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  • richardmitnick 11:13 am on January 3, 2016 Permalink | Reply
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    From Nautilus: “Five Things We Still Don’t Know About Water” June 2015 but Important 



    June 11, 2015 [Just found this]
    Richard Saykally
    Illustration by Jackie Ferrentino

    Temp 1

    From steam to ice, water continues to mystify.

    “What could we not know about water? It’s wet! It’s clear. It comes from rain. It boils. It makes snow and it makes ice! Does our government actually spend taxpayer money for you to study water?”

    This excerpt is from one of the last conversations I had with my dear late mother, who passed away some seven years ago, still remarkably frugal at age 99. Her words reflect a view seemingly held by half the world’s population: Water is boring.

    The other half of the world, though, fanned by pseudoscience and new-age gurus, seems to buy into magical properties like homeopathy, structured water, polywater, and water memory.

    The truth lies somewhere in the middle. Yes, water is common—in fact, it is the third most common molecule in the universe. But, contrary to Mother’s views, it is also deceptively complex. Here are just a few of the scientific problems related to water that remain open today:

    1. How Many Kinds of Ice Are There?

    At latest count, there are 17 different crystalline forms of solid water. However, only one form—Ice Ih—exists commonly on Earth outside of the laboratory. A second crystalline form called Ice Ic is present in very minor amounts in the upper atmosphere, and another 15 forms occur only at very high pressures. (There is also a lot of water in interstellar space, but it is usually an amorphous, non-crystalline, glassy ice frozen onto dust grains.)

    The remarkable variety of crystalline ice forms results from the tetrahedral network of strong hydrogen bonds formed among neighboring water molecules.

    Regular Tetrahedron

    In the condensed phases of water, each molecule optimizes its hydrogen bonding capacity by forming four hydrogen bonds at near-tetrahedral angles. The hydrogen bonds inside Ice Ih form an open, three-dimensional structure with a low density.

    Big Ice: Liquid water (left) is composed of hydrogen (white) and oxygen (red) atoms arranged in a nearly tetrahedral structure. Common ice, or Ice Ih (right), shows a three-dimensional network that is less dense, explaining why ice floats on water.Wikimedia

    The application of pressure to tetrahedral substances, including crystalline ice, elemental carbon, silicon, and phosphorus, can collapse low-density solid forms into a variety of structures of sequentially higher density, presumably until the close-packed limit is reached. This produces the 17 forms of crystalline ice we have observed so far. Are there more to discover?

    2. Are There Two Kinds of Liquid Water?

    Several decades ago, Japanese scientists claimed to have observed transitions between two phases of amorphous ice under high pressure. Since we believe that amorphous ice is essentially a frozen snapshot of the corresponding liquid, this observation implied that two types of liquid water must exist: normal, low-density water, and a compact high-density form analogous to high-pressure amorphous ice.

    Subsequent simulations have supported this claim. They investigated water whose temperature was below freezing, but above its “homogeneous nucleation temperature” (the temperature below which liquid water cannot exist). In this so-called “deeply supercooled” region, scientists saw evidence for a phase transition between two liquid forms of water.

    However, other scientists argue that these results are artifacts, and that such transitions are unlikely to occur, based on principles of statistical mechanics. The fact that they occur so far away from equilibrium makes them difficult to observe and model—in fact, behavior far away from equilibrium is a current frontier of condensed matter theory.

    3. How Does Water Evaporate?

    The rate of evaporation of liquid water is one of the principal uncertainties in modern climate modeling. It determines the size distribution of water droplets in clouds, which, in turn, determines how clouds reflect, absorb, and scatter light.

    But the exact mechanism for how water evaporates isn’t completely understood. The evaporation rate is traditionally represented in terms of a rate of collision between molecules, multiplied by a fudge factor called the evaporation coefficient, which varies between zero and one. Experimental determination of this coefficient, spanning several decades, has varied over three orders of magnitude. Theoretical calculations have been hampered by the fact that evaporation is an extremely rare event, requiring prohibitively long and large computer simulations.

    Together with his colleagues, David Chandler, of the University of California, Berkeley, used a theory capable of describing such rare events, called transition path sampling, to calculate the water evaporation coefficient. They arrived at a value near one. This corresponds fairly well to recent liquid microjet experiments that produce a value of 0.6 for both normal water and heavy water.

    However, there are a couple of wrinkles. For one thing, it remains unclear why experiments performed under more atmospherically relevant conditions yield much lower values. Also, the transition path sampling simulations suggest that evaporation relies on an anomalously large capillary wave running along the liquid’s surface, which strains and weakens the hydrogen bonds holding on to an evaporating water molecule. The addition of salts to water raises the surface tension and suppresses the capillary wave amplitude, and so should reduce the evaporation rate. But experimental studies show little or no effect when salts are added.

    4. Is the Surface of Liquid Water Acidic or Basic?

    Temp 2
    Image Source: Unknown at http://www.tourist-destinations.net/2013/09/niagara-falls-canada.html


    There is something remarkable about the mist surrounding Niagara Falls: The individual droplets move as if they are negatively charged. The same is true for most waterfalls. This has long been interpreted as evidence for the accumulation of negative hydroxide (OH-) ions at the droplet surfaces, which would mean that the surfaces are basic—with a pH value greater than the 7 of neutral water. In fact, this thinking has become dogma within the community of colloid scientists.

    The surface of liquid water contains a larger number of broken hydrogen bonds, which produce a rather different chemical environment than that found in the bulk. But recent experiments and calculations suggest that hydrated protons (H+) actually dominate the liquid water surface, producing an acidic (less than 7) pH and a positively charged surface, rather than a basic, negatively charged surface.

    Many important processes in chemistry and biology, like atmospheric aerosol–gas exchanges, enzyme catalysis, and transmembrane proton transport, involve proton exchanges at the water surface, and explicitly depend on the pH at the water’s surface—a quantity which is currently unknown.

    5. Is Nanoconfined Water Different?

    Water isn’t always sloshing around in giant oceans. Both in nature and in man-made devices, water is often confined to unimaginably tiny spaces, like reverse micelles, carbon nanotubes, proton exchange membranes, and xerogels (which are highly porous glassy solids).

    Both experiment and calculation seem to indicate that water confined by solid walls to tiny regions of space, whose size is comparable to that of a few hundred molecules, begins to exhibit quantum mechanical effects, including delocalization and quantum coherence. These properties are strikingly different from those of bulk water, and could influence everything from biological cells to geological structures. It could be also be of considerable practical significance, for example in designing more efficient desalinization systems.

    Current results remain somewhat ambiguous, however, and more work in this area remains to be done in order to determine the nature of water under confinement.

    See the full article here .

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

  • richardmitnick 12:51 pm on December 19, 2015 Permalink | Reply
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    From Eos: “The Coming Blue Revolution” 

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    17 December 2015
    Kate Wheeling

    The dry lakebed visible at Australia’s Lake Hume is a stark reminder that water scarcity is one of modern societies’ most pressing challenges. Credit: Tim J Keegan, CC BY-SA 2.0

    Human civilizations have always sprouted up around bodies of water. We’ve created increasingly efficient infrastructures to harness and store the precious resource, reaching a scale so enormous that human activities now have a substantial impact on the global water cycle. Kumar provides a framework to integrate cross-disciplinary approaches to water scarcity in order to reveal innovative, holistic solutions.

    The water cycle is intimately linked with Earth’s carbon, nutrient, and energy cycles—all of which have been greatly impacted by human activities. The complexity of these interconnected systems ensures that any perturbation—for example, a forest fire, a catastrophic flood, or an extended drought—will have unpredictable consequences as it propagates through each cycle. Because these emergent responses are nearly impossible to plan for or protect against, they pose a great threat to humans

    “We are being called upon to address problems that are complex and messy because no clear pathways of solutions may exists, and often multiple solutions may present equally (un)satisfying outcomes,” the author writes. His integrated framework of the water cycle and humanity’s place in it, which he calls “hydrocomplexity,” aims to identify the best practices for addressing emergent threats against water security that come from climate change, increasing reliance on limited resources, and intensive land management and development.

    The author argues that in order to model how perturbations will propagate through the water, carbon, and nutrient cycles and generate various emergent responses, scientists need a comprehensive understanding of the processes at play in each of the interconnected cycles.

    He also suggests that hydrologic patterns will likely be revealed through the integration of models with a rapidly growing body of diverse observational records by computational systems that crunch large volumes of data.

    Finally, understanding how information flows through institutional networks and triggers human action will also provide insights toward developing effective solutions to water scarcity that people will actually adopt.

    Already, much of the world is dealing with an extreme and chronic shortage of freshwater; essentially, humans are using the resource faster than it can be replenished by the normal hydrologic cycle. The underlying idea of the author’s framework is that understanding our role in the complex water cycle is the first step toward managing inevitable water security challenges of the future. (Water Resources Research, doi:10.1002/2015WR017342, 2015)

    Citation: Wheeling, K. (2015), The coming blue revolution, Eos, 96, doi:10.1029/2015EO041535. Published on 17 December 2015.

    See the full article here .

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 10:10 pm on November 12, 2015 Permalink | Reply
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    From U Hawaii: “UH Researchers Shed New Light on the Origins of Earth’s Water” 

    U Hawaii

    University of Hawaii

    12 November 2015
    Dr. Lydia Hallis
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    Scanning electron microscope image of a Baffin Island picrite (type of basaltic rock). The mineral olivine, shown as abundant mid-gray color cracked grains (A), hosts glassy melt inclusions (B) containing tiny amounts of water sourced from Earth’s deep mantle. Image by Lydia J. Hallis.

    Water covers more than two-thirds of Earth’s surface, but its exact origins are still something of a mystery. Scientists have long been uncertain whether water was present at the formation of the planet, or if it arrived later, perhaps carried by comets and meteorites.

    Now researchers from the University of Hawaii at Manoa, using advanced ion-microprobe instrumentation, have found that rocks from Baffin Island in Canada contain evidence that Earth’s water was a part of our planet from the beginning. Their research is published in the 13 November issue of the journal Science.

    The research team was led by cosmochemist Dr. Lydia Hallis, then a postdoctoral fellow at the UH NASA Astrobiology Institute (UHNAI) and now Marie Curie Research Fellow at the University of Glasgow, Scotland.

    The ion microprobe allowed researchers to focus on minute pockets of glass inside these scientifically important rocks, and to detect the tiny amounts of water within. The ratio of hydrogen to deuterium in the water provided them with valuable new clues as to its origins.

    Hydrogen has an atomic mass of one, while deuterium, an isotope of hydrogen also known as “heavy hydrogen,” has an atomic mass of two. Scientists have discovered that water from different types of planetary bodies in our solar system have distinct hydrogen to deuterium ratios.

    Dr. Hallis explained, “The Baffin Island rocks were collected back in 1985, and scientists have had a lot of time to analyze them in the intervening years. As a result of their efforts, we know that they contain a component from Earth’s deep mantle.

    “On their way to the surface, these rocks were never affected by sedimentary input from crustal rocks, and previous research shows their source region has remained untouched since Earth’s formation. Essentially, they are some of the most primitive rocks we’ve ever found on Earth’s surface, and so the water they contain gives us an invaluable insight into Earth’s early history and where its water came from.

    “We found that the water had very little deuterium, which strongly suggests that it was not carried to Earth after it had formed and cooled. Instead, water molecules were likely carried on the dust that existed in a disk around our Sun before the planets formed. Over time this water-rich dust was slowly drawn together to form our planet.

    “Even though a good deal of water would have been lost at the surface through evaporation in the heat of the formation process, enough survived to form the world’s water.

    “It’s an exciting discovery, and one which we simply didn’t have the technology to make just a few years ago. We’re looking forward to further research in this area in the future.”

    The paper is entitled Evidence for primordial water in Earth’s deep mantle. UH co-authors are Dr. Gary Huss, Dr. Kazuhide Nagashima, Prof. G. Jeffrey Taylor, Prof. Mike Mottl, and Dr. Karen Meech.

    The research was funded by the University of Hawaii NASA Astrobiology Institute under Cooperative Agreement No. NNA09-DA77A.

    See the full article here .

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    The 10 UH campuses and educational centers on six Hawaiian Islands provide unique opportunities for both learning and recreation.

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  • richardmitnick 7:16 am on October 7, 2015 Permalink | Reply
    Tags: , , Pilbara in Australia, Water   

    From CSIRO: “New Pilbara water study to guide sustainable development” 

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    Commonwealth Scientific and Industrial Research Organisation

    7 October 2015

    A new study has delivered an unprecedented account of water resources in Western Australia’s Pilbara region, providing an in-depth understanding of local water systems and the potential impacts of climate change on water availability.

    Water discharging from fractured rock into a gorge in the Hamersley Range.

    The Pilbara Water Resource Assessment project, a $3.5 million partnership between CSIRO, BHP Billiton and the Government of Western Australian, will allow water managers and local industry to plan for future water use in an area rich in resources and environmental assets.

    “Knowing how the water systems operate right across the region, such as how groundwater is affected by rainfall and storm events, helps with the planning and management of local water use,” said CSIRO’s Dr Don McFarlane, the project leader.

    “By helping to put a lot of smaller local water resource investigations into a broader context, this study provides a strong framework for water managers and local industries well into the future.”

    BHP Billiton said its contribution to the project reflected the Company’s commitment to responsible and sustainable water use at its Pilbara-based iron ore operations.

    “The study provided an opportunity to discuss our regional water resource key considerations and highlight the areas requiring further investigation,” said Blair Douglas, BHP Billiton Iron Ore’s Water Practice Lead.

    “The collaboration between industry and scientists in both the state and federal governments has delivered a comprehensive outcome. The fundamental science delivered by the study can be applied by industry to achieve practical and sustainable water management solutions.”

    The study revealed some of the mechanisms responsible for filling the Pilbara’s groundwater stores. It found that between 8 and 30 millimetres of rainfall is required before runoff starts in most catchments, which leaks through streambeds to provide the main source of aquifer replenishment. Water from these shallow alluvial aquifers then recharges deeper paleochannels or dolomite aquifers, which can store large quantities of water in inland areas.

    It also examined how ecosystems dependent on the region’s groundwater sources have changed as a result of wet and dry periods, finding they expand during wet periods and contract during dry periods but have remained relatively stable in number over the past 23 years.

    The Assessment was funded by a $0.5 million contribution from BHP Billiton and $1.5 million each from CSIRO and the Government of Western Australia through the Royalties for Regions program. The research project was led by CSIRO and overseen by officers from the Department of Water, BHP Billiton, the Pilbara Development Commission and the Water Corporation.

    View the final assessment reports at Pilbara Water Resource Assessment.

    The pipeline that takes water to the West Pilbara Water Supply Scheme.

    Ashburton River near the North West Coastal Highway

    The four reporting regions for the Pilbara Water Resource Assessment.

    See the full article here .

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    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

  • richardmitnick 9:20 am on September 4, 2015 Permalink | Reply
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    From Rice: “Rice researchers demo solar water-splitting technology” 

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    Rice University

    September 4, 2015
    Jade Boyd

    Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.

    The technology, which is described online in the American Chemical Society journal Nano Letters, relies on a configuration of light-activated gold nanoparticles that harvest sunlight and transfer solar energy to highly excited electrons, which scientists sometimes refer to as “hot electrons.”

    Isabell Thomann

    “Hot electrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy,” said lead researcher Isabell Thomann, assistant professor of electrical and computer engineering and of chemistry and materials science and nanoengineering at Rice. “For example, most of the energy losses in today’s best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat.”

    Capturing these high-energy electrons before they cool could allow solar-energy providers to significantly increase their solar-to-electric power-conversion efficiencies and meet a national goal of reducing the cost of solar electricity.

    In the light-activated nanoparticles studied by Thomann and colleagues at Rice’s Laboratory for Nanophotonics (LANP), light is captured and converted into plasmons, waves of electrons that flow like a fluid across the metal surface of the nanoparticles. Plasmons are high-energy states that are short-lived, but researchers at Rice and elsewhere have found ways to capture plasmonic energy and convert it into useful heat or light. Plasmonic nanoparticles also offer one of the most promising means of harnessing the power of hot electrons, and LANP researchers have made progress toward that goal in several recent studies.

    Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules

    Thomann and her team, graduate students Hossein Robatjazi, Shah Mohammad Bahauddin and Chloe Doiron, created a system that uses the energy from hot electrons to split molecules of water into oxygen and hydrogen. That’s important because oxygen and hydrogen are the feedstocks for fuel cells, electrochemical devices that produce electricity cleanly and efficiently.

    To use the hot electrons, Thomann’s team first had to find a way to separate them from their corresponding “electron holes,” the low-energy states that the hot electrons vacated when they received their plasmonic jolt of energy. One reason hot electrons are so short-lived is that they have a strong tendency to release their newfound energy and revert to their low-energy state. The only way to avoid this is to engineer a system where the hot electrons and electron holes are rapidly separated from one another. The standard way for electrical engineers to do this is to drive the hot electrons over an energy barrier that acts like a one-way valve. Thomann said this approach has inherent inefficiencies, but it is attractive to engineers because it uses well-understood technology called Schottky barriers, a tried-and-true component of electrical engineering.

    “Because of the inherent inefficiencies, we wanted to find a new approach to the problem,” Thomann said. “We took an unconventional approach: Rather than driving off the hot electrons, we designed a system to carry away the electron holes. In effect, our setup acts like a sieve or a membrane. The holes can pass through, but the hot electrons cannot, so they are left available on the surface of the plasmonic nanoparticles.”

    Rice University researchers (clockwise from left) Chloe Doiron, Hossein Robatjazi, Shah Mohammad Bahauddin and Isabell Thomann.

    The setup features three layers of materials. The bottom layer is a thin sheet of shiny aluminum. This layer is covered with a thin coating of transparent nickel-oxide, and scattered atop this is a collection of plasmonic gold nanoparticles — puck-shaped disks about 10 to 30 nanometers in diameter.

    When sunlight hits the discs, either directly or as a reflection from the aluminum, the discs convert the light energy into hot electrons. The aluminum attracts the resulting electron holes and the nickel oxide allows these to pass while also acting as an impervious barrier to the hot electrons, which stay on gold. By laying the sheet of material flat and covering it with water, the researchers allowed the gold nanoparticles to act as catalysts for water splitting. In the current round of experiments, the researchers measured the photocurrent available for water splitting rather than directly measuring the evolved hydrogen and oxygen gases produced by splitting, but Thomann said the results warrant further study.

    “Utilizing hot electron solar water-splitting technologies we measured photocurrent efficiencies that were on par with considerably more complicated structures that also use more expensive components,” Thomann said. “We are confident that we can optimize our system to significantly improve upon the results we have already seen.”

    Robatjazi is a graduate student in electrical and computer engineering, Bahauddin is a graduate student in physics and astronomy and Doiron is a graduate student in applied physics. The research was supported by the Welch Foundation and a National Science Foundation CAREER Award.

    See the full article here.

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    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

  • richardmitnick 11:49 am on January 3, 2015 Permalink | Reply
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    From Carnegie: “Earth’s Water is Older than the Sun” 

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    Carnegie Institution of Washington

    September 25, 2014

    Water was crucial to the rise of life on Earth and is also important to evaluating the possibility of life on other planets. Identifying the original source of Earth’s water is key to understanding how life-fostering environments come into being and how likely they are to be found elsewhere. New work from a team including Carnegie’s Conel Alexander found that much of our Solar System’s water likely originated as ices that formed in interstellar space. Their work is published in Science.

    Water Through Time
    An illustration of water in our Solar System through time from before the Sun’s birth through the creation of the planets. The image is credited to Bill Saxton, NSF/AUI/NRAO.

    Water is found throughout our Solar System. Not just on Earth, but on icy comets and moons, and in the shadowed basins of Mercury. Water has been found included in mineral samples from meteorites, the Moon, and Mars.

    Comets and asteroids in particular, being primitive objects, provide a natural “time capsule” of the conditions during the early days of our Solar System. Their ices can tell scientists about the ice that encircled the Sun after its birth, the origin of which was an unanswered question until now.

    In its youth, the Sun was surrounded by a protoplanetary disk, the so-called solar nebula, from which the planets were born. But it was unclear to researchers whether the ice in this disk originated from the Sun’s own parental interstellar molecular cloud, from which it was created, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions taking place in the solar nebula.

    “Why this is important? If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars,” Alexander explained. “But if the early Solar System’s water was largely the result of local chemical processing during the Sun’s birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere.”

    In studying the history of our Solar System’s ices, the team—led by L. Ilsedore Cleeves from the University of Michigan—focused on hydrogen and its heavier isotope deuterium. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. The difference in masses between isotopes results in subtle differences in their behavior during chemical reactions. As a result, the ratio of hydrogen to deuterium in water molecules can tell scientists about the conditions under which the molecules formed.

    For example, interstellar water-ice has a high ratio of deuterium to hydrogen because of the very low temperatures at which it forms. Until now, it was unknown how much of this deuterium enrichment was removed by chemical processing during the Sun’s birth, or how much deuterium-rich water-ice the newborn Solar System was capable of producing on its own.

    So the team created models that simulated a protoplanetary disk in which all the deuterium from space ice has already been eliminated by chemical processing, and the system has to start over “from scratch” at producing ice with deuterium in it during a million-year period. They did this in order to see if the system can reach the ratios of deuterium to hydrogen that are found in meteorite samples, Earth’s ocean water, and “time capsule” comets. They found that it could not do so, which told them that at least some of the water in our own Solar System has an origin in interstellar space and pre-dates the birth of the Sun.

    “Our findings show that a significant fraction of our Solar System’s water, the most-fundamental ingredient to fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems,” Alexander said.

    See the full article here.

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    ndrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

  • richardmitnick 4:08 pm on September 25, 2014 Permalink | Reply
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    From SPACE.com: “Much of Earth’s Water Is Older Than the Sun” 

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    September 25, 2014
    Mike Wall

    Much of the water on Earth and elsewhere in the solar system likely predates the birth of the sun, a new study reports.

    Planets form in the presence of abundant interstellar water inherited as ices from the parent molecular cloud.
    Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)/ESO/J. Emerson/VISTA/Cambridge Astronomical Survey Unit

    The finding suggests that water is commonly incorporated into newly forming planets throughout the Milky Way galaxy and beyond, researchers said — good news for anyone hoping that Earth isn’t the only world to host life.

    “The implications of our study are that interstellar water-ice remarkably survived the incredibly violent process of stellar birth to then be incorporated into planetary bodies,” study lead author Ilse Cleeves, an astronomy Ph.D. student at the University of Michigan, told Space.com via email.

    “If our sun’s formation was typical, interstellar ices, including water, likely survive and are a common ingredient during the formation of all extrasolar systems,” Cleeves added. “This is particularly exciting given the number of confirmed extrasolar planetary systems to date — that they, too, had access to abundant, life-fostering water during their formation.”

    Astronomers have discovered nearly 2,000 exoplanets so far, and many billions likely lurk undetected in the depths of space. On average, every Milky Way star is thought to host at least one planet.

    Artist’s concept showing the time sequence of water ice, starting in the sun’s parent molecular cloud, traveling through the stages of star formation, and eventually being incorporated into the planetary system itself.
    Credit: Bill Saxton, NSF/AUI/NRAO

    Water, water everywhere

    Our solar system abounds with water. Oceans of it slosh about not only on Earth’s surface but also beneath the icy shells of Jupiter’s moon Europa and the Saturn satellite Enceladus. And water ice is found on Earth’s moon, on comets, at the Martian poles and even inside shadowed craters on Mercury, the planet closest to the sun.

    Cleeves and her colleagues wanted to know where all this water came from.

    “Why is this important? If water in the early solar system was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars,” study co-author Conel Alexander, of the Carnegie Institution for Science in Washington, D.C., said in a statement.

    “But if the early solar system’s water was largely the result of local chemical processing during the sun’s birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere,” Alexander added.

    Heavy and ‘normal’ water

    Not all water is “standard” H2O. Some water molecules contain deuterium, a heavy isotope of hydrogen that contains one proton and one neutron in its nucleus. (Isotopes are different versions of an element whose atoms have the same number of protons, but different numbers of neutrons. The most common hydrogen isotope, known as protium, for example, has one proton but no neutrons.)

    Because they have different masses, deuterium and protium behave differently during chemical reactions. Some environments are thus more conducive to the formation of “heavy” water — including super-cold places like interstellar space.

    The researchers constructed models that simulated reactions within a protoplanetary disk, in an effort to determine if processes during the early days of the solar system could have generated the concentrations of heavy water observed today in Earth’s oceans, cometary material and meteorite samples.

    The team reset deuterium levels to zero at the beginning of the simulations, then watched to see if enough deuterium-enriched ice could be produced within 1 million years — a standard lifetime for planet-forming disks.

    The answer was no. The results suggest that up to 30 to 50 percent of Earth’s ocean water and perhaps 60 to 100 percent of the water on comets originally formed in interstellar space, before the sun was born. (These are the high-end estimates generated by the simulations; the low-end estimates suggest that at least 7 percent of ocean water and at least 14 percent of comet water predates the sun.)

    While these findings, published online today (Sept. 25) in the journal Science, will doubtless be of interest to astrobiologists, they also resonated with Cleeves on a personal level, she said.

    “A significant fraction of Earth’s water is likely incredibly old, so old that it predates the Earth itself,” Cleeves said. “For me, uncovering these kinds of direct links between our daily experience and the galaxy at large is fascinating and puts a wonderful perspective on our place in the universe.”

    See the full article here.

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  • richardmitnick 8:45 am on August 21, 2014 Permalink | Reply
    Tags: , , , Water,   

    From Astrobiology: “Scientists Detect Evidence of ‘Oceans Worth’ of Water in Earth’s Mantle” 

    Astrobiology Magazine

    Astrobiology Magazine

    Aug 21, 2014
    Andrew Williams

    Researchers have found evidence of a potential “ocean’s worth” of water deep beneath the United States.

    Although not present in a familiar form, the building blocks of water are bound up in rock located deep in the Earth’s mantle, and in quantities large enough to represent the largest water reservoir on the planet, according to the research.

    For many years, scientists have attempted to establish exactly how much water may be cycling between the Earth’s surface and interior reservoirs through the action of plate tectonics. Northwestern University geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma around 400 miles beneath North America — a strong indicator of the presence of H₂O stored in the crystal structure of high-pressure minerals at these depths.

    “The total H₂O content of the planet has long been among the most poorly constrained ‘geochemical parameters’ in Earth science. Our study has found evidence for widespread hydration of the mantle transition zone,” says Jacobsen.

    For at least 20 years geologists have known from laboratory experiments that the Earth’s transition zone — a rocky layer of the Earth’s mantle located between the lower mantle and upper mantle, at depths between 250 and 410 miles — can, in theory, hold about 1 percent of its total weight as H₂O, bound up in minerals called wadsleyite and ringwoodite. However, as Schmandt explains, up until now it has been difficult to figure out whether that potential water reservoir is empty, as many have suggested, or not.

    If there does turn out to be a substantial amount of H₂O in the transition zone, then recent laboratory experiments conducted by Jacobsen indicate there should be large quantities of what he calls “partial melt” in areas where mantle flows downward out of the zone. This water-rich silicate melt is molten rock that occurs at grain boundaries between solid mineral crystals and may account for about 1 percent of the volume of rocks.

    Brandon Schmandt (University of New Mexico, left) and Steve Jacobsen (Northwestern University, right) combined seismic observations from the US-Array with laboratory experiments to detect dehydration melting of hydrous mantle material beneath North America at depths of 700-800 km. Credit: University of New Mexico/Northwestern University

    “Melting occurs because hydrated rocks are carried from the transition zone, where the rocks can hold lots of H₂O, downward into the lower mantle, where the rocks cannot hold as much H₂O. Melting is the way to get rid of the H₂O that won’t fit in the crystal structure present in the lower mantle,” says Jacobsen.

    He adds:

    “When a rock starts to melt, whatever H₂O is bound in the rock will go into the melt right away. So the melt would have much higher H₂O concentration than the remaining solid. We’re not sure how it got there. Maybe it’s been stuck there since early in Earth’s history or maybe it’s constantly being recycled by plate tectonics.”

    Seismic Waves

    Melt strongly affects the speed of seismic waves — the acoustic-like waves of energy that travel through the Earth’s layers as a result of an earthquake or explosion. This is because stiff rocks, like the silicate-rich ones present in the mantle, propagate seismic waves very quickly. According to Schmandt, if just a little melt — even 1 percent or less — is added between the crystal grains of such a rock it causes it to become less stiff, meaning that elastic waves propagate more slowly.

    “We were able to analyse seismic waves from earthquakes to look for melt in the mantle just beneath the transition zone,” says Schmandt.

    “What we found beneath the U.S. is consistent with partial melt being present in areas of downward flow out of the transition zone. Without the presence of H₂O, it is very difficult to explain melting at these depths. This is a good hint that the transition zone H₂O reservoir is not empty, and even if it’s only partially filled that could correspond to about the same mass of H₂O as in Earth’s oceans,” he adds.

    Jacobsen and Schmandt hope that their findings, published in the June issue of the journal Science, will help other scientists to understand how the Earth formed and what its current composition and inner workings are, as well as establish how much water is trapped in mantle rock.

    “I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades,” says Jacobsen

    Mantle Rock Studies

    The study combined Schmandt’s analysis of seismic data from the USArray, a network of over 2,000 seismometers across the U.S., with Jacobsen’s laboratory experiments, in which he examined the behaviour of mantle rock under conditions designed to simulate the high pressures and temperatures present at 400 miles below the Earth’s surface.

    Schematic representation of seismometers placed in the US-Array between 2004 and 2014 and used in the study by Schmandt and Jacobsen to detect dehydration melting at the top of the lower mantle beneath North America. Image Credit: NSF-Earthscope

    The USArray is part of Earthscope, a program sponsored by National Science Foundation. Jacobsen’s experiments were conducted at two Department of Energy. user facilities, the Advanced Photon Source of Argonne National Laboratory and the National Synchrotron Light Source at Brookhaven National Laboratory.

    Argonne APS
    APS at Argonne Lab

    Brookhaven NSLS
    NSLS at Brookhaven

    Taken as a whole, their findings produced strong evidence that melting may occur about 400 miles deep in the Earth, with H₂O stored in mantle rocks, such as those containing the mineral ringwoodite, which is likely to be a dominant mineral at those depths.

    Schmandt explains that he made this discovery after carrying out seismic imaging of the boundary between the transition zone and lower mantle. He found evidence that, in areas where “sharp transitions” like melt are present, some earthquake energy had converted from a compressional, or longitudinal wave, to a shear or S-wave. The phase of the converted S-waves in areas where the mantle is flowing down and out of the transition zone indicated a significantly lower velocity than surrounding mantle. The discovery suggests that water from the Earth’s surface can be driven to such great depths by plate tectonics, eventually resulting in the partial melting of the rocks found deep in the mantle.

    “We used many seismic wave conversions to see that many areas beneath the U.S. may have some melt just beneath the transition zone. The next step was comparing these areas to the areas where mantle flow models predict downward flow out of the transition zone,” says Schmandt.


    Schmandt and Jacobsen’s findings build on a discovery reported in March in the journal Nature in which scientists discovered a piece of the blue mineral ringwoodite inside a diamond brought up from a depth of 400 miles by a volcano in Brazil. That tiny piece of ringwoodite — the only sample we have from within the Earth — contained a surprising amount of water bound in solid form in the mineral.

    “Not only was this the first terrestrial ringwoodite ever seen — all other natural ringwoodite examples came from shocked meteorites — but the tiny inclusion of ringwoodite was also full of H₂O, to about 1.5 percent of total weight,” says Jacobsen. “This is about the maximum amount of water that we are able to put into ringwoodite in laboratory experiments.”

    Although the discovery provided direct evidence of water in the deep mantle at about 700 kilometers (434 miles) deep, the diamond sampled only one point of the mantle. Jacobsen explains that the paper expands the search to question how widespread hydration might be throughout the entire transition zone. This is important because the presence of H₂O in the large volumes of rock found at depths of between 410 to 660 kilometers (255 to 410 miles) would “significantly alter our understanding of the composition of the Earth.”

    Crystals of laboratory-grown hydrous ringwoodite, a high-pressure polymorph of olivine that is stable from about 520-660 km depth in the Earth’s mantle. The ringwoodite pictured here contains around one weight percent of H2O, similar to what was inferred in the seismic observations made by Schmandt and Jacobsen. Image Credit: Steve Jacobsen/Northwestern University

    Crystals of laboratory-grown hydrous ringwoodite, a high-pressure polymorph of olivine that is stable from about 520-660 km depth in the Earth’s mantle. The ringwoodite pictured here contains around one weight percent of H2O, similar to what was inferred in the seismic observations made by Schmandt and Jacobsen. Image Credit: Steve Jacobsen/Northwestern University

    “It would double or triple the known amount of H₂O in the bulk Earth. Just 1 to 2 percent H₂O by weight in the transition zone would be equivalent to 2 to 3 times the amount of H₂O in the oceans,” adds Jacobsen.

    Big Questions

    Looking ahead, Jacobsen admits that some big questions remain. For example, if the transition zone is full of H₂O, what does this tell us about the origin of Earth’s water? And is the presence of ringwoodite in a planet’s mantle necessary for a planet to retain enough original water to form oceans? Moreover, how is the H₂O in the transition zone connected to the surface reservoirs? Is the transition zone, if it contains a geochemical reservoir of H₂O larger than the oceans, somehow buffering the amount of liquid water on the Earth’s surface?

    “An analogy could be that of a sponge, which needs to be filled before liquid water can be supported on top. Was water in the transition zone added through plate tectonics early in Earth’s history, or did the oceans de-gas from the mantle until an equilibrium was reached between surface and interior reservoirs?” asks Jacobsen.

    Either way, the research is likely to be of strong interest to astrobiologists largely because water is often so closely linked to the formation of biological life. Remote geochemical analysis could be one way of detecting if such processes occur elsewhere in the universe, and it is likely that such analysis would involve the use of gamma-ray, neutron, and x-ray spectrometers of the type used by the NASA MESSENGER spacecraft for the remote geochemical mapping of Mercury.

    NASA Messenger satellite
    NASA Messenger

    “On other hard to reach planets it’s not practical to apply the type of seismic imaging that I used. So my guess is that geochemical analysis of volcanic rocks from other planetary bodies may be our best way to test whether volatiles are stored in the planet’s interior,” says Schmandt.

    See the full article here.


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  • richardmitnick 1:08 pm on June 18, 2014 Permalink | Reply
    Tags: , , Water   

    From SLAC Lab: “Scientists Take First Dip into Water’s Mysterious ‘No Man’s Land’” 

    SLAC Lab

    June 18, 2014
    Andy Freeberg, afreeberg@slac.stanford.edu, (650) 926-4359

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory have made the first structural observations of liquid water at temperatures down to minus 51 degrees Fahrenheit, within an elusive “no man’s land” where water’s strange properties are super-amplified.

    The research, made possible by SLAC’s Linac Coherent Light Source (LCLS) X-ray laser and reported June 18 in Nature, opens a new window for exploring liquid water in these exotic conditions, and promises to improve our understanding of its unique properties at the more natural temperatures and states that are relevant to global ocean currents, climate and biology.

    Scientists have known for some time that water can remain liquid at extremely cold temperatures, but they’ve never before been able to examine its molecular structure in this zone.

    “Water is not only essential for life as we know it, but it also has very strange properties compared to most other liquids,” said Anders Nilsson, deputy director of the SUNCAT Center for Interface Science and Catalysis, a joint SLAC/Stanford institute, and leader of the research. “Now, thanks to LCLS, we have finally been able to enter this cold zone that should provide new information about the unique nature of water.”

    Not Your Typical Liquid

    Despite its simple molecular structure, water has many weird traits: Its solid form is less dense than its liquid form, which is why ice floats; it can absorb a large amount of heat, which is carried long distances by ocean currents and has a profound impact on climate; and its peculiar density profile prevents oceans and lakes from freezing solid all the way to the bottom, allowing fish to survive the winter.

    These traits are amplified when purified water is supercooled. When water is very pure, with nothing to seed the formation of ice crystals, it can remain liquid at much lower temperatures than normal. The temperature range of water from about minus 42 to minus 172 degrees (see diagram) has been dubbed no man’s land. For decades scientists have sought to better explore what happens to water molecules at temperatures below minus 42 degrees, but they had to rely largely on theory and modeling.

    This diagram illustrates the rough boundaries of “no man’s land,” a temperature region where supercooled water is difficult to study because of rapid ice formation. Using SLAC’s Linac Coherent Light Source, scientists dipped down to minus 51 degrees Fahrenheit and made the first structural measurements of liquid water in this mysterious region, where water’s unusual properties are amplified. (Greg Stewart/SLAC, Ultrafast Chemical Physics Group/University of Glasgow, Scotland)

    Femtosecond Shutter Speeds

    Now the LCLS, with X-ray laser pulses just quadrillionths of a second long, allows researchers to capture rapid-fire snapshots showing the detailed molecular structure of water in this mysterious zone the instant before it freezes. The research showed that water’s molecular structure transforms continuously as it enters this realm, and with further cooling the structural changes accelerate more dramatically than theoretical models had predicted.

    For this experiment, researchers produced a steady flow of tiny water droplets in a vacuum chamber. As the drops traveled toward the laser beam, some of their liquid rapidly evaporated, supercooling the remaining liquid. (The same process cools us when we sweat.) By adjusting the distance the droplets traveled, the researchers were able to fine-tune the temperatures they reached on arrival at the X-ray laser beam.

    Colder Still

    Nilsson’s team hopes to dive to even colder temperatures where water morphs into a glassy, non-crystalline solid. They also want to determine whether supercooled water reaches a critical point where its unusual properties peak, and to pinpoint the temperature at which this occurs.

    “Our dream is to follow these dynamics as far as we can,” Nilsson said. “Eventually our understanding of what’s happening here in no man’s land will help us fundamentally understand water in all conditions.”

    Scientists at SLAC’s Linac Coherent Light Source, Stanford Synchrotron Radiation Lightsource and Stanford PULSE Institute; Stockholm University; Germany’s DESY laboratory; the Helmholtz Center for Materials and Energy in Germany; and Stony Brook University in New York also contributed to the research. The work was partially funded by the U.S. Department of Energy Office of Science, the SLAC Laboratory Directed Research and Development Program and the Swedish Research Council.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

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  • richardmitnick 12:48 pm on June 18, 2014 Permalink | Reply
    Tags: , , , , Water   

    From Princeton: “Familiar yet strange: Water’s ‘split personality’ revealed by computer model” 

    Princeton University
    Princeton University

    June 18, 2014
    Catherine Zandonella, Office of the Dean for Research

    Seemingly ordinary, water has quite puzzling behavior. Why, for example, does ice float when most liquids crystallize into dense solids that sink?

    Using a computer model to explore water as it freezes, a team at Princeton University has found that water’s weird behaviors may arise from a sort of split personality: at very cold temperatures and above a certain pressure, water may spontaneously split into two liquid forms.

    The team’s findings were reported in the journal Nature.

    “Our results suggest that at low enough temperatures water can coexist as two different liquid phases of different densities,” said Pablo Debenedetti, the Class of 1950 Professor in Engineering and Applied Science and Princeton’s dean for research, and a professor of chemical and biological engineering.

    The two forms coexist a bit like oil and vinegar in salad dressing, except that the water separates from itself rather than from a different liquid. “Some of the molecules want to go into one phase and some of them want to go into the other phase,” said Jeremy Palmer, a postdoctoral researcher in the Debenedetti lab.

    The finding that water has this dual nature, if it can be replicated in experiments, could lead to better understanding of how water behaves at the cold temperatures found in high-altitude clouds where liquid water can exist below the freezing point in a “supercooled” state before forming hail or snow, Debenedetti said. Understanding how water behaves in clouds could improve the predictive ability of current weather and climate models, he said.

    Pressure–temperature phase diagram, including an illustration of the liquid–liquid transition line proposed for several polyamorphous materials. This liquid–liquid phase transition would be a first order, discontinuous transition between low and high density liquids (labelled 1 and 2). This is analogous to polymorphism of crystalline materials, where different stable crystalline states (solid 1, 2 in diagram) of the same substance can exist (e.g. diamond and graphite are two polymorphs of carbon). Like the ordinary liquid–gas transition, the liquid–liquid transition is expected to end in a critical point. At temperatures beyond these critical points there is a continuous range of fluid states, i.e. the distinction between liquids and gasses is lost. If crystallisation is avoided the liquid–liquid transition can be extended into the metastable supercooled liquid regime.

    The new finding serves as evidence for the “liquid-liquid transition” hypothesis, first suggested in 1992 by Eugene Stanley and co-workers at Boston University and the subject of recent debate. The hypothesis states that the existence of two forms of water could explain many of water’s odd properties — not just floating ice but also water’s high capacity to absorb heat and the fact that water becomes more compressible as it gets colder.

    Princeton University researchers conducted computer simulations to explore what happens to water as it is cooled to temperatures below freezing and found that the supercooled liquid separated into two liquids with different densities. The finding agrees with a two-decade-old hypothesis to explain water’s peculiar behaviors, such as becoming more compressible and less dense as it is cooled. The X axis above indicates the range of crystallinity (Q6) from liquid water (less than 0.1) to ice (greater than 0.5) plotted against density (ρ) on the Y axis. The figure is a two-dimensional projection of water’s calculated “free energy surface,” a measure of the relative stability of different phases, with orange indicating high free energy and blue indicating low free energy. The two large circles in the orange region reveal a high-density liquid at 1.15 g/cm3 and low-density liquid at 0.90 g/cm3. The blue area represents cubic ice, which in this model forms at a density of about 0.88 g/cm3. (Image courtesy of Jeremy Palmer)

    At cold temperatures, the molecules in most liquids slow to a sedate pace, eventually settling into a dense and orderly solid that sinks if placed in liquid. Ice, however, floats in water due to the unusual behavior of its molecules, which as they get colder begin to push away from each other. The result is regions of lower density — that is, regions with fewer molecules crammed into a given volume — amid other regions of higher density. As the temperature falls further, the low-density regions win out, becoming so prevalent that they take over the mixture and freeze into a solid that is less dense than the original liquid.

    The work by the Princeton team suggests that these low-density and high-density regions are remnants of the two liquid phases that can coexist in a fragile, or “metastable” state, at very low temperatures and high pressures. “The existence of these two forms could provide a unifying theory for how water behaves at temperatures ranging from those we experience in everyday life all the way to the supercooled regime,” Palmer said.

    Since the proposal of the liquid-liquid transition hypothesis, researchers have argued over whether it really describes how water behaves. Experiments would settle the debate, but capturing the short-lived, two-liquid state at such cold temperatures and under pressure has proved challenging to accomplish in the lab.

    Instead, the Princeton researchers used supercomputers to simulate the behavior of water molecules — the two hydrogens and the oxygen that make up “H2O” — as the temperature dipped below the freezing point.

    The team used computer code to represent several hundred water molecules confined to a box, surrounded by an infinite number of similar boxes. As they lowered the temperature in this virtual world, the computer tracked how the molecules behaved.

    The team found that under certain conditions — about minus 45 degrees Celsius and about 2,400-times normal atmospheric pressure — the virtual water molecules separated into two liquids that differed in density.

    The pattern of molecules in each liquid also was different, Palmer said. Although most other liquids are a jumbled mix of molecules, water has a fair amount of order to it. The molecules link to their neighbors via hydrogen bonds, which form between the oxygen of one molecule and a hydrogen of another. These molecules can link — and later unlink — in a constantly changing network. On average, each H2O links to four other molecules in what is known as a tetrahedral arrangement.

    The researchers found that the molecules in the low-density liquid also contained tetrahedral order, but that the high-density liquid was different. “In the high-density liquid, a fifth neighbor molecule was trying to squeeze into the pattern,” Palmer said.

    Normal ice (left) contains water molecules linked into ring-like structures via hydrogen bonds (dashed blue lines) between the oxygen atoms (red beads) and hydrogen atoms (white beads) of neighboring molecules, with six water molecules per ring. Each water molecule in ice also has four neighbors that form a tetrahedron (right), with a center molecule linked via hydrogen bonds to four neighboring molecules. The green lines indicate the edges of the tetrahedron. Water molecules in liquid water form distorted tetrahedrons and ring structures that can contain more or less than six molecules per ring. (Image courtesy of Jeremy Palmer)

    The researchers also looked at another facet of the two liquids: the tendency of the water molecules to form rings via hydrogen bonds. Ice consists of six water molecules per ring. Calculations by Fausto Martelli, a postdoctoral research associate advised by Roberto Car, the Ralph W. *31 Dornte Professor in Chemistry, found that in this computer model the average number of molecules per ring decreased from about seven in the high-density liquid to just above six in the low-density liquid, but then climbed slightly before declining again to six molecules per ring as ice, suggesting that there is more to be discovered about how water molecules behave during supercooling.

    A better understanding of water’s behavior at supercooled temperatures could lead to improvements in modeling the effect of high-altitude clouds on climate, Debenedetti said. Because water droplets reflect and scatter the sunlight coming into the atmosphere, clouds play a role in whether the sun’s energy is reflected away from the planet or is able to enter the atmosphere and contribute to warming. Additionally, because water goes through a supercooled phase before forming hail or snow, such research may aid strategies for preventing ice from forming on airplane wings.

    “The research is a tour de force of computational physics and provides a splendid academic look at a very difficult problem and a scholarly controversy,” said C. Austen Angell, professor of chemistry and biochemistry at Arizona State University, who was not involved in the research. “Using a particular computer model, the Debenedetti group has provided strong support for one of the theories that can explain the outstanding properties of real water in the supercooled region.”

    In their computer simulations, the team used an updated version of a model noted for its ability to capture many of water’s unusual behaviors first developed in 1974 by Frank Stillinger, then at Bell Laboratories in Murray Hill, N.J., and now a senior chemist at Princeton; and Aneesur Rahman, then at the U.S. Argonne National Laboratory. The same model was used to develop the liquid-liquid transition hypothesis.

    Collectively, the work took several million computer hours, which would take several human lifetimes using a typical desktop computer, Palmer said. In addition to the initial simulations, the team verified the results using six calculation methods. The computations were performed at Princeton’s High-Performance Computing Research Center’s Terascale Infrastructure for Groundbreaking Research in Science and Engineering (TIGRESS).

    The team included Yang Liu, who earned her doctorate at Princeton in 2012, and Athanassios Panagiotopoulos, the Susan Dod Brown Professor of Chemical and Biological Engineering.

    Support for the research was provided by the National Science Foundation (CHE 1213343) and the U.S. Department of Energy (DE-SC0002128 and DE-SC0008626).

    The article, Metastable liquid-liquid transition in a molecular model of water, by Jeremy C. Palmer, Fausto Martelli, Yang Liu, Roberto Car, Athanassios Z. Panagiotopoulos and Pablo G. Debenedetti, appeared in the journal Nature.

    See the full article here.

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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