Scientists fly kites on Earth to study Mars

March 17, 2015

This is a perspective view of the December 1974 lava flow in Hawaii. This image is not a photograph, but rather it was constructed by draping kite-based aerial photography over a digital terrain model. Credit: Christopher Hamilton

Scientists of the University of Arizona’s Lunar and Planetary Laboratory have taken to kites that they fly above lava flows blanketing the Hawaiian landscape to unravel the past mysteries that shaped Mars.

A kite, equipped with off-the-shelf instruments such as a camera, a GPS, and orientation sensors, scans the terrain from high above. The team then employs parallel computing and powerful software algorithms to assemble tens of thousands of images into extremely detailed and accurate 3D digital terrain models.

In terms of studying volcanic landscapes, the project is unprecedented in its scope and in the quality of the data it produces, with a spatial resolution of approximately half an inch per pixel, according to the researchers. They will present their results and methodology at the 46th Lunar and Planetary Science Conference, which is held March 16-20 in The Woodlands, Texas.

The insights gained from these terrain models are used to inform interpretations of images of the surface of Mars, taken with the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter, which has been examining Mars with six instruments since 2006. Led by the UA, HiRISE stands for the High Resolution Imaging Science Experiment and has revealed never-before seen details of the Martian surface.

“The idea is to understand places we can’t go by analyzing places we can go,” said Christopher Hamilton, the principal investigator of the research team, who joined LPL in 2014 to establish a terrestrial analog research group. Hamilton studies volcanic surfaces on Mars to understand the thermal history of the red planet, in other words, how the planet’s internal processes manifest on the surface.

“We can use geologically young and vegetation-free surface features here on Earth — such as Hawaiian lava flows — as terrestrial analogs that can provide us with insights into processes that shape other planets,” he added. “Instead of just saying, ‘this feature looks like X,’ we try to develop diagnostics that help us recognize the actual processes that led to the formation of a certain feature.”

Hamilton’s team chose Kilauea Volcano on the Island of Hawaii as their study area, a “chemical desert” with several geologically very young lava flows, in particular the December 1974 flow, which poured out of the volcano on New Year’s Eve 1974 in a short-lived eruption, which is currently accessible by foot.

When the researchers compared to images of the Martian surface taken by HiRISE, striking similarities appear.

“We think this is how the big lava flows formed on Mars, which strongly suggests they may not be what they seem,” Hamilton said. For example, many features that have been interpreted as channels carved by running water in the red planet’s past are more likely to be the result of volcanic process that Hamilton describes as a “fill-and-spill” lava emplacement, which developed when lava accumulated in enormous “perched ponds” that breached like an overtopped dam, giving way to catastrophic floods of lava.

“It is easy to draw conclusions based on our intuition of how water flows,” Hamilton said, “so it is tempting to interpret similar features on Mars in the same way. But in fact these features formed by flowing lava, not water.”

Pointing to the terrain model of the December 1974 flow, Hamilton said, “We see that in certain areas, the surface is broken up into plates and what superficially looks like channels carved by running water. However, these turn out to be not carved at all, but rather are the result of a complex pattern of lava movements within the flow.”

Hamilton explained that first, liquid lava filled the area between the cliffs from older lava lows like a big bathtub, and when the perched lava pond breached, the lava surged forward causing plates of cooled lava on the surface to break apart and fresh lava to well up from underneath. As the plates were floating toward the drain, they became crumpled.

The digital terrain models even revealed a “bathtub ring” formed when lava filled the pool.

“The question that drives us is, ‘how can we assemble this kind of data for Mars landscapes and decide whether a feature is volcanic or fluvial — shaped by water — and allow us to develop a story?'” Hamilton said, “A single surface texture doesn’t tell you anything if you can’t see the way in which the building blocks combine, such as the tiles that make up the pattern of a mosaic. The relationships between textures allow you where to look and what to look for.”

Stephen Scheidt, a postdoctoral fellow at LPL who studies dune-building processes, designed and built the terrain-mapping kite system that was used for the project in Hawaii. To acquire the images, he launched a robotic camera attached to a delta-wing kite with an 11-foot-wingspan into the wind and steered it by skillfully tugging on its tethering line. This involved spending days crisscrossing jagged lava formations on foot, trying not to be dragged around by the kite, all the while watching carefully to avoid toxic fumes wafting down from the volcanic vent.

“The kite is pretty stable in the air, and depending on the wind swings from side to side only by five to ten degrees or so,” Scheidt explained. “That small motion gives us enough parallax, or difference in viewing angle, to allow the software to calculate a three-dimensional terrain model.”

Although the technique, called Multi-View Stereo-Photogrammetry, produces images that appear like aerial photographs taken from an airplane, they are not actually photographs, they are image mosaics projected onto digital terrain models, Hamilton explained.

“The kite takes an image every two seconds, producing up to tens of thousands of photos of a site,” Scheidt said. “The software then removes any distortion, and stitches those images together to create a virtual representation of the terrain that you would never have otherwise.”

This process, called orthorectification, uses massive computing power and still takes weeks to render a terrain model. The end result boasts a resolution high enough to clearly show footprints in the sand blanketing the lava flow.

“Our approach shows how the combination of ground-based observations and an aerial perspective can help us to decipher the geologic history of Earth and Mars,” Hamilton said.

Note: The above story is based on materials provided by University of Arizona. The original article was written by Daniel Stolte.

Conifers’ helicoptering seeds are result of long evolutionary experiment

March 17, 2015

270 million-year-old fossils from Texas show that early conifers produced a variety of winged seeds to aid dispersal by the wind. Cindy Looy and her team made identical models to test their effectiveness at seed dispersal and find out why only one variety of whirling seed – ones with single wings (left) – exists in today’s conifers. Credit: Cindy Looy

The whirling, winged seeds of today’s conifers are an engineering wonder and, as University of California, Berkeley, scientists show, a result of about 270 million years of evolution by trees experimenting with the best way to disperse their seeds.

The first conifer species that produced seeds that whirl when they fall used a variety of single- and double-winged designs. Whirling, or helicoptering, keeps a seed aloft longer, increasing the chance that a gust of wind will carry a seed to a clearing where it can sprout and grow unimpeded by competitors

“Winged seeds may have contributed to the success of these conifers,” said paleobotanist Cindy Looy, an assistant professor of integrative biology at UC Berkeley, a member of the Berkeley Initiative for Global Change Biology (BiGCB) and a curator with UC Berkeley’s Museum of Paleontology.

Today, however, all conifer species whose seeds whirl as they fall appear to have settled on only one type of design: asymmetrical and single-winged. Several different conifer lineages independently came upon this single-winged design after experimenting with helicoptering winged seeds over millions of years of evolution.

To convince herself that later conifers settled on the most efficient design for windborne seed dispersal, Looy and her colleagues built model seeds inspired by the variety of seed designs found in a unique collection of 270 million-year-old fossil seeds from Texas.

By dropping these model seeds and filming their descent with high-speed cameras, they demonstrated that whirling, single-winged seeds were the most effective at aerial dispersal. Symmetric, double-winged seeds often failed to initiate the descent-slowing spin, but even if they did, they remained airborne only half as long as the single-winged ones.

Moreover, the difference in flight performance of single-winged whirling seeds and asymmetrical or symmetrical double-winged ones increased with increased seed weight or in turbulent air.

Looy, former research assistant Robert Stevenson and former graduate student Dennis Evangelista, now at the University of North Carolina at Chapel Hill, will publish their experimental findings in a featured article in the March 2015 issue of the journal Paleobiology.

Looy has been studying fossils of early conifer groups from deposits in Texas dating to the Permian Period, about 270 million years ago. She was struck by the fact that one of the conifer species produced a range of seed shapes, ranging from single-winged to asymmetrical and symmetrical double-winged seeds

This is unusual, she said, because the single-winged seeds have the clear advantage of enhanced dispersal efficiency, especially during the Permian when seed dispersal by animals was virtually absent. Even more unusual was the fact that different conifer species that independently evolved whirling, or autorotating, seeds ended up with only one optimal seed shape up in today’s conifer species. The same is true for other trees that developed similar seeds or fruits, such as the maple and ash.

The Permian conifer, which she and Stevenson formally described last year and named Manifera talaris, produced the oldest known autorotating conifer seeds roughly 40 million years before dinosaurs evolved.

“Rotating seeds in living conifers are generally asymmetrical and single-winged, so I wondered if the function of the double-winged seeds was very different,” she said. “Until you actually see them in action and compare them, you don’t have any proof.”

Table of Contents

Paper wings and plastic seeds

Looy knew that people had tested the aerodynamics of single-winged, autorotating seeds, but no one had ever studied the other designs because they aren’t found today. Using special tissue paper for wings and plastic film for the heavy seed, she and her colleagues built models of the single-winged seeds of a living conifer that resembled those of the fossil conifer. The actual seeds of this tree, the New Zealand kauri (Agathis australis), were used to confirm that the fabricated models behaved like the real thing.

They then altered the design of the models to match the symmetric and asymmetric double-winged as well as the single-winged seeds common among the Texas fossils. The researchers dropped the seeds from a height of 3 meters (9 feet) and filmed their fall with a high-speed camera. This enabled them to observe the flight performance and measure a range of flight characteristics and aerodynamic properties of the various shapes. They enlisted half a dozen UC Berkeley undergraduates to help determine which type of winged seed works best for wind dispersal and to digitize the flight behavior of the seeds captured on camera.

They found that, in contrast to the single-winged seeds, the symmetric and asymmetric double-winged seeds did not spin as effectively; instead of a slow helicopter descent, they usually fluttered or just plummeted to the ground. But even when seeds with double-winged shapes managed to autorotate, the experiments demonstrated conclusively that single-winged seeds stayed airborne almost twice as long.

Early seed dispersal

Air- and waterborne seeds became more common between the late Carboniferous — 320 million years ago — and early Permian, which began about 300 million years ago. At the time, most plant life consisted of lycopods, ferns, horsetails and seed ferns, with a few of the first cone-bearing trees, like conifers and cycads, appearing.

“There were very different plants around at the time,” Looy said. “Several of these groups produced seeds, but they lacked most of the tricks we see today to spread them.”

Vertebrates, only a few of which were herbivores, were typically large and did not climb trees. The only flying animals were insects, and as far as we know they did not disperse seeds, Looy said.

“For a seed at that time, having wings was actually one of the few ways to spread widely,” she said.

The conifer fossils, which are from north-central Texas, date from a time when Texas was located near the equator, and North America was part of the massive continent of Pangea. Looy studied these fossils when she worked as a postdoctoral researcher at the Smithsonian Institution from 2004 to 2008, and was struck by the seed variety within a single species compared to today.

“In these conifers you can see steps from making winged seeds to making autorotating seeds. It seems that the Permian conifer Manifera first figured out how to produce a range of winged seed shapes -including the highly functional autorotating ones,” she said. “However, fossils of closely related end-Permian conifers suggest that it wasn’t until much later that they discovered how to not produce the less functional types. Around that time, we also see the first slightly succulent conifer seeds appearing in the fossil record, which are attractive to animals and potentially indicative of animal dispersal. Slowly the seeds start to diversify to all the different types we have nowadays.”

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Note: The above story is based on materials provided by University of California – Berkeley. The original article was written by Robert Sanders.

17 million-year-old whale fossil provides 1st exact date for East Africa’s puzzling uplift

March 17, 2015

A 17-million-year-old whale fossil stranded far inland in Kenya now sheds light on the timing and starting elevation of East Africa’s puzzling tectonic uplift, says paleontologist Louis Jacobs, Southern Methodist University, Dallas, who rediscovered the fossil. Credit: Southern Methodist University

Uplift associated with the Great Rift Valley of East Africa and the environmental changes it produced have puzzled scientists for decades because the timing and starting elevation have been poorly constrained.

Now paleontologists have tapped a fossil from the most precisely dated beaked whale in the world — and the only stranded whale ever found so far inland on the African continent — to pinpoint for the first time a date when East Africa’s mysterious elevation began.

The 17 million-year-old fossil is from the beaked Ziphiidae whale family. It was discovered 740 kilometers inland at an elevation of 620 meters in modern Kenya’s harsh desert region, said vertebrate paleontologist Louis L. Jacobs, Southern Methodist University, Dallas.

At the time the whale was alive, it would have been swimming far inland up a river with a low gradient ranging from 24 to 37 meters over more than 600 to 900 kilometers, said Jacobs, a co-author of the study.

The study, published in the Proceedings of the National Academy of Sciences, provides the first constraint on the start of uplift of East African terrain from near sea level.

“The whale was stranded up river at a time when east Africa was at sea level and was covered with forest and jungle,” Jacobs said. “As that part of the continent rose up, that caused the climate to become drier and drier. So over millions of years, forest gave way to grasslands. Primates evolved to adapt to grasslands and dry country. And that’s when — in human evolution — the primates started to walk upright.”

Identified as a Turkana ziphiid, the whale would have lived in the open ocean, like its modern beaked cousins. Ziphiids, still one of the ocean’s top predators, are the deepest diving air-breathing mammals alive, plunging to nearly 10,000 feet to feed, primarily on squid.

In contrast to most whale fossils, which have been discovered in marine rocks, Kenya’s beached whale was found in river deposits, known as fluvial sediments, said Jacobs, a professor in the Roy M. Huffington Department of Earth Sciences of SMU’s Dedman College of Humanities and Sciences. The ancient large Anza River flowed in a southeastward direction to the Indian Ocean. The whale, probably disoriented, swam into the river and could not change its course, continuing well inland.

“You don’t usually find whales so far inland,” Jacobs said. “Many of the known beaked whale fossils are dredged by fishermen from the bottom of the sea.”

Determining ancient land elevation is very difficult, but the whale provides one near sea level.

“It’s rare to get a paleo-elevation,” Jacobs said, noting only one other in East Africa, determined from a lava flow.

Beaked whale fossil surfaced after going missing for more than 30 years

The beaked whale fossil was discovered in 1964 by J.G. Mead in what is now the Turkana region of northwest Kenya.

Mead, an undergraduate student at Yale University at the time, made a career at the Smithsonian Institution, from which he recently retired. Over the years, the Kenya whale fossil went missing in storage. Jacobs, who was at one time head of the Division of Paleontology for the National Museums of Kenya, spent 30 years trying to locate the fossil. His effort paid off in 2011, when he rediscovered it at Harvard University and returned it to the National Museums of Kenya.

The fossil is only a small portion of the whale, which Mead originally estimated was 7 meters long during its life. Mead unearthed the beak portion of the skull, 2.6 feet long and 1.8 feet wide, specifically the maxillae and premaxillae, the bones that form the upper jaw and palate.

The researchers reported their findings in “A 17 million-year-old whale constrains onset of uplift and climate change in East Africa” online at the PNAS web site.

Modern cases of stranded whales have been recorded in the Thames River in London, swimming up a gradient of 2 meters over 70 kilometers; the Columbia River in Washington state, a gradient of 6 meters over 161 kilometers; the Sacramento River in California, a gradient of 4 meters over 133 kilometers; and the Amazon River in Brazil, a gradient of 1 meter over 1,000 kilometers.

Reference:
Henry Wichura, Louis L. Jacobs, Andrew Lin, Michael J. Polcyn, Fredrick K. Manthi, Dale A. Winkler, Manfred R. Strecker, Matthew Clemens. A 17-My-old whale constrains onset of uplift and climate change in east Africa. Proceedings of the National Academy of Sciences, 2015; 201421502 DOI: 10.1073/pnas.1421502112

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

Finding fault: New information may help understand earthquakes

March 17, 2015

The UMass Amherst lab is one of only a handful worldwide to use a state-of-the-art modeling technique based on kaolin clay rather than sand to understand the behavior of the Earth’s crust. Credit: UMass Amherst

New modeling and analyses of fault geometry in the Earth’s crust by geoscientist Michele Cooke and colleagues at the University of Massachusetts Amherst are advancing knowledge about fault development in regions where one geologic plate slides past or over another, such as along California’s San Andreas Fault and the Denali Fault in central Alaska.

Findings may help more accurately predict earthquake hazards and allow scientists to better understand how Earth evolved.

Geologists have long been uncertain about the factors that govern how new faults grow, says Cooke, who was recently elected to the board of directors for the Southern California Earthquake Center. This month in an early online issue of the Journal of Geophysical Research, she and colleagues explain fault evolution near fault bends in greater detail than ever before with experiments using kaolin, or china clay, prepared so its strength scales to that of the Earth’s crust when confined in a clay box.

Fault efficiency refers to a dynamic fault system’s effectiveness at transforming input energy from the motions of tectonic plates into movement. For example, a straight fault is more efficient at accommodating strain than a curving fault. An important question is how the efficiency of fault bends evolves with increasing deformation of Earth’s crust.

Master’s student Alex Hatem, who did much of the work in these experiments, with Cooke and postdoctoral scholar Elizabeth Madden, report that fault efficiency increases as new faults grow and link, then reaches a steady state. This implies that bends along crustal faults may persist. The straight fault is the most efficient geometry, Cooke points out. “It’s interesting that bends increase in efficiency through new fault growth but they never become as efficient as straight faults.”

Because earthquakes may stop at restraining bends, it further suggests a new understanding: faults segmented by restraining bends may remain in a sort of stasis rather than developing into systems where earthquakes would rupture the entire length of the fault. Here Cooke explains that comparing a straight fault with a fault at a bend, it is more likely that the fault with the bend will have smaller earthquakes that stop at the bend rather than long earthquake ruptures that pass all the way along the fault.

Her UMass Amherst lab is one of only a handful worldwide to use a state-of-the-art modeling technique based on kaolin clay rather than sand to understand the behavior of the Earth’s crust. Their advanced techniques with the clay include pixel tracking and other quantitative measurements that allow rich details to be obtained from the models and compared with faults around the world.

When scaled properly, data from clay experiments conducted over several hours in a table-top device are useful in modeling restraining bend evolution over thousands of years and at the scale of tens of kilometers. Digital image correlation allows Cooke’s team to measure the details of deformation throughout the experiments.

For this work, they conducted kaolin experiments to model strike-slip rates measured in a restraining bend along a Dead Sea fault in Israel, a fault growth along the Denali Fault in Alaska, and through the San Gorgonio Knot along the San Andreas Fault in southern California.

“We apply the results to the southern San Andreas Fault where a restraining bend has persisted for 25 million years, but during that time its active fault configuration has changed in ways that resemble what we observed in our experiments,” the authors note.

They add, “Results of the clay box experiments provide critical insights into the evolution of restraining bends. Because the experiments scale to crustal lengths and strengths, we can extrapolate from the experiments to kilometer-scale systems. The models show progressive deformation by the successive outboard growth of dipping faults in some cases and persistence of vertical fault in others.”

Understanding the conditions that foster these distinct patterns helps us interpret the geometry and loading of faults within Earth’s crust in order to better constrain earthquake behavior.

Cooke says, “Using new digital image correlation techniques allows us very detailed measurements of the displacement in the experiments to provide insights we didn’t have before. For the fault bends that we tested, the new analysis reveals that efficiency of the faults increases as new faults grow and link and then reaches a steady state. This suggests that restraining bends along crustal faults may persist,” Cooke says.

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Reference:
Alex E. Hatem, Michele L. Cooke, Elizabeth H. Madden. Evolving efficiency of restraining bends within wet kaolin analog experiments. Journal of Geophysical Research: Solid Earth, 2015; DOI: 10.1002/2014JB011735

Note: The above story is based on materials provided by University of Massachusetts at Amherst.

No limit to life in sediment of ocean’s deadest region

March 17, 2015

A sediment core from the South Pacific gyre is analyzed for its dissolved oxygen content. Credit: Photo courtesy of Fumio Inagaki

An international team of scientists led by a University of Rhode Island oceanographer has found oxygen and oxygen-breathing microbes all the way through the sediment from the seafloor to the igneous basement at seven sites in the South Pacific gyre, considered the “deadest” location in the ocean. Their findings contrast with previous discoveries that oxygen was absent from all but the top few millimeters to decimeters of sediment in biologically productive regions of the ocean.

Their research was published this week in the journal Nature Geoscience.

“Our objective was to understand the microbial community and microbial habitability of sediment in the deadest part of the ocean,” said Professor Steven D’Hondt at the URI Graduate School of Oceanography. “Our results overturn a 60-year-old conclusion that the depth limit to life is in the sediment just meters below the seafloor in such regions. We found that there is no limit to life within this sediment. Oxygen and aerobic microbes hang in there all the way to the igneous basement, to at least 75 meters below the seafloor.”

Based on the researchers’ predictive model and core samples they collected in 2010 from the Integrated Ocean Drilling Program’s research ship JOIDES Resolution, the researchers believe that oxygen and aerobic microbes occur throughout the sediment in up to 37 percent of the world’s oceans and 44 percent of the Pacific. They found that the best predictors of oxygen penetration to the igneous basement are a low sedimentation accumulation rate and a relatively thin sediment layer. Sediment accumulates at just a few decimeters to meters per million years in the regions where the core samples were collected.

In the remaining 63 percent of the ocean, most of the sediment beneath the seafloor is expected to lack dissolved oxygen and to contain anaerobic communities.

While the research team found evidence of life throughout the sediment, it did not detect a great deal of it. The team found extremely slow rates of respiration and approximately 1,000 cells per cubic centimeter of subseafloor sediment in the South Pacific gyre — rates and quantities that were nearly undetectable by previous techniques. “It’s really hard to detect life when it’s not very active and in extremely low concentrations,” said D’Hondt.

According to D’Hondt and co-author Fumio Inagaki of the Japan Agency for Marine-Earth Science and Technology, the discovery of oxygen throughout the sediment may have significant implications for Earth’s chemical evolution. The oxidized sediment is likely carried into the mantle at subduction zones, regions of the seafloor where tectonic plates collide and force one plate beneath the other.

“Subduction of these big regions where oxygen penetrates through the sediment and into the igneous basement introduces oxidized minerals to the mantle, which may affect the chemistry of the upper mantle and the long-term evolution of Earth’s surface oxidation,” D’Hondt said.

The principal research funders were the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science and Technology. The project is part of the NSF-funded Center for Dark Energy Biosphere Investigations, which explores life beneath the seafloor. The research is also part of the Deep Carbon Observatory, a decade-long international science initiative to investigate the 90 percent of Earth’s carbon located deep inside the planet.

“We take a holistic approach to the subseafloor biosphere,” said Rick Murray, co-author of the study. Murray is on leave from Boston University, currently serving as director of the NSF Division of Ocean Sciences. “Our team includes microbiologists, geochemists, sedimentologists, physical properties specialists, and others — a hallmark of interdisciplinary research.”

The research team includes 35 scientists from 12 countries. In addition to D’Hondt, URI scientists contributing to the research are oceanography professors Arthur Spivack and David C. Smith, Marine Research Scientist Robert Pockalny and graduate student Justine Sauvage.

Reference:
Steven D’Hondt et al. Presence of Oxygen an Aerobic Communities from Seafloor to Basement in Deep-Sea Sediments. Nature Geoscience, 2015 DOI: 10.1038/NGEO2387

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

Ancient Caribbean tsunami caused by volcano collapse smaller than thought

March 14, 2015

Monserrat Volcano as seen from the JR research ship. Credit: Adam Stilton, Volcanologist

Tsunamis triggered by the partial collapse of the Caribbean Monserrat volcano, 13,000 years ago, would have been much smaller than previously thought, according to research soon to be published in Geochemistry, Geophysics and Geosystems.

The collapse of a volcano can lead to explosive eruptions or tsunamis, the size of which depends on the dynamics of the failure. For example, the abrupt collapse of a large volume of material into the sea will cause larger tsunamis than a gradual or submarine landslide, although this relationship has been the subject of vigorous debate. It is also important to determine where the slide material comes from. Material that falls a long way from the subaerial part of the volcano will create a bigger tsunami than failure of sediment layers around the submerged base of the volcano.

It was previously thought that a large submarine deposit of sediment at the base of the Monserrat volcano was the result of the abrupt, large scale collapse of the volcanic island into the sea. Therefore it had been thought that a high magnitude tsunami must have followed.

However, by analysing sediment cores drilled during the $8M ‘International Ocean Discovery Programme’ (IODP) expedition to Monserrat in 2012, this research shows that this deposit was in fact largely seafloor sediment. This finding infers that an initial landslide from the volcano triggered much more extensive failure of submarine sediment layers, around the base of the volcano. This would have generated a much smaller tsunami than if all of the material had fallen from the main volcanic edifice.

An international team of geologists including Dr Peter Talling, who leads a NOC group dedicated to studying submarine mass movements and their associated hazard, helped to collect and describe these cores. This involved noting the coarseness and nature of the material in each layer of sediment within the cores and describing the nature of the contact between each layer. In addition, the various physical properties of the sediment were measured, the sediment chemistry was analysed, and specific layers were dated using fossils. From this information the team was able to deduce that the deposits mostly comprised seafloor sediments, and not coarse volcanic debris from the subaerial volcano.

This IODP mission was the first time that sediment from the large-scale collapse of a volcanic island has been successfully drilled for scientific purposes.

Reference:
A. Le Friant, O. Ishizuka, G. Boudon, M. R. Palmer, P. J. Talling, B. Villemant, T. Adachi, M. Aljahdali, C. Breitkreuz, M. Brunet, B. Caron, M. Coussens, C. Deplus, D. Endo, N. Feuillet, A. J. Fraas, A. Fujinawa, M. B. Hart, R. G. Hatfield, M. Hornbach, M. Jutzeler, K. S. Kataoka, J.-C. Komorowski, E. Lebas, S. Lafuerza, F. Maeno, M. Manga, M. Martínez-Colón, M. McCanta, S. Morgan, T. Saito, A. Slagle, S. Sparks, A. Stinton, N. Stroncik, K. S. V. Subramanyam, Y. Tamura, J. Trofimovs, B. Voight, D. Wall-Palmer, F. Wang, S. F. L. Watt. Submarine record of volcanic island construction and collapse in the Lesser Antilles arc: First scientific drilling of submarine volcanic island landslides by IODPExpedition 340. Geochemistry, Geophysics, Geosystems, 2015; DOI: 10.1002/2014GC005652

Note: The above story is based on materials provided by National Oceanography Centre.

Humans adapted to living in rainforests much sooner than thought

March 14, 2015

Pictured is the site of Batadomba-lena where the oldest human teeth (c. 20,000 years old) used in the study were excavated. Credit: Patrick Roberts

An international research team has shed new light on the diet of some of the earliest recorded humans in Sri Lanka. The researchers from Oxford University, working with a team from Sri Lanka and the University of Bradford, analysed the carbon and oxygen isotopes in the teeth of 26 individuals, with the oldest dating back 20,000 years. They found that nearly all the teeth analysed suggested a diet largely sourced from the rainforest.

This study, published in the early online edition of the journal, Science, shows that early modern humans adapted to living in the rainforest for long periods of time. Previously it was thought that humans did not occupy tropical forests for any length of time until 12,000 years after that date, and that the tropical forests were largely ‘pristine’, human-free environments until the Early Holocene, 8,000 years ago. Scholars reasoned that compared with more open landscapes, humans might have found rainforests too difficult to navigate, with less available food to hunt or catch.

The Science paper also notes, however, that previous archaeological research provides ‘tantalising hints’ of humans possibly occupying rainforest environments around 45,000 years ago. This earlier research is unclear as to whether those early human dwellers of the rainforest were engaging in a specialised activity or whether they entered the rainforest for only limited periods of time in certain seasons rather than remaining there all year round.

Co-author Professor Julia Lee-Thorp from Oxford University said: ‘The isotopic methodology applied in our study has already been successfully used to study how primates, including African great apes, adapt to their forest environment. However, this is the first time scientists have investigated ancient human fossils in a tropical forest context to see how our earliest ancestors survived in such a habitat.’

The researchers studied the fossilised teeth of 26 humans of a range of dates — from 20,000 to 3,000 years ago. All of the teeth were excavated from three archaeological sites in Sri Lanka, which are today surrounded by either dense rainforest or more open terrain. The analysis of the teeth showed that all of the humans had a diet sourced from slightly open ‘intermediate rainforest’ environments. Only two of them showed a recognisable signature of a diet found in open grassland. However, these two teeth were dated to around 3,000 years, the start of the Iron Age, when agriculture developed in the region. The new evidence published in this paper argues this shows just how adaptable our earliest ancestors were.

Lead author, Patrick Roberts, a doctoral student specialising in the investigation of early human adaptations from Oxford’s Research Laboratory for Archaeology and the History of Art, said: ‘This is the first study to directly test how much early human forest foragers depended on the rainforest for their diet. The results are significant in showing that early humans in Sri Lanka were able to live almost entirely on food found in the rainforest without the need to move into other environments. Our earliest human ancestors were clearly able to successfully adapt to different extreme environments.’

Co-author Professor Mike Petraglia from Oxford University said: ‘Our research provides a clear timeline showing the deep level of interaction that early humans had with the rainforest in South Asia. We need further research to see if this pattern was also followed in other similar environments in Southeast Asia, Melanesia, Australasia and Africa.’

Reference:
Patrick Roberts, Nimal Perera, Oshan Wedage, Siran Deraniyagala, Jude Perera, Saman Eregama, Andrew Gledhill, Michael D. Petraglia, Julia A. Lee-Thorp. Direct evidence for human reliance on rainforest resources in late Pleistocene Sri Lanka. Science, 2015 DOI: 10.1126/science.aaa1230

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

Double impact crater in Canada formed in two separate impacts

March 14, 2015

Clearwater Lakes double impact crater in Quebec, Canada, view from West. Credit: Wikipedia

An asteroid smashing into a planet can dramatically alter the planet’s habitability by setting back evolution or even encouraging biodiversity.

In order to understand how cosmic impacts influence life and the environment, scientists study the craters left behind. Some of these impact craters come in pairs, most likely caused by binary asteroids. A binary asteroid is two asteroids that are orbiting each other, as well as orbiting the Sun.

The Clearwater lakes in Canada are a double crater, but geologist Martin Schmieder of the University of Western Australia, and colleagues, now believe that the craters were formed in two separate events. Their research was recently published in the journal Geochimica et Cosmochimica Acta.

A number of double impact craters exist on Earth. In 1965, researchers proposed that the craters forming the Clearwater lakes were the result of such a single incident. West Clearwater Lake has a diameter of 36 kilometers (22.5 miles), while its eastern cousin is 10 kilometers smaller. During an impact, rocks from the Earth’s crust can be uplifted to form a central peak, or ring, within the center of the crater.

In the West Lake, this is evident as a ring of islands in the middle of the lake. The East Lake also has a central peak, but it is below the waters of the lake and was only revealed when the Geological Survey of Canada drilled into the frozen lake in the 1960s.

Table of Contents

Measuring the ages of craters

There are a number of different ways to measure the age of an impact crater. Sometimes the layers of rock tell the story as the impact might have occurred at the boundary between two geological time periods. Fossils preserved within rocks can also help place constraints on the age.

It is also possible to use the decay of radioactive isotopes in samples of rocks that were created at the time of the impact to find out the age of a crater. Isotopes can be stable or radioactive, and if they are radioactive, then they will decay into “daughter” products over a known period of time.

There is evidence that the asteroid that formed the East crated impacted a marine environment, which would place the impact during the Ordovician period. The West crater was created in the Permian period and impacted the landmass Pangaea. Credit: Reprinted from Geochimica et Cosmochimica Acta, in press, Schmieder, M. et al., New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) – Not the binary asteroid impact it seems?, Credit: Elsevier

Potassium-40 decays slowly into argon-40, so that the more argon-40 present, the older the sample is. However, measuring the ratio of potassium-40 to argon-40 has the disadvantage of the potassium and argon needing to be measured separately. A more reliable variant of this method is to convert the potassium into argon-39. The rock sample is heated to release both the argon-39 and argon-40, so that the two isotopes can be measured at the same time. The amount of argon-39 that it is released indicates how much potassium-40 was originally in the rock. For the Clearwater dating study, this method was applied at the University of Heidelberg in Germany.

The heating of the sample occurs incrementally, in what is known as “step heating.” Ideally each argon degassing step should yield the same age, so that when all the individual ages are plotted together on a graph, the age is constant for the entire sample and yields a plateau. This is known as a “plateau age.” However, in some cases a plateau age is not found. Instead, the individual steps often make up a “u-shaped” or “staircase” pattern.

Two separate impacts

The West Clearwater Lake has accurate plateau ages from the argon dating. Different rock samples all indicate that the crater was formed around 290 million years ago. The new argon ages of 286 million years determined by Schmieder, and his collaborators also agree with this.

The age of the East Clearwater Lake crater is much more difficult to determine. In previous work performed by other scientists, a different isotope method was used to measure the age of the crater. The rubidium (Rb) to strontium (Sr) ratio suggested that this crater is also around 290 million years old, roughly the same age as the West crater. However, this method of dating is rather unreliable when it comes to dating impact craters.

“Even as a well-established method, Rb/Sr dating has commonly failed in impact crater dating” explains Schmieder. “This is mostly because rubidium is very mobile and the Rb/Sr system is therefore easily disturbed by heating and weathering that affect the impact rocks after their formation.”

As a rock sample ages, the radiometric isotope decays into more and more daughter products. Measuring the ratio of the original isotope to the daughter products can yield the age of the sample. Credit: John Schmidt

Argon ages for the East Lake also show a u-shaped spectrum, rather than a clear plateau age. This makes it more difficult to determine an accurate argon age, but suggests a maximum age of around 460 million years, which would be far older than the dating of the West Clearwater Lake crater. In 1990, researchers initially calculated a 460 million age for the East Lake, but then assumed it to be incorrect out of suspicion that excess argon was contaminating the sample and mimicking an older age for the crater.

However, Schmieder and colleagues also determined an argon age of 460 to 470 million years for the East crater. They consider it highly unlikely that four different rock samples that were collected at different locations and depths at the impact melt layer inside the crater would all yield the same false age.

“We think that the accurate age for the East Clearwater crater was, in fact, already measured back in 1990,” says Schmieder.

Further evidence

Another point in favor of the older age of the East crater comes from studying the magnetization of rocks. The magnetic field of the Earth can be “captured” by certain types of rocks, and this magnetic signature can be used to study the Earth’s magnetic field throughout history. The magnetic poles of the Earth are not fixed, and pole reversals have occurred many times in the past.

The rocks from the West Lake show that they were formed during a “superchron,” which is an unusually extended period of time where no reversals occurred. This superchron, known as the Permo-Carboniferous Reversed Superchron, lasted from 316 to 265 million years ago, which agrees with the age found by the argon dating.

The rocks from the East Lake tell a different story. They have a number of different magnetic polarizations, which indicate viscous remnant magnetization. This is magnetization that is acquired slowly over a long period of time. The more complex magnetic history points to the rocks being much older than the West Lake, as they have had more time to be altered.

The argon-argon age of 460 to 470 million years for the East crater suggests that this impact occurred in the Ordovician time period in a near-coastal environment, when large parts of eastern Canada were occupied by a shallow ocean. There are geological clues that point towards an impact in a shallow marine or coastal environment at the East crater. The rocks from the East crater have more chlorine in them than the West crater, which might be indicative of the presence of sea water. There is also some evidence of the increased movement of hot fluids after the East impact, which altered the rocks. The West crater was formed during the Permian, when the asteroid would have struck the Pangaea landmass.

Despite the fact that it is statistically very unlikely for the two craters to have been formed in two separate impact events, the new evidence unearthed by Schmieder and his team shows that in this case the more unlikely scenario is true.

“Overall, the doublet theory has been so compellingly advocated over the decades that alternative scenarios seem to have been abandoned. In our view, there is a whole line of geologic evidence that argues against the double impact.”

The impact on life

Impacts that leave behind a 100 kilometer (62.5 mile) diameter crater or less, such as those that struck the Clearwater lakes, are widely thought to have no global effects. In fact, impacts can even increase biodiversity. For example, the Great Ordovician Biodiversification Event, which saw an explosion in the number of animal species around 470 million years ago, has been linked to frequent impact events at the time. This is possibly due to the fact that an impact could disrupt local life just enough to let another species dominate, or because slowly cooling craters can provide habitats for life.

Even if the Clearwater Lakes impacts were caused by a double impact, the extra energy released by two bodies smashing into the Earth simultaneously would have had no significant effect on life. While the fireball and earthquake would have decimated any life within a few hundred kilometers, the impacts were not big enough to cause much chaos on a global scale.

Reference:
Martin Schmieder, Winfried H. Schwarz, Mario Trieloff, Eric Tohver, Elmar Buchner, Jens Hopp, Gordon R. Osinski, New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) – Not the binary asteroid impact it seems?, Geochimica et Cosmochimica Acta, Volume 148, 1 January 2015, Pages 304-324, ISSN 0016-7037, dx.doi.org/10.1016/j.gca.2014.09.037

Note : The above story is based on materials provided by Astrobio.net
This story is republished courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net .

Fossil skull sheds new light on transition from water to land

March 12, 2015

Here are the articulated cranium and lower jaws shown in oblique right lateral view (A). Right facial skeleton and skull roof shown in “exploded” view to illustrate the nature of sutural contacts (B); the left side of the cranium (braincase omitted) is shown in internal view (C). The right lower jaw in “exploded” view to illustrate sutural morphology. Individual bones shown in various colors. Credit: Porro et al.; CC-BY

The first 3D reconstruction of the skull of a 360 million-year-old near-ancestor of land vertebrates has been created by scientists from the Universities of Bristol and Cambridge, UK. The 3D skull, which differs from earlier 2D reconstructions, suggests such creatures, which lived their lives primarily in shallow water environments, were more like modern crocodiles than previously thought.

The researchers applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari, one of the ‘four-footed’ vertebrates known as tetrapods which invaded the land during one of the great evolutionary transitions in Earth’s history, 380-360 million years ago. Tetrapods evolved from lobe-finned fishes and display a number of adaptations to help them survive on land.

An iconic fossil species, Acanthostega gunnari is crucial for understanding the anatomy and ecology of the earliest tetrapods. However, after hundreds of millions of years in the ground fossils are often damaged and deformed. No single specimen of Acanthostega preserves a skull that is complete and three-dimensional which has limited scientists’ understanding of how this key animal fed and breathed — until now.

The original fossil skull of Acanthostega gunnari Image Credit: Dr Laura Porro

Using special software, the Bristol and Cambridge researchers ‘digitally prepared’ a number of Acanthostega specimens from East Greenland, stripping away layers of rock to reveal the underlying bones.

They uncovered a number of bones deep within the skull, including some that had never before been seen or described, resulting in a detailed anatomical description of the Acanthostega skull.

Once all of the bones and teeth were digitally separated from each other, cracks were repaired and missing elements duplicated. Bones could then be manipulated individually in 3D space. Using information from other specimens, the bones were fitted together like puzzle pieces to produce the first 3D reconstruction of the skull of Acanthostega, with surprising results.

Lead author, Dr Laura Porro, formerly of Bristol’s School of Earth Sciences and now at the Royal Veterinary College, said: “Because early tetrapods skulls are often ‘pancaked’ during the fossilization process, these animals are usually reconstructed having very flat heads. Our new reconstruction suggests the skull of Acanthostega was taller and somewhat narrower than previously interpreted, more similar to the skull of a modern crocodile.”

The researchers also found clues to how Acanthostega fed. The size and distribution of its teeth and the shape of contacts between individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its jaws using its large front teeth and hook-shaped lower jaw.

Co-author, Professor Emily Rayfield, also from Bristol’s School of Earth Sciences, said: “These new analyses provide fresh clues about the evolution of the jaws and feeding system as the earliest animals with limbs and digits began to conquer the land.”

The researchers plan to apply these methods to other flattened fossils of the earliest tetrapods to better understand how these early animals modified their bones and teeth to meet the challenges of living on land.

Digital models of the original fossils and the 3D reconstruction are also useful in scientific research and education. They can be accessed by researchers around the world, without risking damage to fragile original fossils and without scientists having to travel thousands of miles to see original specimens. Furthermore, digital models and 3D printouts can be easily and safely handled by students taking courses and by the public during outreach events.

Reference:
Laura B. Porro, Emily J. Rayfield, Jennifer A. Clack. Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early Tetrapod Acanthostega gunnari Jarvik, 1952. PLOS ONE, 2015; 10 (3): e0118882 DOI: 10.1371/journal.pone.0118882

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

Epoch-defining study pinpoints when humans came to dominate planet Earth

March 12, 2015

The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, according to new research published today in Nature.

Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. Human actions are now changing the planet, but are we really a geological force of nature driving Earth into a new epoch that will last millions of years?

Scientists at UCL have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.

Defining an epoch requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. Such a marker — like the chemical signature left by the meteorite strike that wiped out the dinosaurs — is called a golden spike.

The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria: 1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth’s history.

They argue that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries. This irreversible exchange of species satisfies the first criteria for dating an epoch — long-term changes to Earth.

The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right — as Earth-changing as a meteorite strike

The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.

The researchers have named the 1610 dip in carbon dioxide the ‘Orbis Spike’. They chose the Latin word for ‘world’ because this golden spike was caused by once-disconnected peoples becoming globally linked.

Lead author, Dr Simon Lewis (UCL Geography and University of Leeds), said: “In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right — as Earth-changing as a meteorite strike.”

He added: “Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth’s last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene.”

The authors also considered the merits of dating the Anthropocene to 1964, which saw a peak in radioactive fallout following nuclear weapons testing. This marker is seen in many geological deposits, and by the 1960s human impact on the Earth was large. However, the researchers note that while nuclear war could dramatically alter Earth, so far it has not. While the fallout from nuclear bomb tests is a very good marker, the testing of nuclear weapons has not been — in geological terms — an Earth-changing event.

The beginning of the Industrial Revolution, in the late 18th century, has most commonly been suggested as the start of the Anthropocene. This linked a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. However, the researchers did not find a golden spike at that time because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker.

The authors’ new paper ends by highlighting some implications of formally defining the Anthropocene.

Co-author, geologist Professor Mark Maslin (UCL Geography) said: “A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognising it.”

An official decision on whether to formally recognise the Anthropocene, including when it began, will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy, due in 2016.

Reference:
Simon L. Lewis, Mark A. Maslin. Defining the Anthropocene. Nature, 2015; 519 (7542): 171 DOI: 10.1038/nature14258

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

Iron-oxidizing bacteria found along Mid-Atlantic Ridge

March 12, 2015

This is an iron-oxidizing microbial mat at the Trans-Atlantic Geotraverse hydrothermal vent field collected using a novel, syringe-based sampler deploy from the ROV Jason II. Credit: Photo taken by the ROV Jason II (courtesy of Woods Hole Oceanographic Institute and the SNAPMORE cruise)

Bacteria that live on iron were found for the first time at three well-known vent sites along the Mid-Atlantic Ridge, one of the longest undersea mountain ranges in the world. Scientists report that these bacteria likely play an important role in deep-ocean iron cycling, and are dominant members of communities near and adjacent to sulfur-rich, black-smoker hydrothermal vents prevalent along the Mid-Atlantic Ridge. These unique chemosynthetic communities live off the chemical components in the vent fluid, rather than sunlight used by their photosynthetic counterparts. This specialized group of iron-oxidizing bacteria, Zetaproteobacteria, appears to be restricted to environments where iron is plentiful, which suggests that these bacteria are highly evolved to utilize iron as an energy source.

Parts of the ocean floor along the Mid-Atlantic Ridge are covered in patches of what looks like yellowish jelly. Scientists recovered some of this yellowish material using a novel, syringe-based sampler deployed by the remotely operated vehicle, Jason. The precision sampler was developed jointly by scientists at Bigelow Laboratory and the Woods Hole Oceanographic Institution, and allows for unprecedented retrieval of delicate microbial mats from miles deep in the ocean. The collected material was found to be comprised of millions of Zetaproteobacteria living off the iron. The results were reported in a PLoS ONE article published on March 11th.

“With each expedition to the Mid-Atlantic Ridge we learn more about its complex ecology,” says Jarrod Scott, a postdoctoral researcher at Bigelow Laboratory for Ocean Sciences and lead author of the PLoS One article.

Researchers also conducted a meta-analysis, a review of published literature, to determine locations where Zetaproteobacteria have been observed. They found that Zetaproteobacteria were only detected in samples from iron-rich environments, which suggests these bacteria are highly evolved to utilize iron. Because iron is such a common element in the Earth’s crust, it is possible these bacteria acquired these traits billions of years ago and have evolved to form their own unique lineage within the microbial world.

“Zetaproteobacteria do not appear to be common members of water column microbial communities. Yet, if I were to hang an iron bar in the ocean, wait a few days, they would appear there because of an available food source. Finding out where and how they know where food is and relocate to use it, is but one of the many mysteries that remain to be solved, ” adds Scott.

The paper also suggested that iron from vent water near and adjacent to hydrothermal vents (diffuse flow systems) may be an important iron source into the deep ocean. This is important because iron can be an important limiting nutrient in the open ocean.

Scott was joined on the paper by John A. Breier of Woods Hole Oceanographic Institution, George W. Luther III of the University of Delaware, and his Bigelow Laboratory colleague, David Emerson.

Video

Reference:
Jarrod J. Scott, John A. Breier, George W. Luther, David Emerson. Microbial Iron Mats at the Mid-Atlantic Ridge and Evidence that Zetaproteobacteria May Be Restricted to Iron-Oxidizing Marine Systems. PLOS ONE, 2015; 10 (3): e0119284 DOI: 10.1371/journal.pone.0119284

Note: The above story is based on materials provided by Bigelow Laboratory for Ocean Sciences.

Giant sea creature hints at early arthropod evolution

March 12, 2015

This artist’s rendering provided by Marianne Collins shows the filter-feeding anomalocaridid Aegirocassis benmoulae from the Early Ordovician (ca 480 million years old) of Morocco feeding on a plankton cloud. Aegirocassis reached a length in excess of 2 meters, making it one of the biggest arthropods to have ever lived, and foreshadows the appearance much later of giant filter-feeding sharks and whales. Credit: ArtofFact, Marianne Collins

Newly discovered fossils of a giant, extinct sea creature show it had modified legs, gills on its back, and a filter system for feeding — providing key evidence about the early evolution of arthropods.
The new animal, named Aegirocassis benmoulae in honor of its discoverer, Mohamed Ben Moula, attained a size of at least seven feet, ranking it among the biggest arthropods that ever lived. It was found in southeastern Morocco and dates back some 480 million years.

“Aegirocassis is a truly remarkable looking creature,” said Yale University paleontologist Derek Briggs, co-author of a Nature paper describing the animal. “We were excited to discover that it shows features that have not been observed in older Cambrian anomalocaridids — not one but two sets of swimming flaps along the trunk, representing a stage in the evolution of the two-branched limb, characteristic of modern arthropods such as shrimps.”

Briggs is the G. Evelyn Hutchinson Professor of Geology and Geophysics at Yale and curator of invertebrate paleontology at the Yale Peabody Museum of Natural History. First author Peter Van Roy, an associate research scientist at Yale, led the research; Allison Daley of the University of Oxford is co-author.

Since their first appearance in the fossil record 530 million years ago, arthropods have been the most species-rich and morphologically diverse animal group on Earth. They include such familiar creatures as horseshoe crabs, scorpions, spiders, lobsters, butterflies, ants, and beetles. Their success is due in large part to the way their bodies are constructed: They have a hard exoskeleton that is molted during growth, and their bodies and legs are made up of multiple segments. Each segment can be modified separately for different purposes, allowing arthropods to adapt to every environment and mode of life.

Modern arthropod legs, in their most basic form, have two branches. Each is highly modified to cater to a specific function on that leg, such as locomotion, sensing its surroundings, respiration, or copulation; or it has been lost altogether. Understanding how these double-branched limbs evolved has been a major question for scientists.

A long-extinct group of arthropods, the anomalocaridids, is considered central to the answer. The youngest known anomalocaridids are 480 million years old, and all of them looked quite alien: They had a head with a pair of grasping appendages and a circular mouth surrounded by toothed plates. Their elongate, segmented bodies carried lateral flaps that they used for swimming. Until now, it was believed that anomalocaridids had only one set of flaps per trunk segment, and that they may have lost their walking legs completely.

But the recent discovery of Aegirocassis benmoulae tells another story. The new animal shows that anomalocaridids in fact had two separate sets of flaps per segment. The upper flaps were equivalent to the upper limb branch of modern arthropods, while the lower flaps represent modified walking limbs, adapted for swimming. Furthermore, a re-examination of older anomalocaridids showed that these flaps also were present in other species, but had been overlooked. These findings show that anomalocaridids represent a stage before the fusion of the upper and lower branches into the double-branched limb of modern arthopods.

“It was while cleaning the fossil that I noticed the second, dorsal set of flaps,” said Van Roy, who spent hundreds of hours working on the specimens. “It’s fair to say I was in shock at the discovery, and its implications. It once and for all resolves the debate on where anomalocaridids belong in the arthropod tree, and clears up one of the most problematic aspects of their anatomy.”

Aegirocassis benmoulae is also remarkable from an ecological standpoint, note the researchers. While almost all other anomalocaridids were active predators that grabbed their prey with their spiny head limbs, the Moroccan fossil has head appendages that are modified into an intricate filter-feeding apparatus. This means that the animal could harvest plankton from the oceans.

“Giant filter-feeding sharks and whales arose at the time of a major plankton radiation, and Aegirocassis represents a much, much older example of this — apparently overarching — trend,” Van Roy said.

Video

Reference:
Peter Van Roy, Allison C. Daley, Derek E. G. Briggs. Anomalocaridid trunk limb homology revealed by a giant filter-feeder with paired flaps. Nature, 2015; DOI: 10.1038/nature14256

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

Saturn moon’s ocean may harbor hydrothermal activity

March 12, 2015

This cutaway view of Saturn’s moon Enceladus is an artist’s rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon’s subsurface ocean, based on recently published results from NASA’s Cassini mission. Credit: NASA/JPL-Caltech

NASA’s Cassini spacecraft has provided scientists the first clear evidence that Saturn’s moon Enceladus exhibits signs of present-day hydrothermal activity which may resemble that seen in the deep oceans on Earth. The implications of such activity on a world other than our planet open up unprecedented scientific possibilities.
“These findings add to the possibility that Enceladus, which contains a subsurface ocean and displays remarkable geologic activity, could contain environments suitable for living organisms,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe.”

Hydrothermal activity occurs when seawater infiltrates and reacts with a rocky crust and emerges as a heated, mineral-laden solution, a natural occurrence in Earth’s oceans. According to two science papers, the results are the first clear indications an icy moon may have similar ongoing active processes.

The first paper, published this week in the journal Nature, relates to microscopic grains of rock detected by Cassini in the Saturn system. An extensive, four-year analysis of data from the spacecraft, computer simulations and laboratory experiments led researchers to the conclusion the tiny grains most likely form when hot water containing dissolved minerals from the moon’s rocky interior travels upward, coming into contact with cooler water. Temperatures required for the interactions that produce the tiny rock grains would be at least 194 degrees Fahrenheit (90 degrees Celsius).

“It’s very exciting that we can use these tiny grains of rock, spewed into space by geysers, to tell us about conditions on — and beneath — the ocean floor of an icy moon,” said the paper’s lead author Sean Hsu, a postdoctoral researcher at the University of Colorado at Boulder.

Cassini’s cosmic dust analyzer (CDA) instrument repeatedly detected miniscule rock particles rich in silicon, even before Cassini entered Saturn’s orbit in 2004. By process of elimination, the CDA team concluded these particles must be grains of silica, which is found in sand and the mineral quartz on Earth. The consistent size of the grains observed by Cassini, the largest of which were 6 to 9 nanometers, was the clue that told the researchers a specific process likely was responsible.

On Earth, the most common way to form silica grains of this size is hydrothermal activity under a specific range of conditions; namely, when slightly alkaline and salty water that is super-saturated with silica undergoes a big drop in temperature.

“We methodically searched for alternate explanations for the nanosilica grains, but every new result pointed to a single, most likely origin,” said co-author Frank Postberg, a Cassini CDA team scientist at Heidelberg University in Germany.

Hsu and Postberg worked closely with colleagues at the University of Tokyo who performed the detailed laboratory experiments that validated the hydrothermal activity hypothesis. The Japanese team, led by Yasuhito Sekine, verified the conditions under which silica grains form at the same size Cassini detected. The researchers think these conditions may exist on the seafloor of Enceladus, where hot water from the interior meets the relatively cold water at the ocean bottom.

The extremely small size of the silica particles also suggests they travel upward relatively quickly from their hydrothermal origin to the near-surface sources of the moon’s geysers. From seafloor to outer space, a distance of about 30 miles (50 kilometers), the grains spend a few months to a few years in transit, otherwise they would grow much larger.

The authors point out that Cassini’s gravity measurements suggest Enceladus’ rocky core is quite porous, which would allow water from the ocean to percolate into the interior. This would provide a huge surface area where rock and water could interact.

The second paper, recently published in Geophysical Research Letters, suggests hydrothermal activity as one of two likely sources of methane in the plume of gas and ice particles that erupts from the south polar region of Enceladus. The finding is the result of extensive modeling to address why methane, as previously sampled by Cassini, is curiously abundant in the plume.

The team found that, at the high pressures expected in the moon’s ocean, icy materials called clathrates could form that imprison methane molecules within a crystal structure of water ice. Their models indicate that this process is so efficient at depleting the ocean of methane that the researchers still needed an explanation for its abundance in the plume.

In one scenario, hydrothermal processes super-saturate the ocean with methane. This could occur if methane is produced faster than it is converted into clathrates. A second possibility is that methane clathrates from the ocean are dragged along into the erupting plumes and release their methane as they rise, like bubbles forming in a popped bottle of champagne.

The authors agree both scenarios are likely occurring to some degree, but they note that the presence of nanosilica grains, as documented by the other paper, favors the hydrothermal scenario.

“We didn’t expect that our study of clathrates in the Enceladus ocean would lead us to the idea that methane is actively being produced by hydrothermal processes,” said lead author Alexis Bouquet, a graduate student at the University of Texas at San Antonio. Bouquet worked with co-author Hunter Waite, who leads the Cassini Ion and Neutral Mass Spectrometer (INMS) team at Southwest Research Institute in San Antonio.

Cassini first revealed active geological processes on Enceladus in 2005 with evidence of an icy spray issuing from the moon’s south polar region and higher-than-expected temperatures in the icy surface there. With its powerful suite of complementary science instruments, the mission soon revealed a towering plume of water ice and vapor, salts and organic materials that issues from relatively warm fractures on the wrinkled surface. Gravity science results published in 2014 strongly suggested the presence of a 6-mile- (10-kilometer-) deep ocean beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. The Cassini CDA instrument was provided by the German Aerospace Center. The instrument team, led by Ralf Srama, is based at the University of Stuttgart in Germany. JPL is a division of the California Institute of Technology in Pasadena.

Reference:
Hsiang-Wen Hsu, Frank Postberg, Yasuhito Sekine, Takazo Shibuya, Sascha Kempf, Mihály Horányi, Antal Juhász, Nicolas Altobelli, Katsuhiko Suzuki, Yuka Masaki, Tatsu Kuwatani, Shogo Tachibana, Sin-iti Sirono, Georg Moragas-Klostermeyer, Ralf Srama. Ongoing hydrothermal activities within Enceladus. Nature, 2015; 519 (7542): 207 DOI: 10.1038/nature14262

Note: The above story is based on materials provided by NASA/Jet Propulsion Laboratory.

Investigation: Unexplored Underwater Volcano Off Solomon Islands

March 11, 2015

Kavachi typically erupts violently and can’t be approached, as in this 2002 photo. Phillips’ project caught Kavachi in a rare quiet state and his team was able to collect data and imagery directly from the peak. Photo credit: Corey Howell.

University of Rhode Island doctoral student Brennan Phillips is on the hunt for underwater volcanoes so he can collect data on the plumes of hot fluids and chemical compounds emanating from hydrothermal vents in and around the craters. It’s the subject of his dissertation, and he’s willing to travel to the ends of the Earth to make new discoveries.
Phillips spent two weeks in January in the Solomon Islands of the Western Pacific investigating the Kavachi submarine volcano, which the URI Graduate School of Oceanography student says is “known for its frequent violent eruptions that blow steam hundreds of feet into the air.” Located 15 miles off the Western Province of the island nation, the unexplored volcano has formed an island at least seven times in the last century, but waves soon erode the island away until the next big eruption.

“The closest anyone had ever gotten to the volcano before us was a couple hundreds meters away, which is really dangerous, but when we got there, the water was calm and allowed us to get even closer,” said Phillips, a resident of Providence. “We worked around the main peak, which was about 24 meters below the surface, and we could see the plume of chemically altered water coming out of it.”

One reason for Phillips’ intense interest in this volcano is because of concerns that mining companies may soon target the area to harvest the massive sulfide deposits on the seafloor in the vicinity. That is already happening in nearby Papua New Guinea, and he believes the Solomon Islands will be next.

“There is a precedent of exploiting natural resources in the area without protecting those resources,” Phillips explained, noting that clearcutting of forests is already underway in the Solomons. “We wanted to explore Kavachi to showcase the natural environments on the seafloor in the area to the Solomon Island government and the scientific community abroad. If we show it off before a mining company gets there, it has a better chance of being protected or managed appropriately.”

Taking calculated risks to collect the data he sought, Phillips deployed instrumentation on loan from the National Oceanic and Atmospheric Administration and camera systems provided by the National Geographic Society, which funded his expedition. His local guide, Corey Howell, attempted to scuba dive to the rim of the crater, but the hot water prevented him from approaching.

“What was most surprising was that fish and sharks swam right through the bubbling hot water that Corey couldn’t withstand,” Phillips said. “And in the caldera, our cameras caught images of schools of sharks, smaller fish and even jellyfish living in the hot acidic plume. This presumably toxic environment supports a whole community of life, even though every once in a while it blows up.”

No one knows how often the Kavachi volcano erupts, since it’s too far offshore for local residents to see clearly and few fishermen approach the area. But those that do travel there occasionally say it is erupting every time they are nearby.

Phillips’ URI colleague Alex DeCiccio videotaped the entire expedition and collected stories from local villagers, as well as images of a massive logging ship that arrived at the village to begin extracting trees.

“We went way farther than I expected with this project,” Phillips concluded. “I didn’t expect to see the issue of natural resource exploitation be highlighted right in front of us like it did. It makes my project all the more relevant.”

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

Friction means Antarctic glaciers more sensitive to climate change than we thought

March 11, 2015

One of the biggest unknowns in understanding the effects of climate change today is the melting rate of glacial ice in Antarctica. Scientists agree rising atmospheric and ocean temperatures could destabilize these ice sheets, but there is uncertainty about how fast they will lose ice.
The West Antarctic Ice Sheet is of particular concern to scientists because it contains enough ice to raise global sea level by up to 16 feet, and its physical configuration makes it susceptible to melting by warm ocean water. Recent studies have suggested that the collapse of certain parts of the ice sheet is inevitable. But will that process take several decades or centuries?

Research by Caltech scientists now suggests that estimates of future rates of melt for the West Antarctic Ice Sheet–and, by extension, of future sea-level rise–have been too conservative. In a new study, published online on March 9 in the Journal of Glaciology, a team led by Victor Tsai, an assistant professor of geophysics, found that properly accounting for Coulomb friction–a type of friction generated by solid surfaces sliding against one another–in computer models significantly increases estimates of how sensitive the ice sheet is to temperature perturbations driven by climate change.

Unlike other ice sheets that are moored to land above the ocean, most of West Antarctica’s ice sheet is grounded on a sloping rock bed that lies below sea level. In the past decade or so, scientists have focused on the coastal part of the ice sheet where the land ice meets the ocean, called the “grounding line,” as vital for accurately determining the melting rate of ice in the southern continent.

“Our results show that the stability of the whole ice sheet and our ability to predict its future melting is extremely sensitive to what happens in a very small region right at the grounding line. It is crucial to accurately represent the physics here in numerical models,” says study coauthor Andrew Thompson, an assistant professor of environmental science and engineering at Caltech.

Part of the seafloor on which the West Antarctic Ice Sheet rests slopes upward toward the ocean in what scientists call a “reverse slope gradient.” The end of the ice sheet also floats on the ocean surface so that ocean currents can deliver warm water to its base and melt the ice from below. Scientists think this “basal melting” could cause the grounding line to retreat inland, where the ice sheet is thicker. Because ice thickness is a key factor in controlling ice discharge near the coast, scientists worry that the retreat of the grounding line could accelerate the rate of interior ice flow into the oceans. Grounding line recession also contributes to the thinning and melting away of the region’s ice shelves–thick, floating extensions of the ice sheet that help reduce the flow of ice into the sea.

According to Tsai, many earlier models of ice sheet dynamics tried to simplify calculations by assuming that ice loss is controlled solely by viscous stresses, that is, forces that apply to “sticky fluids” such as honey–or in this case, flowing ice. The conventional models thus accounted for the flow of ice around obstacles but ignored friction. “Accounting for frictional stresses at the ice sheet bottom in addition to the viscous stresses changes the physical picture dramatically,” Tsai says.

In their new study, Tsai’s team used computer simulations to show that even though Coulomb friction affects only a relatively small zone on an ice sheet, it can have a big impact on ice stream flow and overall ice sheet stability.

In most previous models, the ice sheet sits firmly on the bed and generates a downward stress that helps keep it attached it to the seafloor. Furthermore, the models assumed that this stress remains constant up to the grounding line, where the ice sheet floats, at which point the stress disappears.

Tsai and his team argue that their model provides a more realistic representation–in which the stress on the bottom of the ice sheet gradually weakens as one approaches the coasts and grounding line, because the weight of the ice sheet is increasingly counteracted by water pressure at the glacier base. “Because a strong basal shear stress cannot occur in the Coulomb model, it completely changes how the forces balance at the grounding line,” Thompson says.

Tsai says the idea of investigating the effects of Coulomb friction on ice sheet dynamics came to him after rereading a classic study on the topic by American metallurgist and glaciologist Johannes Weertman from Northwestern University. “I wondered how might the behavior of the ice sheet differ if one factored in this water-pressure effect from the ocean, which Weertman didn’t know would be important when he published his paper in 1974,” Tsai says.

Tsai thought about how this could be achieved and realized the answer might lie in another field in which he is actively involved: earthquake research. “In seismology, Coulomb friction is very important because earthquakes are thought to be the result of the edge of one tectonic plate sliding against the edge of another plate frictionally,” Tsai said. “This ice sheet research came about partly because I’m working on both glaciology and earthquakes.”

If the team’s Coulomb model is correct, it could have important implications for predictions of ice loss in Antarctica as a result of climate change. Indeed, for any given increase in temperature, the model predicts a bigger change in the rate of ice loss than is forecasted in previous models. “We predict that the ice sheets are more sensitive to perturbations such as temperature,” Tsai says.

Hilmar Gudmundsson, a glaciologist with the British Antarctic Survey in Cambridge, UK, called the team’s results “highly significant.” “Their work gives further weight to the idea that a marine ice sheet, such as the West Antarctic Ice Sheet, is indeed, or at least has the potential to become, unstable,” says Gudmundsson, who was not involved in the study.

Glaciologist Richard Alley, of Pennsylvania State University, noted that historical studies have shown that ice sheets can remain stable for centuries or millennia and then switch to a different configuration suddenly.

“If another sudden switch happens in West Antarctica, sea level could rise a lot, so understanding what is going on at the grounding lines is essential,” says Alley, who also did not participate in the research.

“Tsai and coauthors have taken another important step in solving this difficult problem,” he says.

Reference:
Victor C. Tsai, Andrew L. Stewart, Andrew F. Thompson. Marine ice-sheet profiles and stability under Coulomb basal conditions. Journal of Glaciology, 2015; 61 (226): 205 DOI: 10.3189/2015JoG14J221

Note: The above story is based on materials provided by California Institute of Technology.

Tiny new fossil helps rewrite crab evolution, sheds lights on late Jurassic marine world

March 11, 2015

This is a ‘living’ megalopa larva. Credit: Photo by Hsiu-Lin Chin

NHM curator co-authors paper on 150-million-year-old fossilized crab larva, found in southern Germany
A paper in the journal Nature Communications (March 9, 2015) co-written by NHM Crustacea curator Dr. Jody Martin describes a 150-million-year-old crab larva fossil specimen from southern Germany. The new fossil provides critical evidence for understanding the early rise of crabs.

Arthropods (they of a hard outer-skeleton, like crustaceans, spiders, and insects) very often have larval phases that are completely different from the adults — such as caterpillars and butterflies. Allegedly, one of the reasons crabs have been so successful is that their larval life habits (diet, locomotion, etc.) are decoupled from their adult life habits.

Most ancient fossils display a suite of “primitive” features, consistent with their early evolution and allowing them to be distinguished from their modern descendants. But the fossil described in this paper, despite its age, possesses a very modern morphology, indistinguishable from many crab larvae living today. “It’s amazing, but if we did not know this was a 150-million-year-old fossil, we might think that it came from today’s ocean,” Dr. Martin said. “This came as quite a surprise to all of us.”

True crabs are the most successful group of decapod crustaceans, with about 7,000 living species known. This success is most likely coupled to their life history which includes two specialized larval forms, zoea and megalopa. The new fossil is of the latter larval type (the megalopa), and it is the first such fossil ever reported.

True crabs as a group are comparably young, starting to diversify only about 100 million years ago (mya), with a dramatic increase in species richness beginning approximately 50 mya — though the early evolution of crabs is still very incompletely known.

Reference:
Joachim T. Haug, Joel W. Martin, Carolin Haug. A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs. Nature Communications, 2015; 6: 6417 DOI: 10.1038/ncomms7417

Note: The above story is based on materials provided by Natural History Museum of Los Angeles County.

New long-term earthquake forecast for California

March 11, 2015

Three-dimensional perspective view of the likelihood that each region of California will experience a magnitude 6.7 or larger earthquake in the next 30 years (6.7 matches the magnitude of the 1994 Northridge earthquake, and 30 years is the typical duration of a homeowner mortgage). Credit: USGS

A new California earthquake forecast by the U.S. Geological Survey and partners revises scientific estimates for the chances of having large earthquakes over the next several decades.
The Third Uniform California Earthquake Rupture Forecast, or UCERF3, improves upon previous models by incorporating the latest data on the state’s complex system of active geological faults, as well as new methods for translating these data into earthquake likelihoods.

The study confirms many previous findings, sheds new light on how the future earthquakes will likely be distributed across the state and estimates how big those earthquakes might be.

Compared to the previous assessment issued in 2008, UCERF2, the estimated rate of earthquakes around magnitude 6.7, the size of the destructive 1994 Northridge earthquake, has gone down by about 30 percent. The expected frequency of such events statewide has dropped from an average of one per 4.8 years to about one per 6.3 years.

However, in the new study, the estimate for the likelihood that California will experience a magnitude 8 or larger earthquake in the next 30 years has increased from about 4.7% for UCERF2 to about 7.0% for UCERF3.

“The new likelihoods are due to the inclusion of possible multi-fault ruptures, where earthquakes are no longer confined to separate, individual faults, but can occasionally rupture multiple faults simultaneously,” said lead author and USGS scientist Ned Field. “This is a significant advancement in terms of representing a broader range of earthquakes throughout California’s complex fault system.”

Two kinds of scientific models are used to inform decisions of how to safeguard against earthquake losses: an Earthquake Rupture Forecast, which indicates where and when the Earth might slip along the state’s many faults, and a Ground Motion Prediction model, which estimates the ground shaking given one of the fault ruptures. The UCERF3 model is of the first kind, and is the latest earthquake-rupture forecast for California. It was developed and reviewed by dozens of leading scientific experts from the fields of seismology, geology, geodesy, paleoseismology, earthquake physics and earthquake engineering.

The USGS partner organizations that contributed to this product include the Southern California Earthquake Center, the California Geological Survey and the California Earthquake Authority.

“We are fortunate that seismic activity in California has been relatively low over the past century. But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable,” said Tom Jordan, Director of the Southern California Earthquake Center and a co-author of the study. “The UCERF3 model provides our leaders and the public with improved information about what to expect, so that we can better prepare.”

Note : The above story is based on materials provided by U.S. Geological Survey.

Same forces as today caused climate changes 1.4 billion years ago

March 11, 2015

Ice ages come and go on Earth. Credit: University of Southern Denmark

Natural forces have always caused the climate on Earth to fluctuate. Now researchers have found geological evidence that some of the same forces as today were at play 1.4 billion years ago.
Fluctuating climate is a hallmark of Earth, and the present greenhouse effect is by far the only force affecting today’s climate. On a larger scale the Earth’s climate is also strongly affected by how the Earth orbits around the sun; this is called orbital forcing of climate change. These changes happen over thousands of years and they bring ice ages and warming periods.

Now researchers from University of Southern Denmark, China National Petroleum Corporation and others have looked deep into Earth’s history and can reveal that orbital forcing of climate change contributed to shaping the Earth’s climate 1.4 billion years ago.

“This study helps us understand how past climate changes have affected Earth geologically and biologically,” says Donald Canfield, principal investigator and professor at Nordic Center for Earth Evolution, University of Southern Denmark.

The evidence comes from analyses of sedimentary records from the approximately 1.4 billion-year-old and exceptionally well preserved Xiamaling Formation in China.

Changes in wind patterns and ocean circulations

The sediments in the Xiamaling Formation have preserved evidence of repeated climate fluctuations, reflecting apparent changes in wind patterns and ocean circulation that indicates orbital forcing of climate change.

Today Earth is affected by fluctuations called the Milankovich cycles. There are three different Milankovich cycles, and they occur each 20,000, 40,000 and 100,000 years. Over the last one million years these cycles have caused ice ages every 100,000 years, and right now we are in the middle of a warming period that has so far lasted 11,000 years.

“Earth’s climate history is complex. With this research we can show that cycles like the Milankovich cycles were at play 1.4 billion years ago — a period, we know only very little about,” says Donald Canfield, adding:

“This research will also help us understand how Milankovitch cyclicity ultimately controls climate change on Earth.”

In the new scientific paper in the journal PNAS, the researchers report both geochemical and sedimentological evidence for repeated, short-term climate fluctuations 1.4 billion years ago. For example the fossilized sediments show how layers of organic material differed over time, indicating cycle changes in wind patterns, rain fall and ocean circulations.

“These cycles were a little different than today’s Milankovich cycles. They occurred every 12-16,000 years, 20-30,000 years and every 100,000 years. They were a little shorter — probably because the Moon was closer to Earth 1.4 billion years ago,” explains Donald Canfield.

Reference:
Shuichang Zhang, Xiaomei Wang, Emma U. Hammarlund, Huajian Wang, M. Mafalda Costa, Christian J. Bjerrum, James N. Connelly, Baomin Zhang, Lizeng Bian, Donald E. Canfield. Orbital forcing of climate 1.4 billion years ago. Proceedings of the National Academy of Sciences, 2015; 201502239 DOI: 10.1073/pnas.1502239112

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

Oregon researchers detail new insights on arsenic cycling

March 11, 2015

This map shows the location of the aquifer in Oregon’s southern Willamette Valley where the research was conducted. The area is south of Eugene. Credit: Courtesy of Scott C. Maguffin

University of Oregon geologist Qusheng Jin initially labeled his theory “A Wild Hypothesis.” Now his study of arsenic cycling in a southern Willamette Valley aquifer is splashing with potential significance for arsenic-compromised aquifers around the world.
In a paper online ahead of regular publication in the journal Nature Geoscience, Jin’s five-member team reports on a bacterial process that turns toxic inorganic arsenic into organic forms that usually are considered to be less dangerous. Jin’s conclusion now is that organic arsenic should be monitored.

“No one has touched on the link between arsenic on the surface and in groundwater,” said Jin, a professor in the UO Department of Geological Sciences. “Traditionally the presence of the organic form in groundwater has been ignored. The focus has always been on inorganic forms, arsenate and arsenite.”

That approach, Jin said, over-simplifies the view on arsenic levels and overlooks how human activities, including pumping and irrigation, or environmental factors such as heavy rain or drought may influence organic forms.

Water is considered safe to drink when total arsenic levels are below 10 micrograms per liter. Levels above that are considered cancer risks.

Arsenic is a natural element found in abundance in the Earth’s crust. Organic arsenic, Jin said, is made up of a series of carbon-containing forms. Total arsenic is commonly assumed to be a pure metalloid form. Arsenic often changes forms as it moves through the environment. It also is used in some pesticides, herbicides and wood preservatives and in chicken feed.

The organic arsenic that caught the team’s attention is dimethylarsinate (DMA). This intermediate stage is a floating mishmash of dissolved organic forms along with inorganic arsenite and arsenate already floating freely in the water.

DMA’s concentration — sometimes exceeding 10 percent of inorganic arsenic — always correlates with the overall arsenite level, Jin said. Eventually, he added, the conversion process can turn arsenic into arsine, a volatile gas similar to fluorescent phosphine that rises as the result of decomposition in graveyards.

The fieldwork, led by Jin, involved gathering water samples at depths ranging from 20 to 40 meters (66 to 131 feet) from 23 wells located on rural properties near Creswell, Oregon. In 10 of the wells tested, DMA was found with concentrations as high as 16.5 micrograms per liter.

The aquifer consists of volcanic sandstone, tuff and silicic ash, overlaid by lava flows and river sediments. The basin floor dates to 33 million years ago. Organic arsenic in the aquifer, the researchers noted, is similar to that in aquifers in Florida and New Jersey in the United States and in Argentina, China (Inner Mongolia and Datong), Cypress, Taiwan and West Bengal. Arsenic in groundwater is a challenge worldwide, including all 48 contiguous U.S. states.

To test the hypothesis that arsenic cycling was occurring by way of native bacteria, UO doctoral student Scott C. Maguffin conducted a series of three laboratory experiments involving dissolved arsenite and arsenate taken from wells in the study area. The addition of ethanol in the final experiment stimulated bacterial activity, resulting in DMA concentrations much higher than those found in the field.

“I am concerned about the impact of this cycling process in aquifers,” Jin said. “If this process is as important as we believe it is, it will impact the transport and fate of arsenic in groundwater. Many organic arsenic forms are volatile and prone to diffusion. Where will these organic arsenic forms go? Will they ever make to the surface?”

The findings, Jin added, open a window on naturally occurring arsenic cycling and how, eventually, it might be manipulated to treat arsenic-contaminated water. “The cycling is important,” he said. “This basic science provides a conceptual framework to understand arsenic behavior in the environment.”

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

Amid chaos of Libya, newly unearthed fossils give clues to our own evolution

March 10, 2015

This is the team from the University of Kansas unearthing fossils in Libya, despite dangers. Credit: Yaowalak Chaimanee, University of Poitiers, France

Libya hasn’t been terribly hospitable for scientific research lately.

Since the 2011 toppling of Muammar Gaddafi, fighters tied to various tribes, regions and religious factions have sewn chaos across that nation. Most recently, ISIS militants in Libya committed mass beheadings that triggered retaliatory bombings by neighboring Egypt.
“Currently, it is obviously very dangerous to be a Western scientist in Libya,” said Christopher Beard, Distinguished Foundation Professor of Ecology and Evolutionary Biology at the University of Kansas. “Even Libyan citizens are not immune to random violence.”

In spite of this turmoil, Beard and a team including fellow scientists from KU’s Biodiversity Institute have just published a discovery of mammal fossils uncovered in the Zallah Oasis in the Sirt Basin of central Libya. The fossils date back to the early Oligocene, between about 30 and 31 million years ago.

According to Beard, their paper in the Journal of African Earth Sciences sheds light on a poorly documented interval of our own evolutionary history, and shows climate and environmental change can utterly alter a local ecosystem — from a wet, subtropical forest in the Eocene to a dry desert today.

This valuable knowledge makes taking calculated risks in a war-torn land worth the risk.

“The most important factor is to have local collaborators who are experienced and who have a good feeling for what is impossible or dangerous,” Beard said. “Our Libyan collaborator is an experienced and highly accomplished professor of geology at Tripoli University. He has excellent ties to the Libyan petroleum industry, and he knows the Sahara Desert of Libya as well as anyone. We consulted closely with him prior to our 2013 expedition, and when he gave us the green light that it was safe to return to the country — thanks largely to his logistical arrangements with a local oil company — we felt safe about going back, despite State Department warnings against travel to Libya.”

Beard, who participated in both the Libyan fieldwork and subsequent analysis of the fossil finds, said taking care of logistics was the hardest part of the work.

“The arrangements were hard to put in place, because we had to coordinate among a team of four different nationalities, and we required the consent and active participation of our colleagues working at Zuetina Oil Company in Zallah,” he said.

Working in the Zallah Oasis in Libya’s Sirt Basin — an area that has “sporadically” produced fossil vertebrates since the 1960s — the team discovered a highly diverse and unique group of fossil mammals dating to the Oligocene, the final epoch of the Paleogene period, a time marked by a broad diversity of animals that would seem strange to us today, but also development of species critical to human evolution.

Beard said that the fossil species his team discovered in Libya were surprisingly different from previous fossils tied to the Oligocene discovered in next-door Egypt.

“The fact that we are finding different species in Libya suggests that ancient environments in northern Africa were becoming very patchy at this time, probably because of global cooling and drying which began a short time earlier,” he said. “That environmental patchiness seems to have promoted what we call ‘allopatric speciation.’ That is, when populations of the same species become isolated because of habitat fragmentation or some other barrier to free gene flow, given enough time, different species will emerge. We are still exploring how this new evolutionary dynamic may have impacted the evolution of primates and other mammals in Africa at this time.”

Because Beard’s work focuses on the origin and evolution of primates and anthropoids — the precursors to humans — he found the Libyan discovery of a new species of the primate Apidium to be the most exciting of the fossils uncovered by the team.

“These are the first anthropoid primate fossils known from the Oligocene of Libya and the only anthropoid fossils of this age known from Africa outside of Egypt,” said the researcher. “Earlier hypotheses suggested that anthropoids as a group may have evolved in response to the global cooling and drying that occurred at the Eocene-Oligocene boundary. Our new research indicates this was certainly not the case, because anthropoids had already been around for several million years in Africa prior to that boundary. But the climate change still had a deep impact on anthropoid evolution, because habitat fragmentation and an increased level of allopatric speciation took place as a result. Anthropoids, being forest dwellers, would have been particularly impacted by forest fragmentation during the Oligocene.”

Unfortunately, ongoing strife in Libya makes a return visit to the Sirt Basin site impossible at the moment. Indeed, armed conflict in that nation prohibits outside scientist from visiting to safely conduct any kind of field research.

“The window has now passed,” Beard said. “Field research like that which our team conducts cannot begin again until the country is stabilized and the personal security of scientific researchers in the field can be assured.”

Reference:
Pauline M.C. Coster, K. Christopher Beard, Mustafa J. Salem, Yaowalak Chaimanee, Michel Brunet, Jean-Jacques Jaeger. A new early Oligocene mammal fauna from the Sirt Basin, central Libya: Biostratigraphic and paleobiogeographic implications. Journal of African Earth Sciences, 2015; 104: 43 DOI: 10.1016/j.jafrearsci.2015.01.006

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

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