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  • richardmitnick 5:50 pm on November 26, 2019 Permalink | Reply
    Tags: , , , Brown University, , , Great cosmic dark age,   

    From Brown University: “Scientists inch closer than ever to signal from cosmic dawn” 

    Brown University
    From Brown University

    November 26, 2019
    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    Researchers using the Murchison Widefield Array radio telescope have taken a new and significant step toward detecting a signal from the period in cosmic history when the first stars lit up the universe.

    SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)

    Around 12 billion years ago, the universe emerged from a great cosmic dark age as the first stars and galaxies lit up. With a new analysis of data collected by the Murchison Widefield Array (MWA) radio telescope, scientists are now closer than ever to detecting the ultra-faint signature of this turning point in cosmic history.

    In a paper in The Astrophysical Journal, researchers present the first analysis of data from a new configuration of the MWA designed specifically to look for the signal of neutral hydrogen, the gas that dominated the universe during the cosmic dark age. The analysis sets a new limit — the lowest limit yet — for the strength of the neutral hydrogen signal.

    “We can say with confidence that if the neutral hydrogen signal was any stronger than the limit we set in the paper, then the telescope would have detected it,” said Jonathan Pober, an assistant professor of physics at Brown University and corresponding author on the new paper. “These findings can help us to further constrain the timing of when the cosmic dark ages ended and the first stars emerged.”

    The research was led by Wenyang Li, who performed the work as a Ph.D. student at Brown. Li and Pober collaborated with an international group of researchers working with the MWA.

    Despite its importance in cosmic history, little is known about the period when the first stars formed, which is known as the Epoch of Reionization (EoR). The first atoms that formed after the Big Bang were positively charged hydrogen ions — atoms whose electrons were stripped away by the energy of the infant universe. As the universe cooled and expanded, hydrogen atoms reunited with their electrons to form neutral hydrogen. And that’s just about all there was in the universe until about 12 billion years ago, when atoms started clumping together to form stars and galaxies. Light from those objects re-ionized the neutral hydrogen, causing it to largely disappear from interstellar space.

    The goal of projects like the one happening at MWA is to locate the signal of neutral hydrogen from the dark ages and measure how it changed as the EoR unfolded. Doing so could reveal new and critical information about the first stars — the building blocks of the universe we see today. But catching any glimpse of that 12-billion-year-old signal is a difficult task that requires instruments with exquisite sensitivity.

    When it began operating in 2013, the MWA was an array of 2,048 radio antennas arranged across the remote countryside of Western Australia. The antennas are bundled together into 128 “tiles,” whose signals are combined by a supercomputer called the Correlator. In 2016, the number of tiles was doubled to 256, and their configuration across the landscape was altered to improve their sensitivity to the neutral hydrogen signal. This new paper is the first analysis of data from the expanded array.

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    Neutral hydrogen emits radiation at a wavelength of 21 centimeters. As the universe has expanded over the past 12 billion years, the signal from the EoR is now stretched to about 2 meters, and that’s what MWA astronomers are looking for. The problem is there are myriad other sources that emit at the same wavelength — human-made sources like digital television as well as natural sources from within the Milky Way and from millions of other galaxies.

    “All of these other sources are many orders of magnitude stronger than the signal we’re trying to detect,” Pober said. “Even an FM radio signal that’s reflected off an airplane that happens to be passing above the telescope is enough to contaminate the data.”

    To home in on the signal, the researchers use a myriad of processing techniques to weed out those contaminants. At the same time, they account for the unique frequency responses of the telescope itself.

    “If we look at different radio frequencies or wavelengths, the telescope behaves a little differently,” Pober said. “Correcting for the telescope response is absolutely critical for then doing the separation of astrophysical contaminants and the signal of interest.”

    Those data analysis techniques combined with the expanded capacity of the telescope itself resulted in a new upper bound of the EoR signal strength. It’s the second consecutive best-limit-to-date analysis to be released by MWA and raises hope that the experiment will one day detect the elusive EoR signal.

    “This analysis demonstrates that the phase two upgrade had a lot of its desired effects and that the new analysis techniques will improve future analyses,” Pober said. “The fact that MWA has now published back-to-back the two best limits on the signal gives momentum to the idea that this experiment and its approach has a lot of promise.”

    The research was supported in part by the U.S. National Science Foundation (grant #1613040). The MWA receives support from the Australian government and acknowledges Wajarri Yamatji people as the traditional owners of the observatory site.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 8:57 am on October 21, 2019 Permalink | Reply
    Tags: Brown University, Ice on lunar south pole,   

    From Brown University: “Study suggests ice on lunar south pole may have more than one source” 

    Brown University
    From Brown University

    October 10, 2019
    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    New research sheds light on the ages of ice deposits reported in the area of the Moon’s south pole — information that could help identify the sources of the deposits and help in planning future human exploration.

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    Shackleton Crater, the floor of which is permanently shadowed from the sun, appears to be home to deposits of water ice. A new study sheds light on how old these and other deposits on the Moon’s south pole might be. Credit: NASA/GSFC/Arizona State University

    The discovery of ice deposits in craters scattered across the Moon’s south pole has helped to renew interest in exploring the lunar surface, but no one is sure exactly when or how that ice got there. A new study published in the journal Icarus suggests that while a majority of those deposits are likely billions of years old, some may be much more recent.

    Ariel Deutsch, a graduate student in Brown University’s Department of Earth, Environmental and Planetary Sciences and the study’s lead author, says that constraining the ages of the deposits is important both for basic science and for future lunar explorers who might make use of that ice for fuel and other purposes.

    “The ages of these deposits can potentially tell us something about the origin of the ice, which helps us understand the sources and distribution of water in the inner solar system,” Deutsch said. “For exploration purposes, we need to understand the lateral and vertical distributions of these deposits to figure out how best to access them. These distributions evolve with time, so having an idea of the age is important.”

    For the study, Deutsch worked with Jim Head, a professor at Brown, and Gregory Neumann from the NASA Goddard Space Flight Center. Using data from NASA’s Lunar Reconnaissance Orbiter, which has been orbiting the Moon since 2009, the researchers looked at the ages of the large craters in which evidence for south pole ice deposits was found.

    NASA/Lunar Reconnaissance Orbiter

    To date the craters, researchers count the number of smaller craters that have accrued inside the larger ones. Scientists have an approximate idea of the pace of impacts over time, so counting craters can help establish the ages of terrains.

    The majority of the reported ice deposits are found within large craters formed about 3.1 billion years or longer ago, the study found. Since the ice can’t be any older than the crater, that puts an upper bound on the age of the ice. Just because the crater is old doesn’t mean that the ice within it is also that old too, the researchers say, but in this case there’s reason to believe the ice is indeed old. The deposits have a patchy distribution across crater floors, which suggests that the ice has been battered by micrometeorite impacts and other debris over a long period of time.

    If those reported ice deposits are indeed ancient, that could have significant implications in terms of exploration and potential resource utilization, the researchers say.

    “There have been models of bombardment through time showing that ice starts to concentrate with depth,” Deutsch said. “So if you have a surface layer that’s old, you’d expect more underneath.”

    While the majority of ice was in the ancient craters, the researchers also found evidence for ice in smaller craters that, judging by their sharp, well-defined features, appear to be quite fresh. That suggests that some of the deposits on the south pole got there relatively recently.

    “That was a surprise,” Deutsch said. “There hadn’t really been any observations of ice in younger cold traps before.”

    If there are indeed deposits of different ages, the researchers say, that suggests they may also have different sources. Older ice could have been sourced from water-bearing comets and asteroids impacting the surface, or through volcanic activity that drew water from deep within the Moon. But there aren’t many big water-bearing impactors around in recent times, and volcanism is thought to have ceased on the Moon over a billion years ago. So more recent ice deposits would require different sources — perhaps bombardment from pea-sized micrometeorites or implantation by solar wind.

    The best way to find out for sure, the researchers say, is to send spacecraft there to get some samples. And that appears to be on the horizon. NASA’s Artemis program aims to put humans on the Moon by 2024, and plans to fly numerous precursor missions with robotic spacecraft in the meantime. Head, a study co-author and Deutsch’s Ph.D. advisor, says studies like this one will help to shape those future missions.

    “When we think about sending humans back to the Moon for long-term exploration, we need to know what resources are there that we can count on, and we currently don’t know,” Head said. “Studies like this one help us make predictions about where we need to go to answer those questions.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brownis the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 4:02 pm on September 5, 2019 Permalink | Reply
    Tags: "Research shows why there’s a ‘sweet spot’ depth for underground magma chambers", A new study reveals why the magma chambers that feed recurrent and often explosive volcanic eruptions tend to reside in a very narrow depth range within the Earth’s crust., , Brown University, Depths of six to 10 kilometers generally correspond to pressures of about 1.5 kilobars on the shallow side and 2.5 kilobars on deep side., The research makes use of computer models that capture the physics of how magma chambers reservoirs in the crust that contain partially molten rock evolve over time.,   

    From Brown University: “Research shows why there’s a ‘sweet spot’ depth for underground magma chambers” 

    Brown University
    From Brown University

    Computer models show why eruptive magma chambers tend to reside between six and 10 kilometers underground.

    1
    2

    A new study reveals why the magma chambers that feed recurrent and often explosive volcanic eruptions tend to reside in a very narrow depth range within the Earth’s crust. The findings, published in Nature Geoscience, could help scientists to better understand volcanic processes the world over.

    The research makes use of computer models that capture the physics of how magma chambers, reservoirs in the crust that contain partially molten rock, evolve over time. The models showed that two factors — the ability of water vapor to bubble out of the magma, and the ability of the crust to expand to accommodate chamber growth — are the key factors constraining the depth of magma chambers, which are generally found between six and 10 kilometers deep.

    “We know from observations that there seems to be a sweet spot in terms of depth for magma chambers that erupt repeatedly,” said Christian Huber, a geologist at Brown University and the study’s lead author. “Why that sweet spot exists has been an open question for a long time, and this is the first study that explains the processes that control it.”

    Depths of six to 10 kilometers generally correspond to pressures of about 1.5 kilobars on the shallow side and 2.5 kilobars on deep side. The models showed that at pressures less than 1.5 kilobars, water trapped within the magma forms bubbles readily, leading to violent volcanic explosions that blast more magma out of a chamber than can be replaced. These chambers quickly cease to exist. At pressures more than 2.5 kilobars, warm temperatures deep inside the Earth make the rocks surrounding the magma chamber soft and pliable, which enables the chamber to grow comfortably without erupting to the surface. These systems cool and solidify over time without ever erupting.

    “Between 1.5 and 2.5, the systems are happy,” Huber said. “They can erupt, recharge and keep going.”

    The key to the models, Huber said, is that they capture the dynamics of both the host crust and of the magma in the chamber itself. The ability of deep magma chamber to grow without erupting was fairly well understood, but the limit that water vapor exerts on shallow magma chambers hadn’t been appreciated.

    “There hadn’t been a good explanation for why this habitable zone should end at 1.5 kilobars,” Huber said. “We show that the behavior of the gas is really important. It simply causes more mass to erupt out than can be recharged.”

    Huber says the findings will be helpful in understanding the global magma budget.

    “The ratio of magma that stays in the crust versus how much is erupted to the surface is a huge question,” Huber said. “Magma supplies CO2 and other gases to the atmosphere, which influences the climate. So having a guide to understand what comes out and what stays in is important.”

    Coauthors on the paper Meredith Townsend, WimDegruyter and Olivier Bachmann. The work was supported by the National Science Foundation (NSF-EAR 1760004) and the Swiss National Fund (200021_178928).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 12:44 pm on January 3, 2019 Permalink | Reply
    Tags: , Brown University, , Chemists create new quasicrystal material from nanoparticle building blocks,   

    From Brown University: “Chemists create new quasicrystal material from nanoparticle building blocks” 

    Brown University
    From Brown University

    December 20, 2018

    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    1
    Quasicrystal lattice, Researchers have shown that special nanoparticle building blocks can assemble themselves into a quasicrystalline lattice, an ordered structure with no discernible repeating pattern and exotic symmetries. Chen Lab / Brown University

    2
    Powerful pyramids, Ou Chen, assistant professor of chemistry, holds a mock-up of the tetrahedral quantum dot building blocks used to create macro-scale superstructures.

    Brown University researchers have discovered a new type of quasicrystal, a class of materials whose existence was thought to be impossible until the 1980s.

    The strange class of materials known as quasicrystals has a new member. In a paper published on Thursday, Dec. 20, in Science, researchers from Brown University describe a quasicrystalline superlattice that self-assembles from a single type of nanoparticle building blocks.

    This is the first definitive observation of a quasicrystalline superlattice formed from a single component, the researchers say. The discovery provides new insight into how these strange crystal-like structures can emerge.

    “Single-component quasicrystal lattices have been predicted mathematically and in computer simulations, but hadn’t been demonstrated before this,” said Ou Chen, an assistant professor of chemistry at Brown and the paper’s senior author. “It’s a fundamentally new type of quasicrystal, and we’ve been able to figure out the rules for making it, which will be useful in the continued study of quasicrystal structures.”

    Quasicrystal materials were first discovered in the 1980s by the chemist Dan Shechtman, who in 2011 was awarded the Nobel Prize for the discovery. Unlike crystals, which consist of ordered patterns that repeat, quasicrystals are ordered but their patterns don’t repeat. Quasicrystals also have symmetries that aren’t possible in traditional crystals. Normal crystals, for example, can have three-fold symmetries that emerge from repeating triangles or four-fold symmetry from repeating cubes. Two- and six-fold symmetries are also possible. But quasicrystals can have exotic five-, 10- or 12-fold symmetries, all of which are “forbidden” in normal crystals.

    The first quasicrystalline materials discovered were metal alloys, usually aluminum with one or more other metals. So far, these materials have found use as non-stick coatings for frying pans and anti-corrosive coatings for surgical equipment. But there’s been much interest in making new types of quasicrystal materials — including materials made from self-assembling nanoparticles.

    Chen and his colleagues hadn’t originally set out to research quasicrystals. Much of Chen’s work has been about bridging the gap between the nanoscale and macroscale worlds by building superstructures out of nanoparticle building blocks. About two years ago, he designed a new type of nanoparticle building block — a tetrahedral (pyramid-shaped) quantum dot. Whereas most research on building structures from nanoparticles has been done with spherical particles, Chen’s tetrahedra can pack more tightly and potentially form more complex and robust structures.

    Another key feature of Chen’s particles is that they’re anisotropic, meaning they have different properties depending upon their orientation relative to each other. One face of each pyramid particle has a different ligand (a bonding agent) than all other faces. Faces with like ligands tend to bond with each other when the particles assemble themselves into larger structures. That directed bonding makes for more interesting and complex structures compared with particles lacking anisotropy.

    In research published recently in the journal Nature, Chen and his team demonstrated one of the most complex superstructures created to date from nanoparticle building blocks. In that work, the superstructures were assembled while the particles interacted with a solid substrate. For this latest work, Chen and his colleagues wanted to see what kind of structures the particles would make when assembled on top of a liquid surface, which gives the particles more degrees of freedom when assembling themselves.

    The team was shocked to find that the resulting structure was actually a quasicrystalline lattice.

    “When I realized the pattern I was seeing was a quasicrystal, I emailed Ou and said ‘I think I’ve found something super-great,’” said Yasutaka Nagaoka, a postdoctoral scholar in Chen’s lab and the lead author of the new paper. “It was really exciting.”

    Using transmission electron microscopy, the researchers showed the particles assembled into discrete decagons (10-sided polygons), which stitched themselves together to form a quasicrystal lattice with 10-fold rotational symmetry. That 10-fold symmetry, forbidden in regular crystals, was a telltale sign of a quasicrystalline structure.

    The researchers were also able to divine the “rules” by which their structure formed. While decagons are the primary units of the structure, they are not — and cannot be — the only units in the structure. Forming a quasicrystal is a little like tiling a floor. The tiles have to fit together in a way that covers the entire floor without leaving any gaps. That can’t be done using only decagons because there’s no way to fit them together that doesn’t leave gaps. Other shapes are needed to fill the holes.

    The same goes for this new quasicrystal structure — they require secondary “tiles” that can fill the gaps between decagons. The researchers found that what enabled their structure to work is that the decagons have flexible edges. When necessary, one or more of their points could be flattened out. By doing that, they could morph into polygons with nine, eight, seven, six or five sides — whatever was required to fill the space between decagons.

    3
    The researchers showed how the nanoparticle decagons flexed their edges to in order to fit together in a quasicrystalline lattice.

    “These decagons are in this confined space that they have to share peacefully,” Chen said. “So they do it by making their edges flexible when they need to.”

    From that observation, the researchers were able to develop a new rule for forming quasicrystals that they call the “flexible polygon tiling rule.” That rule, Chen says, will be useful in continued study of the relatively new area of quasicrystals.

    “We think this work can inform research in material science, chemistry, mathematics and even art and design,” Chen said.

    Nagaoka’s and Chen’s co-authors on the paper were Hua Zhu and Dennis Eggert.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 1:45 pm on December 17, 2018 Permalink | Reply
    Tags: Brown University, , , , PMT's-photomultiplier tubes, ,   

    From Brown University: “Massive new dark matter detector gets its ‘eyes’” 

    Brown University
    From Brown University

    1
    The detector’s “eyes”
    Powerful light sensors assembled at Brown into two large arrays will keep watch on the LUX-ZEPLIN dark matter detector, looking for the tell-tale flashes of light that indicate interaction of a dark matter particle inside the detector. Credit: Nick Dentamaro

    LBNL Lux Zeplin project at SURF

    December 17, 2018
    Kevin Stacey

    Brown University researchers have assembled two massive arrays of photomultiplier tubes, powerful light sensors that will serve as the “eyes” for the LUX-ZEPLIN dark matter detector, which will start its search for dark matter particles in 2020.

    The LUX-ZEPLIN (LZ) dark matter detector, which will soon start its search for the elusive particles thought to account for a majority of matter in the universe, had the first of its “eyes” delivered late last week.

    The first of two large arrays of photomultiplier tubes (PMTs) — powerful light sensors that can detect the faintest of flashes — arrived last Thursday at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, where LZ is scheduled to begin its dark matter search in 2020. The second array will arrive in January. When the detector is completed and switched on, the PMT arrays will keep careful watch on LZ’s 10-ton tank of liquid xenon, looking for the telltale twin flashes of light produced if a dark matter particle bumps into a xenon atom inside the tank.

    The two arrays, each about 5 feet in diameter and holding a total of 494 PMTs, were shipped to South Dakota via truck from Providence, Rhode Island, where a team of researchers and technicians from Brown University spent the past six months painstakingly assembling them.

    “The delivery of these arrays is the pinnacle of an enormous assembly effort that we’ve executed here in our cleanroom at the Brown Department of Physics,” said Rick Gaitskell, a professor of physics at Brown University who oversaw the construction of the arrays. “For the last two years, we’ve been making sure that every piece that’s going into the devices is working as expected. Only by doing that can we be confident that everything will perform the way we want when the detector is switched on.”

    The Brown team has worked with researchers and engineers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and from Imperial College London to design, procure, test, and assemble all of the components of the array. Testing of the PMTs, which are manufactured by the Hamamatsu Corporation in Japan, was performed at Brown and at Imperial College “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    Catching a WIMP

    Nobody knows exactly what dark matter is. Scientists can see the effects of its gravity in the rotation of galaxies and in the way light bends as it travels across the universe, but no one has directly detected a dark matter particle. The leading theoretical candidate for a dark matter particle is the WIMP, or weakly interacting massive particle. WIMPs can’t be seen because they don’t absorb, emit or reflect light. And they interact with normal matter only on very rare occasions, which is why they’re so hard to detect even when millions of them may be traveling through the Earth and everything on it each second.

    The LZ experiment, a collaboration of more than 250 scientists worldwide, aims to capture one of those fleetingly rare WIMP interactions, and thereby characterize the particles thought to make up more than 80 percent of the matter in the universe. The detector will be the most sensitive ever built, 50 times more sensitive than the LUX detector, which wrapped up its dark matter search at SURF in 2016.

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    This rendering shows a cutaway view of the LZ xenon tank (center), with PMT arrays at the top and bottom of the tank. (Credit: Greg Stewart/SLAC National Accelerator Laboratory)

    The PMT arrays are a critical part of the experiment. Each PMT is a six-inch-long cylinder that is roughly the diameter of a soda can. To form arrays large enough to monitor the entire LZ xenon target, hundreds of PMTs are assembled together within a circular titanium matrix. The array that will sit on top of the xenon target has 253 PMTs, while the lower array has 241.

    PMTs are designed to amplify weak light signals. When individual photons (particles of light) enter a PMT, they strike a photocathode. If the photon has sufficient energy, it causes the photocathode to eject one or more electrons. Those electrons strike then an electrode, which ejects more electrons. By cascading through a series of electrodes the original signal is amplified by over a factor of a million to create a detectable signal.

    LZ’s PMT arrays will need every bit of that sensitivity to catch the flashes associated with a WIMP interaction.

    “We could be looking for events emitting as few as 20 photons in a huge tank containing 10 tons of xenon, which is something that the human visual system wouldn’t be able to do,” Gaitskell said. “But it’s something these arrays can do, and we’ll need them to do it in order to see the signal from rare particle events.”

    The photons are produced by what’s known as a nuclear recoil event, which produces two distinct flashes. The first comes at the moment a WIMP bumps into a xenon nucleus. The second, which comes a few hundred microseconds afterward, is produced by the ricochet of the xenon atom that was struck. It bounces into the atoms surrounding it, which knocks a few electrons free. The electrons are then drifted by an electric field to the top of the tank, where they reach a thin layer of xenon gas that converts them into light.

    In order for those tiny flashes to be distinguishable from unwanted background events, the detector needs to be protected from cosmic rays and other kinds of radiation, which also cause liquid xenon to light up. That’s why the experiment takes place underground at SURF, a former gold mine, where the detector will be shielded by about a mile of rock to limit interference.

    A clean start

    The need to limit interference is also the reason that the Brown University team was obsessed with cleanliness while they assembled the arrays. The team’s main enemy was plain old dust.

    “When you’re dealing with an instrument that’s as sensitive as LZ, suddenly things you wouldn’t normally care about become very serious,” said Casey Rhyne, a Brown graduate student who had a leading role in building the arrays. “One of the biggest challenges we had to confront was minimizing ambient dust levels during assembly.”

    Each dust particle carries a minuscule amount of radioactive uranium and thorium decay products. The radiation is vanishingly small and poses no threat to people, but too many of those specks inside the LZ detector could be enough to interfere with a WIMP signal.

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    Much of the assembly work was done while the arrays sat inside PALACE, an ultraclean enclosure designed to keep the arrays dust-free. Nick Detamaro

    In fact, the dust budget for the LZ experiment calls for no more than one gram of dust in the entire 10-ton instrument. Because of all their nooks and crannies, the PMT arrays could be significant dust contributors if pains were not taken to keep them clean throughout construction.

    The Brown team performed most of its work in a “class 1,000” cleanroom, which allows no more than 1,000 microscopic dust particles per cubic foot of space. And within that cleanroom was an even more pristine space that the team dubbed “PALACE (PMT Array Lifting And Commissioning Enclosure).” PALACE was essentially an ultraclean exoskeleton where much of the actual array assembly took place. PALACE was a “class 10” space — no more than 10 dust particles bigger than one hundredth the width of a human hair per cubic foot.

    But the radiation concerns didn’t stop at dust. Before assembly of the arrays began, the team prescreened every part of every PMT tube to assess radiation levels.

    “We had Hamamatsu send us all of the materials that they were going to use for the PMT construction, and we put them in an underground germanium detector,” said Samuel Chan, a graduate student and PMT system team leader. “This detector is very good at detecting the radiation that the construction materials are emitting. If the intrinsic radiation levels were low enough in these materials, then we told Hamamatsu to go ahead and use them in the manufacture of these PMTs.”

    7
    A PMT is carefully inserted into the array inside PALACE. Nick Dentamaro

    The team is hopeful that all the work contributed over the past six months will pay dividends when LZ starts its WIMP search.

    “Getting everything right now will have a huge impact less than two years from now when we switch on the completed detector and we’re taking data,” Gaitskell said. “We’ll be able to see directly from that data how good of a job we and other people have done.”

    Given the major increase in dark matter search sensitivity that the LUX-ZEPLIN detector can deliver compared to previous experiments, the team hopes that this detector will finally identify and characterize the vast sea of stuff that surrounds us all. So far, the dark stuff has remained maddeningly elusive.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 11:29 am on September 21, 2018 Permalink | Reply
    Tags: Andrew Peterson, Brown awarded $3.5M to speed up atomic-scale computer simulations, Brown University, Computational power is growing rapidly which lets us perform larger and more realistic simulations, Different simulations often have the same sets of calculations underlying them- so finding what can be re-used saves a lot of time and money, ,   

    From Brown University: “Brown awarded $3.5M to speed up atomic-scale computer simulations” 

    Brown University
    From Brown University

    September 20, 2018
    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    1
    Andrew Peterson. No photo credit.

    With a new grant from the U.S. Department of Energy, a Brown University-led research team will use machine learning to speed up atom-level simulations of chemical reactions and the properties of materials.

    “Simulations provide insights into materials and chemical processes that we can’t readily get from experiments,” said Andrew Peterson, an associate professor in Brown’s School of Engineering who will lead the work.

    “Computational power is growing rapidly, which lets us perform larger and more realistic simulations. But as the size of the simulations grows, the time involved in running them can grow exponentially. This paradox means that even with the growth in computational power, our field still cannot perform truly large-scale simulations. Our goal is to speed those simulations up dramatically — ideally by orders of magnitude — using machine learning.”

    The grant provides $3.5 million dollars for the work over four years. Peterson will work with two Brown colleagues — Franklin Goldsmith, assistant professor of engineering, and Brenda Rubenstein, assistant professor of chemistry — as well as researchers from Carnegie Mellon, Georgia Tech and MIT.

    The idea behind the work is that different simulations often have the same sets of calculations underlying them. Peterson and his colleagues aim to use machine learning to find those underlying similarities and fast-forward through them.

    “What we’re doing is taking the results of calculations from prior simulations and using them to predict the outcome of calculations that haven’t been done yet,” Peterson said. “If we can eliminate the need to do similar calculations over and over again, we can speed things up dramatically, potentially by orders of magnitude.”

    The team will focus their work initially on simulations of electrocatalysis — the kinds of chemical reactions that are important in devices like fuel cells and batteries. These are complex, often multi-step reactions that are fertile ground for simulation-driven research, Peterson says.

    Atomic-scale simulations have demonstrated usefulness in Peterson’s own work in the design of new catalysts. In a recent example, Peterson worked with Brown chemist Shouheng Sun on a gold nanoparticle catalyst that can perform a reaction necessary for converting carbon dioxide into useful forms of carbon. Peterson’s simulations showed it was the sharp edges of the oddly shaped catalyst that were particularly active for the desired reaction.

    “That led us to change the geometry of the catalyst to a nanowire — something that’s basically all edges — to maximize its reactivity,” Peterson said. “We might have eventually tried a nanowire by trial and error, but because of the computational insights we were able to get there much more quickly.”

    The researchers will use a software package that Peterson’s research group developed previously as a starting point. The software, called AMP (Atomistic Machine-learning Package) is open-source and already widely used in the simulation community, Peterson says.

    The Department of Energy grant will bring atomic-scale simulations — and the insights they produce — to bear on ever larger and more complex simulations. And while the work under the grant will focus on electrocatalysis, the tools the team develops should be widely applicable to other types of material and chemical simulations.

    Peterson is hopeful that the investment that the federal government is making in machine learning will be repaid by making better use of valuable computing resources.

    “Modern supercomputers cost millions of dollars to build, and simulation time on them is precious,” Peterson said. “If we’re able to free up time on those machines for additional simulations to be run, that translates into vastly increased return-on-investment for those machines. It’s real money.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 3:07 pm on August 31, 2018 Permalink | Reply
    Tags: , Brown University, , Ethnobotany, Rhode Island School of Design, Rhode Island’s flora, RISD’s Edna Lawrence Nature Lab, ,   

    From University of Rhode Island: “Plant life: RISD SURFs visualize flora of RI salt marshes” 

    From University of Rhode Island

    8.30.18
    Shaun Kirby

    1
    Nadia Lahlaf and Shannon Kingsley show the plant pressing and visuals they produced during the SURF program this summer at RISD’s Edna Lawrence Nature Lab.

    When Shannon Kingsley and Nadia Lahlaf first arrived at the Rhode Island School of Design’s Nature Lab in May, their goal was clear: produce a tangible product highlighting how climate change has affected plant life in Rhode Island’s salt marshes since the 1950s.

    Getting there, however, was a road left wide-open by mentors Dr. Timothy Whitfeld, assistant professor of Ecology & Evolutionary Biology at Brown, and the Nature Lab’s Jennifer Bissonnette and Lucia Monge.

    “They told us from the start that it was up to us to find our own direction and decide what kind of concrete thing we would be producing,” explains Lahlaf, a fourth year student from Billerica, Mass. earning a dual degree in Computer Science and Illustration from Brown and RISD. “Every day we had a different thing on the agenda, and our experiences were about finding what was interesting to us and then figuring out how to convey the information about salt marsh ecology that seemed important.”

    Kingsley, a sophomore studying English and Ethnobotany at Brown, and Lahlaf some days collected plant specimens from salt marshes at Tillinghast Place, a RISD satellite campus located alongside the Providence River.

    On others, they were examining plant species at Brown’s Herbarium or pressing plant leaves and taking highly detailed images with the Nature Lab’s “macro pod,” a camera which takes nearly 65 images of an item over time and compresses them into one to create the highest resolution possible.

    After about six weeks, the SURF students had to decide upon the medium through which they would showcase their research: an illustrated book detailing specific plant species and how they had been impacted by climate changes in Narragansett Bay.

    “As an Ethnobotany major, I have taken a lot of classes about the history of science and people’s uses of plants for medicine and religious rituals,” says Kingsley, a North Attleboro, Mass. native, about her interest in the SURF project. “We can learn a lot by combining humanities and sciences.”

    2
    Nadia Lahlaf, a dual degree student in Computer Science and Illustration from Brown and RISD, explains their project at the 11th annual SURF Conference on July 27.

    Both SURFs were able to explore their educational interests through creating the booklet. While Kingsley took charge of writing compelling, scientifically accurate copy about Rhode Island’s flora, Lahlaf put her creative juices to work by organizing the book’s plant images and developing salt marsh illustrations.

    “We have different strengths and backgrounds, and the biggest challenge was finding our own direction,” emphasizes Lahlaf. “I really enjoy the problem solving aspect of computer science, and drawing and painting are things I have done since I was little.”

    “I love to read and write, it is really as simple as that,” adds Kingsley.

    Although Kingsley Lahlaf are unsure of what they will do after graduation, the SURFs have produced an informative and visually compelling product, the fruit of a successful 10-week partnership.

    “We did everything collaboratively, which was an awesome experience,” says Lahlaf as Kingsley laughs in agreement.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The University of Rhode Island is a diverse and dynamic community whose members are connected by a common quest for knowledge.

    As a major research university defined by innovation and big thinking, URI offers its undergraduate, graduate, and professional students distinctive educational opportunities designed to meet the global challenges of today’s world and the rapidly evolving needs of tomorrow. That’s why we’re here.

    The University of Rhode Island, commonly referred to as URI, is the flagship public research as well as the land grant and sea grant university for the state of Rhode Island. Its main campus is located in the village of Kingston in southern Rhode Island. Additionally, smaller campuses include the Feinstein Campus in Providence, the Rhode Island Nursing Education Center in Providence, the Narragansett Bay Campus in Narragansett, and the W. Alton Jones Campus in West Greenwich.

    The university offers bachelor’s degrees, master’s degrees, and doctoral degrees in 80 undergraduate and 49 graduate areas of study through eight academic colleges. These colleges include Arts and Sciences, Business Administration, Education and Professional Studies, Engineering, Health Sciences, Environment and Life Sciences, Nursing and Pharmacy. Another college, University College for Academic Success, serves primarily as an advising college for all incoming undergraduates and follows them through their first two years of enrollment at URI.

    The University enrolled about 13,600 undergraduate and 3,000 graduate students in Fall 2015.[2] U.S. News & World Report classifies URI as a tier 1 national university, ranking it tied for 161st in the U.S.

     
  • richardmitnick 3:16 pm on July 18, 2018 Permalink | Reply
    Tags: , , Brown University, , , Meenakshi Narain, , , ,   

    From Brown University: Women in STEM- “Brown physicist elected to represent U.S. in Large Hadron Collider experiment” Meenakshi Narain 

    Brown University
    From Brown University

    July 18, 2018
    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    1
    Meenakshi Narain

    Meenakshi Narain will lead the collaboration board for U.S. institutions participating the CMS experiment at the Large Hadron Collider, an experiment pushing the frontiers of modern particle physics.

    Brown University physics professor Meenakshi Narain has been tapped to chair the collaboration board of U.S. institutions in the Compact Muon Solenoid (CMS) experiment, one of two large-scale experiments happening at the Large Hadron Collider particle accelerator headquartered in Geneva.

    CERN CMS Higgs Event


    CERN/CMS Detector

    The CMS experiment is an international collaboration of 4,000 particle physicists, engineers, computer scientists, technicians and students from approximately 200 institutes and universities around the world. With more than 1,200 participants, the U.S. CMS collaboration is the largest national group in the global experiment. As collaboration board chair, Narain will represent U.S. institutions within the broader collaboration, as well as with U.S. funding agencies. The board also plays a key role in shaping the vision and direction of the U.S. collaboration.

    “I’m honored that my colleagues from the 50 U.S. institutions that collaborate with the CMS Experiment have chosen me to represent them,” Narain said. “I see this position as an opportunity to help U.S. CMS to become a more inclusive community and to enable all young scientists to contribute to their full potential to CMS and find rewarding career opportunities in academia and industry.”

    Narain and other Brown physicists working with the CMS experiment played key roles in the discovery in 2012 of the Higgs Boson, which at the time was the final missing piece in the Standard Model of particle physics. After the Higgs, the CMS experiment has been searching for particles beyond the Standard Model, including a potential candidate particle for dark matter, the mysterious stuff thought to account for a majority of matter in the universe.

    Narain says part of her job is to maintain the research synergy created by the numerous U.S. scientists and institutions involved in the collaboration as they analyze data from the collider’s latest run. At the same time, the experiment must also prepare for the next stage of the Large Hadron Collider program slated to start around 2026. The next stage involves beam intensities five times higher the current level and 10 times more data than has been acquired to date. That will require parts of the CMS detector to be rebuilt.

    “We need the resources to maintain the detector during the current run as well as to start building the upgrades,” Narain said. “I will work with funding agencies to communicate what we’ll need to both maintain our involvement in the data analysis and play a leading role in the upgrade of the detector.”

    Narain says that as the first woman to chair the collaboration board, she plans to work toward cultivating more diversity in what is currently the largest physics collaboration in the U.S.

    “With this comes the opportunity to promote women and other underrepresented minorities to have the opportunity to develop their careers to their fullest potential,” she said. “I hope that I will be able to improve our community in the U.S. and in CMS in general to be more inclusive during my two-year term.”

    Narain joined the Brown faculty in 2007 and has worked at the Large Hadron Collider together with the Brown team that includes professors David Cutts, Ulrich Heintz and Greg Landsberg. She was also a member of the DZero experiment at the Fermi National Accelerator Laboratory, where she played a prominent role in the discoveries of the top quark and the anti-top quark, two fundamental constituents of matter. She is a fellow of the American Physical Society and the author of more than 500 journal articles.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 6:38 pm on June 5, 2018 Permalink | Reply
    Tags: A regular quantum computer — one without non-Abelian anyons — would require error correction, Abelian anyons behave more or less like conventional fermions, Brown University, But an even more powerful computational platform would come from what’s known as parafermions which have been theorized but not yet shown to exist. Perhaps their existence could also be proven with , Eliminate error correction which is a major stumbling block in the development of quantum computers, For one useful quantum bit of information you need multiple additional quantum bits to correct errors that arise from random fluctuations in the system, Non-Abelian anyons are for lack of a better way of saying it completely insane. They have very strange properties that could be used in quantum computing or more specifically for what’s known as top, Non-Abelian anyons- quantum quasi-particles that retain a “memory” of their relative positions in the past, , Quantum Hall liquid, This work suggests that a particular entity known as a Majorana particle is at work in the particular system that we studied. And that suggests that a Majorana-based quantum computer is possible., topological quantum computing — which requires the presence of non-Abelian anyons — is unique in that it doesn’t need error correction to make the quantum bits useful,   

    From Brown University: “New research hints at ‘insane’ particles useful in quantum computing” 

    Brown University
    From Brown University

    June 5, 2018
    Kevin Stacey
    kevin_stacey@brown.edu

    1
    Quantum heat. An image of the experimental setup used to produce evidence of strange quasi-particles called non-Abelian anyons.
    A new measurement of heat conduction in an exotic state of matter points to the presence of strange particles that could be useful in quantum computers.

    In a paper published this week in the journal Nature, a research team including a Brown University physicist has characterized how heat is conducted in a matter state known as a quantum Hall liquid, in which electrons are confined to two dimensions. The findings suggest the presence of non-Abelian anyons, quantum quasi-particles that retain a “memory” of their relative positions in the past. Theorists have suggested that the ability of these particles to retain information could be useful in developing ultra-fast quantum computing systems that don’t require error correction, which is a major stumbling block in the development of quantum computers.

    The research was led by an experimental group at the Weizmann Institute of Science in Rehovot, Israel.

    Weizmann Institute Campus


    Dmitri Feldman, a professor of physics at Brown, was part of the research group. He discussed the findings in an interview.

    Q: Could you explain more about what you and your colleagues found?

    A: We were looking at thermal conductance — which simply means the flow of heat from a higher temperature to a lower temperature — in what’s known as a 5/2 quantum Hall liquid. Quantum Hall liquids are not ‘liquids’ in the conventional sense of the word. The term refers to the behavior of electrons inside certain materials when the electrons become confined in two dimensions in a strong magnetic field.

    What we found was that the quantized heat conductance — meaning a fundamental unit of conductance — in this system is fractional. In other words, the value was not an integer, and that has interesting implications for what’s happening in the system. When the quantum thermal conductance is not an integer, it means that quasi-particles known as non-Abelian anyons are present in this system.

    Q: Can you explain more about non-Abelian anyons?

    A: In the Standard Model of particle physics, there are only two categories of particles: fermions and bosons.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Standard Model of Particle Physics from Symmetry Magazine

    That’s all there is in the world we experience on a daily basis. But in two-dimensional systems like quantum Hall liquids, there can be other types of particles known as anyons. Generally speaking, there are two types of anyons: Abelian anyons and non-Abelian anyons. Abelian anyons behave more or less like conventional fermions, but non-Abelian anyons are, for lack of a better way of saying it, completely insane. They have very strange properties that could be used in quantum computing, or more specifically, for what’s known as topological quantum memory.

    Q: What’s the connection between non-Abelian anyons and quantum computing?

    A: A regular quantum computer — one without non-Abelian anyons — would require error correction. For one useful quantum bit of information, you need multiple additional quantum bits to correct errors that arise from random fluctuations in the system. That’s extremely demanding and a big problem in quantum computing. But topological quantum computing — which requires the presence of non-Abelian anyons — is unique in that it doesn’t need error correction to make the quantum bits useful. That’s because in a non-Abelian system, you can produce states that are completely indistinguishable locally, but globally the states are completely different. So you can have random perturbations of these local quantum numbers, but it won’t change the global quantum numbers, which means the information is safe.

    Q: Where does this line of research go from here?

    A: This work suggests that a particular entity known as a Majorana particle is at work in the particular system that we studied. And that suggests that a Majorana-based quantum computer is possible. But an even more powerful computational platform would come from what’s known as parafermions, which have been theorized but not yet shown to exist. Perhaps their existence could also be proven with similar experimental tools in the future.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition
    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 11:15 pm on April 28, 2018 Permalink | Reply
    Tags: , Brown University, , Experiments using a high-powered projectile cannon show how impacts by water-rich asteroids can deliver surprising amounts of water to planetary bodies, The findings could have significant implications for understanding the presence of water on Earth, The origin and transportation of water and volatiles is one of the big questions in planetary science, Water delivered to Earth by steroids?   

    From Brown University: “Projectile cannon experiments show how asteroids can deliver water” 

    Brown University
    Brown University

    April 25, 2018
    Kevin Stacey
    kevin_stacey@brown.edu
    401-863-3766

    1
    Special delivery. Experiments using a high-powered projectile cannon suggest that asteroids can deliver surprising amounts of water when they smash into planetary bodies.
    Schultz Lab / Brown University

    New research shows that a surprising amount of water survives simulated asteroid impacts, a finding that may help explain how asteroids deposit water throughout the solar system.

    Experiments using a high-powered projectile cannon show how impacts by water-rich asteroids can deliver surprising amounts of water to planetary bodies. The research, by scientists from Brown University, could shed light on how water got to the early Earth and help account for some trace water detections on the Moon and elsewhere.

    “The origin and transportation of water and volatiles is one of the big questions in planetary science,” said Terik Daly, a postdoctoral researcher at Johns Hopkins University who led the research while completing his Ph.D. at Brown. “These experiments reveal a mechanism by which asteroids could deliver water to moons, planets and other asteroids. It’s a process that started while the solar system was forming and continues to operate today.”

    The research is published in Science Advances.

    The source of Earth’s water remains something of a mystery. It was long thought that the planets of the inner solar system formed bone dry and that water was delivered later by icy comet impacts. While that idea remains a possibility, isotopic measurements have shown that Earth’s water is similar to water bound up in carbonaceous asteroids. That suggests asteroids could also have been a source for Earth’s water, but how such delivery might have worked isn’t well understood.

    “Impact models tell us that impactors should completely devolatilize at many of the impact speeds common in the solar system, meaning all the water they contain just boils off in the heat of the impact,” said Pete Schultz, co-author of the paper and a professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “But nature has a tendency to be more interesting than our models, which is why we need to do experiments.”

    2
    Hypervelocity impact experiments, like the one shown here, reveal key clues about how impacts deliver water to asteroids, moons, and planets. In this experiment, a water-rich impactor collides with a bone-dry pumice target at around 11,200 miles per hour. The target was designed to rupture partway through the experiment in order to capture materials for analysis. This high-speed video, taken at 130,000 frames per second, slows down the action, which in real time is over in less than a second.

    For the study, Daly and Schultz used marble-sized projectiles with a composition similar to carbonaceous chondrites, meteorites derived from ancient, water-rich asteroids. Using the Vertical Gun Range at the NASA Ames Research Center, the projectiles were blasted at a bone-dry target material made of pumice powder at speeds around 5 kilometers per second (more than 11,000 miles per hour). The researchers then analyzed the post-impact debris with an armada of analytical tools, looking for signs of any water trapped within it.

    They found that at impact speeds and angles common throughout the solar system, as much as 30 percent of the water indigenous in the impactor was trapped in post-impact debris. Most of that water was trapped in impact melt, rock that’s melted by the heat of the impact and then re-solidifies as it cools, and in impact breccias, rocks made of a mish-mash of impact debris welded together by the heat of the impact.

    The research gives some clues about the mechanism through which the water was retained. As parts of the impactor are destroyed by the heat of the collision, a vapor plume forms that includes water that was inside the impactor.

    “The impact melt and breccias are forming inside that plume,” Schultz said. “What we’re suggesting is that the water vapor gets ingested into the melts and breccias as they form. So even though the impactor loses its water, some of it is recaptured as the melt rapidly quenches.”

    3
    Samples of impact glasses created during an impact experiment. In impact experiments, these glasses capture surprisingly large amounts of water delivered by water-rich, asteroid-like impactors.

    The findings could have significant implications for understanding the presence of water on Earth. Carbonaceous asteroids are thought to be some of the earliest objects in the solar system — the primordial boulders from which the planets were built. As these water-rich asteroids bashed into the still-forming Earth, it’s possible that a process similar to what Daly and Schultz found enabled water to be incorporated in the planet’s formation process, they say. Such a process could also help explain the presence of water within the Moon’s mantle, as research has suggested that lunar water has an asteroid origin as well.

    The work could also explain later water activity in the solar system. Water found on the Moon’s surface in the rays of the crater Tycho could have been derived from the Tycho impactor, Schultz says. Asteroid-derived water might also account for ice deposits detected in the polar regions of Mercury.

    “The point is that this gives us a mechanism for how water can stick around after these asteroid impacts,” Schultz said. “And it shows why experiments are so important because this is something that models have missed.”

    The research was supported by NASA (NNX13AB75G), the National Science Foundation (DGE-1058262) and the NASA Rhode Island Space Grant (NNX15AI06H).

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
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