Ecology team improves understanding of valley-wide stream chemistry

April 23, 2014

Researcher Kevin McGuire takes a water sample from a forest stream. Credit: Virginia Tech

A geostatistical approach for studying environmental conditions in stream networks and landscapes has been successfully applied at a valley-wide scale to assess headwater stream chemistry at high resolution, revealing unexpected patterns in natural chemical components.

“Headwater streams make up the majority of stream and river length in watersheds, affecting regional water quality,” said Assistant Professor Kevin J. McGuire, associate director of the Virginia Water Resources Research Center in Virginia Tech’s College of Natural Resources and Environment. “However, the actual patterns and causes of variation of water quality in headwater streams are often unknown.”

“Understanding the chemistry of these streams at a finer scale could help to identify factors impairing water quality and help us protect aquatic ecosystems,” said Gene E. Likens, president emeritus and distinguished senior scientist emeritus with the Cary Institute of Ecosystem Studies and the University of Connecticut.

Results of the study that used a new statistical tool to describe spatial patterns of water chemistry in stream networks are published in the April 21 issue of the Proceedings of the National Academies of Science by a team of ecosystem scientists, including McGuire and Likens.

The data used in the new analysis consist of 664 water samples collected every 300 feet throughout all 32 tributaries of the 14-square-mile Hubbard Brook Valley in New Hampshire. The chemistry results were originally reported in 2006 in the journal Biogeochemistry by Likens and Donald C. Buso, manager of field research with the Cary Institute.

McGuire and other members of the National Science Foundation’s Long-Term Ecological Research team at the Hubbard Brook Ecosystem Study decided that the huge, high-resolution dataset was ideal for a new statistical approach that examines how water flows both within the stream network and across the landscape.

“The goal was to visualize patterns that no one has been able to quantify before now and describe how they vary within headwater stream networks,” said McGuire. “Some chemical constituents vary at a fine scale, that is patterns of chemical change occur over very short distances, for example several hundred feet, but some constituents vary over much larger scales, for example miles. Several chemical constituents that we examined even varied at multiple scales suggesting that nested processes within streams and across the landscape influence the chemistry of stream networks.”

“The different spatial relationships permit the examination of patterns controlled by landscape versus stream network processes,” the article reports. Straight-line and unconnected network spatial relationships indicate landscape influences, such as soil, geology, and vegetation controls of water chemistry, for instance. In contrast, flow-connected relationships provide information on processes affected within the flowing streams.

The researchers are very familiar with the Hubbard Brook Valley and could point to the varying influences of the geology and distinct soil types, including areas of shallow acidic organic-rich soils.

The findings revealed by the analysis technique showed how chemistry patterns vary across landscapes with two scales of variation, one around 1,500 feet and another at about 4 miles. However, when chemistry patterns were examined only in the downstream direction, there was predominantly one scale of variation, which was less than about 1 mile.

The journal article concludes, “This spatially explicit, network-level analysis is crucial to refining long-held assumptions and stream structure and function.”

“One assumption that is typical in streams is that the chemical variation is controlled primarily by the way in which water flows in streams, which would cause gradients or patterns that are strongly oriented downstream,” said McGuire.

“Of course we found that to be the case; however, we were able to show that patterns affected different dissolved chemical elements at different scales, or distances, along the stream network,” he continued. “In addition to downstream gradients, we show that there were also ‘patches’ of variation in the patterns of dissolved chemicals that were caused by processes related to the watershed or landscape.

“In other words, natural chemical variation is not just influenced by the flow accumulation in rivers but processes operating within the landscape or watershed that affect the gradual downstream variation in chemistry, which is probably intuitive to most, but has never been quantified at both the fine scale and broad valley-wide extent as examined this study,” McGuire said.

“It really highlights the complexity of spatial patterns in stream networks, particularly in these small headwater streams that aggregate to create larger rivers that we all depend on for ecosystem services,” he said. “Understanding the natural variation of water chemistry in these headwater regions may help watershed managers choose better monitoring sites or at least be able to better interpret monitoring data and more efficiently track changes in water quality as land use and climate conditions change.”

Note : The above story is based on materials provided by Virginia Tech

Researchers find 3-million-year-old landscape beneath Greenland Ice Sheet

April 23, 2014

This is a piece of the GISP2 ice core showing silt and sand embedded in ice. Soon after this picture was taken, the ice was crushed in the University of Vermont clean lab and the sediment was isolated for analysis. Credit: Paul Bierman, University of Vermont

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised to discover an ancient tundra landscape preserved under the Greenland Ice Sheet, below two miles of ice.

“We found organic soil that has been frozen to the bottom of the ice sheet for 2.7 million years,” said University of Vermont geologist Paul Bierman—providing strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming.

He led an international team of scientists that reported their discovery on April 17 in the journal Science.

Greenland is a place of great interest to scientists and policymakers since the future stability of its huge ice sheet—the size of Alaska, and second only to Antarctica—will have a fundamental influence on how fast and high global sea levels rise from human-caused climate change.

“The ancient soil under the Greenland ice sheet helps to unravel an important mystery surrounding climate change,” said Dylan Rood a co-author on the new study from the Scottish Universities Environmental Research Centre and the University of California, Santa Barbara, “how did big ice sheets melt and grow in response to changes in temperature?”

The new discovery indicates that even during the warmest periods since the ice sheet formed, the center of Greenland remained stable; “it’s likely that it did not fully melt at any time,” Vermont’s Bierman said. This allowed a tundra landscape to be locked away, unmodified, under ice through millions of years of global warming and cooling.

“The traditional knowledge about glaciers is that they are very powerful agents of erosion and can effectively strip a landscape clean,” said study co-author Lee Corbett, a UVM graduate student who prepared the silty ice samples for analysis. Instead, “we demonstrate that the Greenland Ice Sheet is not acting as an agent of erosion; in fact, at it’s center, it has performed incredibly little erosion since its inception almost three million years ago.”

Rather than scraping and sculpting the landscape, the ice sheet has been frozen to the ground, “a refrigerator that’s preserved this antique landscape,” Bierman said.

The scientists tested seventeen “dirty ice” samples from the bottommost forty feet of the 10,019-foot GISP2 ice core extracted from Summit, Greenland, in 1993. “Over twenty years, only a few people had looked hard at the sediments from the bottom of the core,” Bierman said. From this sediment, he and a team at the University of Vermont’s Cosmogenic Nuclide Laboratory extracted a rare form of the element beryllium, an isotope called beryllium-10. Formed by cosmic rays, it falls from the sky and sticks to rock and soil. The longer soil is exposed at Earth’s surface, the more beryllium-10 it accumulates. Measuring how much is in soil or a rock gives geologists a kind of exposure clock.

The researchers expected to only find soil eroded from glacier-scoured bedrock in the sediment at the bottom of the ice core. “So we thought we were going looking for a needle in haystack,” Bierman said. They planned to work diligently to find vanishingly small amounts of the beryllium—since the landscape under the ice sheet would have not been exposed to the sky. “It turned out that we found an elephant in a haystack,” he said; the silt had very high concentrations of the isotope when the team measured it on a particle accelerator at Lawrence Livermore National Laboratory.

“On a global basis, we only find these sorts of beryllium concentrations in soils that have developed over hundreds of thousands to millions of years,” said Joseph Graly, who analyzed the beryllium data while at the University of Vermont.

The new research, supported by funding from the National Science Foundation, shows that “the soil had been stable and exposed at the surface for somewhere between 200,000 and one million years before being covered by ice,” notes Ben Crosby, a member of the research team from Idaho State University.

To help interpret these unexpected findings, the team also measured nitrogen and carbon that could have been left by plant material in the core sample. “The fact that measurable amounts of organic material were found in the silty ice indicates that soil must have been present under the ice,” said co-author Andrea Lini at the University of Vermont—and its composition suggests that the pre-glacial landscape may have been a partially forested tundra.

“Greenland really was green! However, it was millions of years ago,” said Rood, “Greenland looked like the green Alaskan tundra, before it was covered by the second largest body of ice on Earth.” To confirm their findings about this ancient landscape, the researchers also measured beryllium levels in a modern permafrost tundra soil on the North Slope of Alaska. “The values were very similar,” said Bierman, “which made us more confident that what we found under Greenland was tundra soil.”

Many geologists are seeking a long-term view of the history of the Greenland Ice Sheet, including how it moves and has shaped the landscape beneath it—with an eye toward better understanding its future behavior. It’s 656,000 square miles of ice, containing enough water, if fully melted, to raise global sea levels twenty-three feet—”yet we have very little information about what is happening at the bed with regards to erosion and landscape formation,” said Corbett.

What is clear, however, from an abundance of worldwide indicators, is that global temperatures are on a path to be “far warmer than the warmest interglacials in millions of years,” said Bierman. “There is a 2.7-million-year-old soil sitting under Greenland. The ice sheet on top of it has not disappeared in the time in which humans became a species. But if we keep on our current trajectory, the ice sheet will not survive. And once you clear it off, it’s really hard to put it back on.”

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

Hetaerolite

April 22, 2014

Chemical Formula:ZnMn₂O₄
Locality: Franklin, Sussex County, New Jersey, USA.
Name Origin: From the Greek for “companian”, for its occasional association with chalcophanite.

The mineral hetaerolite (ZnMn₂O₄) which is chemically similar to the mineral hausmannite, was first described from the Sterling Hill deposit, New Jersey, by Moore (1877) and later studied in detail by Palache (1910). Other localities where hetaerolite is known to occur include the Franklin Mine, New Jersey, and Leadville, Colorado (Frondel and Heinrich, 1942). Recently Hewett and Fleischer (1960) have reported hetaerolite from the Contact Mine, Grant County, New Mexico, and the Lucky Cuss Mine, Tombstone, Arizona.

They as well as Ramdohr and Frenzel (1956) before them, expressed the opinion that hetaerolite – as a product of weathering of Mn-bearing zinc ores – is much more abundant than previously thought. Now hetaerolite has also been found in the Pb-Zn-deposit at Rodna, Rumania, probably the first locality in Europe. The Rodna deposit belongs to the neogene metallogenetic province of the Carpathian Mountains (Giusca, Cioflica, and Udubasa, 1969) and consists of metasomatic ore-bodies in metasomatic limestones and of injections in andesitic explosion-breccias.

The ores consist predominantly of pyrite, sphalerite, pyrrhotite, and galena (Udubasa, 1970). The hetaerolite discussed here was found in cavities within the crystalline limestones where it occurs in a matrix of limonitic ochre together with broken-off fragments of galena crystals, which have been partially coated by cerussite.

Physical Properties

Cleavage: {001} Indistinct, {112} Poor, {011} Poor
Color: Black.
Density: 4.85 – 5.18, Average = 5.01
Diaphaneity: Subtranslucent to opaque
Fracture: Brittle – Uneven – Very brittle fracture producing uneven fragments.
Hardness: 6 – Orthoclase
Luminescence: Non-fluorescent.
Luster: Sub Metallic
Magnetism: Nonmagnetic
Streak: brownish black

Photos :

Mineral: Hodgkinsonite, Hetaerolite, Willemite, Franklinite, Zincite Locality: Sterling Mine, Ogdensburg, Sterling Hill, Sussex County, New Jersey (Type Locality for Hetaerolite, Zincite and Franklinite) Overall Size: 7.5x4x2 cm Crystals: 0.1-0.8 mm © JohnBetts-FineMinerals

Mineral: Zincite, Fluorite, Hetaerolite Locality: Sterling Mine, Ogdensburg, Sterling Hill, Sussex County, New Jersey (Type Locality for Zincite and Hetaerolite) Overall Size: 5.5x2x0.5 cm Crystals: micro to 1 mm © JohnBetts-FineMinerals

Mohawk Mine (Clark Station Mine; Pactolus Mine; Wilshire prospect), Mohawk Hill, Pactolus, Clark Mountain District, Clark Mts (Clark Mountain Range), San Bernardino Co., California, USA © 2003 ROM

Krypton used to accurately date ancient Antarctic ice

April 22, 2014

This is the ice core driller Tanner Kuhl with the blue ice drill on Taylor Glacier in Antarctica. The field camp is visible in the background. Credit: Photo courtesy of Xavier Fain

A team of scientists has successfully identified the age of 120,000-year-old Antarctic ice using radiometric krypton dating — a new technique that may allow them to locate and date ice that is more than a million years old.

The ability to discover ancient ice is critical, the researchers say, because it will allow them to reconstruct the climate much farther back into Earth’s history and potentially understand the mechanisms that have triggered the planet to shift into and out of ice ages.

Results of the discovery are being published this week in the Proceedings of the National Academy of Sciences. The work was funded by the National Science Foundation and the U.S. Department of Energy.

“The oldest ice found in drilled cores is around 800,000 years old and with this new technique we think we can look in other regions and successfully date polar ice back as far as 1.5 million years,” said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author on the PNAS article. “That is very exciting because a lot of interesting things happened with Earth’s climate prior to 800,000 years ago that we currently cannot study in the ice core record.”

Krypton dating is much like the more-heralded carbon-14 dating technique that measures the decay of a radioactive isotope — which has constant and well-known decay rates — and compares it to a stable isotope. Unlike carbon-14, however, krypton is a noble gas that does not interact chemically and is much more stable with a half-life of around 230,000 years. Carbon dating doesn’t work well on ice because carbon-14 is produced in the ice itself by cosmic rays and only goes back some 50,000 years.

Krypton is produced by cosmic rays bombarding Earth and then stored in air bubbles trapped within Antarctic ice. It has a radioactive isotope (krypton-81) that decays very slowly, and a stable isotope (krypton-83) that does not decay. Comparing the proportion of stable-to-radioactive isotopes provides the age of the ice.

Though scientists have been interested in radiokrypton dating for more than four decades, krypton-81 atoms are so limited and difficult to count that it wasn’t until a 2011 breakthrough in detector technology that krypton-81 dating became feasible for this kind of research. The new atom counter, named Atom Trap Trace Analysis, or ATTA, was developed by a team of nuclear physicists led by Zheng-Tian Lu at Argonne National Laboratory near Chicago.

In their experiment at Taylor Glacier in Antarctica, the researchers put several 300-kilogram (about 660 pounds) chunks of ice into a container and melted it to release the air from the bubbles, which was then stored in flasks. The krypton was isolated from the air at the University of Bern, Switzerland, and sent to Argonne for krypton-81 counting.

“The atom trap is so sensitive that it can capture and count individual atoms,” said Buizert, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “The only problem is that there isn’t a lot of krypton in the air, and thus there isn’t much in the ice, either. That’s why we need such large samples to melt down.”

The group at Argonne is continually improving the ATTA detector, researchers there say, and they aim to perform analysis on an ice sample as small as 20 kilograms in the near future.

The researchers determined from the isotope ratio that the Taylor Glacier samples were 120,000 years old, and validated the estimate by comparing the results to well-dated ice core measurements of atmospheric methane and oxygen from that same period.

Now the challenge is to locate some of the oldest ice in Antarctica, which may not be as easy as it sounds.

“Most people assume that it’s a question of just drilling deeper for ice cores, but it’s not that simple,” said Edward Brook, an Oregon State University geologist and co-author on the study. “Very old ice probably exists in small isolated patches at the base of the ice sheet that have not yet been identified, but in many places it has probably melted and flowed out into the ocean.”

There also are special regions where old ice is exposed at the edges of an ice field, Brook pointed out.

“The international scientific community is really interested in exploring for old ice in both types of places and this new dating will really help,” Brook said. “There are places where meteorites originating from Mars have been pushed out by glaciers and collect at the margins. Some have been on Earth for a million years or more, so the ice in these spots may be that old as well.”

Buizert said reconstructing Earth’s climate back to 1.5 million years is important because a shift in the frequency of ice ages took place in what is known as the Middle Pleistocene transition. Earth is thought to have shifted in and out of ice ages every 100,000 years or so during the past 800,000 years, but there is evidence that such a shift took place every 40,000 years prior to that time.

“Why was there a transition from a 40,000-year cycle to a 100,000-year cycle?” Buizert said. “Some people believe a change in the level of atmospheric carbon dioxide may have played a role. That is one reason we are so anxious to find ice that will take us back further in time so we can further extend data on past carbon dioxide levels and test this hypothesis.”

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

Today’s Antarctic region once as hot as California, Florida

April 22, 2014

Antarctica today. Parts of ancient Antarctica were as warm as today’s California coast, and polar regions of the southern Pacific Ocean registered 21st-century Florida heat, according to scientists using a new way to measure past temperatures. Credit: © doethion / Fotolia

Parts of ancient Antarctica were as warm as today’s California coast, and polar regions of the southern Pacific Ocean registered 21st-century Florida heat, according to scientists using a new way to measure past temperatures.

But it wasn’t always that way, and the new measurements can help improve climate models used for predicting future climate, according to co-author Hagit Affek of Yale, associate professor of geology & geophysics.

“Quantifying past temperatures helps us understand ancient Antarctica were as warm as today’s California coast, and polar regions of the southern Pacific Ocean registered 21st-century Florida heat, according to scientists using a new way to measure past temperatures.

The findings, published the week of April 21 in the Proceedings of the National Academy of Sciences, underscore the potential for increased warmth at Earth’s poles and the associated risk of melting polar ice and rising sea levels, the researchers said.

Led by scientists at Yale, the study focused on Antarctica during the Eocene epoch, 40-50 million years ago, a period with high concentrations of atmospheric CO2 and consequently a greenhouse climate.

the sensitivity of the climate system to greenhouse gases, and especially the amplification of global warming in polar regions,” Affek said.

The paper’s lead author, Peter M.J. Douglas, performed the research as a graduate student in Affek’s Yale laboratory. He is now a postdoctoral scholar at the California Institute of Technology. The research team included paleontologists, geochemists, and a climate physicist.

By measuring concentrations of rare isotopes in ancient fossil shells, the scientists found that temperatures in parts of Antarctica reached as high as 17 degrees Celsius (63F) during the Eocene, with an average of 14 degrees Celsius (57F) — similar to the average annual temperature off the coast of California today.

Eocene temperatures in parts of the southern Pacific Ocean measured 22 degrees Centigrade (or about 72F), researchers said — similar to seawater temperatures near Florida today.

Today the average annual South Pacific sea temperature near Antarctica is about 0 degrees Celsius.

These ancient ocean temperatures were not uniformly distributed throughout the Antarctic ocean regions — they were higher on the South Pacific side of Antarctica — and researchers say this finding suggests that ocean currents led to a temperature difference.

“By measuring past temperatures in different parts of Antarctica, this study gives us a clearer perspective of just how warm Antarctica was when the Earth’s atmosphere contained much more CO2 than it does today,” said Douglas. “We now know that it was warm across the continent, but also that some parts were considerably warmer than others. This provides strong evidence that global warming is especially pronounced close to the Earth’s poles. Warming in these regions has significant consequences for climate well beyond the high latitudes due to ocean circulation and melting of polar ice that leads to sea level rise.”

To determine the ancient temperatures, the scientists measured the abundance of two rare isotopes bound to each other in fossil bivalve shells collected by co-author Linda Ivany of Syracuse University at Seymour Island, a small island off the northeast side of the Antarctic Peninsula. The concentration of bonds between carbon-13 and oxygen-18 reflect the temperature in which the shells grew, the researchers said. They combined these results with other geo-thermometers and model simulations.

The new measurement technique is called carbonate clumped isotope thermometry.

“We managed to combine data from a variety of geochemical techniques on past environmental conditions with climate model simulations to learn something new about how the Earth’s climate system works under conditions different from its current state,” Affek said. “This combined result provides a fuller picture than either approach could on its own.”

Support for the research was provided by the National Science Foundation, Statoil, and the European Research Council.

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

Hessite

April 22, 2014

Chemical Formula: Ag₂Te
Locality: Calaveras, Nevada
Name Origin: Named after the Swiss chemist, G. H. Hesse (1802-1850).

Hessite is a mineral form of disilver telluride Ag₂Te). It is a soft, dark grey telluride mineral which forms monoclinic crystals.

It is named after Germain Henri Hess (1802–1850).

Hessite is found in the USA in Eagle County, Colorado and in Calaveras County, California and in many other locations.

Stützite (Ag₇Te₄) and empressite (AgTe) are related silver telluride minerals.

Physical Properties

Cleavage: {100} Indistinct
Color: Lead gray, Steel gray.
Density: 7.2 – 7.9, Average = 7.55
Diaphaneity: Opaque
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 1.5-2 – Talc-Gypsum
Luminescence: Non-fluorescent.
Luster: Metallic
Magnetism: Nonmagnetic
Streak: light gray

Photos :

Gold with Coloradoite, Hessite and Sylvanite in Quartz Locality: Bessie G Mine, La Plata District (California District), La Plata County, Colorado Specimen Size: 12.1 x 9.3 x 5.3 cm (cabinet) © minclassics

Taking the pulse of mountain formation in the Andes

April 22, 2014

Sedimentary deposits near Cerdas in the Altiplano plateau of Bolivia are shown. These rocks contain ancient soils used to decipher the surface temperature and surface uplift history of the southern Altiplano. Credit: Photo by Carmala Garzione/University of Rochester.

Scientists have long been trying to understand how the Andes and other broad, high-elevation mountain ranges were formed. New research by Carmala Garzione, a professor of earth and environmental sciences at the University of Rochester, and colleagues sheds light on the mystery.

In a paper published in the latest Earth and Planetary Science Letters, Garzione explains that the Altiplano plateau in the central Andes—and most likely the entire mountain range—was formed through a series of rapid growth spurts.

“This study provides increasing evidence that the plateau formed through periodic rapid pulses, not through a continuous, gradual uplift of the surface, as was traditionally thought,” said Garzione. “In geologic terms, rapid means rising one kilometer or more over several millions of years, which is very impressive.”

It’s been understood that the Andes mountain range has been growing as the Nazca oceanic plate slips underneath the South American continental plate, causing the Earth’s crust to shorten (by folding and faulting) and thicken. But that left two questions: How quickly have the Andes risen to their current height, and what was the actual process that enabled their rise?

Several years ago (2006-2008), Garzione and several colleagues provided the first estimates of the timing and rates of the surface uplift of the central Andes (“Mountain Ranges Rise Much More Rapidly than Geologists Expected”) by measuring the ancient surface temperatures and rainfall compositions preserved in the soils of the central Altiplano, a plateau in Bolivia and Peru that sits about 12,000 feet above sea level. Garzione concluded that portions of the dense lower crust and upper mantle that act like an anchor on the base of the crust are periodically detached and sink through the mantle as the thickened continental plate heats up. Detachment of this dense anchor allows the Earth’s low density upper crust to rebound and rise rapidly.

More recently, Garzione and Andrew Leier, an assistant professor of Earth and Ocean Sciences at the University of South Carolina, used a relatively new temperature-recording technique in two separate studies in different regions of the Andes to determine whether pulses of rapid surface uplift are the norm, or the exception, for the formation of mountain ranges like the Andes.

Garzione and Leier (“Stable isotope evidence for multiple pulses of rapid surface uplift in the Central Andes, Bolivia”) both focused on the bonding behavior of carbon and oxygen isotopes in the mineral calcite that precipitated from rainwater; their results were similar.

Garzione worked in the southern Altiplano, collecting climate records preserved in ancient soils at both low elevations (close to sea level), where temperatures remained warm over the history of the Andes, and at high elevations where temperatures should have cooled as the mountains rose. The calcite found in the soil contains both the lighter isotopes of carbon and oxygen—12C and 16O—as well as the rare heavier isotopes—13C and 18O. Paleo-temperature estimates from calcite rely on the fact that heavy isotopes form stronger bonds. At lower temperatures, where atoms vibrate more slowly, the heavy isotope 13C-18O bonds would be more difficult to break, resulting in a higher concentration of 13C-18O bonds in calcite, compared to what is found at warmer temperatures. By measuring the abundance of heavy isotope bonds in both low elevation (warm) sites and high elevation (cooler) sites over time, Garzione used the temperature difference between the sites to estimate the elevation of various layers of ancient soils at specific points in time.

She found that the southern Altiplano region rose by about 2.5 kilometers between 16 million and 9 million years ago, which is considered a rapid rate in geologic terms. Garzione speculates that the pulsing action relates to a dense root that grows at the boundary of the lower crust and upper mantle. As the oceanic plate slips under the continental plate, the continental plate shortens and thickens, increasing the pressure on the lower crust. The basaltic composition of the lower crust converts to a very high-density rock called eclogite, which serves as an anchor to the low-density upper crust. As this root is forced deeper into the hotter part of the mantle, it heats to a temperature where it can be rapidly removed (over several million years), resulting in the rapid rise of the mountain range.

“What we are learning is that the Altiplano plateau formed by pulses of rapid surface uplift over several million years, separated by long periods (several tens of million years) of stable elevations,” said Garzione. “We suspect this process is typical of other high-elevation ranges, but more research is needed before we know for certain.”

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

Atmospheric boundary layer exacerbated mega heat waves

April 22, 2014

The extreme nature of the heat waves of 2003 in Western Europe and of 2010 in Russia and Eastern Europe even surprised scientists at the time. NWO Veni researcher Ryan Teuling from Wageningen University says that the extreme temperatures can be explained by the interaction between dry soils with the atmospheric boundary layer – the lowest part of the atmosphere. The role of this boundary layer has received too little attention in studies using existing weather models, he claims in Nature Geoscience.

The mega heat wave of August 2003 in Western Europe broke various temperature records at the time, with temperatures of 40°C in France. The economic damage was estimated at between five and ten billion euros, due to forest fires, air pollution and loss of agricultural productivity . In Paris alone, thousands died as a consequence of the high temperatures. Researchers were unfamiliar with such heat waves in Europe and thought that it was a one-off, exceptional event. At least that was the case until 2010 when new records were set, this time in Eastern Europe and Russia.

Atmospheric boundary layer

In case of an atmospheric blocking situation, soil desiccation and a build-up of heat in the atmospheric boundary layer all occur at the same time, then exceptional heat waves are possible. That is the conclusion of Dr Ryan Teuling, assistant professor in hydrology and quantitative water management in Wageningen. The unusual atmospheric situation had previously been demonstrated to be the most important cause of the two heat waves. A high-pressure area blocked the penetration of low-pressure areas with colder air and wind. The researchers demonstrated that for both heat waves the same developments in the boundary layer conditions occurred in combination with an enhanced interaction between soil desiccation and heat accumulation in the atmospheric boundary layer. This lowest part of the troposphere is several tens to hundreds of metres thick at night, and up to several kilometres thick during the day.

Over a period of several days to several weeks heat was built up in an increasingly thicker atmospheric boundary layer, helped by heat convection from more southerly situated warm areas. During this period the soil dried out even further , leading to a reduced cooling effect of water evaporation from the surface. This process was enhanced by the high temperatures. Due to cooling at night, the warm air layer became decoupled from the earth’s surface, as a result of which the heat of the following day could lead to increasingly higher temperatures. The blanket of warm air above the earth’s surface became increasingly thicker during the heat wave.

45 degrees Celsius

Teuling: ‘With this new knowledge we can make predictions about possible temperatures during heat waves. Temperatures that gradually build up to 40°C are indeed possible in this part of the world. However, sudden temperature rises to 45°C as occurred during heat waves in, for example, Melbourne are unlikely here. Therefore the distance to the Equator and to large desert areas is too great.’

The researchers made use of satellite data and measurements from weather balloons of the situation in France in 2003 and Russia in 2010. They combined these data with a coupled soil-water-atmosphere model.

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

Herderite

April 20, 2014

Chemical Formula: CaBePO₄(F,OH)
Locality: Ehrenfriedersdorf, Saxony, Germay..
Name Origin: Named for Siegmund August Wolfgang von Herder (1776-1838), mining official in Freiberg, Saxony, Germany.Herderite is a phosphate mineral belonging to the apatite, phosphate group, with formula CaBePO₄(F,OH) . It forms monoclinic crystals, often twinned and variable in colour from colourless through yellow to green. It forms a series with the more common hydroxylherderite, which has more hydroxyl ion than fluoride.It is found in many parts of the world, often in pegmatites and associated with other apatite minerals.It was first described in 1828 for an occurrence in the Sauberg Mine, Erzgebirge, Saxony, Germany. It was named for Saxon mining official Sigmund August Wolfgang von Herder (1776–1838).

Physical Properties

Cleavage: {110} Indistinct
Color: White, Yellowish white, Greenish white.
Density: 3
Diaphaneity: Transparent to Translucent
Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces.
Hardness: 5 – Apatite
Luminescence: Non-fluorescent.
Luster: Vitreous (Glassy)
Streak: white

Photos :

Herderite Brazil Thumbnail, 9.5 x 5.5 mm ; 1.41 carats © irocks

Herderite Brazil Thumbnail, 7.6 x 5.9 mm ; 1.66 carats © irocks

Davib East Farm 61 (Davib Ost Farm), Karibib District, Erongo Region, Namibia © 2005 M. Kampf

Impact glass from asteroids and comets stores biodata for millions of years

April 20, 2014

The scorching heat produced by asteroid or comet impacts can melt tons of soil and rock, some of which forms glass as it cools. Some of that glass preserves bits of ancient plant material. Credit: A snapshot of ancient environmental conditions

Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists exploring large fields of impact glass in Argentina suggest that what happened on Earth might well have happened on Mars millions of years ago. Martian impact glass could hold traces of organic compounds.

Asteroid and comet impacts can cause widespread ecological havoc, killing off plants and animals on regional or even global scales. But new research from Brown University shows that impacts can also preserve the signatures of ancient life at the time of an impact.

A research team led by Brown geologist Pete Schultz has found fragments of leaves and preserved organic compounds lodged inside glass created by a several ancient impacts in Argentina. The material could provide a snapshot of environmental conditions at the time of those impacts. The find also suggests that impact glasses could be a good place to look for signs of ancient life on Mars.

The work is published in the latest issue of Geology Magazine.

The scorching heat produced by asteroid or comet impacts can melt tons of soil and rock, some of which forms glass as it cools. The soil of eastern Argentina, south of Buenos Aires, is rife with impact glass created by at least seven different impacts that occurred between 6,000 and 9 million years ago, according to Schultz. One of those impacts, dated to around 3 million years ago, coincides with the disappearance of 35 animal genera, as reported in the journal Science a few years back.

“We know these were major impacts because of how far the glass is distributed and how big the chunks are,” Schultz said. “These glasses are present in different layers of sediment throughout an area about the size of Texas.”

Within glass associated with two of those impacts — one from 3 million years ago and one from 9 million years ago — Schultz and his colleagues found exquisitely preserved plant matter. “These glasses preserve plant morphology from macro features all the way down to the micron scale,” Schultz said. “It’s really remarkable.”

The glass samples contain centimeter-size leaf fragments, including intact structures like papillae, tiny bumps that line leaf surfaces. Bundles of vein-like structures found in several samples are very similar to modern pampas grass, a species common to that region of Argentina.

Chemical analysis of the samples also revealed the presence of organic hydrocarbons, the chemical signatures of living matter.

To understand how these structures and compounds could have been preserved, Schultz and his colleagues tried to replicate that preservation in the lab. They mixed pulverized impact glass with fragments of pampas grass leaves and heated the mixture at various temperatures for various amounts of time. The experiments showed that plant material was preserved when the samples were quickly heated to above 1,500 degrees Celsius.

It appears, Schultz says, that water in the exterior layers of the leaves insulates the inside layers, allowing them to stay intact. “The outside of the leaves takes it for the interior,” he said. “It’s a little like deep frying. The outside fries up quickly but the inside takes much longer to cook.”

Implications for Mars

If impact glass can preserve the signatures of life on Earth, it stands to reason that it could do the same on Mars, Schultz says. And the soil conditions in Argentina that contributed to the preservation of samples in this study are not unlike soils found on Mars.

The Pampas region of Argentina is covered with thick layers of windblown sediment called loess. Schultz believes that when an object impacts this sediment, globs of melted material roll out from the edge of the impact area like molten snowballs. As they roll, they collect material from the ground and cool quickly — the dynamics that the lab experiments showed were important for preservation. After the impact, those glasses are slowly covered over as dust continues to accumulate. That helps to preserve both the glasses and the stowaways within them for long periods — in the Argentine case, for millions of years.

Much of the surface of Mars is covered in a loess-like dust, and the same mechanism that preserved the Argentine samples could also work on Mars.

“Impact glass may be where the 4 billion-year-old signs of life are hiding,” Schultz said. “On Mars they’re probably not going to come out screaming in the form of a plant, but we may find traces of organic compounds, which would be really exciting.”

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

Scientists find Earth-sized world in orbit friendly to life

April 20, 2014

Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone?a range of distance from a star where liquid water might pool on the planet’s surface, is seen in a NASA artist’s concept released April 17, 2014. Credit: Reuters/NASA/JPL-Caltech/Handout

(Reuters) – For the first time, scientists have found an Earth-sized world orbiting in a life-friendly zone around a distant star.

The discovery, announced on Thursday, is the closest scientists have come so far to finding a true Earth twin. The star, known as Kepler-186 and located about 500 light years away in the constellation Cygnus, is smaller and redder than the sun.

The star’s outermost planet, designated Kepler-186f, receives about one-third the radiation from its parent star as Earth gets from the sun, meaning that high noon on this world would be roughly akin to Earth an hour before sunset, said astronomer Thomas Barclay, with NASA’s Ames Research Center in Moffett Field, California.

The planet is the right distance from its host star for water — if any exists — to be liquid on the surface, a condition that scientists suspect is necessary for life.

“This planet is an Earth cousin, not an Earth twin,” said Barclay, who is among a team of scientists reporting on the discovery in the journal Science this week.

NASA launched its Kepler space telescope in 2009 to search about 150,000 target stars for signs of any planets passing by, or transiting, relative to the telescope’s point of view. Kepler was sidelined by a positioning system failure last year.

Analysis of archived Kepler data continues. From Kepler’s observational perch, a planet about the size and location of Earth orbiting a sun-like star would blot out only about 80 to 100 photons out of every million as it transits.

The pattern is repeated every 365 days and at least three transits would be needed to rule out other possibilities, so the search takes time.

“It’s very challenging to find Earth analogs,” Barclay said. “Most candidates don’t pan out, but things change as we get more measurements.”

Scientists don’t know anything about the atmosphere of Kepler-186f, but it will be a target for future telescopes that can scan for telltale chemicals that may be linked to life.

“This planet is in the habitable zone, but that’s doesn’t mean it is habitable,” Barclay said.

So far, scientists have found nearly 1,800 planets beyond the solar system.

“The past year has seen a lot of progress in the search for Earth-like planets. Kepler-168f is significant because it is the first exoplanet that is the same temperature and is (almost) the same size as Earth,” astronomer David Charbonneau, with the Harvard-Smithsonian Center for Astrophysics, wrote in an email.

“For me the impact is to prove that yes, such planets really do exist,” Charbonneau said. “Now we can point to a star and say, “There lies an Earth-like planet.'”

The above story is based on materials provided by Leslie Adler for Reuters

Hemimorphite

April 20, 2014

Chemical Formula: Zn₄Si₂O₇(OH)₂·H₂O
Locality: Nerchinak in Transbaikalia, Siberia.
Name Origin: Named after the hemimorphic nature of the crystals.Hemimorphite, is a sorosilicate mineral which has been historically mined from the upper parts of zinc and lead ores, chiefly associated with smithsonite. It was often assumed to be the same mineral and both were classed under the same name of calamine. In the second half of the 18th century it was discovered that there were two different minerals under the heading of calamine – a zinc carbonate and a zinc silicate, which often closely resembled each other.
The silicate was the more rare of the two, and was named hemimorphite because of the hemimorph development of its crystals. This unusual form, which is typical of only a few minerals, means that the crystals are terminated by dissimilar faces. Hemimorphite most commonly forms crystalline crusts and layers, also massive, granular, rounded and reniform aggregates, concentrically striated, or finely needle-shaped, fibrous or stalactitic, and rarely fan-shaped clusters of crystals.Some specimens show strong green fluorescence in shortwave ultraviolet light (253.7 nm) and weak light pink fluorescence in longwave UV.

Physical Properties

Cleavage: {110} Perfect
Color: Brown, Colorless, Greenish gray, Yellow brown, White.
Density: 3.4 – 3.5, Average = 3.45
Diaphaneity: Transparent to translucent
Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Hardness: 5 – Apatite
Luminescence: Fluorescent, Short UV=dull white, Long UV=dull white.
Luster: Vitreous (Glassy)
Streak: white

Photos:

Hemimorphite Ojuela Mine, Mapimi, Durango, Mexico Cabinet, 10.9 x 6.8 x 5.3 cm © irocks

Hemimorphite Wenshan Mine, Dulong ore field, Wenshan Co., Wenshan Autonomous Prefecture, Yunnan Province, China Size: 6.5 x 6.5 x 3.0 cm (small cabinet) © danweinrich

Hemimorphite Ojuela Mine, Mapimi, Mun. de Mapimi, Durango, Mexico Size: (thumbnail) © danweinrich

Hemimorphite Wenshan Mine, Dulong ore field, Wenshan Co., Wenshan Autonomous Prefecture, Yunnan Province, China Size: 10.5 x 9.5 x 6.5 cm (cabinet) © danweinrich

Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico

Researchers Find 3-million-year-old Landscape Beneath Greenland Ice Sheet

April 20, 2014

Under the Greenland Ice Sheet, scientists were greatly surprised to discover an ancient tundra landscape. The finding provides strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming. Image Credit: Joshua Brown, University of Vermont

Glaciers and ice sheets are commonly thought to work like a belt sander. As they move over the land they scrape off everything — vegetation, soil and even the top layer of bedrock. So a team of university scientists and a NASA colleague were greatly surprised to discover an ancient tundra landscape preserved under the Greenland Ice Sheet, below two miles of ice.

“We found organic soil that has been frozen to the bottom of the ice sheet for 2.7 million years,” said University of Vermont geologist and lead author Paul Bierman. The finding provides strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming.

The team reported their discovery on April 17 in the journal Science.

Greenland is a place of great interest to scientists and policymakers because the future stability of its huge ice sheet — the size of Alaska — will have a fundamental influence on how fast and high global sea levels rise from human-caused climate change.

“The ancient soil under the Greenland ice sheet helps to unravel an important mystery surrounding climate change,” said Dylan Rood, a co-author on the new study, from the Scottish Universities Environmental Research Centre and the University of California, Santa Barbara. “How did big ice sheets melt and grow in response to changes in temperature?”

The new discovery indicates that even during the warmest periods since the ice sheet formed, the center of Greenland remained stable. “It’s likely that it did not fully melt at any time,” Bierman said. This allowed a tundra landscape to be locked away, unmodified, under ice through millions of years of global warming and cooling.

“Some ice sheet models project that the Greenland Ice Sheet completely melted during previous interglacial periods. These data suggest that did not happen,” said co-author Tom Neumann, a cryospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We don’t know how much of the ice sheet remained – to estimate it, we’d have to study other ice cores in Greenland that have sediment in the bottom to see if ancient soil is preserved under those sites as well.”

The scientists tested seventeen samples of “dirty ice” – ice with sediment mixed in — from the bottommost 40 feet of the 10,019-foot GISP2 ice core extracted from Summit, Greenland, in 1993. From this sediment, Bierman and a team at the University of Vermont’s Cosmogenic Nuclide Laboratory extracted a rare form of the element beryllium, an isotope called beryllium-10. Formed by cosmic rays, it falls from the sky and sticks to rock and soil. The longer soil is exposed at Earth’s surface, the more beryllium-10 it accumulates. Measuring how much is in soil or a rock gives geologists a kind of exposure clock.

The researchers expected to only find soil eroded from glacier-scoured bedrock in the sediment at the bottom of the ice core. But the silt they did find had very high concentrations of beryllium-10 when the team measured it on a particle accelerator at Lawrence Livermore National Laboratory, in Livermore, Calif.

“On a global basis, we only find these sorts of beryllium concentrations in soils that have developed over hundreds of thousands to millions of years,” said co-author Joseph Graly, who analyzed the beryllium data while at the University of Vermont, Burlington, Vt.

The new research, supported by funding from the National Science Foundation, shows that the soil had been stable and exposed at the surface for somewhere between 200,000 and one million years before being covered by ice.

To help interpret these unexpected findings, the team also measured nitrogen and carbon that could have been left by plant material in the core sample. “The fact that measurable amounts of organic material were found in the silty ice indicates that soil must have been present under the ice,” said co-author Andrea Lini at the University of Vermont. The composition of the material suggested that the pre-glacial landscape may have been a partially forested tundra.

“Greenland really was green! However, it was millions of years ago,” said Rood. “Before it was covered by the second largest body of ice on Earth, Greenland looked like the green Alaskan tundra.” To confirm their findings about this ancient landscape, the researchers also measured beryllium levels in a modern permafrost tundra soil on the North Slope of Alaska and found that the values were very similar.

With an eye toward better understanding its future behavior, many geologists are seeking a long-term view of the history of the Greenland Ice Sheet, including how it moves and has shaped the landscape beneath it. Its 656,000 square miles of ice contain enough water, if fully melted, to raise global sea levels twenty-three feet. “Yet, we have very little information about what is happening at the bed with regards to erosion and landscape formation,” said Corbett.

Note : The above story is based on materials provided by Joshua Brown, University of Vermont

Hematite

April 19, 2014

Iron Rose St Christophe-en-Oisans, Bourg d’Oisans, Isère, Rhône-Alpes, France © JM. Johannet

Chemical Formula: Fe₂O₃
Locality: Matto Grosso, Brazil. Mesabi iron ore range, Minnesota, USA.
Name Origin: From the Greek, haimatites, “bloodlike'” in allusion to vivid red color of the powder.

Hematite, also spelled as haematite, is the mineral form of iron(III) oxide (Fe₂O₃), one of several iron oxides. Hematite crystallizes in the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above 950 °C (1,740 °F).

Hematite is a mineral, colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Varieties include kidney ore, martite (pseudomorphs after magnetite), iron rose and specularite (specular hematite). While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle. Maghemite is a hematite- and magnetite-related oxide mineral.

Huge deposits of hematite are found in banded iron formations. Gray hematite is typically found in places where there has been standing water or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. Hematite can also occur without water, however, usually as the result of volcanic activity.

Clay-sized hematite crystals can also occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides or oxyhydroxides such as goethite, is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils.

Physical Properties

Cleavage: None
Color: Reddish gray, Black, Blackish red.
Density: 5.3
Diaphaneity: Subtranslucent to opaque
Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Hardness: 6.5 – Pyrite
Luminescence: Non-fluorescent.
Luster: Metallic
Magnetism: Magnetic after heating
Streak: reddish brown

Photos :

Hematite (var. Iron Rose), quartz and chlorite Fibbia – Fontana – Central St Gotthard Massif – Leventina – Ticino – Switzerland Specimen weight:155 gr. Crystal size:mm. 16 Overall size: 63mm x 42 mm x 41 mm © minservice

Hematite (pseudocubic) Ouro Preto, Minas Gerais, Brazil Small Cabinet, 6.9 x 6.2 x 2.8 cm © irocks

Hematite (twin!) N’Chwaning II Mine, Kuruman, Kalahari manganese fields, Northern Cape Province, South Africa Size: 4.0 x 2.5 x 1.5 cm (miniature) © danweinrich

Hematite San Carlos, Chihuahua, Mexico Miniature, 2.9 x 2.0 x 0.9 cm © irocks

Image: Grand Canyon geology lessons on view

April 19, 2014

The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of the Colorado River canyon and its many side canyons make an intricate landscape that contrasts with the dark green, forested plateau to the north and south.

The Colorado River has done all the erosional work of carving away cubic kilometers of rock in a geologically short period of time. Visible as a darker line snaking along the bottom of the canyon, the river lies at an altitude of 715 meters (2,345 feet), thousands of meters below the North and South Rims. Temperatures are furnace-like on the river banks in the summer. But Grand Canyon Village, the classic outlook point for visitors, enjoys a milder climate at an altitude of 2,100 meters (6,890 feet).

The Grand Canyon has become a geologic icon—a place where you can almost sense the invisible tectonic forces within the Earth. The North and South Rims are part of the Kaibab Plateau, a gentle tectonic swell in the landscape. The uplift of the plateau had two pronounced effects on the landscape that show up in this image. First, in drier parts of the world, forests usually indicate higher places; higher altitudes are cooler and wetter, conditions that allow trees to grow. The other geologic lesson on view is the canyon itself. Geologists now know that a river can cut a canyon only if the Earth surface rises vertically. If such uplift is not rapid, a river can maintain its course by eroding huge quantities of rock and forming a canyon.

This astronaut photograph (ISS039-E-5258) was taken on March 25, 2014 by the Expedition 39 crew, with a Nikon D3S digital camera using a 180 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed.

Note : The above story is based on materials provided by NASA Image of the Day

Helvite

April 17, 2014

Chemical Formula: Mn₄(Be₃Si₃O₁₂)S
Locality: Schwarzenberg and Breitenbrunn, Germany.
Name Origin: From the Greek helios – “sun.”

Physical Properties

Cleavage: {111} Indistinct, {111} Indistinct, {111} Indistinct
Color: Brown, Brownish yellow, Gray, Yellow, Yellow green.
Density: 3.16 – 3.36, Average = 3.26
Diaphaneity: Translucent to opaque
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 6-6.5 – Orthoclase-PyriteLuminescence: Fluorescent, Short UV=deep red, Long UV=deep red.
Luster: Vitreous – Resinous
Streak: grayish white

Photos :

Helvite Tongbei, Fujian Province, China Miniature, 4.5 x 3.3 x 2.7 cm © irocks

Helvite Tongbei, Fujian Province, China Miniature, 4.3 x 2.1 x 1.9 cm © irocks

Helvine Antonsthal, Breitenbrunn District, Erzgebirge, Saxony, Germany Specimen weight:110 gr. Crystal size:0,3 cm Overall size: 60mm x 37 mm x 40 mm © minservice

Helvite Rincon, California, USA Thumbnail, 2.6 x 2.2 x 2.5 cm © irocks

Mars: Meteorites yield clues to Red Planet’s early atmosphere

April 17, 2014

Late spring on Mars (centered on roughly 305 degrees longitude). Credit: David Crisp and the WFPC2 Science Team (Jet Propulsion Laboratory/California Institute of Technology)

Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published April 17 in the journal Nature, shows that the atmospheres of Mars and Earth diverged in important ways very early in the 4.6 billion year evolution of our solar system.

The results will help guide researchers’ next steps in understanding whether life exists, or has ever existed, on Mars and how water — now absent from the Martian surface — flowed there in the past.

Heather Franz, a former University of Maryland research associate who now works on the Curiosity rover science team at the NASA Goddard Space Flight Center, led the study with James Farquhar, co-author and UMD geology professor. The researchers measured the sulfur composition of 40 Mars meteorites — a much larger number than in previous analyses. Of more than 60,000 meteorites found on Earth, only 69 are believed to be pieces of rocks blasted off the Martian surface.

The meteorites are igneous rocks that formed on Mars, were ejected into space when an asteroid or comet slammed into the red planet, and landed on Earth. The oldest meteorite in the study is about 4.1 billion years old, formed when our solar system was in its infancy. The youngest are between 200 million and 500 million years old.

Studying Martian meteorites of different ages can help scientists investigate the chemical composition of the Martian atmosphere throughout history, and learn whether the planet has ever been hospitable to life. Mars and Earth share the basic elements for life, but conditions on Mars are much less favorable, marked by an arid surface, cold temperatures, radioactive cosmic rays, and ultraviolet radiation from the Sun. Still, some Martian geological features were evidently formed by water — a sign of milder conditions in the past. Scientists are not sure what conditions made it possible for liquid water to exist on the surface, but greenhouse gases released by volcanoes likely played a role.

Sulfur, which is plentiful on Mars, may have been among the greenhouse gases that warmed the surface, and could have provided a food source for microbes. Because meteorites are a rich source of information about Martian sulfur, the researchers analyzed sulfur atoms that were incorporated into the rocks.

In the Martian meteorites, some sulfur came from molten rock, or magma, which came to the surface during volcanic eruptions. Volcanoes also vented sulfur dioxide into the atmosphere, where it interacted with light, reacted with other molecules, and settled on the surface.

Sulfur has four naturally occurring stable isotopes, or different forms of the element, each with its own atomic signature. Sulfur is also chemically versatile, interacting with many other elements, and each type of interaction distributes sulfur isotopes in a different way. Researchers measuring the ratios of sulfur isotopes in a rock sample can learn whether the sulfur was magma from deep below the surface, atmospheric sulfur dioxide or a related compound, or a product of biological activity.

Using state-of-the-art techniques to track the sulfur isotopes in samples from the Martian meteorites, the researchers were able to identify some sulfur as a product of photochemical processes in the Martian atmosphere. The sulfur was deposited on the surface and later incorporated into erupting magma that formed igneous rocks. The isotopic fingerprints found in the meteorite samples are different than those that would have been produced by sulfur-based life forms.The researchers found the chemical reactions involving sulfur in the Martian atmosphere were different than those that took place early in Earth’s geological history. This suggests the two planets’ early atmospheres were very different, Franz said.

The exact nature of the differences is unclear, but other evidence suggests that soon after our solar system formed, much of Mars’ atmosphere was lost, leaving it thinner than Earth’s, with lower concentrations of carbon dioxide and other gases. That is one reason why Mars is too cold for liquid water today — but that may not always have been the case, said Franz.

“Climate models show that a moderate abundance of sulfur dioxide in the atmosphere after volcanic episodes, which have occurred throughout Mars’ history, could have produced a warming effect which may have allowed liquid water to exist at the surface for extended periods,” Franz said. “Our measurements of sulfur in Martian meteorites narrow the range of possible atmospheric compositions, since the pattern of isotopes that we observe points to a distinctive type of photochemical activity on Mars, different from that on early Earth.”

Periods of higher levels of sulfur dioxide may help explain the red planet’s dry lakebeds, river channels and other evidence of a watery past. Warm conditions may even have persisted long enough for microbial life to develop.

The team’s work has yielded the most comprehensive record of the distribution of sulfur isotopes on Mars. In effect, they have compiled a database of atomic fingerprints that provide a standard of comparison for sulfur-containing samples collected by NASA’s Curiosity rover and future Mars missions. This information will make it much easier for researchers to zero in on any signs of biologically produced sulfur, Farquhar said.

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

Ancient shark fossil reveals new insights into jaw evolution

April 17, 2014

This photo shows the exceptionally well-preserved fossil of Ozarcus mapesae from two different lateral views. The scale bar is 10 millimeters. Credit: Copyright AMNH/F. Ippolito

The skull of a newly discovered 325-million-year-old shark-like species suggests that early cartilaginous and bony fishes have more to tell us about the early evolution of jawed vertebrates — including humans — than do modern sharks, as was previously thought. The new study, led by scientists at the American Museum of Natural History, shows that living sharks are actually quite advanced in evolutionary terms, despite having retained their basic “sharkiness” over millions of years. The research is published today in the journal Nature.”Sharks are traditionally thought to be one of the most primitive surviving jawed vertebrates. And most textbooks in schools today say that the internal jaw structures of modern sharks should look very similar to those in primitive shark-like fishes,” said Alan Pradel, a postdoctoral researcher at the Museum and the lead author of the study. “But we’ve found that’s not the case. The modern shark condition is very specialized, very derived, and not primitive.”

The new study is based on an extremely well-preserved shark fossil collected by Ohio University professors Royal Mapes and Gene Mapes in Arkansas, where an ocean basin once was home to a diverse marine ecosystem. The fossilized skull of the new species, named Ozarcus mapesae, along with similar specimens from the same location, were part of a recent donation of 540,000 fossils from Ohio University to the Museum.

The heads of all fishes — sharks included — are segmented into the jaws and a series of arches that support the jaw and the gills. These arches are thought to have given rise to jaws early in the tree of life.

Because shark skeletons are made of cartilage, not bone, their fossils are very fragile and are usually found in flattened fragments, making it impossible to study the shape of these internal structures. But the Ozarcus mapesae specimen was preserved in a nearly three-dimensional state, giving researchers a rare glimpse at the organization of the arches in a prehistoric animal.

“This beautiful fossil offers one of the first complete looks at all of the gill arches and associated structures in an early shark. There are other shark fossils like this in existence, but this is the oldest one in which you can see everything,” said John Maisey, a curator in the Museum’s Division of Paleontology and one of the authors on the study. “There’s enough depth in this fossil to allow us to scan it and digitally dissect out the cartilage skeleton.”

Working with scientists at the European Synchrotron, the ESRF, Pradel imaged the specimen with high-resolution x-rays to get a detailed view of each individual arch shape and organization. “We discovered that the arrangement of the arches is not like anything you’d see in a modern shark or shark-like fish,” said Pradel. “Instead, the arrangement is fundamentally the same as bony fishes.”

The authors say it’s not unexpected that sharks — which have existed for about 420 million years — would undergo evolution of these structures. But the new work, especially when considered alongside other recent developments about early jawed vertebrates, has significant implications for the future of evolutionary studies of this group. “Bony fishes might have more to tell us about our first jawed ancestors than do living sharks,” Maisey said.

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

Earliest ancestor of land herbivores discovered

April 17, 2014

The smallest and largest caseid: this is a reconstruction of 300-million-year-old tiny carnivorous Eocasea in the footprint of 270-million-year-old largest known herbivore of its time, Cotylorhynchus. Credit: Artwork by Danielle Dufault

New research from the University of Toronto Mississauga demonstrates how carnivores transitioned into herbivores for the first time on land.

“The evolution of herbivory was revolutionary to life on land because it meant terrestrial vertebrates could directly access the vast resources provided by terrestrial plants,” says paleontologist Robert Reisz, a professor in the Department of Biology. “These herbivores in turn became a major food resource for large land predators.”

Previously unknown, the 300-million-year old fossilized juvenile skeleton of Eocasea martini is less than 20 cm long. Found in Kansas, it consists of a partial skull, most of the vertebral column, the pelvis and a hind limb.

By comparing the skeletal anatomy of related animals, Reisz and colleague Jörg Fröbisch of the Museum für Naturkunde and Humboldt-University in Berlin, discovered that Eocasea martini belonged to the caseid branch of the group Synapsid. This group, which includes early terrestrial herbivores and large top predators, ultimately evolved into modern living mammals.

Eocasea lived nearly 80 million years before the age of dinosaurs. “Eocasea is one of the oldest relatives of modern mammals and closes a gap of about 20 million years to the next youngest members of the caseid family,” says Fröbisch. “This shows that caseid synapsids were much more ancient than previously documented in the fossil record.”

It’s also the most primitive member and was carnivorous, feeding on insects and other small animals. Younger members were herbivorous, says Reisz, clear evidence that large terrestrial herbivores evolved from the group’s small, non-herbivorous members, such as Eocasea.

“Eocasea is the first animal to start the process that has resulted in a terrestrial ecosystem with many plant eaters supporting fewer and fewer top predators,” he says.

Interestingly, Reisz and Fröbisch also found that herbivory, the ability to digest and process high-fibre plant material such as leaves and shoots, was established not just in the lineage that includes Eocasea. It arose independently at least five times, including twice in reptiles.

“When the ability to feed on plants occurred after Eocasea, it seems as though a threshold was passed,” says Reisz. “Multiple groups kept re-evolving the same herbivorous traits.”

The five groups developed the novel ability to live off plants in staggered bursts with synapsids such as Eocasea preceding reptiles by nearly 30 million years. This shows that herbivory as a feeding strategy evolved first among distant relatives of mammals, instead of ancient reptiles — the branch that eventually gave rise to dinosaurs, birds, and modern reptiles.

The adoption of plant-eating also caused dramatic shifts in the size of early herbivores. When the team mapped the animals on an evolutionary tree, they found that four of the groups showed a tremendous increase in size during the Permian Period, at the end of the Paleozoic Era.

Caseids were the most extreme example of this size increase, says Reisz. The oldest member of the group, Eocasea, was very small, less than 2 kilograms as an adult, while the youngest, last member exceeded 500 kilograms.

Reisz says that the discovery of Eocasea creates questions even as it answers them. “One of the great mysteries to my mind is: why did herbivory not happen before and why did it happen independently in several lineages? That’s what’s fascinating about this event. It’s the first such occurrence, and it resulted in a colossal change in our terrestrial ecosystem.”

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

Crucial new information about how the ice ages came about

April 17, 2014

An international team of scientists has discovered new relationships between deep-sea temperature and ice-volume changes to provide crucial new information about how the ice ages came about.

Researchers from the University of Southampton, the National Oceanography Centre and the Australian National University developed a new method for determining sea-level and deep-sea temperature variability over the past 5.3 million years. It provides new insight into the climatic relationships that caused the development of major ice-age cycles during the past two million years.

The researchers found, for the first time, that the long-term trends in cooling and continental ice-volume cycles over the past 5.3 million years were not the same. In fact, for temperature the major step toward the ice ages that have characterised the past two to three million years was a cooling event at 2.7 million years ago, but for ice-volume the crucial step was the development of the first intense ice age at around 2.15 million years ago. Before these results, these were thought to have occurred together at about 2.5 million years ago.

The results are published in the scientific journal Nature.

Co-author Dr Gavin Foster, from Ocean and Earth Science at the University of Southampton, says: “Our work focused on the discovery of new relationships within the natural Earth system. In that sense, the observed decoupling of temperature and ice-volume changes provides crucial new information for our understanding of how the ice ages developed.

“However, there are wider implications too. For example, a more refined sea-level record over millions of years is commercially interesting because it allows a better understanding of coastal sediment sequences that are relevant to the petroleum industry. Our record is also of interest to climate policy developments, because it opens the door to detailed comparisons between past atmospheric CO2 concentrations, global temperatures, and sea levels, which has enormous value to long-term future climate projections.”

The team used records of oxygen isotope ratios (which provide a record of ancient water temperature) from microscopic plankton fossils recovered from the Mediterranean Sea, spanning the last 5.3 million years. This is a particularly useful region because the oxygen isotopic composition of the seawater is largely determined by the flow of water through the Strait of Gibraltar, which in turn is sensitive to changes in global sea level — in a way like the pinching of a hosepipe.

As continental ice sheets grew during the ice ages, flow through the Strait of Gibraltar was reduced, causing measurable increases in the oxygen isotope O-18 (8 protons and 10 neutrons) relative to O-16 (8 protons and 8 neutrons) in Mediterranean waters, which became preserved in the shells of the ancient plankton. Using long drill cores and uplifted sections of sea-floor sediments, previous work had analysed such microfossil-based oxygen isotope records from carefully dated sequences.

The current study added a numerical model for calculating water exchange through the Strait of Gibraltar as a function of sea-level change, which allowed the microfossil records to be used as a sensitive recorder of global sea-level changes. The new sea-level record was then used in combination with existing deep-sea oxygen isotope records from the open ocean, to work out deep-sea temperature changes.

Lead author, Professor Eelco Rohling of Australian National University, says: “This is the first step for reconstructions from the Mediterranean records. Our previous work has developed and refined this technique for Red Sea records, but in that location it is restricted to the last half a million years because there are no longer drill cores. In the Mediterranean, we could take it down all the way to 5.3 million years ago. There are uncertainties involved, so we included wide-ranging assessments of these, as well as pointers to the most promising avenues for improvement. This work lays the foundation for a concentrated effort toward refining and improving the new sea-level record.”

Noting the importance of the Strait of Gibraltar to the analysis, co-author Dr Mark Tamisiea from the National Oceanography Centre, Southampton adds: “Flow through the Strait will depend not only on the ocean’s volume, but also on how the land in the region moves up and down in response to the changing water levels. We use a global model of changes in the ocean and the ice sheets to estimate the deformation and gravity changes in the region, and how that will affect our estimate of global sea-level change.”

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

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