Sudden draining of glacial lakes explained

June 4, 2015

Thousands of supraglacial lakes form each spring and summer on top of the Greenland Ice Sheet. When they drain, they send torrents of water to the base of the ice sheet, lubricating the interface between rock and ice. That allows the ice sheet to flow faster to the ocean and discharge ice into ocean, which causes sea levels to rise faster Credit: Photo by Laura Stevens, Woods Hole Oceanographic Institution

In 2008 scientists from Woods Hole Oceanographic Institution (WHOI) and the University of Washington documented for the first time how the icy bottoms of lakes atop the Greenland Ice Sheet can crack open suddenly–draining the lakes completely within hours and sending torrents of water to the base of the ice sheet thousands of feet below. Now they have found a surprising mechanism that triggers the cracks.
Scientists had theorized that the sheer weight of the water in these supraglacial lakes applied pressure that eventually cracked the ice, but they could not explain why some lake bottoms cracked while others did not.

“Our discovery will help us predict more accurately how supraglacial lakes will affect ice sheet flow and sea level rise as the region warms in the future,” said lead author Laura Stevens, a graduate student in the Massachusetts Institute of Technology-Woods Hole Oceanographic Institution (MIT/WHOI) Joint Program in Oceanography.

The research was published June 4 in the journal Nature.

To find out what triggers sudden lake drainages, a research team, including Stevens and colleagues from WHOI, the University of Washington, MIT, and the University of Tasmania, deployed a network of 16 GPS units around North Lake, a 1.5-mile-long supraglacial lake in southwest Greenland, where the scientists first documented large-scale cracks and lake drainages. They used these instruments to record movements of the ice before, during, and after three rapid lake drainages in the summers of 2011, 2012, and 2013.

Their study showed that in the 6 to 12 hours before the lake cracked and drained, the ice around the lake moved upward and slipped horizontally. The scientists say that meltwater had begun to drain through a nearby system of moulins (vertical conduits through the ice), which connected the surface to the base of the ice sheet 3,215 feet below. The accumulating water creates a bulge that floats the entire ice sheet, creating tension at the surface underneath the lake. The stress builds up until it is relieved by a sudden large crack in the ice below the lake.

“In some ways, ice behaves like Silly Putty–if you push up on it slowly, it will stretch; if you do it with enough force, it will crack,” said Stevens. “Ordinarily, pressure at the ice sheet surface is directed into the lake basin, compressing the ice together. But, essentially, if you push up on the ice sheet and create a dome instead of a bowl, you get tension that stretches the ice surface apart. You change the stress state of the surface ice from compressional to tensional, which promotes crack formation.”

Once the tension initiates the crack, the volume of water in the lake does play a critical role, surging into the opening, widening and extending it, and keeping it filled with water all the way to base of the thick ice sheet. These are called hydrofractures, and the scientists have documented how they can drain more than 11 billion gallons of water out of North Lake in about 90 minutes. At times, water flowed out of the lake bottom faster than the water goes over Niagara Falls, the scientists estimated.

“You need both conditions–tension to initiate the crack and the large volume of water to amplify it–for hydrofractures to form,” Stevens said. The key finding of this study is that without the former, even large supraglacial lakes will retain their water.

At the base of the ice sheet, the water that drains from the lake lubricates the interface between ice and rock, allowing the ice sheet to slide faster toward the coast. That in turn accelerates the outflow of ice from land to sea and causes sea levels to rise faster. So understanding the mechanisms that trigger the drainages will help scientists predict more precisely how supraglacial lakes will affect sea level rise as climate conditions shift in the future.

The GPS network also recorded the more sudden and momentous movements of the ice sheet surface at the time of the hydrofracture, showing that portions of the ice sheet bed beneath the lake can slip up to a foot and a half. That is equivalent to the movement caused by a magnitude-5.5 earthquake.

“It’s just a different type of solid crystals–ice instead of rock–breaking due to stress,” said Jeff McGuire, a co-author on the study and a seismologist at WHOI. The research team spanned scientific disciplines, including McGuire, a seismologist; Mark Behn, a geophysicist at WHOI who studies faults in Earth’s crust; glaciologists Sarah Das of WHOI, and Ian Joughin and David Shean of the University of Washington; Tom Herring, a GPS expert at MIT, and Matt King, who studies geodesy, Antarctic ice sheets, and sea level at the University of Tasmania.

Thousands of supraglacial lakes form each spring and summer on top of the Greenland Ice Sheet as sunlight returns to the region. The heat melts snow and ice into water that pools in depressions in the ice sheet to form lakes. As the region becomes warmer, more lakes will likely form, leading to a first-order prediction of more hydrofractures, more lubrication, more ice sheet slippage, and faster-rising sea levels.

However, discovering the new trigger mechanism changes the equation, because the trigger is less likely to occur at lakes at higher elevations on the ice sheet–even though water volumes in those lakes can be large. Stevens explained that the ice sheet further inland is thicker and moves more slowly. The ice deeper down flows viscously, dampening impacts on the surface topography. That results in a flatter surface where fewer lake basins and crevasses form. Fewer crevasses mean less water leakage to the base, which reduces bulging that increases surface stresses.

Reference:
Laura A. Stevens, Mark D. Behn, Jeffrey J. McGuire, Sarah B. Das, Ian Joughin, Thomas Herring, David E. Shean, Matt A. King. Greenland supraglacial lake drainages triggered by hydrologically induced basal slip. Nature, 2015; 522 (7554): 73 DOI: 10.1038/nature14480

Note: The above story is based on materials provided by Woods Hole Oceanographic Institution.

Galapagos eruption: Wolf volcano spewing lava for the first time in 33 years

June 4, 2015

Footage released on Monday by the Galapagos National Park showed spectacular images of lava flowing into the ocean as the Wolf Volcano continued its activity after erupting last week for the first time in 33 years. (June 2, 2015)

115-million-year-old remains of a tiny fossil bird from Brazil

June 4, 2015

Cretaceous birds with feathers are very rare fossils with exceptional preservation. Credit: Nature

The 115-million-year-old remains of a tiny toothed bird with a two-pronged tail resembling a pair of darts have filled knowledge gaps about feather evolution, scientists reported Tuesday.
The remarkably-preserved 3-D specimen from northeast Brazil is the oldest bird fossil yet from Gondwana, the supercontinent that broke up into today’s southern landmasses.

Until now, birds with this unusual and now extinct tail design were known to have lived only in China, which was not part of Gondwana, during this period of Earth’s history.

“The bird looks like a small hummingbird,” study co-author Ismar Carvalho of the Federal University of Rio de Janeiro told AFP.

“It has big eyes, plumes (feathers) surrounding the body and two long feathers in the tail. There are also teeth in his beak.”

The critter measured about six centimetres (2.4 iches) from the tip of its nose to the beginning of its double-shafted, ribbon-like tail.

Not yet given a name, the new bird belonged to a group known as Enantiornithes whose members had teeth and clawed wings, and are not thought to have left any living descendants.

The fossil is exceptional in that the impression of the bird, left in rock, has not been totally flattened out.

Instead, the imprint retains some volume, which in turn greatly helps understanding of the bird’s shape and possible motion.

The team also found rows of spots distributed symmetrically along the tail feathers, which they took to be the remains of a colour pattern.

Given that the plumes did not appear to have been useful for body balance or flight, they were probably used for sexual display, species recognition or visual communication, the researchers concluded.

The earliest known relative of birds is generally agreed to be Archaeopteryx, considered a transitional species from non-avian dinosaurs with feathers which lived about 150 million years ago.

The study appears in the journal Nature Communications.

Reference:
Ismar de Souza Carvalho, Fernando E. Novas, Federico L. Agnolín, Marcelo P. Isasi, Francisco I. Freitas & José A. Andrade. A Mesozoic bird from Gondwana preserving feathers. DOI:10.1038/ncomms8141

Note : The above story is based on materials provided by AFP.

Clues to the Earth’s ancient core

June 4, 2015

Illustration of three phases of geodynamo generation: (a) Earliest earth until circa 2.5 Ga, a basal magma ocean in the mantle hosts a thin-shell dynamo. Vertical columns represent rotationally dominant convective fluid motions. (b) Second stage, characterized by an almost fully solidified mantle, where last crystallization products are compositionally Fe enriched and dense. Greater heat flux out of core allows for thermal convection to drive dynamo in fluid core. (c) As core cools, solid inner core initiates and grows. Geodynamo powered by thermal and compositional convection enhanced by core solidification, leading to stronger average field strength.

Old rocks hold on to their secrets. Now, a geophysicist at Michigan Technological University has unlocked clues trapped in the magnetic signatures of mineral grains in those rocks.. These clues will help clear up the murky history of the Earth’s early core.
The journal Earth and Planetary Science Letters published a paper on the subject earlier this year. Aleksey Smirnov, an associate professor of geophysics and adjunct associate professor of physics at Michigan Tech, led the study. The work is a part of a large research program led by Smirnov and supported by the National Science Foundation (NSF), including his CAREER Award, a prestigious NSF grant. Through this work, he has traveled the world seeking rocks that provide insight into the ancient earth’s core.

Table of Contents

Earth’s Ancient Geodynamo

The magnetic field comes from the earth’s core: The solid inner core, made of iron, spins and powers convective currents in the liquid outer core. Those currents create the magnetic field, and the system is called the geodynamo.

“At any point, the field can be described by its direction and strength,” Smirnov says, adding that the modern magnetic field is weaker than that of a refrigerator magnet and that intensity has changed throughout geologic time. “What we call paleointensity in our paper refers to the field’s strength,” he explains.

Smirnov and his co-author, David Evans of Yale University, examined the paleointensity measurements of rocks more than two billion years old. Rocks that old record a magnetic field from a rather mysterious geodynamo.

That’s because the core didn’t always have a solid center—it used to be all liquid. And being liquid would make for a weak, chaotic magnetic field.

“What happened at some point, because the earth is constantly cooling, the center formed a small, solid inner core,” Smirnov says. “But this event is uncertain in terms of timing.”

A number of models analyze what this timing could have been, but they estimate any time between half a billion years ago and three billion years ago—which is like saying an adolescent will hit puberty sometime between ages 8 to 30. To better pinpoint the timing of the inner core’s formation, Smirnov scours the world for old Precambrian rocks.

Magnetic Records in Rocks

Smirnov focuses on rocks that are not just old, but magnetic, and he tests the samples in the Earth Magnetism Lab at Michigan Tech. Within the lab is a room, built above the concrete floor and boxed in with a special steel alloy—it’s a metal-free zone. Inside the room, Smirnov uses a magnetometer: a device that measures magnetic properties in rocks and, more specifically, their iron-rich minerals.

Magnetite is an iron silicate with magnetic properties, and when it crystallizes in a rock, it records the strength and orientation of the earth’s magnetic field. Some rocks record this better than others; an ideal rock cools fast and is well-preserved.

“Because of the rarity of well-preserved extrusive Precambrian rocks,” Smirnov writes in his paper, “relatively quickly cooled shallow intrusions such as mafic dikes and sills represent an attractive alternative target for paleointensity studies.”

The rocks Smirnov and his team sampled in Australia’s Widgiemooltha dike swarm are the best available, considering the cluster of intrusive rock formations has been eroded, buried and baked over the past two billion years. The dike swarm is important because the Widgiemooltha rocks, collected from 24 different field sites, contain key magnetite grains. After some time in the lab’s magnetometer, the minerals begin to reveal their long-held magnetic secrets.

Basal Mantle Ocean and Beyond

Given the rocks’ age and the chaotic nature of the early magnetic field, Smirnov predicted the paleointensity recorded in the magnetite grains would be weak. However, he and his team found the paleointensity readings were relatively strong.

“This contradicts the models that show a young solid inner core—and right now, that’s a mystery,” Smirnov says. Although, he adds, there is a new theory that is consistent with this data.

In the basal mantle ocean theory, the boundary between the solid mantle—the bulk of earth’s interior—and the early earth’s core could have been swaddled in a dense layer of partially melted rock. The difference in composition and density could have been enough to jumpstart a stronger magnetic field.

Delving deeper into the core’s evolution has significance beyond the earth’s interior, too. The magnetic field helps protect life on earth from cosmic radiation. Understanding the ancient geodynamo could also expand our knowledge of earth’s earliest life. Smirnov plans to study that connection—and more exceptionally old rocks—in the next leg of his research.

Reference:
“Geomagnetic paleointensity at ∼2.41 Ga as recorded by the Widgiemooltha Dike Swarm, Western Australia,” Earth and Planetary Science Letters, Volume 416, 15 April 2015, Pages 35-45, ISSN 0012-821X, DOI: 10.1016/j.epsl.2015.02.012

Note : The above story is based on materials provided by Michigan Technological University.

Gloucestershire fossil identified as new species of ancient reptile

June 4, 2015

A reconstruction of what Clevosaurus sectumsemper may have looked like. The scale bar denotes 1cm. C. sectumsemper is the smallest clevosaur species ever described. Credit: Katharine Whiteside

Fossils found in a quarry in Gloucestershire have been identified by a student and her supervisors at the University of Bristol as a new small species of reptile with self-sharpening blade-like teeth that lived 205 million years ago. Part of the name chosen for the new species – Clevosaurus sectumsemper – takes inspiration from a spell cast in the Harry Potter books.
Research by Catherine Klein, an undergraduate in Bristol’s School of Earth Sciences, shows that fossils from the previously unstudied Woodleaze Quarry belong to a new species of the ‘Gloucester lizard’ Clevosaurus (named in 1939 after Clevum, the Latin name for Gloucester).

In the Late Triassic, the hills of the South West of the UK formed an archipelago that was inhabited by small dinosaurs and relatives of the Tuatara, a living fossil from New Zealand. The limestone quarries of the region have many caves or fissures containing sediments filled with the bones of abundant small reptile species that give us a unique insight into the animals that scuttled at the feet of the dinosaurs. The fissures are of worldwide importance in yielding such well- preserved small reptiles.

Catherine Klein, who completed the research as part of a summer project, said: “The new species, Clevosaurus sectumsemper, probably lived near the edge of one of the ancient archipelago’s islands, in a relatively hostile environment. This would explain why nearly all the bones come from one species, and why there is a relatively high occurrence of healed fractures such as one we found in a rib. Possibly the animals were fighting each other due to a limited food source or perhaps they preyed on each other and bones were broken, but some individuals survived and their broken bones healed.”

Like some other clevosaurs, which were found throughout the ancient world, the new species has a self-sharpening dentition: with each bite the teeth are sharpened as they cut past each other very precisely. As a result, old individuals are left with sharp ridges of bone which they use as a cutting surface.

“The species name sectumsemper means ‘always cut’, and was chosen to reflect this,” said Catherine. “It is also a nod to the Harry Potter character Severus Snape, who made a spell called sectumsempra (perhaps meaning sever forever).”

“There were enough differences, particularly in the jaws, to allocate the material to a new species,” said Professor Mike Benton, one of Catherine’s supervisors.

Another supervisor, Dr David Whiteside, added that the new reptile has a specially adapted dentition that allows it to tackle much larger food than would usually be expected for such a small animal, the smallest of the clevosaurs.

Woodleaze Quarry lies 800m to the south of Tytherington Quarry which produced bones of the Bristol dinosaur Thecodontosaurus.

Dr Whiteside, who originally described the Tytherington fauna, said: “It is remarkable from an ancient geography point of view because we have evidence of a gradual decline in species richness from the northern Tytherington fissures to the almost complete dominance of Clevosaurus sectumsemper in the fauna of Woodleaze in the south as the edge of the ancient island is reached. Perhaps we are documenting the details of geographic distribution at the time.”

Catherine, Dr Whiteside and Professor Benton wish to especially thank Hanson Aggregates Ltd. for access and assistance in fieldwork in their quarries.

Reference:
“A distinctive Late Triassic microvertebrate fissure fauna and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia) from Woodleaze Quarry, Gloucestershire, UK,” Proceedings of the Geologists’ Association, Available online 3 June 2015, ISSN 0016-7878, DOI: 10.1016/j.pgeola.2015.05.003

Note : The above story is based on materials provided by University of Bristol.

The curse of the horned dinosaur egg

June 4, 2015

A nest of Oviraptor (formerly Protoceratops) eggs on display at the American Museum of Natural History. Credit: Steve Starer, CC-BY

Horned dinosaurs (ceratopsians) just can’t catch a break when it comes to their fossilized eggs. The first purported examples turned up in Mongolia during the 1920s, attributed to Protoceratops. A few unlucky “Protoceratops” eggs were fossilized next to the jaws of another dinosaur (Oviraptor, which means “egg thief”), presumably in the act of raiding the nest. Decades later, it turned out that the nest raider was probably the parent Oviraptor safeguarding its own eggs. Study of other eggs associated with embryos showed that everything we thought were Protoceratops eggs were actually from Oviraptor and related animals!

So, as a horned dinosaur fancier, I was pretty excited when an authentic ceratopsian egg and embryo were announced in 2008. Amy Balanoff and colleagues described an egg from Late Cretaceous-aged rocks (~90 to 70 million years old; the exact date is uncertain), which had a few tiny bones poking out of the end. Dinosaur embryo! Computed tomography (CT, a technique using x-rays to peek inside objects) revealed more of the bones, including two skull bones that appeared especially ceratopsian. One bone was identified as a predentary, the scoop-shaped bone at the front of the lower jaw used to lop off plants. The other skull bone appeared to be a quadrate, one of the bones of jaw joint. The predentary in particular narrowed identification to a plant-eating dinosaur (the bone doesn’t occur in theropods such as Oviraptor), and the shape of the quadrate further suggested a horned dinosaur. Yamaceratops (closely related to Protoceratops) is a ceratopsian found in the same rock layers and was thought to be the likely source.

One puzzle, though, was the eggshell itself. Eggshell appears simple to the naked eye, but the microscopic details can be pretty distinctive to the egg producer. The number of layers within the eggshell, for instance, and the arrangements of the minerals that make up the layers, vary from group to group. Some eggshells, such as those of turtles, have but a single layer. The Mongolian ceratopsian eggshell had three layers–a characteristic usually associated with theropod dinosaurs (Oviraptor and early birds, for instance). But, given the presence of ceratopsian bones in the egg and the fact that nobody knew what ceratopsian eggshell should look like, this suggested that horned dinosaurs had eggshell that converged on that of theropods. So, the three-layered eggshell evolved multiple times across dinosaurs.

But…things are never that simple. A new paper in PLOS ONE, including the two senior authors from the original work, proposes a new identification. Ceratopsian no more…now it’s a bird!

Incredulity might be the first reaction of many people. How could you mix up a wingy, feathered bipedal thing with a big plant-munching quadruped? It should be obvious to even a casual observer, right?

Actually, no. Embryonic bones (those inside of an egg) can look vastly different from those of their adult counterparts, because many characteristic features don’t appear until the animal is out of the egg. As a result, it can be tough to orient and identify bones correctly. Additionally, even high-tech imaging (such as CT scanning) has a certain degree of interpretation to it. The researcher who digitally separates bone from rock has to make judgement calls all of the time. Is this bone or rock that looks like bone? Are these two bones stuck together, or one bone with a crack down the middle? Even under the best of circumstances, there is room for ambiguity.

Given what everyone knew at the time, and in light of the possible predentary and other bones, “ceratopsian” was a reasonable hypothesis as presented in the initial publication. But a second look at the data never hurts. Movies of the CT scans were posted online, allowing other researchers to take a peek. Undoubtedly following some pretty interesting discussions, two of the original authors (Amy Balanoff and Mark Norell) joined dino-bird expert Dave Varricchio (lead author on the new paper) to present a re-interpretation of all of the data.

It turns out that the egg was turned around in the original interpretation; the front of the animal could be identified instead as the back. Thus, many of the bones were mis-oriented in the original paper. What was thought to be a ceratopsian humerus turned out to be a bird femur, a tibia turned into an ulna, and so on. As described above, this is a pretty easy “mistake” to make, given how nondescript many embryonic bones are. The quadrate and predentary are more mysterious–the former may be a pelvic bone, but the true identification of the “predentary” is highly debatable. Perhaps it’s part of a vertebra, or a wishbone, or something else. In any case, when reoriented, most of the bones are a better match for bird than ceratopsian.

If the Gobi egg is from a bird, that also solves solves the problem of the three-layered eggshell. No longer distributed across dinosaurs, this type of eggshell is now firmly restricted to theropods (including many birds). Additionally, this embyro provides another rare data point for studying the embryology of ancient birds. Previous discoveries have shown some key developmental differences between non-avian dinosaurs, early birds, and modern birds, so the newly identified Gobi bird egg has an important story to tell on how these differences evolved over time.

One mystery remains–what do horned dinosaur eggs and embryos look like? There are undoubtedly unidentified examples in a museum drawer or outcrop. A nest of little Triceratops sure would help right about now.

Reference:
“Reidentification of avian embryonic remains from the Cretaceous of Mongolia.” PLoS ONE 10(6): e0128458. DOI: 10.1371/journal.pone.0128458

Note : The above story is based on materials provided by Public Library of Science.

Australian fossil forces rethink on our ancestors’ emergence onto land

June 4, 2015

The fossilised radius bone of Ossinodus pueri. Credit: Queensland Museum.

A 333-million year old broken bone is causing fossil scientists to reconsider the evolution of land-dwelling vertebrate animals, says a team of palaeontologists, including QUT evolutionary biologist Dr Matthew Phillips, and colleagues at Monash University and Queensland Museum.

Analysis of a fractured and partially healed radius (front-leg bone) from Ossinodus pueri, a large, primitive, four-legged (tetrapod), salamander-like animal, found in Queensland, pushes back the date for the origin of demonstrably terrestrial vertebrates by two million years, said Dr Phillips, a researcher in the Vertebrate Evolution Group in QUT’s School of Earth, Environmental and Biological Sciences.

“Previously described partial skeletons of Ossinodus suggest this species could grow to more than 2m long and perhaps to around 50kg,” Dr Phillips said.

“Its age raises the possibility that the first animals to emerge from the water to live on land were large tetrapods in Gondwana in the southern hemisphere, rather than smaller species in Europe.

“The evolution of land-dwelling tetrapods from fish is a pivotal phase in the history of vertebrates because it called for huge physical changes, such as weight bearing skeletons and dependence on air-breathing.”

Dr Phillips said the nature of the break in the radius bone was studied using high-resolution finite element analysis by Peter Bishop for his honours research at QUT.

“The nature of the fracture suggests the bone broke under high-force impact.

“The break was most plausibly caused by a fall on land because such force would be difficult to achieve with the cushioning effect of water.

“Indeed, the fracture is somewhat reminiscent of people falling on an outstretched arm and the humerus crashing into and fracturing the radius.”

Dr Phillips said the researchers also found two other features that confirmed the tetrapod had spent substantial time on land.

“Firstly, the internal bone structure was consistent with re-modelling during life in accordance with forces generated by walking on land,” he said.

“We also found evidence of blood vessels that enter the bone at low angles, potentially reducing stress concentrations in bones supporting body weight on land.

“The three findings taken together suggest that Ossinodus spent a significant part of its life on land. This is augmented by its exceptional degree of ossification, which is also consistent with weight bearing away from the buoyancy of water.

“This specimen of Ossinodus is our oldest vertebrate relative shown biomechanically to have spent significant time on land. It is two million years older than the previous undoubtedly terrestrial specimens found in Scotland, which were less than 40cm long.”

Dr Phillips said the findings highlighted the value of combining studies on palaeontology, biomechanics and pathology to understand how extinct organisms lived.

Reference:
The study Oldest Pathology in a Tetrapod Bone Illuminates the Origin of Terrestrial Vertebrates was conducted by Peter J. Bishop, Christopher W. Walmsley, Matthew J. Phillips, Michelle R. Quayle, Catherine A. Boisvert, and Colin R. McHenry was published in Plos One: DOI: 10.1371/journal.pone.0125723

Note : The above story is based on materials provided by Queensland University of Technology.

The invisible key to methane hydrates

June 4, 2015

This image shows a methane hydrate being subjected to heat. Credit: John Ripmeester, National Research Council (Canada)

Like the carbon dioxide in a fizzing glass of soda, most bubbles of gas in a liquid don’t last long. But nanobubbles persist. These bubbles are thousands of times smaller than the tip of a pencil lead — so small they are invisible even under most optical microscopes — and their stability makes them useful in a variety of applications, from targeted drug delivery to water treatment procedures.
Now a team of Canadian researchers from the University of British Columbia and National Research Council of Canada is studying the role that methane nanobubbles might play in the formation and dissociation of natural gas hydrates — crystalline lattices of hydrogen-bonded water molecules with gas molecules nestled between. Hydrates are a currently untapped source of natural gas, one of the chief energy sources in the United States. Gaining a better understanding of how nanobubbles impact their formation and dissociation could help design procedures to more efficiently and safely harvest hydrates for natural gas capture. The findings are published this week in The Journal of Chemical Physics, from AIP Publishing.

Naturally-occurring methane hydrates, hidden deep under the sea floor or tucked under Arctic permafrost, contain substantial natural gas reserves locked up in a form that is difficult to extract. When these hydrates decompose (with the injection of heat or depressurization), the gas inside is liberated and can then be used for energy.

Whether, and how, to take advantage of this resource is a complicated question. Hydrates have shaped the history of our planet: by locking away methane produced in the earth’s crust instead of allowing it to accumulate in the atmosphere, they helped to make the earth a hospitable place for life. Their role in this regard continues today — while the methane trapped in hydrates is a potential source of future energy, it may also serve as a potent source of greenhouse gas if it escapes into the atmosphere. Thus, in order to extract methane without contributing to climate change, understanding the precise mechanics of the hydrate decomposition process is crucial.

The researchers used molecular dynamics simulations to model the solid hydrates’ decomposition into liquid and gaseous states. Whether or not nanobubbles formed during decomposition was influenced, among other factors, by the temperature — higher heat made the hydrate dissociate more quickly. When methane was released from the hydrate into the liquid state faster than it could diffuse out, it became supersaturated and formed nanobubbles.

“If the decomposition of the methane hydrate phase is fast enough, which depends on temperature, the methane gas in the aqueous phase forms nanobubbles,” said Saman Alavi, one of the lead researchers on the project.

Alavi, along with colleagues A. Bagherzadeh, J. A. Ripmeester and P. Englezos, also briefly studied the other side of the process: hydrate formation. Because they are stable under relatively mild conditions, hydrates could be a potential means to safely transport flammable gasses. But in nature, methane hydrates can take years to form.

That’s where the nanobubbles come into play: through their simulations, the researchers found that if temperature and pressure conditions were favorable for hydrate formation, methane nanobubbles in the aqueous solution sped up the rate at which the hydrate formed. “Nanobubbles may bring more methane into contact with water and enhance hydrate formation efficiency,” said Alavi.

Separately, these findings provide insight into nanobubble dynamics that could allow researchers to take advantage of the unique properties of hydrates.

Taken together, they also provide a potential explanation for the so-called memory effect — the fact that “aqueous solutions in contact with methane form solid methane hydrate at a much faster rate if they have already undergone a methane hydrate formation-decomposition cycle,” said Alavi, almost as if the hydrate “remembers” its previous state.

Nanobubbles might explain why. If a hydrate dissociates fast enough, it leads to the formation of nanobubbles. If these bubbles persist, they could hasten the formation of future hydrates by providing sites for nucleation.

Next, the researchers plan to more thoroughly investigate the composition and long-term fate of nanobubbles resulting from hydrate decomposition.

Reference:
The article, “Formation of methane nano-bubbles during hydrate decomposition and their effect on hydrate growth,” is authored by S. Alireza Bagherzadeh, Saman Alavi, John Ripmeester and Peter Englezos. It will appear in The Journal of Chemical Physics on June 2, 2015.DOI: 10.1063/1.4920971

Note : The above story is based on materials provided by American Institute of Physics.

Origins of feathered dinosaurs more complex than first thought

June 3, 2015

The new study shows that dinosaurs experimented extensively with their ‘outer look’ during their evolution. Credit: The Natural History Museum

It is too soon to claim that the common ancestor of dinosaurs had feathers, according to research by scientists at the Natural History Museum, Royal Ontario Museum and Uppsala University.
A new study, published in the journal Biology Letters this week, suggests that feathers were less prevalent among dinosaurs than previously believed. Scientists examined the fossil record of dinosaur skin and combined this with an evolutionary tree to assess the probability of feathers appearing in different dinosaur groups. This analysis demonstrated that the majority of non-avian dinosaurs were more likely to have scales than to exhibit signs of ‘feather-like’ structures.

“As palaeontologists we are at the mercy of available data, which given the interest in the field are ever changing. Our study shows that dinosaurs experimented extensively with their ‘outer look’ and potentially independently along separate evolutionary lineages. That is what the data allow us to say at present” says Nicolàs Campione, researcher at the Department of Earth Sciences, Palaeobiology, Uppsala University.

The controversial findings will add further fuel to a fierce debate among scientists as to whether the majority of dinosaurs were feathered or scaly.

Over the past two decades a number of spectacularly preserved dinosaur fossils with feathers have revolutionised the field of palaeontology. Due to the conflicting presence of scales and feathers in these new specimens, many scientists are convinced that this is an area of study that deserves further research.

The presence of feathers in birds and their immediate ancestors – theropod dinosaurs like Velociraptor – is uncontroversial, but their presence or absence in other dinosaur groups, such as those including Triceratops and Diplodocus, has been highly debated. Several recent discoveries had suggested that filament-like ‘protofeathers’ might be ubiquitous among dinosaurs, but the new research suggests that the common ancestor of dinosaurs did not necessarily have protofeathers and that the quills and filaments in some major plant-eating dinosaur groups were evolutionary experiments that were independent of true feather origins.

Dinosaur biology remains a disputed and competitive area of research.

“Using a comprehensive database of dinosaur skin impressions, we attempted to reconstruct and interpret the evolutionary history of dinosaur scales and feathers. Most of our analyses provide no support for the appearance of feathers in the majority of non-avian dinosaurs and although many meat-eating dinosaurs were feathered, the majority of other dinosaurs, including the ancestor of all dinosaurs, were probably scaly” says Paul Barrett professor at the Natural History Museum.

“Current data, for the most part, suggest that the common ancestor of dinosaurs was not feathered. However, this is a hypothesis that can only be tested with the discovery of new fossils with preserved skin and/or feathers. In particular, we need fossils that fill key locations in the evolutionary tree of dinosaurs” says Nicolàs Campione.

Reference:
Paul M. Barrett, David C. Evans, Nicolás E. Campione. Evolution of dinosaur epidermal structures. DOI: 10.1098/rsbl.2015.0229

Note : The above story is based on materials provided by Uppsala University.

Paleo study shows how elevation may affect evolution

June 3, 2015

The rise of the Rockies extended from British Columbia to Nevada in three phases between 56 and 23 million years ago. The rising mountains dried out the interior, preparing mammals for a major climate change event 34 million years ago, researchers say. European mammals were not so prepared. Credit: Courtesy of Eronen et. al.

Paleontologists have documented how dramatic shifts in climate have led to dramatic shifts in evolution. One such event, the Grande Coupure, was a wipeout of many European mammal species 33.9 million years ago when global temperatures and precipitation declined sharply. What has been puzzling is that during the same transition between the Eocene and Oligocene periods, North American mammals fared much better. A new study explains why: the rise of the Rocky Mountains, already underway for millions of years, had predisposed populations to adapt to a cold, dry world.
‘Regional tectonically driven surface uplift resulted in large-scale reorganization of precipitation patterns, and our data show that the mammalian faunas adapted to these changes,’ write the study authors, including Christine Janis, professor of ecology and evolutionary biology at Brown University, in the Proceedings of the Royal Society B. ‘We suggest that the late Eocene mammalian faunas of North America were already ‘pre-adapted’ to the colder and drier global conditions that followed the EO climatic cooling.’

The data in the study led by Jussi Eronen of the Senckenberg Research Institutes in Germany and the University of Helsinki in Finland, come from the authors’ analysis of the fossil record of the two continents, combined with previous oxygen isotope data that reveal precipitation patterns, and tectonic models that show the growth of the Rocky Mountains. Specifically, the study shows that the rise of the range spread south in three phases from Canada starting more than 50 million years ago, down through Idaho, and finally into Nevada by 23 million years ago.

In the meantime, fossil mammal data show, precipitation in the interior regions dropped, and major shifts in mammal populations, such as an almost complete loss of primates, took place. Estimated rainfall based on plant fossils in Wyoming, for example, dropped from about 1,200 millimeters a year 56 million years ago to only 750 millimeters a year about 49 million years ago.

But across the region these correlated shifts occurred over tens of millions of years, leaving a well-adapted mix of mammals behind by the time of the Grand Coupure 34 million years ago.

In Europe, meanwhile, tectonic developments weren’t a major factor driving local climate. When the global climate change happened, that continent’s mammals were evolutionary sitting ducks. Other studies have already suggested that Europe’s mammals were largely overrun and outcompeted by Asian mammals that were already living in colder and drier conditions.

Eronen said the findings should elevate the importance of collaboration across disciplines, for instance by integrating geoscience with paleontology, in the analysis of broad evolutionary patterns.

‘Our results highlight the importance of regional tectonic and surface uplift processes on the evolution of mammalian faunas,’ they wrote.

Reference:
Jussi T. Eronen et al. Mountain uplift explains differences in Palaeogene patterns of mammalian evolution and extinction between North America and Europe. Proceedings of the Royal Society B., June 2015 DOI: 10.1098/rspb.2015.0136

Note: The above story is based on materials provided by Brown University.

Researchers discover deepest known high-temperature hydrothermal vents in Pacific Ocean

June 3, 2015

These delicate carbonate spires formed when scalding hot water emerged from sediments in the Pescadero Basin and came in contact with near-freezing seawater. Dense colonies of tubeworms grow on the sides of the spires. This group of spires is about five meters (15 feet) wide. Credit: MBARI

In spring 2015, MBARI researchers discovered a large, previously unknown field of hydrothermal vents in the Gulf of California, about 150 kilometers (100 miles) east of La Paz, Mexico. Lying more than 3,800 meters (12,500 feet) below the surface, the Pescadero Basin vents are the deepest high-temperature hydrothermal vents ever observed in or around the Pacific Ocean. They are also the only vents in the Pacific known to emit superheated fluids rich in both carbonate minerals and hydrocarbons. The vents have been colonized by dense communities of tubeworms and other animals unlike any other known vent communities in the in the eastern Pacific.
Like another vent field in the Gulf that MBARI discovered in 2012, the Pescadero Basin vents were initially identified in high-resolution sonar data collected by an autonomous underwater vehicle (AUV). MBARI’s yellow, torpedo-shaped seafloor-mapping AUV spent two days flying about 50 meters above the bottom of the Basin, using sound beams to map the depth and shape of the seafloor.

The AUV team, led by MBARI engineer David Caress, pored over the detailed bathymetric map they created from the AUV data and saw a number of mounds and spires rising up from the seafloor. Data from the AUV also showed slightly warmer water over some of the spires, which implied that they might be active hydrothermal-vent chimneys. A team of geologists led by David Clague then used a tethered underwater robot, the remotely operated vehicle (ROV) Doc Ricketts, to dive down to the seafloor, fly around the vents, and collect video and samples of rocks and hot water spewing from the chimneys.

Reflecting on the discovery, Clague commented, ‘Before the AUV survey of Pescadero Basin, all we knew was that this area was really deep and filled with sediment. I was hoping to find a few outcrops of lava on the seafloor. But we got lucky. The vent field was right on the edge of our survey area, along a fault at the western edge of the basin.’

The AUV and ROV dives showed that the new field extends for at least 400 meters (one quarter mile) along this fault. Within this area the researchers found at least three active hydrothermal chimneys up to 12 meters (40 feet) tall, as well as dozens of low mounds that are most likely collapsed chimneys.

After his ROV dive, Clague noted, ‘This site was not at all what I was expecting.’ For one thing, the fragments of chimneys that the ROV brought back to the surface were quite different from those collected at other vents in the area. The Pescadero chimneys consisted entirely of light-colored carbonate minerals instead of the dark sulfide minerals that are abundant in hydrothermal chimneys elsewhere in the Gulf.

The Pescadero Basin is only the second place in the world where carbonate chimneys (instead of ones made primarily of sulfides) have been found in the deep sea. The other known location is the ‘Lost City’ vent field in the middle of the Atlantic Ocean, at a spot on the Mid-Atlantic Ridge.

The geologists also noticed that their rock samples smelled like diesel. They hypothesize that hot hydrothermal fluids migrating upward through the thick sediments of the Pescadero Basin ‘cook’ organic matter in the sediment, converting it into petroleum-like hydrocarbons — a process that has been observed at several other vents in the Pacific. Hydrocarbons may provide nutrition for the unusual microbes that thrive at these vents.

After Clague’s initial ROV dive, MBARI biologist Robert Vrijenhoek made three follow-up dives in the Pescadero Basin. His goal was to determine how and why animal communities at the Pescadero vents differed from those at other vent fields in the Gulf. Clague’s and Vrijenhoek’s dives revealed at least three different types of hydrothermal vents in the southern Gulf of California — black smokers, carbonate chimneys, and hydrothermal seeps. Each environment supports its own unique animal community.

Black smokers form in active volcanic areas. One such area is on the Alarcón Rise, about 160 kilometers (100 miles) south of the Pescadero Basin, where MBARI researchers discovered several hydrothermal fields in 2012. On the Alarcón Rise, massive, dark-colored sulfide chimneys rise more than 37 meters (120 feet) above the lava-covered seafloor. These chimneys gush extremely hot fluids (over 350 degrees Celsius, 660 degrees Fahrenheit) rich in heavy metals and sulfides. When the superheated fluids come in contact with near-freezing seawater, these minerals precipitate, forming dark, smoke-like plumes of particles. The ‘black smoker’ chimneys are often colonized by giant tubeworms in the genus Riftia, which grow over two meters (six feet) long, as well as limpets, crabs, squat lobsters, and Alvinella palmworms.

In contrast, the carbonate chimneys in the Pescadero Basin emerge from a flat, muddy seafloor, and are smaller and more delicate than black smokers. They emit fluids that are slightly cooler (250-290 degrees Celsius) and do not form dark, smoke-like plumes. The Pescadero Basin fluids are, however, rich in oil-like hydrocarbons that form dark, oily crusts on the light colored carbonate chimneys. They also support a very different group of animals, including dense colonies of tubeworms in the genus Oasisia.

In the third type of vent environment, ‘hydrothermal seeps,’ much cooler (less than 30-60 degrees Celsius) water trickles out of lava flows interleaved with seafloor mud. These seeps support an entirely different community of animals, including anemones, tubeworms in the genera Lamellibrachia and Escarpia, and broad, white mats of bacteria. In contrast to the Pescadero and Alarcón vents, each of which hosted a single species of deep-sea clams, the seeps support at least four different types of clams.

One thing that all of these communities have in common is that the dominant tubeworms and clams host specialized intracellular bacteria (symbionts) that allow these animals to exploit potentially toxic chemicals in the vent fluids as sources of nutrition. Vrijenhoek and his collaborators are trying to figure out if the different vent communities in the Gulf are controlled by differences in water depth, geochemistry, symbiotic bacteria, or perhaps other unanticipated factors.

The discovery of the Pescadero Basin hydrothermal field is just the latest example of how MBARI’s extensive use of underwater robotics has accelerated the pace of scientific discovery in the deep sea. As Vrijenhoek noted, ‘In the 1990s, following the discovery of plumes of warm water over the Mid-Atlantic Ridge, researchers from four countries searched for seven years to find what eventually became known as the ‘rainbow vent field.’ They were limited by inaccurate and imprecise bathymetric maps. This spring it took us only two days to do the same thing in the Pescadero Basin, using MBARI’s high-precision seafloor-mapping AUV.’

Note: The above story is based on materials provided by Monterey Bay Aquarium Research Institute.

Large Quakes May Dampen Themselves

June 3, 2015

Snapshots of a 10-Hz rupture propagation and surface wave field. The bottom shot includes the effects of crustal variations, generating a strongly scattered wave field. Credit: Amit Chourasia, SDSC

Most models of ground motion during earthquakes have the earth shifting and grinding, then returning to essentially the same state as before once the temblor ends. But during earthquakes, especially large ones, the earth gets transformed. It crumbles and breaks apart, and in extreme cases even liquefies. These terrestrial transformations are known as nonlinear effects, and they may impact how much damage certain temblors can cause.
If a massive magnitude 8.0 earthquake rocked the San Andreas Fault, certain properties of the Southern California region’s shallow sediments might mean the quake would shake less than previously estimated. Kim Olsen, a geologist and earthquake expert at San Diego State University, recently was awarded a $57,000 grant from the U.S. Geological Survey to study these nonlinear effects.

Table of Contents

Shake and rattle

It’s harder for an earthquake’s waves to transmit as much energy through this broken-up earth, meaning that the quake’s amplitude winds up being dampened in the process. This earthen breakup is more likely to occur in areas with unconsolidated sediment—clay, sand and gravel—and during large, powerful earthquakes. That means, somewhat counterintuitively, that the Big One might be so powerful that nonlinear effects near the fault limit the amplitude of certain waves, dramatically reducing the damage much further away.

“A 7.8 or 8.0 magnitude earthquake on the San Andreas might halve the amplitude of the shaking in certain parts of Los Angeles as a result of nonlinear effects,” Olsen explained.

Olsen and his colleagues in the San Diego Supercomputer Center—made up of researchers from SDSU and the University of California, San Diego—are using supercomputing technology to model earthquakes that incorporate these nonlinear effects.

Prize-winning code

This team of researchers recently won a $150,000 grand prize from the technology company NVIDIA in a competition to find real-world applications for the company’s accelerated graphics processing unit (GPU) technology.

Olsen and his SDSU colleague Steven Day created the code which, for the competition, was used to simulate high-frequency seismic waves in the range of 0-10 Hertz, the kind of waves that tend to cause the most damage to single-level and two-story homes. Their simulations could be used to test and potentially overhaul earthquake building codes to make homes safer, Olsen said

NVIDIA’s accelerated GPU technology allowed the simulation to run about five times faster than it would ordinarily. By incorporating the accelerated GPU, researchers can do their work more quickly and efficiently.

“We’re excited that we got this speed-up,” Olsen said. “Now we want to use it and get some results.”

Note : The above story is based on materials provided by San Diego State University.

Yorkshire’s oldest new addition to the ‘Jurassic World’

June 2, 2015

Experts from the University of Manchester have identified Britain’s oldest sauropod dinosaur from a fossil bone discovered on the Yorkshire coast.

The vertebra (backbone) originates from a group of dinosaurs that includes the largest land animals to have ever walked on Earth. This new sauropod dinosaur, from the Middle Jurassic Period at about 176 million years old, was found near Whitby, Yorkshire, after it fell out of a cliff face. This find represents the earliest skeletal record of this type of dinosaur from the United Kingdom and adds to existing evidence from Yorkshire dinosaur tracks that this part of the country was once Britain’s very own ‘Jurassic World’.

Sauropods (often referred to as ‘brontosaurs’) include some of the largest plant-eating dinosaurs to have roamed the Earth and were a successful group for nearly 150 million years. They possessed distinctive long necks and tails, small heads, a large body and walked on all fours. Some species such as the Argentinosaurus grew up to 115 feet (35 metres) long and possibly weighed as much as 80 tonnes.

The fragmentary nature of the new find from Yorkshire means it is not possible to generate a new species of dinosaur. However, this fossil clearly belongs to this distinctive group of titanic sized animals, the sauropods. This dinosaur fossil is an extremely rare find, given the Middle Jurassic rocks of the world are only exposed in a few areas, such as China and Argentina where similar-aged dinosaur fossils originate.

Professor Phil Manning and his team from The University of Manchester used X-Ray Tomography to study the fossil bone, which is now held in the collections at the Yorkshire Museum in York (UK). They present their description of this new sauropod dinosaur in a paper published today in the journal PLOS ONE.

Professor Manning said: “Many scientists have worked on the amazing dinosaur tracks from the Middle Jurassic rocks of Yorkshire. It was a splendid surprise to come face-to-face with a fossil vertebra from the Jurassic rocks of Yorkshire that was clearly from a sauropod dinosaur

“This fossil offers the earliest ‘body fossil’ evidence for this important group of dinosaurs in the United Kingdom, but it is impossible to define a new species based upon this single bone.”

Whilst this is clearly frustrating for the team, there is possibly more of this Jurassic titan still to be discovered in the future and only then might it get a new species name. Until more bones are discovered the team have simply nicknamed Britain’s oldest sauropod dinosaur, ‘Alan’, after the finder of this prehistoric beastie (Alan Gurr).

Dr Victoria Egerton (co-author on the paper) added: “The Jurassic Park that was once Yorkshire clearly has much more to offer science in our understanding of the distribution and evolution of dinosaurs.”

Dr Mike Romano, another co-author on the paper said: “Dinosaur remains of Middle Jurassic age are generally rare, even on a global scale. So, to find a single distinctive vertebra of that age on the beach at Whitby, and one that represents a new taxon of sauropod dinosaurs, is indeed a (white) feather in the cap for Yorkshire.”

Reference:
Phillip L. Manning , Victoria M. Egerton , Mike Romano. A new sauropod dinosaur from the Middle Jurassic of the United Kingdom. PLOS ONE, June 1, 2015 DOI: 10.1371/journal.pone.0128107

Note: The above story is based on materials provided by Manchester University.

Laser from a plane discovers Roman goldmines in Spain

June 2, 2015

These are ancient goldmines in the Eria river valley, with channels and reservoirs for exploitation. The model generated with LiDAR data (left) allows these structures to be located on aerial photos (right). Credit: J. Fernández Lozano et al.

Hidden under the vegetation and crops of the Eria Valley, in León (Spain), there is a gold mining network created by the Romans two thousand years ago, as well as complex hydraulic works, such as river diversions, to divert water to the mines of the precious metal. Researchers from the University of Salamanca made the discovery from the air with an airborne laser teledetection system.

Las Médulas in León is considered to be the largest opencast goldmine of the Roman Empire, but the search for this metal extended many kilometres further south-east to the Erica river valley. Thanks to a Light Detection and Ranging (LiDAR) laser system attached to an aircraft, the ancient mining works of the area and the complex hydraulics system used by the Romans in the 1st century BC to extract gold (including channels, reservoirs and a double river diversion) have been discovered.

“The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures, which makes this valley extremely important in the context of Roman mining in the north-east of the Iberian Peninsula,” as Javier Fernández Lozano, geologist at the University of Salamanca and co-author of this study published in the Journal of Archaeological Science, said.

The specialists consider that the systems for the transport and storage of water were copied from those already existing in North Africa, where the Egyptians had been employing them for centuries. Some details of the methodology used appear in texts such as those of the Pliny the Elder, the Roman procurator in charge of overseeing mining in Hispania.

“We have established that the labour that went into extracting the resource until its exhaustion was so intensive that after removing the gold from surface sediments, operations continued until reaching the rocks with the auriferous quartz veins underneath,” explains Fernández Lozano.

The researcher stresses that the real discoverer was the LiDAR technology: “Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas.”

From aircraft or drones

LiDAR comprises a laser sensor which scans the ground from an aircraft or drone with geographical references provided by GPS ground stations. The data obtained is represented by point clouds, which are processed with a piece of software to construct a cartographic model where the forms are identified, such as old reservoirs or channels.

This technology was developed by NASA in the sixties to analyse the retreating sea ice in the Arctic and composition of the oceans. Since then their use has been extended to topography, cadastral mapping, geology and archaeology. According to the authors, the study of Roman mining in the Eria valley is the first piece of ‘geo-archaeology’ performed with LiDAR in Spain.

“Our intention is to continue working with this technique to learn more about mineral mining in the Roman Empire and clear up any mysteries such as why Rome abandoned such a precious resource as gold from one day to the next,” concludes the researcher.

Reference:
Javier Fernández-Lozano, Gabriel Gutiérrez-Alonso, Miguel Fernández-Morán. Using airborne LiDAR sensing technology and aerial orthoimages to unravel roman water supply systems and gold works in NW Spain (Eria valley, León). Journal of Archaeological Science, 2014. DOI:10.1016/j.jas.2014.11.003

Note: The above story is based on materials provided by Plataforma SINC.

Radiocarbon dates of mollusc shells show that modern humans occupied the Near East at least 45,900 years ago

June 2, 2015

Phorcus turbinatus shells. Top and side views of: (1) A complete specimen (inventory no.: RGM-606318a). (2) A shell of which the top was removed by Upper Palaeolithic people to aid flesh extraction (RGM-606318b). Scale bar is 1 cm.

New high precision radiocarbon dates of mollusk shells show that modern humans occupied the Near East at least 45,900 years ago and colonized Europe from there.
A multinational team, which included researchers from the University of York, analysed shells recovered at Ksâr ‘Akil, a site in Lebanon. Ksâr ‘Akil is one of the few sites in the Near East where modern human fossils are associated with Upper Palaeolithic (UP) tools.

The researchers radiocarbon-dated the shell carbonates of the mollusck species Phorcus turbinatus that was eaten by prehistoric humans. The analysis revealed that modern humans carrying UP tools occupied the eastern Mediterranean at least 45,900 years ago. This confirms UP modern human presence in the Levant prior to their arrival in Europe and suggests that it served as a corridor for the colonization of Europe by modern humans.

Dr Beatrice Demarchi, of the Department of Archaeology at York, and Sheila Taylor, of the University’s Department of Chemistry, were part of the team which studied around 3500 shells comprising 49 species. The researchers found that the best-preserved shells were those of mollusks gathered by prehistoric humans for consumption as food and they used new techniques to ensure that the samples had not been compromised during burial before radiocarbon dating them.

“One of these approaches is a technique called ‘intra-crystalline protein diagenesis’ which evaluates the integrity of amino acids preserved in the intra-crystalline structure of the shell carbonates” says Dr Demarchi. Amino acid analyses were undertaken at the University’s Natural Environment Research Council-recognised facility for amino acid analysis.

The study, which is published in Proceedings of the National Academy of Sciences (PNAS), has allowed the researchers to propose a robust new chronology for Ksâr ‘Akil. Their results confirm the presence of modern humans carrying a UP toolkit in the Levant prior to any modern human fossils in Europe.

The timing of the spread of modern humans out of Africa and into Eurasia is a topic of major debate among archaeologists, human paleontologists and geneticists. They have been seeking to establish when modern humans first arrived in Europe, the route they took and if the Levant serve as a corridor facilitating Upper Palaeolithic modern human dispersal.

The importance of Ksâr ‘Akil lies in the fact that there are two modern human fossils, nicknamed ‘Ethelruda’ and ‘Egbert’ by the original excavators, associated with Upper Palaeolithic toolkits from the site.

However, the new research shows that Egbert lived around 43,000 years ago and Ethelruda at least 45,900 years ago, possibly earlier. Therefore, Ethelruda pre-dates all European modern humans.

Marjolein Bosch, from the Max Planck Institute for Evolutionary Anthropology, the lead author of the study added: “Toolkits similar to those associated with Ethelruda and Egbert are also found in other sites in the Levant as well as in Europe. These similar toolkits and the earlier ages in the Near East suggest population dispersals from the Near East to Europe between 55,000 and 40,000 years ago.”

Reference:
Marjolein D. Bosch, Marcello A. Mannino, Amy L. Prendergast, Tamsin C. O’Connell, Beatrice Demarchi, Sheila M. Taylor, Laura Niven, Johannes van der Plicht, and Jean-Jacques Hublin. New chronology for Ksâr ‘Akil (Lebanon) supports Levantine route of modern human dispersal into Europe. Proceedings of the National Academy of Sciences, 2015; DOI: 10.1073/pnas.1501529112

Note: The above story is based on materials provided by University of York.

New evidence emerges on the origins of life

June 2, 2015

In the beginning, there were simple chemicals. And they produced amino acids that eventually became the proteins necessary to create single cells. And the single cells became plants and animals. Recent research is revealing how the primordial soup created the amino acid building blocks, and there is widespread scientific consensus on the evolution from the first cell into plants and animals. But it’s still a mystery how the building blocks were first assembled into the proteins that formed the machinery of all cells.

Now, two long-time University of North Carolina scientists — Richard Wolfenden, PhD, and Charles Carter, PhD — have shed new light on the transition from building blocks into life some 4 billion years ago.

“Our work shows that the close linkage between the physical properties of amino acids, the genetic code, and protein folding was likely essential from the beginning, long before large, sophisticated molecules arrived on the scene,” said Carter, professor of biochemistry and biophysics at the UNC School of Medicine. “This close interaction was likely the key factor in the evolution from building blocks to organisms.”

Their findings, published in companion papers in the Proceedings of the National Academy of Sciences, fly in the face of the problematic “RNA world” theory, which posits that RNA — the molecule that today plays roles in coding, regulating, and expressing genes — elevated itself from the primordial soup of amino acids and cosmic chemicals to give rise first to short proteins called peptides and then to single-celled organisms.

Wolfenden and Carter argue that RNA did not work alone; in fact, it was no more likely that RNA catalyzed peptide formation than it was for peptides to catalyze RNA formation.

The finding adds a new layer to the story of how life evolved billions of years ago.

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Its name was LUCA

The scientific community recognizes that 3.6 billion years ago there existed the last universal common ancestor, or LUCA, of all living things presently on Earth. It was likely a single-cell organism. It had a few hundred genes. It already had complete blueprints for DNA replication, protein synthesis, and RNA transcription. It had all the basic components — such as lipids — that modern organisms have. From LUCA forward, it’s relatively easy to see how life as we know it evolved.

Before 3.6 billion years, however, there is no hard evidence about how LUCA arose from a boiling caldron of chemicals that formed on Earth after the creation of the planet about 4.6 billion years ago. Those chemicals reacted to form amino acids, which remain the building blocks of proteins in our own cells today.

“We know a lot about LUCA and we are beginning to learn about the chemistry that produced building blocks like amino acids, but between the two there is a desert of knowledge,” Carter said. “We haven’t even known how to explore it.”

The UNC research represents an outpost in that desert.

“Dr. Wolfenden established physical properties of the twenty amino acids, and we have found a link between those properties and the genetic code,” Carter said. “That link suggests to us that there was a second, earlier code that made possible the peptide-RNA interactions necessary to launch a selection process that we can envision creating the first life on Earth.”

Thus, Carter said, RNA did not have to invent itself from the primordial soup. Instead, even before there were cells, it seems more likely that there were interactions between amino acids and nucleotides that led to the co-creation of proteins and RNA.

Complexity from simplicity

Proteins must fold in specific ways to function properly. The first PNAS paper, led by Wolfenden, shows that both the polarities of the twenty amino acids (how they distribute between water and oil) and their sizes help explain the complex process of protein folding — when a chain of connected amino acids arranges itself to form a particular 3-dimensional structure that has a specific biological function.

“Our experiments show how the polarities of amino acids change consistently across a wide range of temperatures in ways that would not disrupt the basic relationships between genetic coding and protein folding,” said Wolfenden, Alumni Distinguished Professor of Biochemistry and Biophysics. This was important to establish because when life was first forming on Earth, temperatures were hot, probably much hotter than they are now or when the first plants and animals were established.

A series of biochemical experiments with amino acids conducted in Wolfenden’s lab showed that two properties — the sizes as well as the polarities of amino acids — were necessary and sufficient to explain how the amino acids behaved in folded proteins and that these relationships also held at the higher temperatures of Earth 4 billion years ago.

The second PNAS paper, led by Carter, delves into how enzymes called aminoacyl-tRNA synthetases recognized transfer ribonucleic acid, or tRNA. Those enzymes translate the genetic code.

“Think of tRNA as an adapter,” Carter said. “One end of the adapter carries a particular amino acid; the other end reads the genetic blueprint for that amino acid in messenger RNA. Each synthetase matches one of the twenty amino acids with its own adapter so that the genetic blueprint in messenger RNA faithfully makes the correct protein every time.”

Carter’s analysis shows that the two different ends of the L-shaped tRNA molecule contained independent codes or rules that specify which amino acid to select. The end of tRNA that carried the amino acid sorted amino acids specifically according to size.

The other end of the L-shaped tRNA molecule is called the tRNA anticodon. It reads codons, which are sequences of three RNA nucleotides in genetic messages that select amino acids according to polarity.

Wolfenden and Carter’s findings imply that the relationships between tRNA and the physical properties of the amino acids — their sizes and polarities — were crucial during the Earth’s primordial era. In light of Carter’s previous work with very small active cores of tRNA synthetases called Urzymes, it now seems likely that selection by size preceded selection according to polarity. This ordered selection meant that the earliest proteins did not necessarily fold into unique shapes, and that their unique structures evolved later.

Carter said, “Translating the genetic code is the nexus connecting pre-biotic chemistry to biology.”

He and Wolfenden believe that the intermediate stage of genetic coding can help resolve two paradoxes: how complexity arose from simplicity, and how life divided the labor between two very different kinds of polymers: proteins and nucleic acids.

“The fact that genetic coding developed in two successive stages — the first of which was relatively simple — may be one reason why life was able to emerge while the earth was still quite young,” Wolfenden noted.

An earlier code, which enabled the earliest coded peptides to bind RNA, may have furnished a decisive selective advantage. And this primitive system could then undergo a natural selection process, thereby launching a new and more biological form of evolution.

“The collaboration between RNA and peptides was likely necessary for the spontaneous emergence of complexity,” Carter added. “In our view, it was a peptide-RNA world, not an RNA-only world.”

The National Institutes of Health funded this work. Dr. Wolfenden holds a joint appointment in the department of chemistry in the College of Arts and Sciences at UNC-Chapel Hill.

Reference:
Richard Wolfenden, Charles A. Lewis Jr., Yang Yuan, and Charles W. Carter Jr. Temperature dependence of amino acid hydrophobicities. Proceedings of the National Academy of Sciences, 2015; DOI: 10.1073/pnas.1507565112

Note: The above story is based on materials provided by University of North Carolina Health Care.

Ancient algae found deep in tropical glacier

June 2, 2015

Pennate (elongated) diatoms found in an ice core from the Quelccaya Summit Dome Glacier were among many samples identified by scientists at Rice University, the University of Nebraska-Lincoln and Ohio State University. They suspect the freshwater diatoms, a type of algae, were blown there from nearby high-elevation ponds as far back as the sixth century. Credit: Images by Bruce Brinson/Rice University

The remains of tiny creatures found deep inside a mountaintop glacier in Peru are clues to the local landscape more than a millennium ago, according to a new study by Rice University, the University of Nebraska-Lincoln and Ohio State University.
The unexpected discovery of diatoms, a type of algae, in ice cores pulled from the Quelccaya Summit Dome Glacier demonstrate that freshwater lakes or wetlands that currently exist at high elevations on or near the mountain were also there in earlier times. The abundant organisms would likely have been transported in air currents to the glacier, where they were deposited on its surface, dead or alive, and ultimately became frozen within the glacial ice and persisted there for hundreds of years.

The study is the first to show the presence of diatoms in glacial ice from tropical regions. The diatoms offer useful information about conditions in and around the Andes when they were deposited on the ice.

The paper is the result of a unique collaboration among Rice chemists Ed Billups and Bruce Brinson, Ohio State climatologist Lonnie Thompson and lead author Sherilyn Fritz, a geoscientist at Nebraska. It appears this week in Arctic, Antarctic, and Alpine Research, a journal published by the University of Colorado-Boulder.

Of the four scientists, Billups, Brinson and even Thompson had something in common with the focus of their study: They were all, figuratively, fish out of water.

“I was the lucky latecomer to the group,” said Fritz, who studies diatoms from cores she and her students drill from South American lakebeds. “It’s only because Bruce was so observant and curious and did such a nice job on documenting the diatoms that it happened at all.”

Over a long and storied career, Thompson has collected ice cores from many of the world’s hard-to-reach locations, including Quelccaya in 2003. The cores contain a climate record that spans millennia, but Thompson’s ability to pull hard data from his samples was complicated by the sheer number he had preserved.

Thompson said the first record of diatoms in tropical glaciers “points to the potential of these archives for investigating how not just diatoms but other life forms such as ancient microbes survived, thrived and evolved under extreme conditions and under very different climatic regimes.”

The collaboration began when Thompson visited Rice for a conference and struck up a conversation with Billups, with whom he shares West Virginia roots.

“We got to talking,” said Billups of their first encounter. “He knew we were working on carbon materials and said, ‘You know, sometimes my ice is black, and I think that’s carbon.'” Billups, whose wide-ranging research includes the study of all forms of carbon, suspected wind currents carried fullerenes from forest fires to the mountaintop and offered to have a look.

Thompson sent ice core filtrates in silica filter paper that preserved the contents of water from three layers corresponding to the years 1161 to 1176, 807 to 837 and 460 to 511 A.D. (The earliest samples tested for the study were from about 540 feet below the surface of the 18,000-foot mountain.) “When I looked at the samples, I thought, ‘Whatever are we going to do with these?'” Billups recalled.

“We realized they weren’t appropriate for searching for fullerenes,” said Brinson, a Rice research scientist.

Brinson looked at the samples through a Rice electron microscope and quickly recognized their significance. Rather than fullerenes, they contained what the paper described as “a serendipitous byproduct”: an abundance of diatoms, the study of which is generally well outside the realm of either chemists or glaciologists.

“When we saw the first diatom and realized it possessed periodic nanoscale structure, we knew we were documenting irreplaceable snapshots in archeological time and space,” Brinson said.

“Thompson was very excited about this,” Billups said. “Diatoms are found in Arctic and Antarctic ice, but he said nobody’s ever found them in equatorial glaciers.”

Brinson hit the books and identified many of the diatoms, which ranged in size from a few to 70 microns in length. “I don’t have a biological background, but I knew they were unique,” he said. He also realized the team needed a specialist.

Thompson, who knew of Fritz’s work in South America, suggested they enlist her.

“There are diatoms in dust that is transported globally, and people have found them in glaciers in Antarctica and Greenland, so my first thought was they’d be like those,” Fritz said. “But these are beautifully preserved, and most of the ecology we know about indicates they’re not from global diatom dust sources.”

Fritz said the diatoms’ excellent condition suggested they hadn’t traveled far. “Most but not all of them are species you would find in very dilute freshwater, either lakes or wetlands, and there are lots of those in the tropical Andes at varied elevations,” she said. The presence of Volvox, green algae found in the two older samples, confirmed the diatoms’ freshwater source.

The study has Fritz thinking about gathering diatoms from lakes near the ice cap to see how diatom populations have changed over the centuries. “I’ve contemplated doing some more sampling, just because it’s an interesting question,” she said. She does plan to have her students take a closer look at the original samples, which Brinson sent her, “to do some quantitative counts, just to get a better sense of the relative abundance of things.”

The researchers wrote that continuing study of diatoms in relation to other materials found in the ice core record could provide valuable information about local or even global environmental change.

“I’m convinced there’s no end to what you can find in these glaciers,” Billups said.

“One thing is clear,” Thompson said. “The greatest scientific progress going forward will be made with increased collaboration among many different disciplines. Unfortunately, these valuable ice archives of our past are rapidly disappearing under the present climate conditions.”

Reference:
Lonnie G. Thompson et al. Diatoms at >5000 Meters in the Quelccaya Summit Dome Glacier, Peru. Arctic, Antarctic, and Alpine Research, June 2015 DOI: 10.1657/AAAR0014-075

Note: The above story is based on materials provided by Rice University.

The ebb and flow of Greenland’s glaciers

June 2, 2015

These icebergs are easily visible in the fjord from an area just outside of Ilulissat. They calved from Jakobshavn Isbrae (aka Ilulissat Glacier) earlier in the season, from the calving front which peaks at speeds of nearly 17 km/yr in mid summer. Credit: Ian Joughin, University of Washington

In northwestern Greenland, glaciers flow from the main ice sheet to the ocean in see-sawing seasonal patterns. The ice generally flows faster in the summer than in winter, and the ends of glaciers, jutting out into the ocean, also advance and retreat with the seasons.
Now, a new analysis shows some important connections between these seasonal patterns, sea ice cover and longer-term trends. Glaciologists hope the findings, accepted for publication in the June issue of the American Geophysical Union’s Journal of Geophysical Research-Earth Surface and available online now, will help them better anticipate how a warming Greenland will contribute to sea level rise.

“Rising sea level can be hard on coastal communities, with higher storm surges, greater flooding and saltwater encroachment on freshwater,” said lead author Twila Moon, a researcher at the National Snow and Ice Data Center (NSIDC). NSIDC is part of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.

“We know that sea level will go up in the future,” Moon said. “The challenge is to understand how quickly it will rise, and one element of that is better understanding how Greenland glaciers behave.”

Moon and colleagues from the University of Washington focused on 16 glaciers in northwest Greenland, collecting detailed information on glacier speed, terminus position (the “end” of the glacier in the ocean) and sea ice conditions, during the years 2009-2014.

Sea ice had an important influence on the glaciers: When the waters in front of the glacier were completely covered by sea ice, the ends of the glaciers often advanced out away from land; icebergs that might otherwise have broken off and floated away stayed attached. When sea ice broke up in the spring, the ends of the glaciers usually quickly retreated back toward land as icebergs broke away.

By contrast, seasonal swings in glacier speed had little to do with sea ice conditions or glacier terminus location. Rather, the speed (velocity) of ice flow is likely responding to changes in the surface melt on top of the ice sheet and the movement of meltwater through and under the ice sheet.

Over the longer-term, however, Moon and her colleagues found a tight relationship between the speed of glaciers and terminus location. When sea ice levels were especially low and glaciers’ toes (termini) retreated more than normal and then didn’t re-advance, the glaciers sped up, moving ice toward the sea more quickly. While low sea ice is likely not the full cause of the changes, it may be a visible indication of other processes, such as subsurface ice melt, that also affect terminus retreat, Moon said.

It’s important to recognize that the mechanisms driving seasonal glacier changes–in northwestern Greenland and around the world–are not necessarily the same ones driving longer-term trends, Moon said. Knowing the differences may help researchers better anticipate the impact of anomalously low sea ice years, for example.

“We do know we’re going to see sea ice reduction in this area, and it’s possible we can begin to estimate how that may affect glacier velocities,” Moon said. It’s also possible, she said, that researchers and communities interested in long-term glacial changes–the kind that affect sea levels–may not need to focus as much on seasonal advance and retreat of the rivers of ice.

“It may be that we need to instead pay more attention to these out-of-bounds events, these anomalous years of very low sea ice or very high melt that likely have the greatest influence on longer-term trends.”

Reference:
Ben Smith et al. Seasonal to multiyear variability of glacier surface velocity, terminus position, and sea ice/ice mélange in northwest Greenland. Journal of Geophysical Research-Earth Surface, June 2015 DOI: 10.1002/2015JF003494

Note: The above story is based on materials provided by American Geophysical Union.

Astronomers make real-time, 3D movies of plasma tubes drifting overhead

June 2, 2015

This is an artist’s impression of tubular plasma structures in the Earth’s magnetosphere, 600 kilometres above the ground. Credit: CAASTRO/Mats Bjorkland

By creatively using a radio telescope to see in 3D, astronomers have detected the existence of tubular plasma structures in the inner layers of the magnetosphere surrounding Earth.
“For over 60 years, scientists believed these structures existed but by imaging them for the first time, we’ve provided visual evidence that they are really there,” said Cleo Loi of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) and School of Physics at the University of Sydney in Australia.

Ms Loi is the lead author on this research, undertaken as part of her award-winning undergraduate thesis and recently published in Geophysical Research Letters. In collaboration with international colleagues, she identified the structures.

“The discovery of the structures is important because they cause unwanted signal distortions that could, as one example, affect our civilian and military satellite-based navigation systems. So we need to understand them,” Ms Loi said.

The region of space around Earth occupied by its magnetic field, called the magnetosphere, is filled with plasma that is created by the atmosphere being ionised by sunlight.

The innermost layer of the magnetosphere is the ionosphere, and above that is the plasmasphere. They are embedded with a variety of strangely shaped plasma structures including, as has now been revealed, the tubes.

“We measured their position to be about 600 kilometres above the ground, in the upper ionosphere, and they appear to be continuing upwards into the plasmasphere. This is around where the neutral atmosphere ends, and we are transitioning to the plasma of outer space,” explained Ms Loi.

Using the Murchison Widefield Array (MWA), a radio telescope located in the Western Australian desert, Ms Loi found that she could map large patches of the sky and even exploit the MWA’s rapid snapshot capabilities to create a movie — effectively capturing the real-time motions of the plasma.

“We saw a striking pattern in the sky where stripes of high-density plasma neatly alternated with stripes of low-density plasma. This pattern drifted slowly and aligned beautifully with the Earth’s magnetic field lines, like aurorae,” Ms Loi said.

“We realised we may be onto something big and things got even better when we invented a new way of using the MWA.”

The MWA consists of 128 antenna ’tiles’ spread over an area roughly three by three kilometres that work together as one instrument — but by separating the signals from tiles in the east from the ones in the west, the astronomers gave the MWA the power to see in 3D.

“This is like turning the telescope into a pair of eyes, and by that we were able to probe the 3D nature of these structures and watch them move around,” said Ms Loi.

“We were able to measure the spacing between them, their height above the ground and their steep inclination. This has never been possible before and is a very exciting new technique.”

This ability adds yet another accolade to the MWA’s name after it had already proven its worth as a powerful precursor instrument to the Square Kilometre Array (SKA), and now the MWA’s 3D vision has the potential to provide many more in-depth analyses of the formation of plasma structures.

“It is to Cleo’s great credit that she not only discovered this but also convinced the rest of the scientific community. As an undergraduate student with no prior background in this, that is an impressive achievement,” said Ms Loi’s supervisor Dr Tara Murphy, also of CAASTRO and School of Physics at the University of Sydney.

“When they first saw the data, many of her senior collaborators thought the results were literally ‘too good to be true’ and that the observation process had somehow corrupted the findings, but over the next few months, Cleo managed to convince them that they were both real and scientifically interesting.”

Video

Reference:
S.T. Loi et al. Real-time imaging of density ducts between the plasmasphere and ionosphere. Geophysical Research Letters, 2015 DOI: 10.1002/2015GL063699

Note: The above story is based on materials provided by University of Sydney.

M8.5 Earthquake Hits Japan, May 30, 2015

May 30, 2015

Sudden draining of glacial lakes explained

Galapagos eruption: Wolf volcano spewing lava for the first time in 33 years

115-million-year-old remains of a tiny fossil bird from Brazil

Clues to the Earth’s ancient core

Earth’s Ancient Geodynamo

Magnetic Records in Rocks

Basal Mantle Ocean and Beyond

Gloucestershire fossil identified as new species of ancient reptile

The curse of the horned dinosaur egg

Australian fossil forces rethink on our ancestors’ emergence onto land

The invisible key to methane hydrates

Origins of feathered dinosaurs more complex than first thought

Paleo study shows how elevation may affect evolution

Researchers discover deepest known high-temperature hydrothermal vents in Pacific Ocean

Large Quakes May Dampen Themselves

Shake and rattle

Prize-winning code

Yorkshire’s oldest new addition to the ‘Jurassic World’

Laser from a plane discovers Roman goldmines in Spain

From aircraft or drones

Radiocarbon dates of mollusc shells show that modern humans occupied the Near East at least 45,900 years ago

New evidence emerges on the origins of life

Its name was LUCA

Complexity from simplicity

Ancient algae found deep in tropical glacier

The ebb and flow of Greenland’s glaciers

Astronomers make real-time, 3D movies of plasma tubes drifting overhead

Video

M8.5 Earthquake Hits Japan, May 30, 2015

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