive changes take place in the magnetic field composition in the area between the solar wind -- the stream of energetic particles flowing from the sun -- and Earth's magnetic field and this triggers powerful energy transfers.

"The forerunner of the phenomenon is a violent eruption on the sun's surface, called a coronal mass ejection, or CME, where the sun bubbles up, and slings 'hot' magnetized plasma in the form of very energetic ions and electrons in the direction of Earth," said Per Høeg.

The geomagnetic storm in the ionosphere over the Arctic in February 2014 was measured via satellites and from terrestrial stations. Among other sensors the GPS network GNET in Greenland provided a wealth of data.

Critical factors in satellite navigation

The research goes beyond the discovery of electrons being sucked out of the ionosphere during solar storms.

"There are two aspects of the research. First, it can be used for practical purposes;, also there is a theoretical part, which is about fundamentally better understanding these phenomena," said Tibor Durgonics who is a Ph.D. student at DTU Space and the main author of the new article in Radio Science.

"Our work can help to make navigation safer during geomagnetic storms in the Arctic. Through the new research, we have identified some critical factors affecting the quality of satellite navigation, and looked at the likelihood of when these factors may occur. On a more theoretical level, we found out, that these kind of storms can remove electrons from the ionosphere, which is the opposite of what one would expect intuitively."

When the magnetic field in solar eruptions impacts Earth's magnetic field in the ionosphere, their force fields get merged and, through a series of complex physical processes, ultimately cause unstable areas in the ionosphere called patches. These patches extend over large areas of 500 to 1000 km near the pole and also give rise to strong northern lights displays.

Interferes with navigation and communication systems

Knowledge of geomagnetic storms is important as communications via satellites and terrestrial radio channels can be impacted. The storms can disrupt the signals from GPS and other satellites and can cause widespread electricity outages, as for example happened in Sweden in 2003 and Canada in 1989.

"It is becoming increasingly important to be able to manage the impact of geomagnetic storms in that more and more of our infrastructure relies on radio signals for communications and navigation. Therefore, we are working to be able to describe and predict the geophysical changes at high latitudes, more accurately, so that among other things they can be taken into account in the design and operation of future communications systems," explains Per Høeg.

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Hawaiian biodiversity has been declining for millions of years

A silversword, one of Hawaii's unique, endemic plants. Silverswords filled all of Kauai's carrying capacity -- the number of species a particular ecosystem can support - within about 3 million years after the island formed, and the plants have been losing species since then. The photo was taken on the slopes of Haleakala on East Maui.

The team concluded that the shrinking land areas of the older islands began putting stress on the flora and fauna several million years after the islands formed. Today, all of the islands except the Big Island of Hawaii -- the only island still growing -- have experienced a decrease in species diversity, albeit imperceptibly on human time scales, since even before the extinction caused by human activity.


"On the older islands, Kauai, Oahu and the four islands that were once parts of a bigger island called Maui Nui, it looks like most groups are now in long-term evolutionary decline," said senior author Charles Marshall, a UC Berkeley professor of integrative biology and director of the University of California Museum of Paleontology. "The older islands were all much larger than they are now, and it looks like the the flora and fauna filled up the ecological space fast enough that once the islands began to contract the crowding generated drove species to extinction."

Biologists have debated whether Hawaii's birds, spiders, insects and plants -- there are no native mammals -- have radiated fully throughout the relatively young island chain, and some have claimed that evolutionary diversity has not yet peaked, based on comparisons of species' DNA. The new study by Marshall and UC Berkeley graduate student Jun Ying Lim shows that the older islands had, in fact, peaked in diversity long ago.

"Biologists don't often think about the evolutionary trajectory of their group because without a fossil record they have no data that bear on whether diversity is increasing or decreasing," Marshall said. "This study adds weight to the argument that there might be a lot of groups living today that are actually in long-term evolutionary decline. So this paper also serves as a consciousness-raising exercise -- how might we identify living groups that are in decline in the absence of a fossil record?"



Hot spot


Each newly formed island was colonized by plants and animals from the older islands, leading to a wealth of new species that filled each island's ecological niches. For example, honeycreepers, an endemic group of bird species, and the unique silverswords filled all of Kauai's carrying capacity -- the number of species a particular ecosystem can support -- within about 3 million years, while beetles took a little longer, about 4.5 million years. Some species, like the spider group Orsonwelles, have yet to completely fill Kauai's available niches.

Marshall realized that "the progression of islands of the Hawaiian archipelago can be viewed as an evolutionary time machine," revealing "rates of species-richness change for endemic species of the archipelago," which has virtually no fossil record.

"It is increasingly appreciated that the biota of any particular place is a dynamic, ever-changing association of species," Lim said. "The beauty of islands like Hawaii is that their geologic setting provides multiple temporal snapshots, and in so doing provides us a window to understanding the processes that have shaped its assembly though time."



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Operation of ancient biological clock uncovered


William Faulkner


New combination


Zooming in


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Fossil or inorganic structure? Scientists dig into early life forms

Illustration of molecule model (stock image). New research suggests that inorganic chemicals can self-organize into complex structures that mimic primitive life on Earth.

Florida State University Professor of Chemistry Oliver Steinbock and Professor Juan Manuel Garcia-Ruiz of the Consejo Superior de Investigaciones Científicas (Spanish Research Council) in Granada, Spain published an article in Science Advances that shows fossil-like objects grew in natural spring water abundant in the early stages of the planet. But they were inorganic materials that resulted from simple chemical reactions.

This complicates the identification of Earth's earliest microfossils and redefines the search for life on other planets and moons.

"Inorganic microstructures can potentially be indistinguishable from ancient traces of life both in morphology and chemical composition," Garcia-Ruiz said. Scientists had seen hints of this in past lab work, but now through Steinbock and Garcia-Ruiz's research, it is clear that this also happened in nature.

To do this work, the team of scientists collected and analyzed an extreme form of soda water from the Ney Springs in Northern California. Today this type of water is found in only a few spots worldwide, but it was widespread during the early stages of Earth's existence.

By addition of just one other ubiquitous chemical -- calcium or barium salt -- this water produces tiny structures, such as tubes, helices, and worm-like objects that are reminiscent of the shapes of primitive organisms. The water also generates complex mineral structures that are similar to nacre -- the shiny substance of sea shells. The similarities between actual fossils and these inorganic structures go beyond appearance and extend to their chemical nature. This will make it even more complicated for scientists examining early evidence of life on Earth.

"Our findings reveal an unusual convergence of simple biological shapes and complex inorganic structures and make the job of identifying earliest microfossils on Earth and life on other planets even harder," Steinbock said. "It's fascinating. How could I identify a fossil if I went to Mars? How could I convince myself that it was once alive? In the future, scientists will need to be even more alert that everything that looks like life is not necessarily life."

From Science Daily

Mar 16, 2017

Nose form was shaped by climate

Differences in the human nose may have accumulated among populations through time as a result of a random process called genetic drift. However, divergent selection -- variation in natural selection across populations -- may also be the reason that different populations have differing noses. Teasing the two apart is difficult, especially in humans.









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Scientists identify a black hole choking on stardust

In the center of a distant galaxy, almost 300 million light years from Earth, scientists have discovered a supermassive black hole that is "choking" on a sudden influx of stellar debris.

In a paper published in Astrophysical Journal Letters, researchers from MIT, NASA's Goddard Space Flight Center, and elsewhere report on a "tidal disruption flare" -- a dramatic burst of electromagnetic activity that occurs when a black hole obliterates a nearby star. The flare was first discovered on Nov. 11, 2014, and scientists have since trained a variety of telescopes on the event to learn more about how black holes grow and evolve.

The MIT-led team looked through data collected by two different telescopes and identified a curious pattern in the energy emitted by the flare: As the obliterated star's dust fell into the black hole, the researchers observed small fluctuations in the optical and ultraviolet (UV) bands of the electromagnetic spectrum. This very same pattern repeated itself 32 days later, this time in the X-ray band.

The researchers used simulations of the event performed by others to infer that such energy "echoes" were produced from the following scenario: As a star migrated close to the black hole, it was quickly ripped apart by the black hole's gravitational energy. The resulting stellar debris, swirling ever closer to the black hole, collided with itself, giving off bursts of optical and UV light at the collision sites. As it was pulled further in, the colliding debris heated up, producing X-ray flares, in the same pattern as the optical bursts, just before the debris fell into the black hole.

"In essence, this black hole has not had much to feed on for a while, and suddenly along comes an unlucky star full of matter," says Dheeraj Pasham, the paper's first author and a postdoc in MIT's Kavli Institute for Astrophysics and Space Research. "What we're seeing is, this stellar material is not just continuously being fed onto the black hole, but it's interacting with itself -- stopping and going, stopping and going. This is telling us that the black hole is 'choking' on this sudden supply of stellar debris."

Pasham's co-authors include MIT Kavli postdoc Aleksander Sadowski and researchers from NASA's Goddard Space Flight Center, the University of Maryland, the Harvard-Smithsonian Center for Astrophysics, Columbia University, and Johns Hopkins University.

A "lucky" sighting

Pasham says tidal disruption flares are a potential window into the universe's many "hidden" black holes, which are not actively accreting, or feeding on material.

"Almost every massive galaxy contains a supermassive black hole," Pasham says. "But we won't know about them if they're sitting around doing nothing, unless there's an event like a tidal disruption flare."


"You'd have to stare at one galaxy for roughly 10,000 to 100,000 years to see a star getting disrupted by the black hole at the center," Pasham says.

Nevertheless, on Nov. 11, 2014, a global network of robotic telescopes named ASASSN (All Sky Automated Survey for SuperNovae) picked up signals of a possible tidal disruption flare from a galaxy 300 million light years away. Scientists quickly focused other telescopes on the event, including the X-ray telescope aboard NASA's Swift satellite, an orbiting spacecraft that scans the sky for bursts of extremely high energy.

"Only recently have telescopes started 'talking' to each other, and for this particular event we were lucky because a lot of people were ready for it," Pasham says. "It just resulted in a lot of data."

A light-on collision

With access to these data, Pasham and his colleagues wanted to solve a longstanding mystery: Where did a flare's bursts of light first arise? Using models of black hole dynamics, scientists have been able to estimate that as a black hole rips a star apart, the resulting tidal disruption flare can produce X-ray emissions very close to the black hole. But it's been difficult to pinpoint the origin of optical and UV emissions. Doing so would be an added step toward understanding what happens when a star gets disrupted.

"Supermassive black holes and their host galaxies grow in-situ," Pasham says. "Knowing exactly what happens in tidal disruption flares could help us understand this black hole and galaxy coevolution process."

The researchers studied the first 270 days following the detection of the tidal disruption flare, named ASASSN-14li. In particular, they analyzed X-ray and optical/UV data taken by the Swift satellite and the Las Cumbres Observatory Global Telescope. They identified fluctuations, or bursts, in the X-ray band -- two broad peaks (one around day 50, and the other around day 110) followed by a short dip around day 80. They identified this very same pattern in the optical/UV data some 32 days earlier.

To explain these emission "echoes," the team ran simulations of a tidal disruption flare produced from a black hole obliterating a star. The researchers modeled the resulting accretion disc -- an elliptical disc of stellar debris swirling around the black hole -- along with its probable speed, radius, and rate of infall, or speed at which material falls onto the black hole.


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Gigantic Jupiter-type planet reveals insights into how planets evolve

An image of the HD 106906 stellar debris disk, created by Erika Nesvold's simulation, showing the ring of rocky and icy planet-forming material rotating around the star. (The star is removed from the image, masked by the black circle.) The different hues represent gradients of brightness in the disk material; yellow is the brightest and blue the dimmest.














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Earth's first example of recycling -- its own crust!

Rock samples from northeastern Canada retain chemical signals that help explain what Earth's crust was like more than 4 billion years ago, reveals new work from Carnegie's Richard Carlson and Jonathan O'Neil of the University of Ottawa. Their work is published by Science.

There is much about Earth's ancient crust that scientists don't understand. This is because most of the planet's original crust simply isn't around any longer to be studied directly -- it has either sunk back into the planet's interior due to the action of plate tectonics or been transformed by geological activity at Earth's surface to make new, younger rocks.

"Finding remnants of this ancient crust has proven difficult, but a new approach offers the ability to detect the presence of truly ancient crust that has been reworked into 'merely' really old rocks," Carlson said.


Isotopes are versions of an element that have the same number of protons, but different numbers of neutrons, causing each isotope to have a different mass. The isotope of samarium with a mass of 146 is unstable and decays to the isotope of neodymium with a mass of mass 142. (If you're interested in knowing how, it does this by emitting what's called an alpha particle -- composed of two neutrons and two protons -- from its nucleus.)

Samarium-146 is a radioactive isotope that has a half-life of only 103 million years. That may sound like a long time, but in geological terms it is really quite short. While samarium-146 was present when Earth formed, it became extinct very early in Earth's history. We know of its existence from the study of very ancient rocks, especially meteorites and samples from Mars and the Moon.

Variations in the relative abundance of neodymium-142 compared to other isotopes of neodymium that didn't originate from decaying samarium reflect chemical processes that changed the ratio of samarium to neodymium in the rock while samarium-146 was still present -- basically before about 4 billion years ago.

Carlson and O'Neil studied 2.7 billion-year-old granitic rocks that make up a good portion of the eastern shore of Hudson Bay. The abundances of neodymium-142 in these granites indicates that they were derived from the re-melting of much older rocks -- rocks that were more than 4.2 billion years old -- and that these ancient rocks were compositionally similar to the abundant magnesium-rich rock type known as basalt, which makes up all of the present day oceanic crust as well as large volcanoes such as Hawaii and Iceland.

In more-recent times in Earth's history, basaltic oceanic crust survives at Earth's surface for less than 200 million years before it sinks back into Earth's interior due to the action of plate tectonics. The results presented in this paper, however, suggest that basaltic crust, which may have formed not long after Earth's formation, survived at Earth's surface for at least 1.5 billion years before later being re-melted into rocks that form a good portion of the northernmost Superior craton, a geological formation that extends roughly from the Hudson Bay in Quebec to Lake Huron in Ontario.


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Mar 15, 2017

From the butterfly's wing to the tornado: Predicting turbulence





'Butterfly Effect' catchphrase

The new Georgia Tech research befits the origins of that adage.



Order in chaos





Turbulent flow snapshots





Pendulum on its head







Turbulence roads to ECS cities

That all may feel unusual for a reason.





Mining weather data





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Dark matter less influential in galaxies in early universe

Schematic representation of rotating disc galaxies in the early Universe (right) and the present day (left). Observations with ESO's Very Large Telescope suggest that such massive star-forming disc galaxies in the early Universe were less influenced by dark matter (shown in red), as it was less concentrated. As a result the outer parts of distant galaxies rotate more slowly than comparable regions of galaxies in the local Universe.
We see normal matter as brightly shining stars, glowing gas and clouds of dust. But the more elusive dark matter does not emit, absorb or reflect light and can only be observed via its gravitational effects. The presence of dark matter can explain why the outer parts of nearby spiral galaxies rotate more quickly than would be expected if only the normal matter that we can see directly were present.


What they found was intriguing: unlike spiral galaxies in the modern Universe, the outer regions of these distant galaxies seem to be rotating more slowly than regions closer to the core -- suggesting there is less dark matter present than expected.





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Marine recovery after mass extinction was likely delayed by further biotic crises

William Foster in the field pointing to the late Permian mass extinction horizon.
Biotic crises during the Triassic period may have delayed marine recovery after a mass extinction during the late Permian, according to a study published March 15, 2017 in the open-access journal PLOS ONE by William Foster from University of Texas, Austin, USA, and colleagues.

The late Permian mass extinction was a catastrophic biotic crisis- an estimated 81 percent of marine species were lost, and recovery took longer than for any other extinction event. Some researchers had previously hypothesized that biotic crises subsequently impeded the recovery of life at the bottom of the oceans. To investigate further, Foster and colleagues examined marine invertebrate fossils in the Werfen Formation in the Dolomites, Italy. They assessed diversity and other measures of ocean floor marine communities during the Triassic, the geological period which followed the mass extinction. They were able to gather the highest-resolution, most continuous dataset from this formation to date.

The researchers found that extinction rates of these marine invertebrates peaked twice during the early Triassic. Moreover, these raised extinction rates were associated with carbon isotope shifts, possibly indicating increased stress in the environment which could have affected species' ability to survive and diversify. After the second biotic crisis, ecological diversity increased, possibly following a relaxation of the environmental stresses that had previously limited marine recovery. Taken together, these findings support the hypothesis that after the late Permian mass extinction, marine recovery was delayed by subsequent biotic crises.

William Foster, the lead author on the study, says, "The early evolution of marine ecosystems 252 million years ago wasn't only ushered by the greatest mass extinction of all time, but also affected by two more subsequent extinction events associated with climate change. This is not only interesting from an evolutionary point of view, but also because those environmental conditions that life had to adapt to, to survive back then, are similar to those predicted for future climate warming scenarios."

From Science Daily

Ice age thermostat prevented extreme climate cooling

During the ice ages, an unidentified regulatory mechanism prevented atmospheric carbon dioxide concentrations from falling below a level that could have led to runaway cooling, say researchers.


"When we took a close look at measurements from ice cores, we noticed that atmospheric CO2 concentrations hovered close to 190 ppm during much of the past 800,000 years, but very rarely fell any lower," said Sarah Eggleston, a researcher at the Institut of Environmental Science and Technology (ICTA-UAB) and co-author of the study. "This was surprising, because it suggests that these very low CO2 concentrations were quite stable. What's more, we know that CO2 was often very high in the distant geological past, but we have no evidence that CO2 concentrations were ever lower than 190 ppm."

"We know that, over hundreds of thousands of years, CO2 is regulated by slowly reacting with exposed rocks" explained Eric Galbraith, lead author of the study and an ICREA professor at ICTA-UAB. "But this would be too slow to explain the stability during periods of only a few thousand years, as we see in the ice cores. So it must have been some other mechanism that kicked in at very low CO2."


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Mar 14, 2017

Did humans create the Sahara desert?

Dunes of the Sahara Desert.
New research investigating the transition of the Sahara from a lush, green landscape 10,000 years ago to the arid conditions found today, suggests that humans may have played an active role in its desertification.

The desertification of the Sahara has long been a target for scientists trying to understand climate and ecological tipping points. A new paper published in Frontiers in Earth Science by archeologist Dr. David Wright, from Seoul National University, challenges the conclusions of most studies done to date that point to changes in the Earth's orbit or natural changes in vegetation as the major driving forces.

"In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland," explains Wright, also noting in his paper that evidence of human-driven ecological and climatic change has been documented in Europe, North America and New Zealand. Wright believed that similar scenarios could also apply to the Sahara.


Growing agricultural addiction had a severe effect on the region's ecology. As more vegetation was removed by the introduction of livestock, it increased the albedo (the amount of sunlight that reflects off the earth's surface) of the land, which in turn influenced atmospheric conditions sufficiently to reduce monsoon rainfall. The weakening monsoons caused further desertification and vegetation loss, promoting a feedback loop which eventually spread over the entirety of the modern Sahara.


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Leap onto land saves fish from being eaten

An amphibious blenny fish on Rarotonga.
Fish on the South Pacific island of Rarotonga have evolved the ability to survive out of water and leap about on the rocky shoreline because this helps them escape predators in the ocean, a ground-breaking new study shows.

"Avoiding predators might be an explanation of why some animals move from their ancestral homes into starkly different environments, but evidence for this is rare because it is difficult to collect," says study first author Dr Terry Ord of UNSW Sydney.

"Our study of blennies on Rarotonga is the first to examine the pressures driving fish out of the water. There obviously have to be some major benefits for fish to make the dramatic shift onto land. Otherwise, why would they do it?


The study, by scientists at UNSW and the Australian National University, is published in The American Naturalist.

Rarotonga in the Cook Islands provides an extraordinary opportunity to study fish evolution in action because four species of blennies have independently emerged from the water to spend various amounts of time times on land.

The researchers observed the behaviour of three of these amphibious species, which divide their time between the water, the rock shelf in the intertidal zone, and the exposed land above the high tide mark.

"At low tide most of the blennies were on the rock shelf in the intertidal zone. Those remaining in the water actively avoided areas where there were predators, such as flounders, trevallies, wrasses and moray eels," says Dr Ord.

"As the tide came in and the rock shelf became submerged, most of the blennies moved to higher ground, above the high tide mark, apparently to avoid being eaten by the aquatic predators coming in with the rising water."

The team also created 250 replica blennies out of plasticine, and placed them in the water and on land above the high tide mark.

"There were far more attacks on the model fish from predators in the ocean than predators on the shore, showing there are obvious benefits for blennies in becoming fish out of water and colonising the land," says Dr Ord.

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X-ray tomographic picture (false colors) of fossil thread-like red algae.
Scientists at the Swedish Museum of Natural History have found fossils of 1.6 billion-year-old probable red algae. The spectacular finds, publishing on 14 March in the open access journal PLOS Biology, indicate that advanced multicellular life evolved much earlier than previously thought.

The scientists found two kinds of fossils resembling red algae in uniquely well-preserved sedimentary rocks at Chitrakoot in central India. One type is thread-like, the other one consists of fleshy colonies. The scientists were able to see distinct inner cell structures and so-called cell fountains, the bundles of packed and splaying filaments that form the body of the fleshy forms and are characteristic of red algae.

"You cannot be a hundred per cent sure about material this ancient, as there is no DNA remaining, but the characters agree quite well with the morphology and structure of red algae," says Stefan Bengtson, Professor emeritus of palaeozoology at the Swedish Museum of Natural History.

The earliest traces of life on Earth are at least 3.5 billion years old. These single-celled organisms, unlike eukaryotes, lack nuclei and other organelles. Large multicellular eukaryotic organisms became common much later, about 600 million years ago, near the transition to the Phanerozoic Era, the "time of visible life."

Discoveries of early multicellular eukaryotes have been sporadic and difficult to interpret, challenging scientists trying to reconstruct and date the tree of life. The oldest known red algae before the present discovery are 1.2 billion years old. The Indian fossils, 400 million years older and by far the oldest plant-like fossils ever found, suggest that the early branches of the tree of life need to be recalibrated.

"The 'time of visible life' seems to have begun much earlier than we thought," says Stefan Bengtson.

The presumed red algae lie embedded in fossil mats of cyanobacteria, called stromatolites, in 1.6 billion-year-old Indian phosphorite. The thread-like forms were discovered first, and when the then doctoral student Therese Sallstedt investigated the stromatolites she found the more complex, fleshy structures.


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Enormous Dust Storms on Mars Highlight the Red Planet's Weather Mysteries

Last week, scientists were surprised to see a second regional dust storm on Mars blooming only two weeks after another one in the same storm track.

NASA's Mars Reconnaissance Orbiter (MRO) showed both storms generated in the Acidalia area of northern Mars, then moving to the southern hemisphere and expanding to sizes bigger than the United States. While the path is normal, the frequency of the storms is unexpected.

"What we're trying to understand is the weather of Mars," said Richard Zurek, chief scientist for the Mars program at NASA's Jet Propulsion Laboratory and the project scientist for MRO.

One mystery is what determines the scale of a dust storm. There are many local storms, a few that become more regional, and then even fewer where enough dust is lofted into the atmosphere to become global, Zurek said.

So far, scientists see that global dust storms tend to happen during the spring and summer in the southern hemisphere, when Mars is closest to the sun and heating is at a maximum to generate winds. The orbit tends to change every 100,000 years. So in older times, when Mars' elliptical orbit exposed other parts of the planet to maximum heating, dust generation may have happened differently — but scientists don't know that for sure yet, Zurek pointed out.

Only the smallest dust particles are lifted high in the atmosphere; sometimes, larger bits of dust hop along the surface and dislodge finer materials that float up. Global dust storms have happened a few times since NASA started observing Mars. One famous example was a 1971 dust storm that raged as Mariner 9 orbited the planet. Scientists saw the peaks of volcanoes peeking above the clouds, but not much else. The last global dust storm was 2007.

While Martian dust dominates the lower atmosphere, dust from other sources, like the planet's moons Phobos and Deimos, is sprinkled in the upper part. A new model based on NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft suggests that most dust is from interplanetary sources.

"It has been found that flux rate at Mars is dominated (~2 orders of magnitude higher) by interplanetary particles in comparison with the satellite originated dust," say Jayesh Pabari and P.J. Bhalodi in an article published in the journal Icarus.

"It is inferred that the dust at high altitudes of Mars could be interplanetary in nature," they continue, "and our expectation is in agreement with the MAVEN observation."

Zurek said scientists are monitoring the infall of dust into Mars' atmosphere, and saw a spike when Comet Siding Spring zoomed close to the planet in October 2014, shortly after MAVEN arrived. The spacecraft detected a particular kind of dust — magnesium — that was ionized as it fell into the atmosphere, generating auroras.

At upper altitudes, however, dust does not have much effect on the climate, Zurek said. Occasionally particles will seed clouds, but that's about it. Zurek added that the effects could have been different in the ancient past, when there were more asteroids jumbled around the solar system and thus more dust was falling into Mars.

Read more at Discovery News

Drought, Deforestation Set to Propel Vicious Amazon Die Off

Reduced rainfall across the Amazon basin is causing large areas of forests to die, which could be amplifying drought conditions across the region.

Researchers from the Potsdam Institute for Climate Impact Research believe that this process, known as self-amplifying forest loss, could cause a vicious circle of drought and further forest loss across the Amazon region, according to a study published in Nature Communications.

"We already know that on the one hand, reduced rainfall increases the risk of forest dieback, and on the other hand, forest loss can intensify regional droughts," lead-author of the study, Delphine Clara Zemp, said in a statement, calling the Amazon "one of the tipping elements in the Earth system."

The survival of tropical forests depends on the very water that they hold, according to PIK researchers, who studied water fluxes across the region to determine the level of interaction between vegetation and the atmosphere.

In the Amazon, one of the most important carbon sinks on the planet, trees evaporate the moisture that will eventually rain back onto them.

"As powerful as the cycle is, it is also surprisingly susceptible to environmental changes," co-author Henrique M.J. Barbosa from the Universidade de Sao Paulo said in a statement. "And humankind is imposing massive perturbations on Amazonia by both cutting down the trees and heating up the air with greenhouse gases."

This, Barbosa explained, has the effect of reducing large-scale moisture transportation and rainfall.

(a) Amazon system in equilibrium. (b) Initial forest loss triggered by decreasing oceanic moisture inflow, which reduces evapotranspiration. (c) As a result, the rainfall regime is altered in another location, leading to further forest loss and reduced moisture transport.
While the Amazon spans nine countries, covering an estimated 2.6 million square miles, some 60 percent of the basin lies in Brazil.

After many years of decelerated deforestation across the Amazon basin, in 2015, Brazil reported a rise for the first time in nearly a decade and at the end of 2016, the government released a study showing that deforestation in the Amazon had jumped 26 percent from the previous year.

Researchers at the Postdam Institute worry that another logging spike could push the Amazon into a vicious dieback cycle that would include hotter dry seasons, more forest loss, and continued drought. They estimate that in addition to direct forest loss due to reduced rainfall, 10 percent of the forest could be lost due to the effects of self-amplification.

This forest–atmosphere feedback cycle could cause forest dieback in 38 percent of the Amazon basin. Combined with the direct effects of drought, this could mean that most of the Amazon would eventually be at risk. Even if rainfall were to remain stable, the intensification of the dry season could be strong enough to tip the ecosystem, turning large swaths of the Amazon into savannah.

"Projected rainfall changes for the end of the 21st century will not lead to complete Amazon dieback," Carl Schleussner, from Berlin-based scientific think tank Climate Analytics and PIK, said. "But our findings suggest that large parts of it are certainly at risk."

Read more at Discovery News

Mar 13, 2017

Star discovered whipping around a black hole twice an hour










Read more at Science Daily


About 700 million years ago, runaway glaciers covered the entire planet in ice. Harvard researchers modeled the conditions that may have led to this so-called 'snowball Earth.'

Now, Harvard University researchers have a new hypothesis about what caused the runaway glaciation that covered Earth pole-to-pole in ice.

The research is published in Geophysical Research Letters.


Harvard professors Francis Macdonald and Robin Wordsworth thought not.




The answer: yes, under the right conditions.




"In periods of Earth's history when it was very warm, volcanic cooling would not have been very important because Earth would have been shielded by this warm, high tropopause," said Wordsworth. "In cooler conditions, Earth becomes uniquely vulnerable to having these kinds of volcanic perturbations to climate."









Read more at Science Daily

Red tides can be predicted, new study shows

A red tide turns bioluminescent off Scripps Oceanography Pier.












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Final biomedical trial on captive chimpanzees is first oral Ebola vaccine for saving wild apes

One of the captive chimpanzees in the research trial receiving the oral Ebola vaccination.
The results from the final biomedical research trial on captive chimpanzees for the foreseeable future have been published in the journal Scientific Reports.


In addition to poaching and forest loss, diseases such as Ebola and anthrax have devastated wild ape populations. Ebola alone is estimated to have killed one third of the world's wild gorillas over the last three decades.


However, after decades using chimpanzees to test vaccines destined for humans, changes in the law have seen enforced retirement of captive populations and the closing of chimpanzee research facilities in the US -- the last developed country where biomedical testing on chimpanzees was legal.

In what researchers describe as a "horrible irony," they say these reforms -- a victory for long-standing campaigns by animal welfare groups -- will ultimately prove detrimental to chimpanzees and gorillas in the wild, as any vaccination for wild animals must be tested in captivity first to ensure its safety.


"In 2014 the world was gripped by fears of an Ebola virus pandemic. Yet few people realise that Ebola has already inflicted pandemic scale mortality on our closest relatives," says lead researcher Dr Peter Walsh from the University of Cambridge.




Previous attempts to vaccinate wild apes have resorted to administering individual animals with hypodermic darts -- a laborious task feasible for only a small number of apes habituated to human approach. By contrast, oral vaccines encased in appealingly edible baits could be distributed across wild ape territories to inoculate large numbers over longer periods.



All the animals displayed a robust immunity without side effects after 28 days -- when the trial was terminated due to new Endangered Species Act regulations banning biomedical research on chimpanzees.


"Some pressure groups argue that all research on captive chimpanzees is tantamount to torture, not just because of procedures but also due to confinement," says Walsh.


Captive chimpanzee trials are technically still legal in the US in instances that benefit the species. However, Walsh says that the limited funds available for conservation research makes it unviable for biomedical facilities to retain populations, while zoos and sanctuaries are either "ideologically opposed" or unwilling to risk any public backlash from testing.


"In an ideal world, there would be no need for captive chimpanzees," says Walsh. "But this is not an ideal world. It is a world where diseases such as Ebola, along with rampant commercial poaching and habitat loss, are major contributors to rapidly declining wild ape populations.

Read more at Science Daily