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.

Read more at Science Daily

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.

Read more at Science Daily

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.
Hawaii's unique animal and plant diversity has been declining on all but the Big Island for millions of years, long before humans arrived, according to a new analysis of species diversity on the islands by University of California, Berkeley, evolutionary biologists.

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.

They reached this conclusion with a new method for analyzing the species diversity on the different islands in the multiple-island chain, deducing the history of diversification on each island with their new approach for 14 different groups, or clades, of birds, insects, spiders and plants.

"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?"

He is currently developing ways to extend the new approach developed to analyze Hawaii to other parts of the globe.

Marshall and Lim published their findings online March 15 in advance of publication in the journal Nature.

Hot spot

The volcanic Hawaiian islands we see today emerged from the waves over a period of about 6 million years, carried northwestward as the ocean crust moved over from the hot spot that brought the magma from inside Earth to the sea floor to build the islands. Kauai emerged slightly more than 6 million years ago, the newest, the Big Island of Hawaii, only about 1.3 million years ago.

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."

This insight came after previous work suggested that the only way to explain why, in the past, some mammal groups declined over millions of years was that the carrying capacity of the ecosystem had crashed, leading to severe overcrowding, more than expected by equilibrium theory.

The Hawaiian archipelago proved a good place to test that hypothesis, since the islands, once active volcanism ceases, steadily shrink. Maui Nui is less than one-third its original size 2-3 million years ago.

Read more at Science Daily

Operation of ancient biological clock uncovered

At ambient temperature, the circadian clock of cyanobacteria is constantly ticking and its 'molecular cogwheels' keep spinning. This makes it difficult to understand the clockwork mechanism. Cooling down the clock puts its cogwheels to rest, allowing to visualize details of their appearance and assembly.
Ten years ago, researchers discovered that the biological clock in cyanobacteria consists of only three protein components: KaiA, KaiB and KaiC. These are the building blocks -- the gears, springs and balances -- of an ingenious system resembling a precision Swiss timepiece. In 2005, Japanese scientists published an article in Science showing that a solution of these three components in a test tube could run a 24-hour cycle for days when a bit of energy was added. However, the scientists were not able to uncover the exact operation of the system, despite its relative simplicity.

William Faulkner

How could the scientists resolve the working of the individual pieces? "In the end, the trick to understand the ticking biological clock in cyanobacteria was to literally make time stop," tells research leader Albert Heck from Utrecht University. "Or as William Faulkner, Nobel Prize Laureate in Literature said: 'Only when the clock stops does time come to life.' Faulkner spoke taking a pause in the constant haste of life. That was also the trick here. We slowed the biological clock by running it in the fridge for a week. In the literal sense we have frozen the time."

New combination

In addition to stopping time, the researchers applied a new combination of cutting-edge research techniques. With one technique, they were able to determine how often each of the three protein complexes -- KaiA, KaiB and KaiC -- assembled or disassembled in a single 24-hour cycle. This taught them which collections of protein components -- combinations of gears, springs and balances -- determine the daily rhythm.

Zooming in

They then stopped the clock at specific moments by reducing the temperature. This allowed them to use a variety of techniques to zoom in in great detail on the structure of the collection of protein components at that moment -- the position of the gears, springs and balances. In so doing, they identified the two structures that are vital to understanding how the clock works. The researchers could then derive how the wheels turn by determining the transitions from one structure to another. This produced a model that shows exactly how only three protein components form a precision timepiece that operates on a 24-hour cycle.

Read more at Science Daily

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.
An international team of researchers discovered 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.
Big, small, broad, narrow, long or short, turned up, pug, hooked, bulbous or prominent, humans inherit their nose shape from their parents, but ultimately, the shape of someone's nose and that of their parents was formed by a long process of adaptation to our local climate, according to an international team of researchers.

"We are interested in recent human evolution and what explains the evident variation in things like skin color, hair color and the face itself," said Mark D. Shriver, professor of anthropology, Penn State. "We focused on nose traits that differ across populations and looked at geographical variation with respect to temperature and humidity." The researchers noted today (Mar. 17) in PLOS Genetics that "An important function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tract."

They considered a variety of nose measurements, looking at the width of the nostrils, the distance between nostrils, the height of the nose, nose ridge length, nose protrusion, external area of the nose and the area of the nostrils. The measurements were made using 3D facial imaging.

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.

The researchers found that the width of the nostrils and the base of the nose measurements differed across populations more than could be accounted for by genetic drift, indicating a role for natural selection in the evolution of nose shape in humans. To show that the local climate contributed to this difference, the researchers looked at the spatial distribution of these traits and correlated them with local temperatures and humidity. They showed that the width of the nostrils is strongly correlated with temperature and absolute humidity The researchers noted that "the positive direction of the effects indicate that wider noses are more common in warm-humid climates, while narrower noses are more common in cold-dry climates."

"It all goes back to Thompson's Rule (Arthur Thompson)," said Shriver. "In the late 1800s he said that long and thin noses occurred in dry, cold areas, while short and wide noses occurred in hot, humid areas. Many people have tested the question with measurements of the skull, but no one had done measurements on live people."

One purpose of the nose is to condition inhaled air so that it is warm and moist. The narrower nostrils seem to alter the airflow so that the mucous-covered inside of the nose can humidify and warm the air more efficiently. It was probably more essential to have this trait in cold and dry climates, said Shriver. People with narrower nostrils probably fared better and had more offspring than people with wider nostrils, in colder climates. This lead to a gradual decrease in nose width in populations living far away from the equator.

Shriver notes that this is not the only explanation for nose-shape variation in humans. The researchers also found differences between men and women in nose features across the board. This sexual dimorphism is not unusual, as human men tend to be larger than human women, and their noses would be larger as well.

He thinks another way that the cross-population differences in nose size may occur is through sexual selection. People may choose mates simply because they find a smaller or larger nose more attractive. If an entire group thinks small is better, then those with large noses will have less success in reproducing and fewer large-nosed people will be in the group. Over time, the nose size in the group will shrink relative to other groups where large noses are favored. These notions of beauty may be linked to how well-adapted the nose is to the local climate.

Read more at Science Daily

Scientists identify a black hole choking on stardust

In this artist's rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole.
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."

Such flares occur when a star, migrating close to a black hole, gets pulled apart from the black hole's immense gravitational energy. This stellar obliteration can give off incredible bursts of energy all along the electromagnetic spectrum, from the radio band, through the optical and UV wavelengths, and on through the X-ray and high-energy gamma ray bands. As extreme as they are, tidal disruption flares are difficult to observe, as they happen infrequently.

"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.

From simulations run by others, the researchers conclude that the optical and UV bursts likely originated from the collision of stellar debris on the outer perimeter of the black hole. As this colliding material circles closer into the black hole, it heats up, eventually giving off X-ray emissions, which can lag behind the optical emissions, similar to what the scientists observed in the data.

Read more at Science Daily

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.
An enormous young planet approximately 300 light-years from Earth has given astrophysicists a rare glimpse into planetary evolution.

The planet, known as HD 106906b, was discovered in 2014 by a team of scientists from the U.S., the Netherlands and Italy. It is 11 times the mass of Jupiter and is extremely young by celestial standards -- not more than 13 million years old, compared with our solar system's 4.6 billion years.

"This is such a young star; we have a snapshot of a baby star that just formed its planetary system -- a rare peek at the final stage of planet formation," said Smadar Naoz, a UCLA assistant professor of physics and astronomy, and a co-author of the study.

Another of the planet's unusual characteristics is its distance from its star. Astronomers believe that the vast majority of planets outside of our solar system exist inside a vast dusty disk of debris relatively close to the center of the solar system. But HD 106906b is far beyond its solar system's disk -- so far away that it takes 1,500 years for the planet to orbit its star. HD 106906b is currently at least 650 times as far from its star as the Earth is from our sun.

"Our current planet formation theories do not account for a planet beyond its debris disk," Naoz said.

The study's lead author is Erika Nesvold, a postdoctoral fellow at the Carnegie Institution for Science whom Naoz mentors. She wrote software called Superparticle-Method Algorithm for Collisions in Kuiper belts and debris disks, or SMACK, that allowed the researchers to create a model of the planet's orbital path -- a critical step because HD 106906b orbits so slowly that the researchers can barely see it move.

The research, published online in the Astrophysical Journal Letters, suggests that the planet formed outside the disk, where it's visible it today, as opposed to having been formed inside the debris disk and then having been thrust far beyond it.

Naoz said that conclusion helps explain the shape of the debris disk. "It works perfectly," she said.

The planet's orbit is elliptical; it gets much closer to the star on one side of its orbit than on the other side. And its gravity produces an elliptical shape in the disk as well. One side of the disk is closer to the star than the other side, and the dust on that side is warmer and glows brighter as a result.

The debris disk was photographed in 2016 by American and European astronomers. According to Naoz, the disk is an analog to our solar system's Kuiper belt -- an enormous cluster of small bodies like comets and minor planets located beyond Neptune.

The researchers don't know if there are additional planets inside the disk, but using Nesvold's software -- which also been used to study other debris disks in the universe -- they were able to re-create the shape of the disk without adding another planet into the model, as some astronomers had thought would be required.

Debris disks are composed of gas, dust and ice, and they play a key role in the formation of planets. Typically, Naoz said, planets form after a gas cloud collapses due to its own gravity, forming a disk -- where planets are created -- and a star. As the gas slowly evaporates, the dust and debris rotate and collide around the young star until gravity pushes them away, forming a structure like our solar system's Kuiper belt.

"In our solar system, we've had billions of years of evolution," said Michael Fitzgerald, UCLA associate professor of physics and astronomy, and the study's other co-author. "We're seeing this young system revealed to us before it has had a chance to dynamically mature."

Naoz said the researchers' conclusions do not require any exotic physics or hidden planets to explain them, which is not always the case in studying other solar systems.

Read more at Science Daily

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

Photograph of the ancient crust such as these found along the eastern shores of the Hudson Bay.
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.

The approach employed in this study examined variations in the abundance of an isotope of the element neodymium, which is created by the radioactive decay of a different element, samarium.

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.

"Whether this result implies that plate tectonics was not at work during the earliest part of Earth history can now be investigated using our tool of studying neodymium-142 variation to track the role of truly ancient crust in building up younger, but still old, sections of Earth's continental crust," Carlson explained.

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Mar 15, 2017

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

This is an analyzed snapshot of a moment of turbulent flow, in this case, an exact coherent structure (ECS).
An old adage holds that the flap of a butterfly's wing in Brazil can trigger a tornado in Texas weeks later. Though chaos theory says it's basically impossible to compute exactly how that might happen, scientists have made advances in applying math to predict the phenomenon behind it called turbulence.

Recent progress by physicists from the Georgia Institute of Technology could one day help sharpen weather forecasts and extend their range by making better use of masses of weather and climate data.

Turbulence can curve as a puff of air, swirl past a river bend or churn as a hurricane, and though its curlicues may appear random, turbulence lays down signature patterns that the physicists are investigating. They have developed a simple mathematical model that has helped them show how turbulent flows will evolve over intervals.

And, in a novel experiment, they verified their predictions physically in a two-dimensional turbulent flow produced in a lab.

'Butterfly Effect' catchphrase

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

It was coined more than 55 years ago by MIT meteorology professor Edward Lorenz after he established that tiny forces influenced major weather enough to throw long-range forecasts for a loop. The title of his paper, "Predictability: Does the Flap of a Butterfly's Wing in Brazil Set Off a Tornado in Texas?" morphed into the well-known catchphrase.

Michael Schatz and Roman Grigoriev, professors in Georgia Tech's School of Physics, along with graduate researchers Balachandra Suri and Jeffrey Tithof, published their research results online in the journal Physical Review Letters on Wednesday March 15, 2017. The research was funded by the National Science Foundation.

Order in chaos

For hundreds of years, while scientists used math to get a grip on Newton's falling apple, substantiate the Theory of Relativity and theorize the existence of the Higgs boson, turbulence has been like wet soap in math's grasp. But for all its elusiveness, turbulence impresses with visibly coherent, recurring, recognizable shapes.

Fluid swirls quickly establish themselves then shift or disappear, but they reappear persistently at different locations, producing transient and varying, yet repeating patterns.

"People have seen these patterns in turbulent flows for centuries, but we're finding ways to relate the patterns to mathematical equations describing fluid flows," Grigoriev said. Some recurrent patterns, in particular, interest Grigoriev and Schatz. They're called exact coherent structures (ECSs).

They give the physicists convenient entry points into computing predictions about what turbulence will do next.

Turbulent flow snapshots

But what are these exact coherent structures? Visually, in turbulence, they may show up as fleeting moments when the patterns stop changing. And it can look like the flow is temporarily slowing down.

To the untrained eye, an ECS doesn't look much different from the rest of the swirls and curls, but one can learn to spot them. "That's exactly how we go about finding them," Schatz said. "We watch the turbulence, continually taking snapshots. The flow is moving around, moving around. We look for the instant when it slows down the most, and we pick out a snapshot."

"We feed that into the mathematical model," Schatz said, "and it indicates that we're close, and shows what the math looks like at that point." That math solution describes a point in the turbulent flow that can be worked with to compute a prediction of what the turbulence will do next.

To understand what an exact coherent structure is dynamically, we need to step back from what turbulence looks like visually with bunches of curls and swirls. Instead, let's look at a turbulent flow as a single physical entity by translating it into a crude metaphor, a swinging pendulum -- with some marked oddities.

Pendulum on its head

This is going to get a bit abstract: First, invert the pendulum.

Instead of picturing the bottom point of a normal pendulum's swing, the equilibrium, as a stable point in a stable swing, now, with the upside-down pendulum, the equilibrium is the top-most point. And it's unstable. Also, it doesn't swing in just two directions but in all directions.

A turbulent flow's reliable patterns reflect dynamics that are back-and-forth-to-and-fro but in all kinds of variations.

As the metaphorical pendulum swings up toward its peak, it comes to a near but never complete stop. Instead it flops over to some other side. That near-halt point is analogous to an exact coherent structure, but there are a few more kinks in the metaphor.

"If we change initial dynamics ever so slightly, an inverted pendulum can swing past its unstable equilibrium at the peak, or it can stop and then start moving in the opposite direction. In the same way, the turbulent flow can evolve in various different ways after passing by an ECS," Grigoriev said.

Multiple exact coherent structures with varying qualities turn up in a turbulent flow.

Turbulence roads to ECS cities

That all may feel unusual for a reason.

"Usually, people like to look at stable things that are unchanging like the even, symmetric normal pendulum," Schatz said. "It turns out it's really these unstable patterns that form a rough core alphabet that we use to build a sort of predictive theory."

Staying with the dynamics of that floppy inverted pendulum, now picture each exact coherent structure as being a city on a map. There are paths that guide the turbulent flow "traffic" toward, from, and around each city just like roadways. "This road map around and between cities does not change in time, which enables us to predict the evolution of the flow," Grigoriev said.

ECSs occur regularly, almost like clockwork, opening up the possibility of refining predictions at regular intervals.

Exact coherent structures were already known to exist, Schatz said. "What no one has done before is demonstrate in a lab experiment how they can be harnessed to describe dynamics, the behavior evolving in time, which is really what you need for prediction."

Mining weather data

In the 19th century, math equations were developed to describe the basic flow of fluids. Those who took high school physics may remember Newton's Second Law relating forces, acceleration and mass. The Navier-Stokes equations, used in this study, apply it to fluids.

Turbulence is challenging to describe mathematically because its swirls contain myriad dimensions, with the flow in each small region appearing to dance to its own tune. But there is clear order that emerges upon finding exact coherent structures.

To make their predictions, Schatz and Grigoriev's research team devised a way to mathematically connect that high dimensionality to the much simpler roadway concept.

They broke down the turbulent flow into regions, each small enough to apply the equations, then used their solutions to precisely place the flows on the road map.

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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.

Now, an international team of astronomers led by Reinhard Genzel at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany have used the KMOS and SINFONI instruments at ESO's Very Large Telescope in Chile to measure the rotation of six massive, star-forming galaxies in the distant Universe, at the peak of galaxy formation 10 billion years ago.

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.

"Surprisingly, the rotation velocities are not constant, but decrease further out in the galaxies," comments Reinhard Genzel, lead author of the Nature paper. "There are probably two causes for this. Firstly, most of these early massive galaxies are strongly dominated by normal matter, with dark matter playing a much smaller role than in the Local Universe. Secondly, these early discs were much more turbulent than the spiral galaxies we see in our cosmic neighbourhood."

Both effects seem to become more marked as astronomers look further and further back in time, into the early Universe. This suggests that 3 to 4 billion years after the Big Bang , the gas in galaxies had already efficiently condensed into flat, rotating discs, while the dark matter halos surrounding them were much larger and more spread out. Apparently it took billions of years longer for dark matter to condense as well, so its dominating effect is only seen on the rotation velocities of galaxy discs today.

This explanation is consistent with observations showing that early galaxies were much more gas-rich and compact than today's galaxies.

The six galaxies mapped in this study were among a larger sample of a hundred distant, star-forming discs imaged with the KMOS and SINFONI instruments at ESO's Very Large Telescope at the Paranal Observatory in Chile. In addition to the individual galaxy measurements described above, an average rotation curve was created by combining the weaker signals from the other galaxies. This composite curve also showed the same decreasing velocity trend away from the centres of the galaxies. In addition, two further studies of 240 star forming discs also support these findings.

Read more at Science Daily

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.
During the ice ages, an unidentified regulatory mechanism prevented atmospheric CO2 concentrations from falling below a level that could have led to runaway cooling, reports a study conducted by researchers of the ICTA-UAB and published online in Nature Geoscience this week. The study suggests the mechanism may have involved the biosphere, as plants and plankton struggled to grow under very low CO2 levels.

Atmospheric CO2 concentrations swung over a range of 100 ppm (parts per million, by volume) during the ice ages. The exact processes behind this variation have been difficult to pinpoint, but it is known that changes in the storage of carbon by photosynthetic organisms played an important role.

"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."

The authors suggest that it was most likely the biosphere that maintained habitable temperatures, since at very low CO2 levels, plants and phytoplankton struggle to photosynthesize. Slower growth of these organisms would have meant less carbon in the soils and deep ocean leaving more in the atmosphere, and preventing CO2 concentrations from falling further. This might have prevented extreme cooling that would have led to Earth freezing over as a 'snowball'.

Read more at Science Daily

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.

To test his hypothesis, Wright reviewed archaeological evidence documenting the first appearances of pastoralism across the Saharan region, and compared this with records showing the spread of scrub vegetation, an indicator of an ecological shift towards desert-like conditions. The findings confirmed his thoughts; beginning approximately 8,000 years ago in the regions surrounding the Nile River, pastoral communities began to appear and spread westward, in each case at the same time as an increase in scrub vegetation.

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.

There is much work still to do to fill in the gaps, but Wright believes that a wealth of information lies hidden beneath the surface: "There were lakes everywhere in the Sahara at this time, and they will have the records of the changing vegetation. We need to drill down into these former lake beds to get the vegetation records, look at the archaeology, and see what people were doing there. It is very difficult to model the effect of vegetation on climate systems. It is our job as archaeologists and ecologists to go out and get the data, to help to make more sophisticated models."

Read more at Science Daily

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?

"It turns out the aquatic environment is a nasty place for blennies, full of enemies wanting to eat these small fish. But life is less hostile on the rocks, with birds their main worry," he says.

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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World's oldest plant-like fossils show multicellular life appeared earlier than thought

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.

"I got so excited I had to walk three times around the building before I went to my supervisor to tell him what I had seen!" she says.

Read more at Science Daily

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.

Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed.
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

Astronomers have found evidence for a star that whips around a black hole about twice an hour. This may be the tightest orbital dance ever witnessed for a black hole and a companion star.
Astronomers have found evidence for a star that whips around a black hole about twice an hour. This may be the tightest orbital dance ever witnessed for a black hole and a companion star.

Michigan State University scientists were part of the team that made this discovery, which used NASA's Chandra X-ray Observatory as well as NASA's NuSTAR and the Australia Telescope Compact Array.

The close-in stellar couple -- known as a binary -- is located in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years away from Earth. While astronomers have observed this binary for many years, it wasn't until 2015 that radio observations revealed the pair likely contains a black hole pulling material from a companion star called a white dwarf, a low-mass star that has exhausted most or all of its nuclear fuel.

New Chandra data of this system, known as X9, show that it changes in X-ray brightness in the same manner every 28 minutes, which is likely the length of time it takes the companion star to make one complete orbit around the black hole. Chandra data also shows evidence for large amounts of oxygen in the system a characteristic of white dwarfs. A strong case can, therefore, be made that that the companion star is a white dwarf, which would then be orbiting the black hole at only about 2.5 times the separation between Earth and the moon.

"This white dwarf is so close to the black hole that material is being pulled away from the star and dumped onto a disk of matter around the black hole before falling in," said Arash Bahramian, lead author with the University of Alberta (Canada) and MSU. "Luckily for this star, we don't think it will follow this path into oblivion, but instead will stay in orbit."

Although the white dwarf does not appear to be in danger of falling in or being torn apart by the black hole, its fate is uncertain.

"For a long time astronomers thought that black holes were rare or totally absent in globular star clusters," said Jay Strader, MSU astronomer and co-author of the paper. "This discovery is additional evidence that, rather than being one of the worst places to look for black holes, globular clusters might be one of the best."

How did the black hole get such a close companion? One possibility is that the black hole smashed into a red giant star, and then gas from the outer regions of the star was ejected from the binary. The remaining core of the red giant would form into a white dwarf, which becomes a binary companion to the black hole. The orbit of the binary would then have shrunk as gravitational waves were emitted, until the black hole started pulling material from the white dwarf.

The gravitational waves currently being produced by the binary have a frequency that is too low to be detected with Laser Interferometer Gravitational-Wave Observatory, LIGO, that has recently detected gravitational waves from merging black holes. Sources like X9 could potentially be detected with future gravitational wave observatories in space.

Read more at Science Daily

A perfect storm of fire and ice may have led to snowball Earth

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.'
What caused the largest glaciation event in Earth's history, known as 'snowball Earth'? Geologists and climate scientists have been searching for the answer for years but the root cause of the phenomenon remains elusive.

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.

Researchers have pinpointed the start of what's known as the Sturtian snowball Earth event to about 717 million years ago -- give or take a few 100,000 years. At around that time, a huge volcanic event devastated an area from present-day Alaska to Greenland. Coincidence?

Harvard professors Francis Macdonald and Robin Wordsworth thought not.

"We know that volcanic activity can have a major effect on the environment, so the big question was, how are these two events related," said Macdonald, the John L. Loeb Associate Professor of the Natural Sciences.

At first, Macdonald's team thought basaltic rock -- which breaks down into magnesium and calcium -- interacted with CO2 in the atmosphere and caused cooling. However, if that were the case, cooling would have happened over millions of years and radio-isotopic dating from volcanic rocks in Arctic Canada suggest a far more precise coincidence with cooling.

Macdonald turned to Wordsworth, who models climates of non-Earth planets, and asked: could aerosols emitted from these volcanos have rapidly cooled Earth?

The answer: yes, under the right conditions.

"It is not unique to have large volcanic provinces erupting," said Wordsworth, assistant professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Science. "These types of eruptions have happened over and over again throughout geological time but they're not always associated with cooling events. So, the question is, what made this event different?"

Geological and chemical studies of this region, known as the Franklin large igneous province, showed that volcanic rocks erupted through sulfur-rich sediments, which would have been pushed into the atmosphere during eruption as sulfur dioxide. When sulfur dioxide gets into the upper layers of the atmosphere, it's very good at blocking solar radiation. The 1991 eruption of Mount Pinatubo in the Philippines, which shot about 10 million metric tons of sulfur into the air, reduced global temperatures about 1 degree Fahrenheit for a year.

Sulfur dioxide is most effective at blocking solar radiation if it gets past the tropopause, the boundary separating the troposphere and stratosphere. If it reaches this height, it's less likely to be brought back down to earth in precipitation or mixed with other particles, extending its presence in the atmosphere from about a week to about a year. The height of the tropopause barrier all depends on the background climate of the planet -- the cooler the planet, the lower the tropopause.

"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."

"What our models have shown is that context and background really matters," said Macdonald.

Another important aspect is where the sulfur dioxide plumes reach the stratosphere. Due to continental drift, 717 million years ago, the Franklin large igneous province where these eruptions took place was situated near the equator, the entry point for most of the solar radiation that keeps Earth warm.

So, an effective light-reflecting gas entered the atmosphere at just the right location and height to cause cooling. But another element was needed to form the perfect storm scenario. After all, the Pinatubo eruption had similar qualities but its cooling effect only lasted about a year.

The eruptions throwing sulfur into the air 717 million years ago weren't one-off explosions of single volcanoes like Pinatubo. The volcanoes in question spanned almost 2,000 miles across Canada and Greenland. Instead of singularly explosive eruptions, these volcanoes can erupt more continuously like those in Hawaii and Iceland today. The researchers demonstrated that a decade or so of continual eruptions from this type of volcanoes could have poured enough aerosols into the atmosphere to rapidly destabilize the climate.

"Cooling from aerosols doesn't have to freeze the whole planet; it just has to drive the ice to a critical latitude. Then the ice does the rest," said Macdonald.

The more ice, the more sunlight is reflected and the cooler the planet becomes. Once the ice reaches latitudes around present-day California, the positive feedback loop takes over and the runaway snowball effect is pretty much unstoppable.

"It's easy to think of climate as this immense system that is very difficult to change and in many ways that's true. But there have been very dramatic changes in the past and there's every possibility that as sudden of a change could happen in the future as well," said Wordsworth.

Understanding how these dramatic changes occur could help researchers better understand how extinctions occurred, how proposed geoengineering approaches may impact climate and how climates change on other planets.

Read more at Science Daily

Red tides can be predicted, new study shows

A red tide turns bioluminescent off Scripps Oceanography Pier.
When certain types of algae accumulate at the ocean surface in high numbers, they turn large swaths of water a reddish-brown color, attracting attention for both good and bad reasons.

Off the coast of Southern California these events, known as "red tides," can produce awe-inspiring nighttime light shows by illuminating breaking waves and creating eerie blue trails behind surf fish. However, in other areas such as off Florida and in the the Great Lakes these blooms can be toxic, causing fish die-offs, shellfish poisoning, and triggering respiratory problems in humans and marine mammals.

For over a century, scientists have been trying to understand what causes red tides to form in coastal areas seemingly out of nowhere. Using a novel technique developed by Scripps Institution of Oceanography at the University of California San Diego scientist George Sugihara and colleagues, that mystery is finally being unraveled.

A student-led Scripps research team analyzed data on the primary pigment in algae -- chlorophylla -- as well as nutrient concentrations and various physical aspects of the ocean collected off Scripps Pier as part of a continuous observation program, led by Scripps Emeritus Professor John McGowan, that is part of the Scripps Shore Stations Program.

When the ecological data were fed into Sugihara's equation-free models, known as empirical dynamic modeling (EDM), the researchers were able to identify patterns in the apparent randomness that can be used to predict red tides off Southern California.

The new study, to be published in the journal Ecology and available online, found that red tides are not purely random. It offers opportunities to predict these harmful algal blooms that could not be forecast using traditional ecological modeling methods.

"Red tides were a mystery for so many years because we were looking at the ecosystem as if it was in equilibrium and unchanging and therefore could be studied a piece at a time," said Sugihara, the McQuown Chair Distinguished Professor of Natural Science and a senior author on the study. "It was a mystery only because we were looking at it the wrong way. Looking for things that simply 'correlate' with red tides will fail."

The EDM method is based on the idea that the ecosystem is always changing and must be studied as a whole system rather than as separate pieces. Analyzing the ecosystems holistically enabled Sugihara and his team to use the 30-year archive of field data to identify the mechanisms causing red tides.

"Even with vast improvements in 'ecosystem forecasting' over the past few decades, it remains a major challenge for scientists," said Alan Tessier, deputy director of the National Science Foundation's (NSF) Division of Environmental Biology. "This research shows that the challenge is being overcome using innovative techniques that offer us information such as how to predict red tides. That's important for knowing when to close fisheries and swimming areas, and for the health of residents who live along affected waters."

"The approach allowed us to find factors that come together as a perfect storm to produce a red tide," said Sugihara. "These factors include having a stable water column and low nutrient levels in surface waters."

With further model improvements to incorporate real-time observations, Sugihara and team believe that these algal blooms could be predicted as part of an early-warning system for future red-tide events.

In addition to the public health concerns, these algal blooms cause operational issues at power and desalinization plants, and create oxygen-depleted zones in the ocean. Advanced prediction of red tides can help provide more proactive responses to the human and animal health repercussions, guide temporary shutdowns of desalinization plants, and aid in the planning of military training exercise in coastal waters.

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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.

The trial was of a vaccination for Ebola: the first orally administered vaccine for any disease developed specifically for the purpose of conserving wild apes.

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.

Now, new findings have shown an effective oral vaccine for Ebola in chimpanzees, and that the captive animals involved in the trial exhibited very few signs of stress as a result. Researchers say the work demonstrates a model that could be harnessed for other diseases and ape species in the wild.

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.

Consequently, the promising new vaccine model may never progress to the point where it can be used to inoculate endangered wild apes, say the research team from the universities of Cambridge, UK, and Thomas Jefferson and Louisiana, US.

"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.

"African apes are also threatened by naturally occurring pathogens like anthrax, and the increasing overspill of human pathogens such as measles. A glimmer of hope lies in the fact that many of the disease threats are now vaccine preventable.

"We have developed a very promising tool for inoculating ape species against the myriad deadly diseases they face in the wild, but continued progress relies on access to a small number of captive animals.

"This may be the final vaccine trial on captive chimpanzees: a serious setback for efforts to protect our closest relatives from the pathogens that push them ever closer to extinction in the wild."

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.

Such an approach has already proved successful in other species: almost eliminating fox rabies (and the consequent need to cull foxes) across continental Europe.

The latest study was carried out with ten chimpanzees in one of the last remaining chimpanzee research facilities in the US in New Iberia, Louisiana. Six received the oral vaccine, while four were injected as a control group.

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.

Throughout the trial, scientists closely monitored animal behaviour and physiology for signs of severe stress. Other than very minor weight loss (2% of body mass), they say that signs of trauma were "entirely absent."

"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.

"Enclosures and animal care are now of a very high standard, with chimpanzees housed in large social spaces. The modest traces of stress we detected during our trial were akin to the values observed in college students anticipating exams."

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.

Further work to enhance the vaccine, such as ensuring effectiveness after exposure to high tropical forest temperatures, may now never get done due to the closure of captive chimpanzee facilities.

"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.

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