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  • richardmitnick 1:13 pm on April 13, 2018 Permalink | Reply
    Tags: A tiny bit of water ice known as ICE-VII inside several other deep diamonds, Diamonds, Diamonds and the bits of minerals gases and water encased in them offer a unique opportunity to probe the deepest regions of our planet, ICE-VII is a global phenomenon, Kimberlites, Lamproites, , Perovskite   

    From Many Worlds: “Diamonds are a Deep-Earth Geologist’s Best Friend” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2018-04-13
    Marc Kaufman

    1
    Deep Earth diamond with garnet inside. These inclusions, which occur during the diamond formation process, provide not only a way to date the diamonds, but also a window into conditions in deep Earth when they wee formed. (M. Gress, VU Amsterdam)

    We all know that cut diamonds sparkle and shine, one of the great aesthetic creations from nature.

    Less well known is that diamonds and the bits of minerals, gases and water encased in them offer a unique opportunity to probe the deepest regions of our planet.

    Thought to be some of the oldest available materials found on Earth — some dated at up to 3.5 billion years old — they crystallize at great depth and under great pressure.

    But from the point of view of those who study them, it’s the inclusions that loom large because allow them to know the age and depth of the diamond’s formation. And some think they can ultimately provide important clues to major scientific questions about the origin of water on Earth and even the origin of life.

    The strange and remarkable subterranean world where the diamonds are formed has, of course, never been visited, but has been intensively studied using a variety of indirect measurements. And this field has in recent weeks gotten some important discoveries based on those diamond inclusions.

    First is the identification by Fabrizio Nestola of the University of Padua and colleagues of mineral that has been theorized to be the fourth most common on Earth, yet had never been found in nature or successfully synthesized in a laboratory. As reported in the journal Nature, the mineral is a variant of calcium silicate (CaSiO3), created at a high pressure that gives it a uniquely deep-earth crystal structure called “perovskite,” which is the name of a mineral, too.

    Mineral science does not allow a specimen to be named until it has actually been found in name, and now this very common form of mineral finally will get a name. But more important, it moves forward our understanding of what happens far below the Earth’s surface.

    2
    Where diamonds are formed and found on Earth. The super-deep are produced very far into the mantle and are pushed up by volcanoes and convection The lithospheric diamonds are from the rigid upper mantle and crust and the alluvial diamonds are those which came to the surface and then were transported elsewhere by natural forces. (Fabrio Nestola, Joseph R Smyth)

    The additional discovery was of a tiny bit of water ice known as ICE-VII inside several other deep diamonds. While samples of H2O ice have been identified in diamonds before, none were ICE-VII which is formed only under tremendous deep-Earth pressure.

    In addition to being a first, the ICE-VII discovery adds to the growing confidence of scientists that much H2O remains deep underground, with some inferring as much deep subsurface water as found in the surface oceans. That paper was authored by University of Nevada, Las Vegas geoscientist Oliver Tschauner and colleagues, and appeared in the journal Science.

    Diamonds are a solid form of carbon with a distinctive cubic crystal structure. They are generally formed at depths of 100 to 150 miles in the Earth’s mantle, although a few have come from as deep as 500 to 600 miles down.

    Those super-deep diamonds form in a cauldron up to 1,000 degrees F and at 240,000 times the atmospheric pressure at sea level. They are made from carbon-containing fluids that dissolve minerals and replace them with what over time become diamonds.

    Much more recently (tens to hundreds of million years ago), the would have been pushed to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites (blue-tinged in color and coarse grained) and lamproites (rich in potassium and also from deep in the mantle.)

    The mantle – which makes up more than 80 percent of the Earth’s volume – is made of silicate minerals containing iron, aluminum, and calcium among others. Blue diamonds are that color because of the presence of the trace mineral boron in the mantle.

    And now we can add water the list as well.

    3
    Professor of Mineralogy Fabrizio Nestola while a visiting professor at the University of Alberta. One of his collaborators on the recent high-pressure calcium silicate paper is Alberta professor Graham Pearson. Here Nestola presented on his recent work in advances in X-ray crystallography on diamonds and their inclusions.

    Nestola, who has been conducting his deep-Earth studies with a major grant from the European Union, is eager to take his already substantial work much further.

    First he is looking for answers to the basic question of the origin of water on Earth (from incoming asteroids and comets or an integral component at formation) and ultimately to the origin of life. Diamonds, he says, offer a pathway to study both subjects.

    For water, his goal is to find a range of diamond-encircled samples that can be measured for their deuterium to hydrogen ratio — a key diagnostic to determining where in the solar system an object and its H2O originated, Deuterium, or heavy hydrogen, is an isotope of hydrogen with an extra neutron.

    4
    An example of a super-deep diamond from the Cullinan Mine, where scientists recently discovered a diamond that provides first evidence in nature of Earth’s fourth most abundant mineral–calcium silicate perovskite. (Petra Diamonds)

    As the number of diamond samples with evidence of water grows, Nestola says it will be possible to determine how the D/H ratio changes over time and as a result gain a better understanding of where the Earth’s water came from.

    When it comes to clues regarding the origin of life, Nestola will be looking for carbon isotopes in the diamonds.

    Regarding the high-pressure form of calcium silicate that he and his colleagues recently identified, Nestola said that many scientists have tried to reproduce it in their labs but have found there’s no way to keep the mineral stable at surface pressures. So the discovery had to be made from inside the nearly impermeable container of a diamond.

    The diamond that contained the common yet never before found mineral was just 0.031 millimeters across, is also a super-rare specimen.

    Adding to the interest in this discovery is that other trace minerals and elements found in the inclusion strongly suggest that the material was once on the Earth’s crust. The logic is that it would have been subducted as a function of plate tectonics billions of years ago, then encased in a forming diamond deep in the mantle, and ultimately sent back up near the surface again.

    Most diamonds are born much closer to Earth’s surface, between 93 and 124 miles deep. But this particular diamond would have formed at a depth of around 500 miles, the researchers said.
    “The diamond keeps the mineral at the pressure where it was formed, and so it tells us a lot about the ancient deep-Earth environment,” Nestola said. “This is how we’ll learn about deep Earth and ancient Earth. And we hope about those central origin questions too.”

    5
    A South African diamond crystal on kimberlite, an igneous rock formed deep in the mantle and famous for the frequency with which it contains diamonds. (Shutterstock)

    For his ICE-VII study, Tschauner used diamonds found in China, the Republic of South Africa, and Botswana that had been pushed up from inside Earth. He believes the range of locations strongly suggests that the presence of the ICE-VII is a global phenomenon.

    Scientists theorize the diamonds used in the study were born in the mantle under temperatures reaching more than 1,000-degrees Fahrenheit.

    “One essential question that we are working on is how much water is actually stored in the mantle. Is it oceans, or just a bit?” Tschauner said. “This work shows there can be free excess fluids in the mantle, which is important.”

    The mantle is a vast reservoir of mostly solid and very hot rock under immense pressure beneath the crust. It has an upper layer, a transition zone, and a lower layer. The upper layer has a little bit of water, but scientist estimate 10 times more water may be in the transition zone, where the enormous pressure is changing crystal structures and minerals seem to be more soluble. Minerals in the lower layer don’t seem to hold water as well.

    There’s already evidence of water in the mantle in different forms, such as water that has been broken up and incorporated into other minerals. But these diamonds contain water frozen into a special kind of ice crystal. There are lots of different ways water can crystallize into ice, but ice-VII is formed under higher pressures.

    While the diamond was forming, it must have encapsulated some liquid water from around the transition zone. The high temperatures prevented this water from crystalizing under the high pressures. As geologic activity moved the diamonds to the surface, they maintained the high pressures in their rigid crystal structures—but the temperature dropped. This would have caused the water to freeze into ice-VII.

    The discovery of Ice-VII in the diamonds is the first known natural occurrence of the aqueous fluid from the deep mantle. Ice-VII had been found as a solid in prior lab testing of materials under intense pressure. As described before, it begins as a liquid in the mantle.

    “These discoveries are important in understanding that water-rich regions in the Earth’s interior can play a role in the global water budget and the movement of heat-generating radioactive elements,” Tschauner said.

    This discovery can help scientists create new, more accurate models of what’s going on inside the Earth, specifically how and where heat is generated under the Earth’s crust.

    In other words: “It’s another piece of the puzzle in understanding how our planet works,” Tschauner said.

    6
    A polished and enlarged section of the Esquel pallasite meteoritemeteorite that delivered tiny nano-diamonds to Earth. This is a common occurrence, as there is believed to be substantial amounts of high-pressure carbon in the galaxies, and thus some diamonds. (Trustees of the NHM, London)

    Diamonds are by no means exclusive to Earth. Not only are they contained in minute form in meteorites, but atmospheric data for the gas giant planets indicates that carbon is abundant in its famous crystal form elsewhere in the solar system and no doubt beyond.

    Lightning storms turn methane into sooty carbon which, as it falls, hardens under great pressure into graphite and then diamond.

    These diamond “hail stones” eventually melt into a liquid sea in the planets’ hot cores, researchers told a an American Astronomical Society conference in 2013.

    The biggest diamonds would likely be about a centimeter in diameter – “big enough to put on a ring, although of course they would be uncut,” says Dr Kevin Baines, of the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory.

    “The bottom line is that 1,000 tons of diamonds a year are being created on Saturn. People ask me – how can you really tell? Because there’s no way you can go and observe it.

    “It all boils down to the chemistry. And we think we’re pretty certain.”

    These potential raining diamonds, and all sorts of other extraterrestrial diamonds including possible diamond worlds, doubtless have their own scientifically compelling and important stories to tell.

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 12:23 pm on January 1, 2018 Permalink | Reply
    Tags: , , , , Perovskite, , , Standardizing perovskite aging measurements   

    From EPFL: “Standardizing perovskite aging measurements” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne

    01.01.18
    Nik Papageorgiou


    EPFL scientists have produced a data-driven proposal for standardizing the measurements of perovskite solar cell stability and degradation. Published in Nature Energy, the work aims to create consensus in the field and overcome one of the major hurdles on the way to commercializing perovskite photovoltaics.

    1
    Perovskite (pronunciation: /pəˈrɒvskaɪt/) is a calcium titanium oxide mineral composed of calcium titanate (CaTiO3). It lends its name to the class of compounds which have the same type of crystal structure as CaTiO3 (XIIA2+VIB4+X2−3), known as the perovskite structure. Many different cations can be embedded in this structure, allowing for the development of diverse engineered materials.
    The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856). Perovskite’s notable crystal structure was first described by Victor Goldschmidt in 1926, in his work on tolerance factors. The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw. Wikipedia.

    2
    A schematic of a perovskite crystal structure. Clean Energy Institute – University of Washington

    Perovskite solar cells are an alternative to conventional silicon solar cells, and are poised to overtake the market with their high power-conversion efficiencies (over 22% now) and lower capital expenditure and manufacturing costs. But one of the greatest obstacles on this road is stability: to be commercially viable, perovskite solar cells must also be able to maintain their efficiency over time, meaning that they must not degrade significantly over 25 years of service.

    “As a first-order approximation, we are talking about stabilities of several years for the most stable perovskite solar cells,” says Konrad Domanksi, first author on the paper. “We still need an increase of an order of magnitude to reach the stabilities of silicon cells.”

    While research efforts are continuously made to improve perovskite stability, the community is hamstrung by the fact that there are no general standards by which scientists can measure the stability of perovskite solar cells. Consequently, the results coming in from different laboratories and companies cannot be easily compared to each other. And even though dedicated stability measurement standards have been developed for other photovoltaic technologies, they have to be adapted for perovskite solar cells, which show new types of behavior.

    Now, the labs of Michael Grätzel and Anders Hagfeldt at EPFL have carried out a study that proposes to standardize the measurements of perovskite solar cell stability across the entire field. The researchers investigated the effects of different environmental factors on the ageing of perovskite solar cells, looking at the impact of illumination (sunlight-level light), temperature, atmospheric, electrical load, and testing a systematic series of combinations of these.

    “We designed and built a dedicated system to carry out this study,” says Domanski. “It is state-of-the-art for measuring stability of solar cells – we can vary light intensity over samples and control temperature, atmosphere etc. We load the samples, program the experiments, and the data is plotted automatically.”

    The study shows how certain behaviors specific to perovskite solar cells can distort the results of experiments. For example, when the cells are left in the dark, they can recover some of the losses caused by illumination and “start fresh in the morning”. As solar cells naturally undergo day-night cycles, this has important implications on how we define that a solar cell degrades in the first place. It also changes our perception on the metrics used by industry to describe lifetime of solar cells.

    “The work can lay the foundations for standardizing perovskite solar cell ageing,” says Wolfgang Tress, last author on the paper. “The field can use it to develop objective and comparable stability metrics, just like stabilized power is now used as a standard tool for assessing power-conversion efficiency in perovskite solar cells. More importantly, systematically isolating specific degradation factors will help us better understand degradation of perovskite solar cells and improve their lifetimes.”

    “We are not trying to impose standards on the community,” says Domanski. “Rather, being on the forefront on perovskite solar cells and their stability research, we try to lead by example and stimulate the discussion on how these standards should look like. We strongly believe that specific protocols will be adopted by consensus, and that dedicated action groups involving a broad range of researchers will be formed for this purpose.”

    Funding

    Swiss National Science Foundation (FNS)
    King Abdulaziz City for Science and Technology (KACST)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
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