Oct 20, 2016
The large and distant planet may be adding a wobble to the solar system, giving the appearance that the Sun is tilted slightly.
"Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment," says Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery.
All of the planets orbit in a flat plane with respect to the Sun, roughly within a couple degrees of each other. That plane, however, rotates at a six-degree tilt with respect to the Sun giving the appearance that the Sun itself is cocked off at an angle. Until now, no one had found a compelling explanation to produce such an effect. "It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it," says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.
Brown and Batygin's discovery of evidence that the Sun is orbited by an as-yet-unseen planet that is about 10 times the size of Earth with an orbit that is about 20 times farther from the Sun on average than Neptune's changes the physics. Planet Nine, based on their calculations, appears to orbit at about 30 degrees off from the other planets' orbital plane in the process, influencing the orbit of a large population of objects in the Kuiper Belt, which is how Brown and Batygin came to suspect a planet existed there in the first place.
"It continues to amaze us; every time we look carefully we continue to find that Planet Nine explains something about the solar system that had long been a mystery," says Batygin, an assistant professor of planetary science.
Their findings have been accepted for publication in an upcoming issue of the Astrophysical Journal, and will be presented this week at the American Astronomical Society's Division for Planetary Sciences 48th annual meeting, held jointly in Pasadena, California, with the 11th European Planetary Science Congress.
The tilt of the solar system's orbital plane has long befuddled astronomers because of the way the planets formed: as a spinning cloud slowly collapsing first into a disk and then into objects orbiting a central star.
Planet Nine's angular momentum is having an outsized impact on the solar system based on its location and size. A planet's angular momentum equals the mass of an object multiplied by its distance from the Sun, and corresponds with the force that the planet exerts on the overall system's spin. Because the other planets in the solar system all exist along a flat plane, their angular momentum works to keep the whole disk spinning smoothly.
Planet Nine's unusual orbit, however, adds a multi-billion-year wobble to that system. Mathematically, given the hypothesized size and distance of Planet Nine, a six-degree tilt fits perfectly, Brown says.
The next question, then, is how did Planet Nine achieve its unusual orbit? Though that remains to be determined, Batygin suggests that the planet may have been ejected from the neighborhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the solar system's extreme past.
Read more at Science Daily
|This is the Lithodytes lineatus.|
This type of chemical-based mimicry and camouflage is often used by parasitic invertebrates and allows them to live unhindered within the protective confines of social insect-colonies. However, the strategy is not often seen in vertebrates, much less among frogs, and is only known in two other African frog species.
Lithodytes lineatus is a South American frog that is mainly found in the Amazon region. In Spanish the frog is known as "Sapito Listado." It shelters, breeds and builds its nest peacefully in the midst of leaf-cutting ants of the genus Atta without ever being attacked by them.
Leaf-cutting ants use chemical odors, such as pheromones, to recognize and communicate with members of their colony. Barros' team therefore speculated that the skin of Lithodytes lineatus must also be covered with a similar type of chemical that makes leaf-cutting ants recognize them as "friendly" and cheats them into allowing the frog into their midst.
They ran two sets of field experiments to test this. First Lithodytes lineatus frogs and four similar species were held in a glass vessel for ten minutes along with leaf-cutting ants. The Lithodytes lineatus frogs made no escape plans, in contrast with the members of the four other species that tried to jump or climb out and that were attacked by the ants.
The researchers then watched what happened when they covered 20 Rhinella major frogs that are common in the Amazon region with either the skin extract of Lithodytes lineatus or with ultrapure water. The skin extract protected the 10 frogs that were covered with it and that were placed within the nests, while the rest was attacked by the ants.
"Our results demonstrate that the skin of frog Lithodytes lineatus has chemicals that prevent the attack of two species of leaf-cutting ants," says Barros. "It therefore seems that Lithodytes lineatus has chemical skin compounds that are recognized by ants of genus Atta, which may allow for coexistence between ants and frogs."
Read more at Science Daily
|The genome of the frog X. laevis (top) is roughly double that of its relative, X. tropicalis (bottom).|
In the evolution of species, different events have occurred over millions of years that have increased the number of chromosomes in some organisms. Polyploidy describes an event that increases the number of copies of each chromosome. Vertebrates have undergone at least two different polyploidy events since their original divergence. While it is relatively rare nowadays to observe a mammal, reptile or bird with an abnormal number of chromosomes, polyploidy is common in fish, amphibians and plants.
Prof. Daniel Rokhsar, Professor of Genetics, Genomics and Development at the University of California, Berkeley and head of the Molecular Genetics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), Prof. Masanori Taira from the University of Tokyo and Prof. Richard M. Harland from the University of California at Berkeley led groups of researchers in examining the genome evolution of the African clawed frog. This large, collaborative project included scientists from a variety of universities and institutions across the globe. The study, published in Nature and featured on the cover, revealed that the X. laevis genome is composed of two different sets of chromosomes from two extinct ancestors.
Dr. Oleg Simakov, a postdoctoral scholar in the Molecular Genetics Unit at OIST, developed an algorithm to determine the length of time, in millions of years, between the divergence and subsequent fusion of the X. laevis ancestral species. In order to be able to calculate these times, the X. laevis genome had to be correctly annotated. Annotation involves identifying which regions of DNA contain coding genes or non-coding regions. While automation can simplify this process, many mistakes are made. Dr. Yuuri Yasuoka of the Marine Genomics Unit at OIST helped to manually correct the gene annotation. His graduate studies at the University of Tokyo under the guidance of Prof. Masanori Taira allowed him to develop the skills necessary for his role in this project. "Taking advantage of my experiences on the field of developmental biology, I examined genes involved in developmental processes," he clarified.
Dr. Adam Session, a former graduate student in Prof. Rokhsar's lab at the University of California at Berkeley and co-lead author of the Nature publication, elaborated "The most exciting finding from our study is that we can partition the current X. laevis genome into two distinct sets of chromosomes, each descended from a unique ancestral species. While plant studies have been able to show similar results using related species still in existence, this study is the first time this has been done with two extinct progenitor species."
Read more at Science Daily
|Extensive heat treatment in Middle Stone Age shows that controlled use of fire may have occurred at early stage of tool and blade production. The photo shows heated artefacts in silcrete made by Homo sapiens at Klipdrift Shelter, South Africa.|
According to a new study published in the open-access journal PLOS ONE, humans living in South Africa in the Middle Stone Age after 65,000 years ago deliberately heated silcrete, a hard, fine-grained, local rock used in stone tool manufacture, so that they could more easily obtain blades from the core material.
A major effect on hunting
These blades were then crescent shaped and glued into arrow heads. This era, known as the Howiesons Poort, has produced the first known evidence for the use of the bow and arrow.
“This is the first time anywhere that bows and arrows were used. This would have had a major effect on hunting practices as both spears and bow and arrow could be used to hunt animals,” says Professor Christopher Henshilwood.
He and Postdoctoral Fellow Karen van Niekerk, from the Department of Archaeology, History, Cultural Studies and Religion at the University of Bergen (UiB) in Norway, are among the co-authors of the study.
Creating early transformative technology
The heat treatment enabled early humans to produce tougher, harder tools – the first evidence of a transformative technology. However, the exact role of this important development in the Middle Stone Age technological repertoire was not previously clear.
Novel analytical research approach
Delagnes, Henshilwood, van Niekerk and the rest of the research team, from South Africa and Germany, used a novel non-destructive approach to analyse the heating technique used in the production of silcrete artefacts at the Klipdrift Shelter, a recently discovered Middle Stone Age site located on the southern Cape of South Africa, including unheated and heat-treated comparable silcrete samples from 31 locations around the site. The site was discovered by Henshilwood and van Niekerk and first excavated in 2011.
“Based on the development of a non-destructive method using geological heated and unheated comparative reference samples, we have shown that more than 90 per cent of the silcrete used for the production of blades has been intentionally heated,” says Henshilwood.
“Heating was applied, non-randomly, at an early stage of core exploitation and was sometimes preceded by an initial knapping stage. As a consequence, the whole operational chain, from core preparation to blade production and tool manufacturing, benefited from the advantages of the heating process,” explains van Niekerk.
The hardening, toughening effect of the heating step would therefore have impacted all subsequent stages of silcrete tool production and use.
Heat treatment: a major asset
The authors suggest that silcrete heat treatment at the Klipdrift Shelter may provide the first direct evidence of the intentional and extensive use of fire applied to a whole lithic chain of production. Along with other fire-based activities, intentional heat treatment was a major asset for Middle Stone Age humans in southern Africa, and has no known contemporaneous equivalent elsewhere.
“The advantages of the heating process are multiple: by reducing the material’s fracture toughness and increasing its hardness, less force was needed to detach blades after heat treatment, resulting in better control and precision during percussion,” explains Henshilwood.
“An additional advantage relates to the heat-induced fracturing of the silcrete blocks at an early stage of core exploitation,” adds van Niekerk.
Read more at Science Daily
In a race against the clock, scientists have been looking for a way—a cure or vaccine—to save the carnivorous marsupials, which live exclusively on the Australian island state with which they share a name.
Strange facial tumors showed up in the mid-1990s, and have since wiped out some 80 percent of the population.
The disease—nearly 100 percent fatal—spreads through facial biting, a common behavior among both males and females.
Some 20,000 individuals are thought to remain.
In the study, a team led by Ruth Pye of the University of Tasmania collected blood samples from 52 closely monitored wild animals from 2008 through 2014.
The scientists checked for the presence of cancer cells, and antibodies that might attack them.
Thirty-four of the animals either had the disease at the outset or developed it during the monitoring period.
The researchers were surprised to find six devils that developed serum antibodies against the cancer cells.
Such a response has been induced in captivity through immunization with killed cancer cells, but had not—before this—been observed in the wild.
The result "suggests that a proportion of wild devils can produce a protective immune response against naturally acquired devil facial tumor disease," the researchers concluded.
A study published in August reported that the famously aggressive animals, the size of a heavy-set small dog, seem to be pulling back from the brink through lightning-fast genetic evolution.
A detailed comparison of the genomes of 294 devils—before and after the cancer emerged 20 years ago—revealed species-wide adaptations in seven genes in a span of just a handful of generations.
From Discovery News
Oct 19, 2016
He told them to comb through archived Chandra and XMM-Newton telescope data for examples of bright X-ray emissions coming from galaxies beyond the Milky Way. The catch was to find examples emanating from globular cluster galaxies, a type of very old galaxy.
"It seemed like a suitably straightforward project for undergraduates who can only dedicate a few hours a week to work on," Irwin wrote in an email to Seeker.
Chandra had picked up a puzzling signal once before.
In 2005, astronomers detected a flare from the general direction of galaxy NGC4697, a globular cluster located some 40 million to 50 million light-years away in the constellation Virgo.
"Two brief flares were seen, separated by four years," Irwin writes in this week's Nature.
Both times, the flares grew 90 times brighter in less than a minute, and there were no associated optical emissions in the position of the flares.
"It is still a bit of a mystery," Irwin said. "It is possible that (the flare) lies far beyond NGC4697, along the same line of sight, making it much more luminous than is believed, or the opposite case -- it is much closer to us, within our own Milky Way galaxy in fact, in which case it would be much less luminous than we think."
So the students went hunting.
"We were only hoping to find objects that varied by modest factors of three – to five or so on time scales of an hour or so," Irwin said.
But the searching software Irwin wrote for them to use could search for variability on all time scales, and the kids pulled in two whoppers: X-ray flares that brightened 100- to 200 percent in less than a minute.
"We were quite surprised," Irwin said.
At its peak, one source, located in Virgo galaxy NGC4636, was 30 times brighter than the X-ray luminosity of the entire Milky Way, he said.
The second source, located near the Centaurus A galaxy NGC 5181, had a big surprise too. So far, it has flared six times in X-ray light, with some pulses as short as 22 seconds. All flares peaked in less than a minute and lasted for about an hour.
Read more at Discovery News
The species at risk range from rats to rhinoceros, and include docile, ant-eating pangolins as well as flesh-ripping big cats.
The findings, published in the journal Royal Society Open Science, are evidence of a "global crisis" for warm-blooded land animals, 15 top conservation scientists concluded.
"Terrestrial mammals are experiencing a massive collapse in their population sizes and geographical ranges around the world," the study warned.
This decline, it said, was part of a larger trend known as a "mass extinction event," only the sixth time in half a billion years that Earth's species are dying out at more than 1,000 times the usual rate.
Besides eating them, humans are robbing mammals of their natural habitats through agriculture and urbanization, and decimating them through pollution, disease and climate change.
According to the Union for the Conservation of Nature's (IUCN) Red List of endangered species, a quarter of 4,556 land mammals assessed are on the road to annihilation.
For 301 of these threatened species, "hunting by humans" -- mainly for food, but also as purported health and virility boosters, and trophies such as horns or pelts -- is the main threat, according to the comprehensive review of scientific literature.
The likelihood of extinction, the team found, depends on body size: the bigger the animals, the greater the danger.
More than 100 primates, including gorillas and snub-nosed monkeys, and dozens of hoofed animals from oxen to antelope, are at dire risk from hunting.
"These species will continue to decline unless there is major global action to save them," Bill Ripple, a professor at Oregon State University and lead author of the study, told AFP.
All 301 species identified are found exclusively in developing countries, with the highest concentration in southeast Asia (113), followed by Africa (91), the rest of Asia (61) and Latin America (38).
The countries with the most native species under siege from hunting were Madagascar (46), Indonesia (37), the Philippines (14) and Brazil (10).
The scale of the problem is daunting: some 89,000 tonnes of wild meat -- with a market value of about $200 million (180 million euros) -- is butchered every year from the Brazilian Amazon alone, the study found.
On current trends, the prospects for these and other mammals is not bright, the authors said.
"Forty of these species were already classed as critically endangered by 1996, indicating that there has been little or no conservation progress in reversing their fate," they note.
This, despite dozens of major conservation conferences and summits, and the expansion of protected areas.
The impact of extinction may be felt well beyond the loss of individual species, the scientists cautioned.
"Through cascading effects, the loss of these mammals is altering the structure and function of the environments in which they occur," the study notes.
Read more at Discovery News
Researchers with the university say about 70% of the creature's skeletal mass has been recovered from the Fowler Center for Outdoor Learning, near Mayville.
While parts of hundreds of mastodons have been found in Michigan, the researchers estimate that the new find is more complete than all but a handful of them.
"This is the most complete Michigan mastodon skeleton in many decades," said UM paleontologist and leader of the dig, Daniel Fisher, in a statement. "I think the last time a mastodon this complete was found in Michigan was in the 1940s."
Mastodons, extinct relatives of modern elephants, roamed North and Central America in grazing herds and died out about 10,000 to 11,000 years ago.
Further testing will be done to narrow its age estimate and even the season in which it died, but much is already known about the skeleton. It belonged to a male estimated to have lived between 11,000 and 13,000 years ago, and the animal was likely around 30 years old at time of death, based on tooth size and wear.
What's more, the mastodon looks to have been the victim of early human hunters.
"I would say it is roughly 80 percent likely that humans were involved and responsible for major portions of what we see at this site," Fisher said.
Fisher and his team noted that the mastodon's bones were still aligned correctly, relative to each other. Had it died of natural causes, they said, the animal's carcass would have been scavenged and the bones scattered from their original location. Indeed early indications are the creature was processed by humans, with some fully aligned bone sections seemingly separated into piles.
The location of the bones, near a lake that no longer exists, suggests another intriguing possibility.
The mastodon was "apparently brought to a lake and, we think, stored in this lake as a strategy for meat storage by early humans who lived in this part of the world at that same time," Fisher said. The researcher has studied other Great Lakes pond-storage sites, where the cold pond bottom, coupled with lowered oxygen, would have helped keep the meat from spoiling.
"Finding a specimen like this also tells us something about human history," Fisher said. "What did it take to feed a family, to raise a family? What did it take to make a life in early Michigan, soon after the recession of the ice at the end of the ice age?"
Read more at Discovery News
The new view of Mars comes from the orbiting MAVEN spacecraft, which this month begins a third year of studies about how the planet most like Earth in the solar system lost most of its atmosphere.
When the spacecraft reaches the most distant part its orbit — MAVEN travels as far as 3,900 miles from Mars — its global view of the planet is giving scientists new insights, and in some cases first looks, at global wind circulation, ozone distribution and cloud formation.
The data about the winds comes from MAVEN images of "nightglow," a common phenomenon in which an atmosphere shines at night, despite the complete absence of illumination, MAVEN scientist Nicholas Schneider, with the University of Colorado, Boulder, told reporters at the American Astronomical Society meeting in Pasadena, Calif., this week.
"Nightglow is the result of chemical reactions in an atmosphere," Schneider said. "In the case of Mars, the molecules are broken apart on the day side of the planet … and those atoms are carried by the winds to the night side, primarily the winter pole, where they then descend to higher density and recombine. In that act of re-combining, they have enough energy to give off ultraviolet photons."
The nightglow molecules are nitric oxide and how they apparently spread over Mars means that computer models of the planet's flowing winds are in need of an upgrade.
The new data indicates that the winds around the planet, already subject to strong seasonal changes, are more irregular than expected, Schneider said.
That, in turn, raises questions about the transport of atmospheric molecules, and especially the chemistry that happens as a result, he said.
"The nature of the polar vortex and how long the ozone lasts through Spring provides insight into the evolution of ozone and water vapor, a coupled chemistry in the Mars atmosphere," Schneider said.
Perhaps the most striking new look at Mars is time-lapse imagery of clouds forming and moving across the planet.
Clouds provide a way to trace atmospheric flows, and they affect the planet's energy balance, depending on whether sunlight is absorbed or reflected back into space, Schneider said.
"They also tell us about the inventory of water vapor that would be available for forming clouds," he added.
The images show which regions of Mars are relatively thick with atmosphere, such as the low-lying Meridiani Planum, where Europe's Schiaparelli lander will attempt to touch down on Wednesday.
Read more at Discovery News
Oct 18, 2016
|Larsen and Lamb apply their new model to the “channeled scablands” in eastern Washington State, an area that, like some on Mars, has very deep canyons cut into fractured basalt bedrock.|
Now geoscience researchers Isaac Larsen at the University of Massachusetts Amherst and Michael Lamb at the California Institute of Technology have proposed and tested a new model of canyon-forming floods which suggests that deep canyons can be formed in bedrock by significantly less water than previously thought. They point out that "reconstructing the magnitude of the canyon-forming floods is essential for understanding how floods modify planetary surfaces, the hydrology of early Mars, and abrupt climate change."
Larsen and Lamb apply their new model to the "channeled scablands" in eastern Washington State, an area that, like some on Mars, has very deep canyons cut into fractured basalt bedrock. The researchers say their results suggest "there may be a rich imprint of both the history and discharge of flooding in the morphology of canyons" such as terraces, valley shapes and slope profiles on Earth and on Mars "that warrant further investigation." Details appear in the current issue of Nature.
The researchers say channels in the scablands today, which are up to 650 feet (200 meters) deep and 3 miles (5 km) wide, were likely formed by flood discharges five- to tenfold smaller than brimful estimates, that is by "significantly lower megaflood discharges than previously thought. The channeled scablands are a classic landscape in the history of geomorphology and we're bringing new views of how it was formed."
Until the 1920s, scientists did not understand what could have formed the tortured landscape of eastern Washington studied for decades by J Harlen Bretz, a giant figure in geosciences, Larsen recalls. Bretz was the first to suggest that they were formed by catastrophic flooding of unknown origin. His views were dismissed for years, but Bretz was later vindicated when glacial Lake Missoula was identified as the floodwater source.
As most scientists came to accept the catastrophic flood explanation for the canyons and then tried to estimate floodwater discharges, they assumed that floods filled canyons to the brim, a huge amount of water. But an alternate hypothesis proposed and now tested by Lamb and and Larsen posits that as floodwater cuts into bedrock, the canyon deepens, meaning less water is required to shape it.
In areas underlain by fractured bedrock, Larsen says, "our general concept is that the channel floor was being cut and lowered as the floods were happening, and you need to account for that when reconstructing the scenario of flood magnitude. This applies to the scablands, to Mars and other areas where there have been catastrophic outburst floods."
He and Lamb combine numerical flood models with estimates of the force required to erode basalt bedrock to show that for Moses Coulee, a canyon carved by catastrophic Lake Missoula floods in eastern Washington when an ice dam repeatedly broke and reformed around 15,000 years ago, their "threshold shear stress model" explains the shape and depth of currently observed channels better than the brimful model.
"We numerically routed floods through the canyon in different states, from current configuration and at four different past scenarios," Larsen notes. "We predicted the discharge from two models and tested which one is most reasonable, based on the depositional evidence from the current bars seen today in the canyons. The size of floods our model predicts from the basalt erosion better match locations of depositional flood bars in the canyon than the brimful model predicts."
Read more at Science Daily