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  • richardmitnick 1:19 pm on February 2, 2017 Permalink | Reply
    Tags: , , Meteorites, Primitive achondrites,   

    From U Chicago: “Today’s rare meteorites were common 466 million years ago, study finds” 

    U Chicago bloc

    University of Chicago

    January 26, 2017
    Kate Golembiewski

    Artist’s rendering of the space collision 466 million years ago that gave rise to many of the meteorites falling to Earth today.
    Illustration by Don Davis/Southwest Research Institute

    About 466 million years ago, there was a giant collision in outer space. Something hit an asteroid and broke it apart, sending chunks of rock falling to Earth as meteorites. But what kinds of meteorites were making their way to Earth before that collision?

    In a study published Jan. 23 in Nature Astronomy, scientists tackled that question by creating the first reconstruction of the distribution of meteorite types before the collision. They discovered that most of the meteorites falling to Earth today are rare, while many meteorites that are rare today were common before the collision.

    “We found that the meteorite flux—the variety of meteorites falling to Earth—was very, very different from what we see today,” said Philipp Heck, associate professor of geophysical sciences at the University of Chicago, the paper’s lead author. “Looking at the kinds of meteorites that have fallen to Earth in the last hundred million years doesn’t give you a full picture. It would be like looking outside on a snowy day and concluding that every day is snowy, even though it’s not snowy in the summer.”

    Meteorites are pieces of rock that have fallen to Earth from outer space. They’re formed from the debris of collisions between bodies like asteroids, moons and even planets. There are many different types of meteorites, which reflect the different compositions of their parent bodies. By studying the different meteorites that have made their way to Earth, scientists can develop a better understanding of how the basic building blocks of the solar system formed and evolved.

    “Before this study, we knew almost nothing about the meteorite flux to Earth in geological deep time,” said co-author Birger Schmitz, professor of nuclear physics at Lund University. “The conventional view is that the solar system has been very stable over the past 500 million years. So it is quite surprising that the meteorite flux at 467 million years ago was so different from (that of) the present.”

    To learn what the meteorite flux was like before the big collision event, Heck and his colleagues analyzed meteorites that fell more than 466 million years ago. Such finds are rare, but the team was able to look at micrometeorites—tiny specks of space-rock less than 2 millimeters in diameter that fell to Earth. They are less rare. Heck’s Swedish and Russian colleagues retrieved samples of rock from an ancient seafloor exposed in a Russian river valley that contained micrometeorites. They then dissolved almost 600 pounds of the rocks in acid so that only microscopic chromite crystals remained.

    Not having changed during hundreds of millions of years, the crystals revealed the nature of meteorites over time. Analysis of their chemical makeup showed that the meteorites and micrometeorites that fell earlier than 466 million years ago are different from the ones that have fallen since. A full 34 percent of the pre-collision meteorites belong to a meteorite type called primitive achondrites; today, only 0.45 percent of the meteorites that land on Earth are this type.

    Other micrometeorites sampled turned out to be relics from Vesta—the brightest asteroid visible from Earth, which underwent its own collision event over a billion years ago.

    Meteorite delivery from the asteroid belt to the Earth is a little like observing landslides started at different times on a mountainside, said co-author William Bottke, senior research scientist at the Southwest Research Institute. “Today, the rocks reaching the bottom of the mountain might be dominated by a few recent landslides. Going back in time, however, older landslides should be more important. The same is true for asteroid breakup events; some younger ones dominate the current meteorite flux, while in the past older ones dominated.”

    “Knowing more about the different kinds of meteorites that have fallen over time gives us a better understanding of how the asteroid belt evolved and how different collisions happened,” said Heck, an associate curator of meteoritics and polar studies at the Field Museum of Natural History. “Ultimately, we want to study more windows in time, not just the area before and after this collision. That will deepen our knowledge of how different bodies in our solar system formed and interact with each other.”

    Funding: European Research Council and Tawani Foundation

    See the full article here .

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  • richardmitnick 3:32 pm on September 2, 2016 Permalink | Reply
    Tags: , , , , Meteorites, Phosphorous, , Schreibersite   

    From astrobio.net via SETI: “Did meteorites bring life’s phosphorus to Earth?” 

    Astrobiology Magazine

    Astrobiology Magazine

    Aug 30, 2016
    Keith Cooper

    An artist’s impression of meteors crashing into water on the young Earth. Did they bring phosphorous with them? Image credit: David A Aguilar (CfA)

    Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life. The meteorites are believed to have contained a phosphorus-bearing mineral called schreibersite, and scientists have recently developed a synthetic version that reacts chemically with organic molecules, showing its potential as a nutrient for life.

    Phosphorus is one of life’s most vital components, but often goes unheralded. It helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP).

    Yet the majority of phosphorus on Earth is found in the form of inert phosphates that are insoluble in water and are generally unable to react with organic molecules. This appears at odds with phosphorus’ ubiquity in biochemistry, so how did phosphorus end up being critical to life?

    In 2004, Matthew Pasek, an astrobiologist and geochemist from the University of South Florida, developed the idea that schreibersite [(Fe, Ni)3P], which is found in a range of meteorites from chondrites to stony–iron pallasites, could be the original source of life’s phosphorus. Because the phosphorus within schreibersite is a phosphide, which is a compound containing a phosphorus ion bonded to a metal, it behaves in a more reactive fashion than the phosphate typically found on Earth.

    Finding naturally-formed schreibersite to use in laboratory experiments can be time consuming when harvesting from newly-fallen meteorites and expensive when buying from private collectors. Instead, it has become easier to produce schreibersite synthetically for use in the laboratory.

    Natural schreibersite is an alloy of iron, phosphorous and nickel, but the common form of synthetic schreibersite that has typically been used in experiments is made of just iron and phosphorus, and is easily obtainable as a natural byproduct of iron manufacturing. Previous experiments have indicated it reacts with organics to form chemical bonds with oxygen, the first step towards integrating phosphorous into biological systems.

    However, since natural schreibersite also incorporates nickel, some scientific criticism has pointed out that the nickel could potentially alter the chemistry of the mineral, rendering it non-reactive despite the presence phosphides. If this were the case it would mean that the experiments with the iron–phosphorous synthetic schreibersite would not represent the behavior of the mineral in nature.

    Since the natural version incorporates nickel, there has always been the worry that the synthetic version is not representative of how schreibersite actually reacts and that the nickel might somehow hamper those chemical reactions.

    “There was always this criticism that if we did include nickel it might not react as much,” says Pasek.

    Pasek and his colleagues have addressed this criticism by developing a synthetic form of schreibersite that includes nickel.

    This 15cm wide fragment of the Seymchan meteorite found in Russia in 1967 is an iron-nickel pallasite. The long filament of dark grey material in the center is schreibersite. Image credit: University of South Florida.

    Nickel-flavored schreibersite

    In a recent paper published in the journal Physical Chemistry Chemical Physics, Pasek and lead author and geochemist Nikita La Cruz of the University of Michigan show how a form of synthetic schreibersite that includes nickel reacts when exposed to water. As the water evaporates, it creates phosphorus–oxygen (P–O) bonds on the surface of the schreibersite, making the phosphorus bioavailable to life. The findings seem to remove any doubts as to whether meteoritic schreibersite could stimulate organic reactions.

    “Biological systems have a phosphorus atom surrounded by four oxygen atoms, so the first step is to put one oxygen atom and one phosphorous atom together in a single P–O bond,” Pasek explains.

    Terry Kee, a geochemist at the University of Leeds and president of the Astrobiology Society of Britain, has conducted his own extensive work with schreibersite and, along with Pasek, is one of the original champions of the idea that it could be the source of life’s phosphorus.

    “The bottom line of what [La Cruz and Pasek] have done is that it appears that this form of nickel-flavored synthetic schreibersite reacts pretty much the same as the previous synthetic form of schreibersite,” he says.

    This puts to rest any criticism that previous experiments lacked nickel.

    A bubbling hydrothermal pool in the Mývatn area of Iceland. Could such pools have pro-moted P–O bonds on the surfaces of schreibersite meteorites that had fallen into the pools? Image credit: Keith Cooper

    Shallow pools and volcanic vents

    Pasek describes how meteors would have fallen into shallow pools of water on ancient Earth. The pools would then have undergone cycles of evaporation and rehydration, a crucial process for chemical reactions to take place. As the surface of the schreibersite dries, it allows molecules to join into longer chains. Then, when the water returns, these chains become mobile, bumping into other chains. When the pool dries out again, the chains bond and build ever larger structures.

    “The reactions need to lose water in some way in order to build the molecules that make up life,” says Pasek. “If you have a long enough system with enough complex organics then, hypothetically, you could build longer and longer polymers to make bigger pieces of RNA. The idea is that at some point you might have enough RNA to begin to catalyze other reactions, starting a chain reaction that builds up to some sort of primitive biochemistry, but there’s still a lot of steps we don’t understand.”

    Demonstrating that nickel-flavored schreibersite, of the sort contained in meteorites, can produce phosphorus-based chemistry is exciting. However, Kee says further evidence is needed to show that the raw materials of life on Earth came from space.

    “I wouldn’t necessarily say that the meteoric origin of phosphorus is the strongest idea,” he says. “Although it’s certainly one of the more pre-biotically plausible routes.”

    Despite having co-developed much of the theory behind schreibersite with Pasek, Kee points out that hydrothermal vents could rival the meteoritic model. Deep sea volcanic vents are already known to produce iron-nickel alloys such as awaruite and Kee says that the search is now on for the existence of awaruite’s phosphide equivalent in the vents: schreibersite.

    “If it could be shown that schreibersite can be produced in the conditions found in vents — and I think those conditions are highly conducive to forming schreibersite — then you’ve got the potential for a lot of interesting phosphorylation chemistry to take place,” says Kee.

    Pasek agrees that hydrothermal vents could prove a good environment to promote phosphorus chemistry with the heat driving off the water to allow the P–O bonds to form. “Essentially it’s this driving off of water that you’ve got to look for,” he adds.

    Pasek and Kee both agree that it is possible that both mechanisms — the meteorites in the shallow pools and the deep sea hydrothermal vents — could have been at work during the same time period and provided phosphorus for life on the young Earth.

    Meanwhile David Deamer, a biologist from the University of California, Santa Cruz, has gone one step further by merging the two models, describing schreibersite reacting in hydrothermal fields of bubbling shallow pools in volcanic locations similar to those found today in locations such as Iceland or Yellowstone.

    Certainly, La Cruz and Pasek’s results indicate that schreibersite becomes more reactive the warmer the environment in which it exists.

    “Although we see the reaction occurring at room temperature, if you increase the temperature to 60 or 80 degree Celsius, you get increased reactivity,” says Pasek. “So, hypothetically, if you have a warmer Earth you should get more reactivity.”

    One twist to the tale is the possibility that phosphorus could have bonded with oxygen in space, beginning the construction of life’s molecules before ever reaching Earth. Schreibersite-rich grains coated in ice and then heated by shocks in planet-forming disks of gas and dust could potentially have provided conditions suitable for simple biochemistry. While Pasek agrees in principle, he says he has “a hard time seeing bigger things like RNA or DNA forming in space without fluid to promote them.”

    See the full article here .

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  • richardmitnick 10:27 am on August 29, 2016 Permalink | Reply
    Tags: Meteorites,   

    From TUM: “Meteorite Impact on a Nano Scale” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    Prof. Friedrich Aumayr
    Institute of Applied Physics
    TU Wien
    Wiedner Hauptstraße 8-10, 1040 Wien
    T: +43-1-58801-13430

    Dipl.-Ing. Elisabeth Gruber
    Institute of Applied Physics
    TU Wien
    Wiedner Hauptstraße 8-10, 1040 Wien
    T: +43-1-58801-13435

    Elisabeth Gruber in the lab at TU Wien

    Nanostructures on a crystal after ion bombardment: Trenches with nanohillocks on either side are created. At the impact site, a particularly large nanohillock is formed.

    Intricate nanostructures can be created on crystal surfaces by hitting them with high energy ions. Scientists from TU Wien (Vienna) can now explain these remarkable phenomena.

    A meteorite impacting the earth under a grazing angle of incidence can do a lot of damage; it may travel a long way, carving a trench into the ground until it finally penetrates the surface. The impact site may be vaporized, there can be large areas of molten ground. All that remains is a crater, some debris, and an extensive trail of devastation on both sides of the impact site.

    Hitting a surface with high-energy, heavy ions has quite similar effects – only on a much smaller scale. At TU Wien (Vienna), Prof. Friedrich Aumayr and his team have been studying the microscopic structures which are formed when ions are fired at crystals at oblique angles of incidence.

    Trenches and Ridges

    “When we take a look at the crystal surface with an atomic force microscope, we can clearly see the similarities between ion impacts and meteorite impacts”, says Elisabeth Gruber, PhD-student in Friedrich Aumayrs team. “At first the projectile, scratching across the surface at a grazing angle, digs a trench into the crystal surface, which can be hundreds of nanometers long. Extensive ridges appear on either side of the trench, consisting of tiny structures called nanohillocks.” When the projectile ultimately enters the crystal and disappears, an especially large hillock is created at the impact site. Beyond that, the ion keeps moving below the surface, until it finally comes to a halt.

    This may sound simple and obvious, as if high energy ions just behaved like tiny, electrically charged bullets. But in fact, it is not at all self-evident that objects on a nano scale behave like macroscopic objects do. When atoms exchange energy, quantum physics always plays an important role.

    “When the high-energy ions interact with crystal surfaces – calcium fluoride, in our case – many different physical effects have to be taken into account”, says Friedrich Aumayr. “Electrons can change their energy state, they can exchange energy with atoms around them and excite vibrations in the crystal lattice, the so-called phonons. We have to carefully consider all these effects when we want to understand how the nanostructures on the crystal surface are created.”

    Melting and Evaporation

    In order to understand the mechanism leading to the nano-trenches and hillocks, the team developed extensive computer simulations, together with colleagues from Germany. “That way we can determine, how much different parts of the crystal surface are heated up”, says Elisabeth Gruber. “There are regions which become so hot that the material melts, at certain points it can even evaporate. When we know how large these regions are, we can predict very accurately what the nanostructures on the crystal surface will look like.”

    The goal of this line of research is not only to understand how tailored nanostructures can be created. It is also important to find out how different materials are harmed by heavy ion bombardment. “Calcium fluoride is often used as an insulator in semiconductor technology”, says Friedrich Aumayr. “We want our electronics to work, even under extreme conditions, for instance in a satellite which is exposed to cosmic radiation.” When the calcium fluoride layer is riddled with tiny holes, it can cause the device to short circuit and fail. Therefore, it is vital to understand the interaction of crystal surfaces and fast ions.

    Original publication:
    E. Gruber et al., Swift heavy ion irradiation of CaF2 – from grooves to hillocks in a single ion track 405001 Journal of Physics: Condensed Matter 28 (2016)

    See the full article here .

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    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

  • richardmitnick 9:51 am on October 17, 2015 Permalink | Reply
    Tags: , , Meteorites, Presolar grains,   

    From U Arizona: “Microscopic Findings, Astronomic Implications” 

    U Arizona bloc

    University of Arizona

    October 16, 2015
    Rebecca Peiffer NASA Space Grant Intern, University Relations – Communications

    The arrow points to a grain of magnetite preserved from an ancient star, discovered by UA researcher Tom Zega and a team of researchers. (Photo: Tom Zega and © AAS. Reproduced with permission.)

    Imagine that you could travel back in time four and a half billion years ago, when the solar system was still just a bunch of rocks and dust and gas mixing together. Imagine watching all those billions of years of history re-created in front of you.

    Now, imagine that scientists are working to reconstruct this history with objects found here on Earth.

    One of the scientists is Tom Zega, an assistant professor in the University of Arizona’s Lunar and Planetary Laboratory. He studies “presolar grains,” which are the remains of ancient stars preserved in meteorites.

    These grains contain clues for scientists looking to build a narrative about the nearby stars before the birth of the solar system. Considering the scale of the undertaking, it is surprising that the evidence found in these presolar grains is microscopic.

    Scientists find the grains in chunks of meteorite mostly made up of rocks that formed after the solar system’s creation.

    “Those of us that are interested in understanding stardust basically have to find needles in the haystack,” Zega says.

    The best samples of presolar grains come from meteorites found soon after their fall to Earth, so that any grains inside are not affected by rain or heat.

    To help find the needles, scientists employ some clever techniques.

    “We’ll take a chunk of a meteorite, we’ll boil it up in these harsh, nasty, aggressive acids, and then we’ll generate a residue,” Zega says.

    The process eliminates some of the excess meteorite and increases the chances of finding a presolar grain. The grains have endured millions of years of exposure to cosmic rays and maintained their original form, so some will withstand the acid and remain in the residue.

    Grains are only a few hundred nanometers wide. For context, a strand of human hair is 100,000 nanometers wide, and one nanometer is about half the width of a strand of DNA. To image the grains, scientists must use microscopes powerful enough to look at individual atoms.

    Through this procedure, Zega and a team of researchers discovered the first grain of magnetite with confirmed presolar origins and published their results in the Astrophysical Journal. From a sample only 650 nanometers wide, Zega estimated the size and chemical composition of its parent star, a star that inhabited this part of the galaxy before the solar system came into existence.

    Even the discovery of this grain was revealing. The chemical reaction that created the magnetite almost certainly required water vapor. This is one of the first experimental confirmations of water vapor around an ancient star.

    With the right approach, Zega says he believes presolar grains could even help construct a timeline for the history of our local part of the galaxy.

    “We know the galaxy itself is about 13 billion years old, and we know the solar system is four and a half billion years old, but there’s a lot of billions of years in between there for things to happen,” he says.

    If we could age-date these grains the way we age-date rocks on Earth, then we could start to document the astrophysical events that took place in this period. That’s one way studies of presolar grains can go beyond traditional observations through telescopes.

    With meteorites, researchers can do more than observe stardust — they can actually hold it in their hands.

    “It’s pretty amazing,” Zega says. “After 17 years in the field, I’m still fascinated by the fact that I can hold a piece of the solar system in my hand, and I can analyze it in the laboratory at the atomic level.”

    This excitement and curiosity inspires missions such as OSIRIS-REx, which aims to bring back samples of an asteroid for further study on Earth. For Zega and people in his field, that mission is like a dream come true.

    NASA Osiris -REx

    “Everything that didn’t go into forming the sun or the planets was left over in the form of asteroids and meteors and dust,” he says. “So you can think of that as a time capsule that’s just sitting out there, and if we could we’d fly out there and grab samples of it. We’d rewrite the books.”

    For the next step in his research, Zega would like to collect more samples of presolar grains and look at the trends among them.

    That could help answer some of the big questions in planetary science about the origin of the solar system. In particular, the grains offer an estimate for how many stars injected their matter into the early solar system — and what kind of stars they were.

    “It just remains to be seen as time progresses whether we can come up with answers to some of these questions,” Zega says, smiling. “But we keep asking them.”

    See the full article here .

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  • richardmitnick 12:45 pm on April 15, 2015 Permalink | Reply
    Tags: , , , Meteorites   

    From ANU: “Meteorites key to the story of Earth’s layers” 

    ANU Bloc

    Australian National University

    14 April 2015
    No Writer Credit

    Dr Yuri Amelin. Image: Stuart Hay

    A new analysis of the chemical make-up of meteorites has helped scientists work out when the Earth formed its layers.

    The research by an international team of scientists confirmed the Earth’s first crust had formed around 4.5 billion years ago.

    The team measured the amount of the rare elements hafnium and lutetium in the mineral zircon in a meteorite that originated early in the solar system.

    “Meteorites that contain zircons are rare. We had been looking for an old meteorite with large zircons, about 50 microns long, that contained enough hafnium for precise analysis,” said Dr Yuri Amelin, from The Australian National University (ANU) Research School of Earth Sciences.

    “By chance we found one for sale from a dealer. It was just what we wanted. We believe it originated from the asteroid Vesta, following a large impact that sent rock fragments on a course to Earth.”

    The heat and pressure in the Earth’s interior mixes the chemical composition of its layers over billions of years, as denser rocks sink and less dense minerals rise towards the surface, a process known as differentiation.

    Determining how and when the layers formed relies on knowing the composition of the original material that formed into the Earth, before differentiation, said Dr Amelin.

    “Meteorites are remnants of the original pool of material that formed all the planets,” he said.

    “But they have not had planetary-scale forces changing their composition throughout their five billion years orbiting the sun.”

    The team accurately measured the ratio of the isotopes hafnium-176 and hafnium-177 in the meteorite, to give a starting point for the Earth’s composition.

    The team were then able to compare the results with the oldest rocks on Earth, and found that the chemical composition had already been altered, proving that a crust had already formed on the surface of the Earth around 4.5 billion years ago.

    The research is published in Proceedings of the National Academy of Sciences.

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  • richardmitnick 5:34 am on January 22, 2015 Permalink | Reply
    Tags: , Meteorites,   

    From Science 2.0: “Hidden Magnetic Messages From Space Discovered” 

    Science 2.0 bloc

    Science 2.0

    January 21st 2015

    Geologists have discovered hidden magnetic messages from the early solar system in meteorites measured using the PEEM-Beamline at the BESSY II synchrotron located in The Helmholtz-Zentrum Berlin für Materialien und Energie (HZB).

    Bessy II Synchrotron
    BESSY II synchrotron

    The information captures the dying moments of the magnetic field during core solidification on a meteorite parent body, providing a sneak preview of the fate of Earth’s own magnetic field as its core continues to freeze.

    Meteorites were previously thought to have poor magnetic memories, with the magnetic signals they carry having been written and rewritten many times during their long journey to Earth. [Dr. Richard] Harrison, however, identified specific regions filled with nanoparticles that were magnetically extremely stable. These “tiny space magnets” retain a faithful record of the magnetic fields generated by the meteorite’s parent body. Harrison and his colleagues could map these tiny magnetic signals using circular polarized X-ray synchrotron radiation at BESSY II.

    The Pallasite meteorite, studied by Harrison, contains information about the early solar system. Image copyright Natural History Museum, London. Sample used from the Natural History Museum Meteorite Collection.

    Meteorites have witnessed a long and violent history; they are fragments of asteroids which formed in the early solar system, 4.5 billion years ago. Shortly after their formation, some asteroids were heated up by radioactive decay, causing them to melt and segregate into a liquid metal core surrounded by a solid rocky mantle. Convection of the liquid metal created magnetic fields, just as the liquid outer core of the Earth generates a magnetic field today. From time to time asteroids crash together and tiny fragments fall to Earth as meteorites, giving scientists the opportunity to study the properties of the magnetic fields that were generated billions of years ago. “They are like natural hard discs”, Dr. Richard Harrison believes. The geologist from the Department of Earth Sciences, University of Cambridge, UK, is searching for methods to decipher the information stored deep inside the space rocks. Now his new approach has yielded its first results.

    Until now it was not clear whether ancient magnetic signals could be retained by stony-iron meteorites at all. Large and highly mobile magnetic domains are found within the iron metal: these domains create huge magnetic signals but are easily overwritten by new events. The probability that these regions might contain useful information about early magnetic fields in the solar system is extremely low.

    But Harrison took a much closer look. At the PEEM-Beamline of BESSY II, Harrison and PhD student James Bryson found dramatic variation in magnetic properties as they went through the meteorite. They saw not only regions containing large, mobile magnetic domains, but also identified an unusual region called the cloudy zone containing thousands of tiny particles of tetrataenite, a super hard magnetic material. “These tiny particles, just 50 to 100 nanometers in diameter, hold on to their magnetic signal and don’t change. So it is only these very small regions of chaotic looking magnetization that contain the information we want”, Bryson concludes.

    The PEEM-Beamline offers X-rays with the specific energy and polarization needed to make sense of these magnetic signals. Since the absorption of the X-rays depends on the magnetization, the scientists could map the magnetic signals on the sample surface in ultrahigh resolution without changing them by the procedure. “The new technique we have developed is a way of analyzing these images to extract real information. So we can do for the first time paleomagnetic measurements of very small regions of these rocks, regions which are less than one micrometer in size. These are the highest resolution paleomagnetic measurements ever made”, Harrison points out.

    By spatially resolving the variations in magnetic signal across the cloudy zone, the team were able to reconstruct the history of magnetic activity on the meteorite parent body, and were even able to capture the moment when the core finished solidifying and the magnetic field shut down. These new measurements answer many open questions regarding the longevity and stability of magnetic activity on small bodies. Their observations, supported by computer simulations, demonstrate that the magnetic field was created by compositional, rather than thermal, convection – a result that changes our perspective on the way magnetic fields were generated during the early solar system and even provides a sneak preview of the fate of Earth’s own magnetic field as its core continues to freeze.

    Article: Long-lived magnetism from solidification-driven convection on the pallasite parent body, Nature on 22 January 2015. Source: Helmholtz-Zentrum Berlin für Materialien und Energie

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  • richardmitnick 3:09 pm on December 26, 2014 Permalink | Reply
    Tags: , , Meteorites   

    From ANL: “Earth’s most abundant mineral finally has a name” 

    News from Argonne National Laboratory

    December 11, 2014
    Tona Kunz

    An ancient meteorite and high-energy X-rays have helped scientists conclude a half century of effort to find, identify and characterize a mineral that makes up 38 percent of the Earth.

    And in doing so, a team of scientists led by Oliver Tschauner, a mineralogist at the University of Las Vegas, clarified the definition of the Earth’s most abundant mineral – a high-density form of magnesium iron silicate, now called Bridgmanite – and defined estimated constraint ranges for its formation. Their research was performed at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Argonne National Laboratory.

    The mineral was named after 1946 Nobel laureate and pioneer of high-pressure research Percy [Williams] Bridgman. The naming does more than fix a vexing gap in scientific lingo; it also will aid our understanding of the deep Earth.

    To determine the makeup of the inner layers of the Earth, scientists need to test materials under extreme pressure and temperatures. For decades, scientists have believed a dense perovskite structure makes up 38 percent of the Earth’s volume, and that the chemical and physical properties of Bridgmanite have a large influence on how elements and heat flow through the Earth’s mantle. But since the mineral failed to survive the trip to the surface, no one has been able to test and prove its existence – a requirement for getting a name by the International Mineralogical Association.

    Shock-compression that occurs in collisions of asteroid bodies in the solar system create the same hostile conditions of the deep Earth – roughly 2,100 degrees Celsius (3,800 degrees Farenheit) and pressures of about 240,000 times greater than sea-level air pressure. The shock occurs fast enough to inhibit the Bridgmanite breakdown that takes place when it comes under lower pressure, such as the Earth’s surface. Part of the debris from these collisions falls on Earth as meteorites, with the Bridgmanite “frozen” within a shock-melt vein. Previous tests on meteorites using transmission electron microscopy caused radiation damage to the samples and incomplete results.

    So the team decided to try a new tactic: non-destructive micro-focused X-rays for diffraction analysis and novel fast-readout area-detector techniques. Tschauner and his colleagues from Caltech and the GeoSoilEnviroCARS, a University of Chicago-operated X-ray beamline at the APS at Argonne National Laboratory, took advantage of the X-rays’ high energy, which gives them the ability to penetrate the meteorite, and their intense brilliance, which leaves little of the radiation behind to cause damage.

    The team examined a section of the highly shocked L-chondrite meteorite Tenham, which crashed in Australia in 1879. The GSECARS beamline was optimal for the study because it is one of the nation’s leading locations for conducting high-pressure research.

    Ordinary chondrite meteorite found in Queensland, Australia, 1879. On display in the Natural History Museum, London

    Bridgmanite grains are rare in the Tenhma meteorite, and they are smaller than 1 micrometer in diameter. Thus the team had to use a strongly focused beam and conduct highly spatially resolved diffraction mapping until an aggregate of Bridgmanite was identified and characterized by structural and compositional analysis.

    This first natural specimen of Bridgmanite came with some surprises: It contains an unexpectedly high amount of ferric iron, beyond that of synthetic samples. Natural Bridgmanite also contains much more sodium than most synthetic samples. Thus the crystal chemistry of natural Bridgmanite provides novel crystal chemical insights. This natural sample of Bridgmanite may serve as a complement to experimental studies of deep mantle rocks in the future.

    Prior to this study, knowledge about Bridgmanite’s properties has only been based on synthetic samples because it only remains stable below 660 kilometers (410 miles) depth at pressures of above 230 kbar (23 GPa). When it is brought out of the inner Earth, the lower pressures transform it back into less dense minerals. Some scientists believe that some inclusions on diamonds are the marks left by Bridgmanite that changed as the diamonds were unearthed.

    The team’s results were published in the November 28 issue of the journal Science as Discovery of bridgmanite, the most abundant mineral in Earth, in a shocked meteorite, by O. Tschauner at University of Nevada in Las Vegas, N.V.; C. Ma; J.R. Beckett; G.R. Rossman at California Institute of Technology in Pasadena, Calif.; C. Prescher; V.B. Prakapenka at University of Chicago in Chicago, IL.

    This research was funded by the U.S. Department of Energy, NASA, and NSF.

    See the full article here

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit http://science.energy.gov/user-facilities/basic-energy-sciences/.

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  • richardmitnick 8:53 am on December 18, 2014 Permalink | Reply
    Tags: , , ESA Space Situational Awareness, Meteorites   

    From ESA: “Preparing For an Asteroid Strike” 

    European Space Agency

    18 December 2014
    No Writer Credit

    ESA and national disaster response offices recently rehearsed how to react if a threatening space rock is ever discovered to be on a collision course with Earth.

    Last month, experts from ESA’s Space Situational Awareness (SSA) programme and Europe’s national disaster response organisations met for a two-day exercise on what to do if an asteroid is ever found to be heading our way.

    In ESA’s first-ever asteroid impact exercise, they went through a countdown to an impact, practising steps to be taken if near-Earth objects, or NEOs, of various sizes were detected.

    The exercise considered the threat from an imaginary, but plausible, asteroid, initially thought to range in size from 12 m to 38 m – spanning roughly the range between the 2013 Chelyabinsk airburst and the 1908 Tunguska event – and travelling at 12.5 km/s.

    Chelyabinsk asteroid trail

    1908 Tunguska event

    ESA Space Situational Awareness: detecting space hazards
    Near-Earth objects

    Teams were challenged to decide what should happen at five critical points in time, focused on 30, 26, 5 and 3 days before and 1 hour after impact.

    “There are a large number of variables to consider in predicting the effects and damage from any asteroid impact, making simulations such as these very complex,” says Detlef Koschny, head of NEO activities in the SSA office.

    “These include the size, mass, speed, composition and impact angle. Nonetheless, this shouldn’t stop Europe from developing a comprehensive set of measures that could be taken by national civil authorities, which can be general enough to accommodate a range of possible effects.

    “The first step is to study NEOs and their impact effects and understand the basic science.”

    Participants came from various departments and agencies of the ESA member states Germany and Switzerland, including Germany’s Federal Office of Civil Protection and Disaster Assista

    ESA’s Optical Ground Station (OGS) is 2400 m above sea level on the volcanic island of Tenerife.

    They studied questions such as: how should Europe react, who would need to know, which information would need to be distributed, and to whom?

    “For example, within about three days before a predicted impact, we’d likely have relatively good estimates of the mass, size, composition and impact location,” says Gerhard Drolshagen of ESA’s NEO team.

    “All of these directly affect the type of impact effects, amount of energy to be generated and hence potential reactions that civil authorities could take.”

    During the 2013 Chelyabinsk event, for instance, the asteroid, with a mass of about 12 000 tonnes and a size of 19 m, hit the upper atmosphere at a shallow angle and a speed of about 18.6 km/s, exploding with the energy of 480 kilotons of TNT at an altitude of 25–30 km.

    SSA-NEO Coordination Centre ESRIN

    While potentially a real hazard, no injuries due to falling fragments were reported. Instead, more than 1500 people were injured and 7300 buildings damaged by the intense overpressure generated by the shockwave at Earth’s surface.

    Many people were injured by shards of flying glass as they peered out of windows to see what was happening.

    “In such a case, an appropriate warning by civil authorities would include simply telling people to stay away from windows, and remain within the strongest portions of a building, such as the cellar, similar to standard practice during tornados in the USA,” says Gerhard.

    In a real strike, ESA’s role would be crucial. It will have to warn both civil protection authorities and decision-makers about the impact location and time. It would also have to share reliable scientific data, including possible impact effects, and provide trustworthy and authoritative information.

    The exercise ended on 25 November, a significant step forward at highlighting the unique factors in emergency planning for asteroid strikes, and possible courses of action. It also clarified a number of open points, including requirements from civil protection agencies and the type and time sequence of information that can be provided by ESA’s SSA.

    It is another step in the continuing effort to set up an internationally coordinated procedure for information distribution and potential mitigation actions in case of an imminent threat.

    ESA’s NEO team is also working with international partners, agencies and organisations, including the UN, to help coordinate a global response to any future impact threat (see “Getting ready for asteroids”).

    With the aim of strengthening ESA’s and Europe’s response, similar exercises will be held in the future. The next, in 2015, will include representatives from additional countries.

    See the full article here.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:01 pm on December 10, 2014 Permalink | Reply
    Tags: , , , , Meteorites,   

    From SPACE.com: “Space Diamonds in Gold Country: California Meteorite’s Secrets Revealed” 

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    December 10, 2014
    Elizabeth Howell

    A meteorite that crashed down in California’s gold country is showing off treasures of a different sort: small diamonds that could tell scientists more about the insides of asteroids.

    The Sutter’s Mill meteorite smashed into the ground on April 22, 2012, after a fiery entry that caught the attention of professional and amateur observers alike. A scientific team raced against rain to pick up meteorite fragments before water polluted the samples. Their efforts helped to produce a cosmic jackpot.

    NASA Ames and SETI Institute meteor astronomer Peter Jenniskens collected fragments of the Sutter’s Mill meteorite fall on April 24, 2012, two days following the fall, the second recovered find.
    Credit: NASA Ames/Eric James

    Embedded in part of the meteorite were 10-micron diamond grains — much smaller than what is used in diamond rings. But their diminutive size is still bigger than what is usually found in meteorites. The finding hints at what could have existed in the parent cosmic body that eventually broke apart and produced the Sutter’s Mill meteoroid before the fragment slammed into Earth’s atmosphere.

    “Sutter’s Mill gives us a glimpse of what future NASA spacecraft may find when they bring back samples from a primitive asteroid,” lead researcher Peter Jenniskens, who holds dual affiliations at the SETI Institute and at NASA’s Ames Research Center, said in a statement. “From what falls naturally to the ground, much does not survive the violent collision with Earth’s atmosphere.”

    Sutter’s Mill Meteorite Composite Image
    A composite image showing how the Sutter’s Mill meteorite fell in California in April 2012.
    Credit: L. Warren; composite by P. Jenniskens/NASA Ames/SETI

    Diamonds weren’t all that researchers found. More fragments revealed isotopes of an element called chromium. The different types of chromium reveal that at least five stars sent material to the young solar system about 4.5 billion years ago, with some of the materials still sticking around in the meteorite, scientists found.

    “The formation of the solar system did not fully erase and homogenize these signatures, and Sutter’s Mill provides the clearest record yet,” Qing-Zhu Yin, the Sutter’s Mill Meteorite Consortium lead in isotope and trace element geochemistry, said in the same statement.

    Diamond Crystals in Sutter’s Mill Meteorite
    A secondary electron image revealing diamond crystals inside a fragment of a meteorite that fell in Sutter’s Mill, California.
    Credit: NASA Johnson/M. Zolensky

    The small body had a complicated history after that, with liquid water permeating some fragments (producing minerals such as calcium and magnesium carbonate). This could have been an indication of radiation in the meteorite’s parent body, which heated ice beyond the melting point.

    Other unusual elements — such as a calcium sulfide called oldhamite — also indicate heating in the parent body, as well as in areas that were not heated at all. Heating also came when the fragment was sailing on its own. Sometime in the past 100,000 years, the meteoroid was heated up to at least 572 degrees Fahrenheit (300 degrees Celsius). This heating could have happened during the entry into Earth’s atmosphere, the researchers said.

    “I don’t know of any similar meteorites that contain both heated and unheated materials,” said team member Mike Zolensky, a space scientist at NASA’s Johnson Space Center in Houston.

    The heated portions caused other changes inside the meteorite’s interior, such as the removal of volatile organic compounds. Scientists also managed to track down amino acids (protein building blocks) inside the meteorite.

    Thirteen papers based on the findings were recently published in the journal Meteoritics and Planetary Science.

    See the full article here.

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  • richardmitnick 12:35 pm on November 29, 2014 Permalink | Reply
    Tags: , , , , Meteorites,   

    From SPACE.com: “Space Rock Sheds Light on Mysterious Mineral on Earth” 

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    November 28, 2014
    Charles Q. Choi

    A rock from space is giving scientists the first glimpse of a mineral long thought to be the most abundant mineral on Earth, but which researchers lacked a natural sample of until now.

    A thin section of a Tenham meteorite reveals a vein of bridgmanite. Credit: Tschauner et al., 2014, Science/AAAS

    This discovery could shed light on the structure and dynamics of the inner Earth, as well as the early history of the solar system, according to the new paper.

    “The search for this mineral in meteorites has been going on for decades — it was just a matter of finding the right method for detecting it,” said lead study author Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas.

    The mineral is a high-density version of magnesium iron silicate. It is the most abundant mineral on Earth, and makes up about 38 percent of the planet’s volume. But it’s only stable at very high pressures and temperatures, so for decades, researchers had only seen lab-generated versions of it.

    Under the heat and pressure found in Earth’s lower mantle, which extends from about 410 to 1,615 miles (660 to 2,600 kilometers) below the planet’s surface, magnesium silicate can form what is called a perovskite structure, which can be imagined as an array of double pyramids that are joined at their corners. The centers of each pyramid are made of silicon, the apexes and corners are made of oxygen, and magnesium and iron reside in the spaces between each double pyramid.

    But scientists had not discovered a naturally occurring version of this mineral until now — the mineral would not survive the long journey from the lower mantle to Earth’s surface because it would readily transform into lower-density minerals.

    The fact that scientists had not found any specimens of magnesium iron silicate perovskite in nature also meant it could not get an official mineral name from the International Mineralogical Association. This presented geologists with the odd situation of a nameless mineral being the most abundant one on Earth.

    Since researchers could not find a naturally occurring version of magnesium iron silicate perovskite from Earth, they instead looked to space. They hypothesized that high-speed cosmic impacts could generate the pressures and temperatures needed to create this mineral, and samples of it could then come to Earth as meteorites knocked off their parent asteroids or planets.

    Recently, Tschauner and his colleagues carefully isolated magnesium iron silicate perovskite in a meteorite. The mineral was given has the official name of “bridgmanite,” after the father of high-pressure experiments, Nobel laureate Percy Bridgman, according to the report, published in the Nov. 28 issue of the journal Science.

    The researchers analyzed a Tenham meteorite, a rock that was part of a meteor shower that rained down on Australia on a spring night in 1879. This meteorite bore signs that it was part of an asteroid that experienced a great impact. The stone also possessed minerals called akimotoite and ringwoodite, which are similar in composition and origin to bridgmanite.

    In prior attempts to find bridgmanite in meteorites, researchers often used electron microscopes. However, this strategy involves probing the rocks with electron beams that can turn bridgmanite to glass. Instead, Tschauner and his colleagues used high-energy X-rays from a synchrotron, a kind of particle accelerator. These intense X-rays do little damage to bridgmanite, thus helping the scientists prove its composition and crystal structure.

    The researchers found that bridgmanite was higher in iron and sodium than they had expected based on synthetic samples. “This gives interesting insights for what might be going on in the lower mantle,” Tschauner said.

    Tschauner added that detecting bridgmanite in other meteorites could shed light on the strength of the impacts their parent bodies experienced. The pressures and durations of these impacts in turn “allow us to estimate the size of the parent bodies of these meteorites, and with enough data, we can, for given points in time in the solar system’s history, figure out how large bodies in the solar system were,” Tschauner said.

    See the full article here.

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