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  • richardmitnick 9:50 am on September 18, 2019 Permalink | Reply
    Tags: , , , , Eos, , , Provide a literal toehold for marine life like barnacles; coral; macroalgae; and mollusks., Pumice spewed out from an undersea volcano,   

    From EarthSky and Eos: “Volcanic Eruption Creates Temporary Islands of Pumice” 

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    From EarthSky

    From AGU
    Eos news bloc

    From Eos

    6 September 2019
    Katherine Kornei, Eos
    Eleanor Imster, EarthSky

    Sailing through rocks is anything but quiet. Last month, vessels in the South Pacific clinked and clanked their way through pumice spewed out from an undersea volcano. These temporary islands of volcanic rock, shaped and propelled by ocean currents, wind, and waves, provide a literal toehold for marine life like barnacles, coral, macroalgae, and mollusks.

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    Last month, rafts of pumice, spewed from an undersea volcano and spanning an area about the size of Washington, D.C., appeared in the South Pacific. Satellite image of a pumice raft floating near the Kingdom of Tonga. Image via NASA Earth Observatory.

    In early August, an unnamed volcano near the Kingdom of Tonga erupted roughly 40 meters underwater. The eruption sent pieces of gray pumice—porous rock filled with gas bubbles—floating to the surface. This volcanic debris, some fragments as large as beach balls, then aggregated into pumice “rafts” spanning roughly 200 square kilometers.

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    August 13, 2019. See detail below. Image via NASA Earth Observatory.

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    Detail of above image, taken August 13, 2019. Image via NASA Earth Observatory.

    Several sailing crews have encountered the rocks.

    “We were in a large area surrounded as far as the eye could see,” said Rachel Mackie, the purser and chef of Olive, a private vessel that sailed into a raft on 9 August near Late Island. There was a strong smell of sulfur, said Mackie, and Olive took a beating. “When the larger rocks hit the steel hull, it reverberated.”

    Several sailing crews have encountered the rocks.

    “We were in a large area surrounded as far as the eye could see,” said Rachel Mackie, the purser and chef of Olive, a private vessel that sailed into a raft on 9 August near Late Island. There was a strong smell of sulfur, said Mackie, and Olive took a beating. “When the larger rocks hit the steel hull, it reverberated.”

    Pumice rafts aren’t that common, said Martin Jutzeler, a volcanologist at the University of Tasmania in Hobart. “We see about two per decade.”

    Not all undersea eruptions produce them, but the rafts that do form tend to stick around. They can last for months or years until the pumice abrades itself into dust or finally sinks. And floating pumice can traverse long distances—when the same unnamed volcano near Tonga erupted in 2001, the pumice raft it created eventually arrived in Queensland, Australia, said Jutzeler.

    These transient, movable islands play an important role in marine ecosystems, scientists agree. Barnacles, coral, and macroalgae have all been found clinging to pumice, riding the waves en route to a new home.

    “It’s a perfect little substrate,” said Jutzeler.

    In 2012, Scott Bryan, a geologist at the Queensland University of Technology in Australia, and his colleagues showed that pumice rafts can significantly increase the dispersal of marine organisms. Bryan and his team found that more than 80 species traveled thousands of kilometers aboard pumice following the 2006 eruption of Home Reef Volcano in Tonga. “Pumice is an extremely effective rafting agent that can…connect isolated shallow marine and coastal ecosystems,” the researchers wrote in PLoS ONE.

    The long-distance journeys of pumice rafts are “definitely a way to get organisms to disperse widely,” said Erik Klemetti, a volcanologist at Denison University in Granville, Ohio, not involved in the research. But the idea that the stowaways aboard pumice rafts might replenish the Great Barrier Reef’s corals is wishful thinking, said Klemetti. “That’s probably an oversell.”

    Jutzeler and his colleagues are planning to study pumice from last month’s eruption. They’ve been in touch with several vessels that passed through the rafts, and they’ve arranged to analyze some of the rocks. (But the samples they’ve been promised are currently stuck in transit in Fiji, said Jutzeler.)

    By analyzing the chemistry of the pumice, Jutzeler and his colleagues hope to learn about the properties of the underwater volcanic eruption. For instance, was it eruptive or effusive?

    Studying the rocks’ surfaces will also reveal how quickly they’re being abraded, which will shed light on how rapidly volcanic dust is being deposited into the ocean. That’s important because some plankton feed on this volcanic debris, which can result in phytoplankton blooms, said Jutzeler.

    Jutzeler and other researchers are keeping a close watch on how the rafts are moving. Satellite imagery—from Terra, Aqua, Sentinel, and Landsat satellites, for instance—provides nearly daily updates. Ocean currents, wind, and waves sculpt and power the rafts, which now number in the hundreds.

    NASA Terra satellite

    ESA Sentinels (Copernicus)

    NASA/Landsat 8

    They’ll likely arrive in Fiji in a few weeks, Jutzeler predicts.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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.

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 8:01 am on September 6, 2019 Permalink | Reply
    Tags: "Forecasting Solar Storms in Real Time", , CME Scoreboard, , Eos, ,   

    From Eos: “Forecasting Solar Storms in Real Time” 

    From AGU
    Eos news bloc

    From Eos

    30 August 2019
    Jenessa Duncombe

    Predicting when solar storms will hit Earth remains a tricky business. To help, scientists can now submit their forecasts of coronal mass ejections online as they unfold in real time.

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    A coronal mass ejection (CME) blasts off from the Sun in these coronagraphs captured on 27 February 2000 by the Solar and Heliospheric Observatory spacecraft. Credit: SOHO ESA & NASA


    ESA/NASA SOHO

    The Sun routinely ejects clouds of gas and sends them hurtling through space at several thousand kilometers per hour. At least a few dozen times a year, those clouds head straight for Earth.

    These natural events, called coronal mass ejections (CMEs), crop up when the Sun’s magnetic field becomes tangled and, in righting itself, releases a swarm of charged particles called superheated plasma. Sent at just the right angle toward Earth, these plasma clouds can wreak havoc on our electrical grids, satellites, and oil and gas pipelines.

    Quebec, Canada, for instance, experienced a blackout related to a solar storm on a winter night in 1989. The province went black after a solar storm sent an electric charge into the ground that shorted the electrical power grid. The outage lasted 12 hours, stranding people in elevators and pedestrian tunnels and closing down airports, schools, and businesses.

    Solar storms can threaten our communication and navigation infrastructure. In the past, solar storms interrupted telegraph messages, and future storms could threaten our cellphones, GPS capabilities, and spacecraft.

    With the right kind of warning, utility operators, space crews, and communications personnel can prepare and steer clear of certain activities during solar storms. But once a CME event is spotted leaving the Sun, our best models struggle to forecast when exactly it will arrive.

    To improve forecasts, a group of scientists is taking a community approach: What if researchers working on CME models around the world could post their forecasts publicly, in real time, before the CME reaches Earth?

    The CME Scoreboard, run by the Community Coordinated Modeling Center at NASA Goddard Space Flight Center, does just that. The online portal with 159 registered users acts as a live feed of CME predictions heading for Earth. The portal gives scientists a simple way to compare forecasts, and the log of past predictions presents a valuable data set to assess forecasters’ accuracy and precision.

    Keeping Score

    The AGU Grand Challenges Centennial Collection features the major questions faced by science today. Editors of Space Weather identified CME predictions as one of them, calling the ability to provide them “essential for our society [Space Weather].”

    CME forecasting still lags behind our capabilities to forecast weather systems here on Earth, and the paper highlights several reasons why. Leila Mays, coauthor on the paper and science lead for the CME Scoreboard at NASA Goddard Space Flight Center, said that CME forecasts are lacking in two key areas: Measurements of solar activity are sparse, and the exact physical details driving the Sun are still unclear.

    Despite the need for improvement, people on Earth still rely on CME forecasts, and scientists have myriad ways to supply them. The National Oceanic and Atmospheric Administration and the United Kingdom’s Met Office both release publicly available CME predictions, and individual research groups build their models from scratch. Forecasting models range from data-driven empirical models to physics-based, equation-driven models.

    The models operate independently, perhaps using unique parameters or data inputs, but they all strive for a shared goal: to determine when a CME, or CME’s shock wave, will impact Earth.

    The CME Scoreboard serves as a repository for a wide range of these models. Mays said that scientists tracking solar activity will notice when a CME event explodes from the surface of the Sun, setting down a ticking clock for when the plasma will hit Earth (or miss it altogether). This sets off a flurry of activity, with scientists running their models with parameters from the most recent eruption, including the plasma’s speed, direction, and size. With the numbers crunched, they post their best guess and wait to see what unfolds.

    Ground Truth

    Since the CME Scoreboard’s inception in 2013, scientists have posted 814 arrival time predictions. Some predictions narrowly miss the mark, skirting the real arrival time of the CME by a mere hour or two. But others are days away, trailing the arrival by 30 or more hours.

    Mays said that the forecasts come from over a hundred users and represent 26 unique prediction methods. She said that the interest in the portal has been strong, which she’s not surprised about. The scoreboard merely gives a platform for ad hoc discussions that researchers were already having, spread across listservs and email chains whenever a new CME would appear.

    Pete Riley, a senior research scientist at Predictive Science Inc., knew of the scoreboard but had never contributed. Looking at years of forecasts on the website, he decided to analyze the accuracy and precision of past predictions.

    “I felt like having knowledge in the field but not having a horse in the race, so to speak, I’d be able to do a fairly independent evaluation,” Riley told Eos.

    His study, published in Space Weather in 2018, is the first analysis of the scoreboard data. Riley and his collaborators compared the difference between the projected arrival times and the actual reported times for 32 models. The analysis showed that the forecasts, on average, predicted the CME arrival with a 10-hour error, and they had a standard deviation of 20 hours. Several models performed the best, he said, but only moderately so, and the few that submitted regularly over the 6 years of data analyzed didn’t seem to be improving their forecasts.

    The paper “serves as kind of a ground truth for where we are at currently,” Riley said, as well as laying the foundation for future analysis. Riley made the code accessible so that future forecasts can be tested against the group. Mays said that in the future, the scoreboard may use the information to create a list of automatically updating metrics.

    Although more work lies ahead, Riley said that the future looks bright for more accurate predictions. He points to new space missions that will help fill in blind spots, including NASA’s Parker Solar Probe and nanosatellites called CubeSats that individual research groups deploy.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    “Space weather is becoming ever more important because as a society, we are so reliant on technology now,” Riley said. With the additional data, he said, “I think it’s promising that in the future we will be able to make predictions more accurate.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 10:57 am on August 28, 2019 Permalink | Reply
    Tags: , Anemic Stars", , , , , Eos   

    From Eos: “Hunting for Planets Around Old, Anemic Stars” 

    AGU
    Eos news bloc

    From Eos

    8.28.19
    Kimberly M. S. Cartier

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    The planetary system depicted here, Kepler-444, formed more than 6 billion years before our Sun was born. Credit: NASA, Tiago Campante/Peter Devine

    The first stars were made of hydrogen and helium. That hasn’t really changed, but each subsequent generation of stars has a bigger fraction of heavy elements like carbon, oxygen, silicon, and iron—elements needed to make planets.

    Heavy elements make up only about 1.3% of the Sun’s mass. Astronomers call these elements metals and abbreviate their abundance with the atomic symbol for iron. Even at that low percentage, the Sun still had enough material to form eight planets, dozens of dwarf planets, and an uncounted number of smaller objects.

    But how low can a star’s metallicity go and still form planets? To answer that question, Ji Wang and his team are turning to the oldest stars in the galaxy: galactic halo stars.

    “Halo stars are the key to understanding planet formation in the very metal-poor regime,” said Wang, an astrophysicist at Ohio State University in Columbus. Wang discussed this project at Extreme Solar Systems IV in Reykjavík, Iceland, on 19 August.

    Hiding in the Halo

    Most stars in the Milky Way galaxy live in one of three places: a compact central bulge, a dense and thin spiral disk, or a diffuse cloudlike halo.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Sometimes, halo stars plunge through the disk at high speeds and from random directions, like a comet streaking in from the cold reaches of the solar system before swooping outward again.

    Those trajectories make halo stars stand out in surveys of stellar motion, like the European Space Agency’s Gaia mission. Halo stars also tend to be older and therefore more chemically primitive than disk stars.

    Wang’s team turned to halo stars to find out how often low-metallicity stars create planets. Of Gaia’s catalog of 1.7 billion stars, the researchers narrowed their search to stars with halolike trajectories that are within about 3,000 light years of us and have less than 10% the amount of metals as the Sun. They narrowed that list to stars bright enough for NASA’s Transiting Exoplanet Survey Satellite (TESS) to observe with high precision.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    During the first half of its mission, TESS searched for planets around about 6,200 of the team’s chemically primitive target stars. The researchers focused on large, short-period objects called hot Jupiters, the type of planet most likely to transit.

    “We didn’t find any planets,” Wang said. “This is okay because, even for the nondetection, we have put a very tight constraint on the occurrence rate around metal-poor stars.”

    The team’s tests showed that TESS could have overlooked roughly half of potential hot Jupiters around these distant stars. On the basis of those statistics, the team calculated that hot Jupiters are born around metal-poor halo stars no more than 0.34% of the time.

    Is It Age or Lack of Metals?

    “This is really cool work. I think it’s a great idea,” Kevin Schlaufman, an astronomer at Johns Hopkins University in Baltimore, Md., commented after the presentation. He pointed out, however, that some recent studies suggest that tidal interactions can make hot Jupiters crash into their stars. “If hot Jupiters are destroyed by tides, it might be the case that old stars, regardless of their metallicity, are unlikely to have a hot Jupiter.”

    One way to resolve that issue, according to Wang, would be to look for metal-poor stars among the younger disk stars. But this would be like looking for a handful of needles in a haystack: Disk stars far outnumber halo stars, and they are mostly metal rich. Finding the few metal-poor stars would be a big task, he said.

    The team estimates that TESS will observe about another 10,000 metal-poor halo stars by the end of next year, which will narrow down how often anemic stars create giant planets, Wang said.

    “With the full sample, we could set a 0.14% upper limit if there are still zero detections,” he said.

    In the meantime, “we can still look for small planets, although with a lower detection efficiency,” Wang said. “There are still a few planets we could detect around these halo stars.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 9:35 am on August 20, 2019 Permalink | Reply
    Tags: "Sampling the Space Between the Stars", , ENAs-energetic neutral atoms, Eos, , Heliosheath, , , ,   

    From Eos: “Sampling the Space Between the Stars” 

    From AGU
    Eos news bloc

    From Eos

    19 August 2019
    Mark Zastrow

    Data from the Cassini and Voyager spacecraft reveal new information about the Sun’s magnetic bubble.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    NASA/Voyager 1


    NASA/Voyager 2

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    The basic shape and properties of the heliosphere, the protective magnetic bubble created by the solar wind, shown in this schematic are based on measurements of heliosheath proton distributions from Voyager 1 and 2 (illustrated in the diagram) and of energetic neutral atoms by Cassini. The location of the inner edge of the heliosheath, called the termination shock, is roughly 10 astronomical units (AU; 1 AU is equivalent to the mean Sun-Earth distance of about 150 million kilometers) farther from the Sun where Voyager 1 crossed it compared with Voyager 2, but the location of the outer edge, the heliopause, is about the same distance at along both Voyager trajectories. Red arrows represent the interstellar plasma flow deflected around the heliosphere bubble. Credit: K. Dialynas, S. M. Krimigis, D. G. Mitchell, R. B. Decker and E. C. Roelof

    Charged particles that spew into space as part of the solar wind create a protective magnetic bubble tens of billions of kilometers wide around the solar system. This bubble, called the heliosphere, plows through the harsh cosmic radiation of interstellar space.

    Understanding the physics at the bubble’s edge, called the heliosheath, is not easy. The boundary is in constant flux and pushes out against the broader interstellar magnetic field that permeates our corner of the Milky Way. Only two spacecraft—Voyager 1 and 2, originally launched by NASA in 1977—have ever traversed the frontiers of our local bubble.

    Now Dialynas et al. [Geophysical Research Letters] have combined Voyager data with observations from NASA’s Cassini mission, which orbited Saturn from 2004 to 2017, to gain more insight into this region of space. The researchers recognized that the missions, although launched 20 years apart, had collected complementary data. Voyager 1 and 2 had instruments that measured energetic ions as the craft crossed the heliosheath and exited the solar system. Cassini, meanwhile, was able to remotely observe energetic neutral atoms (ENAs) arriving in all directions from the heliosheath.

    These two phenomena are related: ENAs come from the heliosheath, where fast solar wind protons collide with neutral hydrogen atoms from interstellar space and “steal” an electron from the interlopers. The Voyager probes took in situ measurements of the parent heliosheath proton distributions as they passed through this region. Meanwhile, the protons with newly added electrons become ENAs and zip off in all directions.

    The synergy among the spacecrafts’ observations allowed the researchers to use Voyager data from the heliosheath to ground truth and calibrate ENA data from Cassini, which was more sensitive to lower energetic particles than Voyager was. Together, the spacecraft extended data on the intensity of both ENAs and ions to include a broader range of energies, which gave the team a window into the physics in the heliosheath as the solar wind and interstellar medium press against each other.

    The researchers found that in the energy range considered in their study (>5 kiloelectron volts), lower-energy ions with energies between about 5 and 24 kiloelectron volts played the largest role in maintaining the pressure balance inside the heliosheath. This allowed the team to calculate the strength of the magnetic field and the density of neutral hydrogen atoms in interstellar space—about 0.5 nanotesla and 0.12 per cubic centimeter, respectively.

    On the basis of calculations from Voyager 2 data, the researchers predict that the heliopause, the outer boundary of the heliosheath, is located roughly 18 billion kilometers from the Sun, or 119 times the distance from the Sun to the Earth—right where Voyager 2 found it in November 2018.

    Furthermore, the finding that the lower-energy ions dominate the pressure balance in the heliosheath means that space physicists will have to rethink their assumptions about the energy distribution of such particles in the heliosheath.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 8:51 am on August 12, 2019 Permalink | Reply
    Tags: "Crystal Clocks Serve as Stopwatch for Magma Storage and Travel Times", , , Eos, , The mineral’s composition changes creating a kind of crystal clock., The team used a volcanic mineral called spinel as a crystal stopwatch., ,   

    From U Cambridge via Eos: “Crystal Clocks Serve as Stopwatch for Magma Storage and Travel Times” 

    U Cambridge bloc

    From University of Cambridge

    Via

    AGU
    Eos news bloc

    Eos

    8.12.19
    Mary Caperton Morton

    Magma stored for 1,000 years in an Icelandic volcano journeyed to the surface in just 4 days.

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    The 2014–2015 eruption of Iceland’s Holuhraun lava field had an eruption style similar to the Borgarhraun eruption of Iceland’s Theistareykir volcano, which took place 10,000 years ago. Credit: Euan J. F. Mutch

    Volcanic eruptions are just the tip of the iceberg: Hidden deep below ground, the preeruption behavior and movements of magma remain largely mysterious. Two new studies centered around a volcano in Iceland are shedding light on how long magma was stored deep underground and how long it took to travel to the surface before erupting, information that may be used to improve existing models of complex magmatic systems.

    Geophysical monitoring methods can see only so deep beneath the surface of Earth, so to figure out what is happening deep inside a volcano, “you have to be a geological detective,” said Euan Mutch, an igneous petrologist at the University of Cambridge in the United Kingdom and lead author on both of the new studies, published in Science and Nature Geoscience.

    Mutch and colleagues at the University of Cambridge focused on the Borgarhraun eruption of Theistareykir, a volcano in northern Iceland, which took place around 10,000 years ago. Previous studies have shown the magma that fed this eruption came directly from the Mohorovičić discontinuity (the Moho), where Earth’s crust meets its mantle, at a depth of about 24 kilometers—far deeper than geophysical methods can see clearly.

    To determine how long the magma was stored at the Moho before erupting, the team used a volcanic mineral called spinel as a crystal stopwatch.

    “The elements in the crystal want to be in equilibrium with the surroundings,” Mutch explained.

    As the elements equilibrate by diffusing out of the spinel, the mineral’s composition changes, creating a kind of crystal clock. Using known diffusion rates for aluminum and chromium, the team was able to determine how long the minerals were stored in the melt before it erupted, in this case about a thousand years, they wrote in Science.

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    Mineral maps like this one show areas of concentrated aluminum in yellow and lower concentrations in red and black. The process of diffusion from high to low concentration can be used to estimate how long the crystal remained in the magma chamber before erupting. Credit: Euan J. F. Mutch

    In the Nature Geoscience study, Mutch and colleagues used a similar diffusion modeling technique on olivine crystals to show that the magma ascended from the Moho to the surface in as little as 4 days, at a rate of 0.02 to 0.1 meter per second.

    The two studies represent some of the first evidence of magmatic timescales for eruptions originating in the deep crust at the Moho boundary, said David Neave, a petrologist at the University of Manchester in the United Kingdom who was not involved in either of the new studies.

    “A lot of progress has been made understanding timescales of shallower volcanoes, but these are the first studies to estimate how long magma is stored in the deep crust before it erupts,” Neave said. “That’s crucial new information.”

    Diffusion modeling is not a new technique. The methods have been around for at least 10 years, Neave said, but Mutch and colleagues “were very clever in working out the uncertainties and arrived at much more precise estimates for these timescales than previous groups have been able to do.”

    The findings also lend support to a growing body of research suggesting that magmatic systems can be much more complex than the textbook model of a volcano fed directly from a single bulbous magma chamber, said Stephen Sparks, a volcanologist at the University of Bristol in the United Kingdom who was not involved in either of the new studies.

    “Their results contribute to the evidence that supports vertically extensive transcrustal magma systems,” Sparks said. The study does not introduce any fundamentally new concepts but “supports this emerging new paradigm. The paper is amongst the most thorough and convincing published so far.”

    Applying the Techniques to Other Volcanoes

    Whether the 1,000-year timescales for magma storage and mere days of travel to the surface are typical of other volcanoes or unique to Theistareykir is unknown, Mutch said. The next steps will be to apply the same diffusion modeling techniques to other eruptions.

    Crystal clocks can be used at a variety of volcano types, not just the basaltic volcanoes found in Iceland, Neave said.

    “Most volcanoes are ultimately underlain by basaltic materials, even if they’re erupting rhyolite or andesite at the surface like at the Cascades volcanoes [in the United States],” he said. “I think this approach will prove to be widely applicable to a range of volcanic settings.”

    The findings may ultimately aid in developing more accurate magmatic and eruption models as well as improving volcanic hazard forecasts, Mutch said. The Nature Geoscience paper in particular showed a link between the magma’s rate of ascent and the release of carbon dioxide, which could be used to predict an impending eruption.

    “At the ascent rates estimated for the Borgarhraun magma, an increase in carbon dioxide flux at the surface would only be detected at most 2 days before the eruption,” Mutch said. However, other volcanic systems may offer more lead time: “This threshold will be different for magmas with different carbon contents and that are stored at different depths before eruption.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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.

    U Cambridge Campus

    The University of Cambridge (abbreviated as Cantab in post-nominal letters) is a collegiate public research university in Cambridge, England. Founded in 1209, Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 constituent colleges and over 100 academic departments organised into six schools. The university occupies buildings throughout the town, many of which are of historical importance. The colleges are self-governing institutions founded as integral parts of the university. In the year ended 31 July 2014, the university had a total income of £1.51 billion, of which £371 million was from research grants and contracts. The central university and colleges have a combined endowment of around £4.9 billion, the largest of any university outside the United States. Cambridge is a member of many associations and forms part of the “golden triangle” of leading English universities and Cambridge University Health Partners, an academic health science centre. The university is closely linked with the development of the high-tech business cluster known as “Silicon Fen”.

     
  • richardmitnick 10:41 am on July 17, 2019 Permalink | Reply
    Tags: , , , , , Eos, ,   

    From Eos: “The Cassini Mission May Be Over, but New Discoveries Abound” 

    AGU
    Eos news bloc

    From Eos

    7.17.19
    Sarah Derouin
    sarah.derouin@gmail.com

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    New analysis of high-resolution images shows ring textures and disruptions within Saturn’s rings in unprecedented detail.

    1
    The embedded moon Daphnis creates three waves in Saturn’s rings in this image taken by the spacecraft Cassini during its grand finale. Credit: NASA/JPL-Caltech /Space Science Institute
    After more than a decade observing Saturn, Cassini completed its mission in style—a grand finale sent the spacecraft on almost 2 dozen dives between the planet and the rings before it took its final descent into Saturn’s atmosphere.

    During these ring-grazing trips during summer 2017, Cassini collected high spatial resolution images and spectral and temperature scans of the rings. Years after its crash, researchers are still working with the piles of data Cassini collected, making new discoveries about the ringed planet.

    In a new paper in Science, researchers dove into these high-resolution data, and their synthesis revealed new features inside the rings that hadn’t been seen before. They found sculpted areas within the rings—including banded textures and disturbances from embedded bodies—that can be used to help theorists narrow in on how Saturn and its rings may have formed.

    Ring Disruptions

    During the grand finale, Cassini took high-resolution images of all the rings, from the ring closest to the planet (ring A) to the F ring, one of the most distant. The images are the highest-fidelity images ever to be taken of the rings, and they revealed some surprises to the research team.

    “We found a number of things that are new—a number of structures that we’d never been close enough to see before,” says Matthew Tiscareno, a senior research scientist at the SETI Institute in Mountain View, Calif., and lead author of the paper.

    The team explored disturbances within the rings related to moons or smaller moonlike debris embedded in the rings. The moon Daphnis, for example, leaves a wide trail of disruption in its wake, including a wide gap in the ring and trailing waves of debris.

    These waves, Tiscareno explains, are created by the rings moving at different speeds: The rings orbiting closer to Saturn move at a faster speed than those farther from the planet. This process creates a sheer flow, and “on the outward edge, the ring part, the ring material is falling behind Daphnis and its orbit,” he says.

    2
    This propeller, informally called Bleriot, formed within Saturn’s rings. Propellers are caused by a central moonlet that alters the ring as it orbits around the planet. Credit: NASA/JPL-Caltech/Space Science Institute

    But it’s not just big moons like Daphnis that disrupt the rings. Smaller objects are trying their best to create ring gaps as well, but with less success. “These are objects that are 10 times smaller, which means they’re a thousand times less massive,” says Tiscareno.

    Instead of forming a gap, Tiscareno says these objects form a propeller-shaped disturbance. The swirled structure forms briefly but doesn’t stick around long enough to create a true gap in the ring.

    The researchers knew the propellers existed, so they asked Cassini to perform some targeted flybys to get a closer look.

    “The details of that [propeller] structure [are] telling us exactly how big the moons are at the center of the propeller…about a kilometer across,” says Tiscareno, adding that at that size, it’s not possible to see the actual moon with these image resolutions.

    Ring Textures

    Cassini’s instruments also revealed new details on textures within the rings. “We knew that there were textures before, but we had not seen them as comprehensively,” says Tiscareno. The team noted that the ring textures ranged from strawlike clumps to feathery regions, with sharp edges on their borders.

    One idea for the different textures within the rings is a changing particle composition, says Douglas Hamilton, an astronomer at the University of Maryland who was not involved with the paper. For example, one part of the ring could be more silicate rich, whereas another area has more ice. But Hamilton says the researchers “make a good case” for these textures being caused by something other than composition.

    The team inferred that the sharp borders along the ring textures were not due to a composition change, says Tiscareno, but instead result from the physical properties of the ring particles.

    One physical property might be the roughness of ring particles. Tiscareno explains: Is a ring particle more like a billiard ball or more like a snowball? Roughness can affect not only the reflection of light but also how particles interact with each other. “Do they bounce off of each other, like billiard balls do?” he asks. “Or are they kind of sticky, like a snowball would be?”

    Forming a Ring

    Getting close-up data from Cassini gives researchers information that reaches beyond our nearby ringed planet.

    “Rings are our only natural laboratory to understand disk processes more generally,” says Tiscareno. “And that goes to understanding baby solar systems, which are disk systems where you have massive objects that are embedded in the disk.”

    “We’re seeing massive objects embedded in the rings, and we’re seeing the disk itself doing things that we didn’t expect,” he adds.

    Hamilton says that papers like this help uncover how features like propellers might form. “The theory is our imagination,” Hamilton says. Work like this paper, he adds, allows theoretical researchers to be able to test their models on Saturn’s rings against observed data.

    “[These data are going] to be the basis for 10 years of effort by the entire field in trying to figure out how to make all this [propellers, textures] happen,” says Hamilton.

    See the full article here .

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  • richardmitnick 8:52 am on July 15, 2019 Permalink | Reply
    Tags: "Seismic Sensors Probe Lipari’s Underground Plumbing", , , Eos,   

    From Eos: “Seismic Sensors Probe Lipari’s Underground Plumbing” 

    AGU
    Eos news bloc

    From Eos

    7.15.19
    Francesca Di Luccio
    Patricia Persaud
    Luigi Cucci
    Alessandra Esposito
    Guido Ventura
    Robert W. Clayton

    An international team of scientists installed a novel, dense network of 48 seismic sensors on the island of Lipari to investigate the active magma system underground.

    1
    The magma system underneath the island of Lipari, shown here, is connected to a regional fault system formed by tectonic activity rather than to volcanoes like nearby Etna and Stromboli. A research team recently deployed a dense network of seismic sensors to investigate Lipari’s unusual setting. Credit: F. Di Luccio

    Just north of the island of Sicily, near the toe of Italy’s “boot,” a chain of volcanic islands traces a delicate arc in the Mediterranean Sea. This chain, the Aeolian Islands, hosts popular tourist resorts in proximity to some of Earth’s most active and well-known volcanoes, including Etna and Stromboli. Lipari, the largest of these islands, lies just north of the island of Vulcano, for which these eruptive features are named. Lipari is less well characterized than some of the other nearby volcanoes, but one research group is setting out to change this.

    Lipari is located ~80 kilometers north of the well-monitored Etna volcano. The island’s hydrothermal system, in which magma heats the water underground, is not connected to eruptive centers, but, rather, is connected to the regional fault system that delimits the western boundary of the active Ionian subduction zone.

    Lipari holds a unique place in our understanding of the tectonic evolution and hydrothermal activity of volcanoes emplaced in subduction zones. Within the framework of the ring-shaped Aeolian arc, the unexpected NNW–SSE alignment of Lipari and Vulcano has been related to a major regional discontinuity, the Tindari-Letojanni subduction transform edge propagator (STEP) fault, a tear in a tectonic plate that allows one part of the plate to plunge downward while an adjacent part remains on the surface (Figure 1).

    2
    Fig. 1. These tectonic and bathymetric maps show (a) southern Italy and (b) the Aeolian Islands. The bathymetric data are from Ryan et al. [2009]. Major faults are shown as black lines. Regional earthquakes larger than magnitude 3 (black dots) were recorded over the past 3 decades by the permanent Italian seismic network (magenta triangles). Events larger than M 3 that occurred in the time window of the current experiment are shown as cyan stars. The yellow star off the northeastern coast of Sicily shows the location of the 1 November 2018 ML 3.2 earthquake whose waveforms are shown in the left-hand plot of Figure 3. In Figure 1a, blue dashed lines in the Tyrrhenian Sea indicate the isodepths (50, 100, 200, and 300 kilometers) of the slab [Barreca et al., 2014]. Shown in Figure 1b are the locations of Lipari, the Sisifo-Alicudi fault (SAf), and the Tindari-Letojanni STEP fault (STEP-TLf).

    One innovative way to monitor the deep and shallow dynamics of magmatic systems is to deploy dense arrays of seismic sensors over active volcanoes [Hansen and Schmandt, 2015; Ward and Lin, 2017; Farrell et al., 2018]. Thus, to understand Lipari’s unusual setting, we deployed a dense array comprising 48 wireless, self-contained seismic instruments. This is the first time that a dense seismic array has been deployed to investigate a hydrothermal system in the volcanically active Aeolian Islands and the volcanism in the proximity of a STEP fault.

    Transporting the seismic sensors, called nodes, to Lipari required a transatlantic shipment from Louisiana State University (LSU) to Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome, followed by a ferry trip to Lipari. Over the course of 2 days, two crews of two people each placed 48 instruments, spaced ~0.1–1.5 kilometers apart, in a wide variety of locales: with homeowners and hotel owners, at the Lipari observatory, on the sides of streets, and buried in the near surface beneath a few centimeters of soil (Figure 2).

    3
    Fig. 2. Three-dimensional perspective view of a Google Earth map of Lipari Island, which covers an area of about 35 square kilometers. The last eruption on this island was in 1220 CE at Monte Pilato. The locations of the ZLand three-component seismic nodes are shown as yellow triangles. A magenta triangle indicates broadband station ILLI of the Italian permanent seismic network. Site photos taken at selected locations are also shown. The inset shows a detailed map of the hydrothermal area (modified from Cucci et al. [2017]) and the locations of photos A, B, and C, which characterize the hydrothermal alteration.

    Researchers from INGV in Rome, the Department of Geology and Geophysics at LSU, and the Seismological Laboratory of the California Institute of Technology deployed the 48 FairfieldNodal ZLand three-component nodes, which have a 5-hertz corner frequency. The nodes recorded one data point every 4 milliseconds from 16 October to 14 November 2018.

    4
    After their transatlantic voyage from Louisiana to Rome, seismic sensors await a ferry trip to Lipari. Credit: A. Esposito

    Lipari’s Tectonic Neighborhood

    Lipari Island belongs to the Aeolian archipelago, a group of subaerial and submarine volcanoes located in southern Italy between the southern Tyrrhenian Sea back-arc basin and the Calabrian Arc, an orogenic belt affected by late Quaternary extensional tectonics. The NNW–SSE Lipari-Vulcano alignment (Figure 1) coincides with the regional tectonic boundary of the Ionian Sea–Calabrian Arc subduction system that is marked by the Tindari-Letojanni STEP fault [Barreca et al., 2014].

    To the west of the archipelago, the WNW–ESE oriented Sisifo-Alicudi fault accommodates shortening related to the eastern termination of the contractional belt (Figure 1). The Tindari-Letojanni and Sisifo-Alicudi fault systems are characterized by shallow seismicity, at depths of less than 25 kilometers, and recorded earthquakes of M 5.8 or less, including the M 4.7 Ferruzzano earthquake in 1978 [Gasparini et al., 1982].

    The Aeolian volcanoes, emplaced on 15- to 20-kilometer-thick continental crust, are the most recent evidence of the magmatism that started during the Pliocene epoch (5.3–2.6 million years ago). This magmatism started in the central sectors of the Tyrrhenian Sea and migrated southeastward toward the Calabrian Arc.

    From about 1 million years ago to the present time, the volcanoes have been producing magma with calc-alkaline, shoshonitic, and alkaline potassic compositions [De Astis et al., 2003; Barreca et al., 2014]. The geochemical affinity of these rocks and the deep seismicity (reaching depths of 550 kilometers) in the southern Tyrrhenian Sea indicate that the Aeolian Islands represent a volcanic arc related to the subduction and rollback of the Ionian slab beneath the Calabrian Arc [Milano et al., 1994; De Astis et al., 2003].

    5
    Early volcanic activity at Lipari ejected lava and rocks into the air, but today, geothermally heated water is more common. Credit: L. Cucci

    Early volcanic activity on Lipari (150,000 years ago and earlier) was concentrated in the western part of the island and focused along north–south aligned vents. Later on, between 119,000 and 81,000 years ago, the Sant’Angelo and Monte Chirica volcanoes deposited lava and pyroclastics (volcanic material that is forcibly ejected into the air) in the central sector of the island (Figure 2).

    From 42,000 years ago to 1220 CE, the activity was concentrated in the southern and northern sectors. This activity included pyroclastics related to subplinian eruptions, domes, and lava flows. Currently, hydrothermal activity (the expulsion of geothermally heated water) characterizes Lipari, Vulcano, and areas offshore of Panarea and Salina. The Lipari hydrothermal field (approximately 0.5 × 0.15 kilometer; see inset in Figure 2) is located along a north–south striking alteration belt in the western and older sector of the island and is characterized by gypsum-filled veins, normal faults with a prevailing NNW–SSE to north–south strike, and active fumaroles.

    Hydrothermalism on Lipari is not associated with centers of recent volcanic activity (less than 40,000 years old), and fluid pathways are strictly controlled by faults and fractures [Cucci et al., 2017]. Vein networks of gypsum (a type of sulfur mineral) affect the hydrothermal system in the lavas and scorias of the oldest Timponi volcanoes, the overlying pyroclastics of Monte Sant’Angelo, the 27,000-year-old Pianoconte pyroclastic deposits, and the present-day soil (inset in Figure 2). The hydrothermal alteration process has been going on for less than 27,000 years and is still active [Cucci et al., 2017].

    A Mountain of Data

    6
    Fig. 3. Seismograms from two earthquakes at local (left) and regional (right) distances recorded at the Lipari array. Vertical components of the ground velocity are low-pass filtered at 5 and 2 hertz for the ML 3.2 and MW 6.8 magnitude events, respectively, to improve the signal-to-noise ratio. Waveforms at the bottom of each plot are the seismograms of the two events recorded by the permanent broadband seismic station ILLI located on the southern tip of Lipari, as shown in Figure 1b, with numbers in bottom left corners indicating the epicentral distances.

    We collected more than 300 gigabytes of data, which include local, regional, and teleseismic (distant) earthquakes as well as ambient noise and volcanic tremor data. During the period of the experiment, about 50 earthquakes occurred within 100 kilometers of Lipari. Half of these had magnitudes of less than 2, but we also recorded 18 events larger than M 5 that occurred in the region and farther away. In Figure 3, we show two examples of recorded seismic waveforms from an ML 3.2 local earthquake and an Mw 6.8 regional earthquake.

    We aim to investigate in detail the crust and upper mantle beneath Lipari Island using receiver functions to characterize Earth’s structural response near the instrument and regional tomography to construct a three-dimensional image of Earth’s nearby interior. We will also analyze ambient noise and local volcanic tremors.

    We plan to merge the seismic data set with other observables such as geochemical measurements and structural data to get a more robust and complete picture of the tectonic setting. We will apply modern and sophisticated processing and analysis techniques used in seismological studies to the nodal seismic array data.

    The deployment of nodal arrays fills a unique niche in monitoring active volcanoes. In comparison to traditional portable seismic stations, nodal arrays enable a high-quality data set to be obtained over a short deployment period, at lower costs, with easier site selection capabilities, and with easy and quick installation procedures.

    Our collaborative field experiment is the latest vehicle for learning about the seismic structure of Lipari and an excellent approach to linking the unrest at depth to volcanic and hydrothermal activity at the surface in similar settings. This project will contribute to the evaluation of the geohazards of the Mediterranean region, where the African and Eurasian plates converge.

    _________________________________________________
    Acknowledgments

    We thank Comune di Lipari for hosting the experiment and INGV Catania and Lipari Observatory (L. Pruiti) for the logistical support. We are grateful to R. Vilardo and M. Martinelli of the Polo Museale di Lipari, Regione Sicilia; the Hotel Antea; Co.Mark and Tenuta Castellaro; and Alessandro (a grocery store) in Acquacalda for hosting some nodes of the experiment. We thank INGV Roma 1 for funding and supporting the project and the Department of Geology and Geophysics at LSU for supporting this project. A.E. was funded by INGV Osservatorio Nazionale Terremoti (ONT). LSU students R. Ajala and E. McCullison assisted with the deployment setup and preparation of the nodes. Data will be available in November 2020 (2 years after the last instrument was retrieved from the field) by contacting the corresponding author.
    _________________________________________________
    References

    Barreca, G., et al. (2014), New insights in the geodynamics of the Lipari–Vulcano area (Aeolian Archipelago, southern Italy) from geological, geodetic and seismological data, J. Geodyn., 82, 150–167, https://doi.org/10.1016/j.jog.2014.07.003.

    Cucci, L., et al. (2017), Vein networks in hydrothermal systems provide constraints for the monitoring of active volcanoes, Sci. Rep., 7, 46, https://doi.org/10.1038/s41598-017-00230-8.

    De Astis, G., G. Ventura, and G. Vilardo (2003), Geodynamic significance of the Aeolian volcanism (southern Tyrrhenian Sea, Italy) in light of structural, seismological, and geochemical data, Tectonics, 22(4), 1040, https://doi.org/10.1029/2003TC001506.

    Farrell, J., et al. (2018), Seismic monitoring of the 2018 Kilauea eruption using a temporary dense geophone array, Abstract V41B-07 presented at 2018 Fall Meeting, AGU, Washington, D.C., 10–14 Dec.

    Gasparini, G., et al. (1982), Seismotectonics of the Calabrian Arc, Tectonophysics, 84, 267–286, https://doi.org/10.1016/0040-1951(82)90163-9.

    Hansen, S. M., and B. Schmandt (2015), Automated detection and location of microseismicity at Mount St. Helens with a large-N geophone array, Geophys. Res. Lett., 42, 7,390–7,397, https://doi.org/10.1002/2015GL064848.

    Milano, G., G. Vilardo, and G. Luongo (1994), Continental collision and basin opening in southern Italy: A new plate subduction in the Tyrrhenian Sea?, Tectonophysics, 230, 249–264, https://doi.org/10.1016/0040-1951(94)90139-2.

    Ryan, W. B. F., et al. (2009), Global Multi-Resolution Topography synthesis, Geochem. Geophys. Geosyst., 10, Q03014, https://doi.org/10.1029/2008GC002332.

    Ward, K. M., and F.-C. Lin (2017), On the viability of using autonomous three-component nodal geophones to calculate teleseismic Ps receiver functions with an application to Old Faithful, Yellowstone, Seismol. Res. Lett., 88(5), 1,268–1,278, https://doi.org/10.1785/0220170051.

    See the full article here .

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  • richardmitnick 8:25 am on July 15, 2019 Permalink | Reply
    Tags: "Teams Invited to Test Coastal Hyperspectral Imaging Algorithms", , , , Eos   

    From Eos: “Teams Invited to Test Coastal Hyperspectral Imaging Algorithms” 

    AGU
    Eos news bloc

    From Eos

    7.15.19
    Margaret A. McManus
    mamc@hawaii.edu

    Eric Hochberg

    Hyperspectral Remote Sensing of Coastal and Inland Waters Webinar; 28 May 2019

    1
    Hyperspectral imagery collected by NASA’s Coral Reef Airborne Laboratory (CORAL) shows part of Swain Reefs off the eastern coast of Australia. Participants in a webinar last May planned an upcoming technology demonstration of hyperspectral remote sensing algorithms applied to coastal and inland waters. Credit: Eric Hochberg

    Satellite remote sensing using a few discrete wave bands of light, selected to fit the specific application (multispectral imaging), is a well-established means of monitoring the world’s open oceans. Coastal and inland waters are often much more complex, and the methods used to study these waters are more complex as well. These waters have greater sediment and algal loads than the open oceans, and light can reflect off the bottoms of these shallower water bodies, which complicates data analysis.

    Remote sensing of coastal and inland environments requires hyperspectral imaging—simultaneously measuring tens to hundreds of narrow, contiguous wave bands (typically visible through near infrared)—to disentangle multiple confounding signals. Efficient manipulation of large hyperspectral image data volumes, as well as subsequent generation of meaningful and accurate data products, requires sophisticated algorithms, which continue to evolve and improve.

    In May 2018, participants in the Hyperspectral Imaging of Coastal Waters workshop, sponsored by the Alliance for Coastal Technologies (ACT) and the National Oceanic and Atmospheric Administration (NOAA), recommended a technology demonstration of hyperspectral remote sensing algorithms applied to coastal and inland waters. In May 2019, ACT followed up with an introductory webinar to plan the demonstration.

    Thirty-seven individuals participated in the webinar, representing academic and government research institutions, as well as technology developers from around the globe. There were representatives from ACT, seven members of a technical advisory committee established for this demonstration, four individuals and teams already registered to participate in the demonstration, and seven prospective individuals and teams.

    NOAA established ACT in 2001 to bring about fundamental changes in environmental technology innovation and research and in operations practices. ACT achieves its goal through specific technology transition efforts involving both emerging and commercial technologies. Its efforts include the explicit involvement of resource managers, small- and medium-sized firms, world-class marine science institutions, NOAA, and other federal agencies. ACT’s core efforts are as follows:

    technology evaluations for independent verification and validation of technologies
    technology workshops and webinars for capacity and consensus building and networking
    technology information clearinghouses, including an online technologies database

    For the hyperspectral technology demonstration, ACT is inviting individuals and teams with established processing routines and algorithms to work with highly described hyperspectral data sets and corresponding in situ validation data sets. The goal of the demonstration is to evaluate the capabilities and maturities of various algorithms. This exercise is not a research project; rather, it is an opportunity to enhance communication within the community and to advance future applications of hyperspectral remote sensing in coastal waters.

    2
    Three views of the Torres Strait, between Australia and Papua New Guinea, from the CORAL mission illustrate an example of applied hyperspectral data: pseudotrue color image of 12 flightlines were acquired by the Portable Remote Imaging Spectrometer (PRISM) on 12 October 2016 (left); the results of CORAL data processing estimate the probabilities that image pixels are dominated by coral, algae, or sand (middle); and a map of the percentages of coral-dominated pixels in 1 × 1 kilometer grid cells, which enables researchers to fulfill CORAL’s science objective of investigating reef condition in relation to large-scale biogeophysical forcings (right). PRISM data collected for CORAL are freely downloadable.

    Data sets being used in the hyperspectral algorithm technology demonstration characterize kelp forests, coral reefs, harmful algal blooms (including those in inland waters), sea grass, and water quality. It is not required that all individuals and teams work with all data sets. Individuals and teams will select the data sets they are most familiar with, and they are welcome to work with more than one data set or contribute additional data sets that will be made available to all demonstration participants.

    The resulting data products are useful to scientists developing a greater understanding of these natural systems, as well as to resource managers tasked with conservation and decision-making. The data products also support future hyperspectral missions such as NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) and Surface Biology and Geology (SBG).

    The hyperspectral algorithm technology demonstration will be conducted over a 4- to 6-month time frame. The original request for technology was released 20 March 2019. The deadline for individuals and teams to register to participate is 31 August 2019.

    ACT anticipates an additional webinar or in-person workshop in fall 2019. Technology demonstration results will then be shared in a final workshop at the University of Hawai‘i at Mānoa in winter 2020. The overarching goal of the demonstration includes publishing individual project results and synthesis papers on learned best practices. Several manuscripts and a final report are expected to result from these collaborations.

    ACT continues to accept applications to participate in the demonstration. Please contact Thomas Johengen with expressions of interest. ACT will pay for travel costs for one to two members of each team to attend workshops.

    See the full article here .

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  • richardmitnick 7:34 am on July 11, 2019 Permalink | Reply
    Tags: "New Proof That Accretion Disks Align with Their Black Holes", , , , , Bardeen-Petterson alignment, , Blue Waters Cray Linux XE/XK hybrid machine supercomputer, , Eos   

    From Eos: “New Proof That Accretion Disks Align with Their Black Holes” 

    AGU
    Eos news bloc

    From Eos

    10 July 2019
    Rachel Crowell

    1
    An image of an accretion disk around a black hole, as seen by an observer nearly edge on to the disk. Credit: NASA GSFC/J. Schnittman

    In 1975, physicist James Bardeen and astrophysicist Jacobus Petterson theorized the existence of a black hole phenomenon that researchers have since been scrambling to show.

    In a study published in the July issue of Monthly Notices of the Royal Astronomical Society, researchers announced that they finally demonstrated Bardeen-Petterson alignment, in which a spinning black hole causes the inner portion of a tilted accretion disk to align with the black hole’s equatorial plane. Finding this effect could change our understanding of how black holes grow and how their presence affects galaxies, according to Sasha Tchekhovskoy, a computational astrophysicist at Northwestern University and colead author of the study.

    2
    In this image, the inner region of the accretion disk (red) aligns with the equatorial plane of the black hole, while the outer disk tilts away. The inner disk (where the black curve dips) is horizontal due to Bardeen-Petterson alignment. Credit: Sasha Tchekhovskoy/Northwestern University and Matthew Liska/University of Amsterdam.

    Powerful Resources Fueled the Simulation

    To accomplish the most detailed and highest-resolution black hole simulation to date, Tchekhovskoy and his team used the Blue Waters supercomputer at the University of Illinois at Urbana-Champaign.

    NCSA U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer

    They also used adaptive mesh refinement, a research method that uses grids that change in response to movements within simulations, and a technique called local adaptive time stepping to bring down the simulation cost by 2 orders of magnitude.

    “It’s very difficult to model the [accretion] disks that show this effect” because they are extremely thin, said Tchekhovskoy. Using graphical processing units instead of central processing units (previously used in similar black hole simulations) enabled the team to “simulate the thinnest disks to date,” Tchekhovskoy said.

    These thin accretion disks have height-to-radius ratios of 0.03, and Tchekhovskoy says the team was surprised to discover that “all of these interesting effects,” including Bardeen-Petterson alignment, appear at that thickness. The thinnest disks simulated prior to this study were more than 1.5 times thicker.

    Cole Miller, an astrophysicist at the University of Maryland in College Park who wasn’t involved with the new study, said he’s impressed with the level of detail in the simulation.

    Unexpected Jets

    “A major surprise of this work is the finding of powerful jets, even in our thin disc accretion system,” the researchers wrote in the study.

    The finding runs counter to the team’s expectation that magnetic fields would rip through the thin accretion disks rather than producing jets, Tchekhovskoy said. Exploring this finding in future work could provide insights into a different phenomenon, he added: why only about 10% of bright, supermassive black holes produce these jets.

    Putting Bardeen-Petterson in Context

    Miller noted that some initial coverage of the new study incorrectly identified John Bardeen, James’s father and a two-time winner of the Nobel Prize in Physics, as one of the two people after which the Bardeen-Petterson effect is named.

    Besides theorizing the Bardeen-Petterson alignment, James Bardeen, now professor emeritus at the University of Washington in Seattle, is also known for formulating (with Stephen Hawking and Brandon Carter) the laws of black hole mechanics. Jacobus Petterson, who died in 1996, was “best known in the astronomical community for his analysis of X-ray binary systems,” according to an obituary written for the American Astronomical Society.

    “This groundbreaking discovery of Bardeen-Petterson alignment brings closure to a problem that has haunted the astrophysics community for more than four decades,” Tchekhovskoy said in a statement.

    “It’s an interesting paper and definitely takes things a step or two beyond previous work,” according to Julian Krolik, an astrophysicist at the University of California, Berkley, who wasn’t involved with the study.

    However, Krolik disagrees about the overall importance of the paper. “It’s not ‘ground-breaking,’ nor does it provide ‘closure.’ ‘Closure’ in this field would mean identification of all the principal mechanisms regulating where the steady-state orientation transition takes place, construction of a method to predict (given relevant disk parameters) the location of this transition, and definition of the boundaries in parameter space separating where alignment is successful and where it isn’t,” Krolik wrote in an email to Eos.

    There is one major question that Krolik said the researchers leave unanswered: why the accretion disk alignment “extends to only a short distance from the black hole, stopping far short of where they expected it to reach.”

    See the full article here .

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    Please help promote STEM in your local schools.

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  • richardmitnick 9:51 am on June 11, 2019 Permalink | Reply
    Tags: "Seeing the Light", , , , , Eos, , Lunar research   

    From Eos: “Seeing the Light” 

    From AGU
    Eos news bloc

    From Eos

    6.11.19
    Damond Benningfield

    1
    Apache Point Observatory’s laser fires at the Apollo 15 retroreflector during a lunar eclipse in 2014. Credit: Dan Long, Apache Point Observatory

    Apache Point Observatory, near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft)

    When Neil Armstrong and Edwin “Buzz” Aldrin blasted off the Moon on 21 July 1969, they left a couple of packages at Tranquility Base. One was a solar-powered seismometer that collected 21 days of observations before expiring in late August. The other was an aluminum frame filled with chunks of fused-silica glass that looked a bit like a high-tech egg crate.

    Along with similar devices left on the Moon by Apollo 14 and 15, the instrument is still working—the only Apollo surface experiment that continues to provide data.

    Known as a lunar laser ranging retroreflector, it bounces pulses of laser light back to their sources on Earth. Scientists time the round-trip travel time of each pulse, allowing them to measure the Earth-Moon distance to within a millimeter. A half century of these observations has provided precise measurements of the shape of the Moon’s orbit, wobbles in the Moon’s rotation, and other parameters. Those, in turn, have helped scientists determine the Moon’s recession rate, probe its interior structure, and test gravitational theory to some of the highest levels of precision yet obtained.

    “This is a venerable technique that’s provided some of our best science about how gravity works,” says Tom Murphy, a professor of physics at the University of California, San Diego, who has headed a lunar laser-ranging project since the early 2000s.

    Peculiar Prisms on the Moon

    The devices left on the Moon by Apollo astronauts (as well as two others aboard Soviet Lunokhod rovers) consist of arrays of corner cube reflectors.

    2
    McDonald Observatory’s 2.7-meter telescope beams a laser toward the Moon. The telescope, part of the University of Texas at Austin, conducted laser observations from 1969 to the mid-1980s, when laser ranging was moved to a smaller telescope. Credit: Frank Armstrong/UT Austin

    U Texas at Austin McDonald Observatory, Altitude 2,070 m (6,790 ft)

    “These are like peculiar prisms—they’re shaped like the upper corner of a room,” says Doug Currie, a professor of physics at the University of Maryland in College Park who has worked in the field since the 1960s. “You could throw a tennis ball in the corner, and it would hit all three sides and bounce back to you. The lunar reflectors do the same thing. The difference is, you can send up to 1023 photons at a time, and you’re happy when one comes back.”

    The Apollo 11 and 14 retroreflectors each contain one hundred 3.8-centimeter corner cubes, whereas the Apollo 15 array contains 300, so it produces the strongest return signal.

    Photons are beamed toward the Moon through a telescope, such as the 3.5-meter telescope at Apache Point Observatory in New Mexico, the largest instrument ever to conduct lunar laser ranging. The laser is fired in 100-picosecond pulses—“bullets of light” just 2 centimeters thick, says Murphy, who heads the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO).

    No more than a few photons from each pulse return to the telescope, but the telescope fires thousands of laser bullets during each ranging session, allowing it to collect thousands of photons per session. Statistical analysis smooths out the differences in ranges between individual photons, producing a distance to the Moon with an accuracy of about 1 millimeter.

    APOLLO ranges to the Moon about six times per month and targets all five of the retroreflectors during each session. France’s Observatoire de la Côte d’Azur, the other major lunar-ranging station, uses a smaller telescope but has begun ranging with an infrared laser, which is about 8 times more efficient than the standard green laser.

    An Array of Scientific Contributions

    3
    All five of the current lunar retroreflectors are located near or north of the Moon’s equator, leaving the southern hemisphere uncovered. Credit: NASA

    Lunar laser ranging’s first scientific contribution was to produce an accurate measurement of how quickly the Moon is moving away from Earth: 3.8 centimeters per year. The retreat is the result of the ocean tides on Earth, which cause our planet’s rotation rate to slowly increase. To balance the books on the overall motion of the Earth-Moon system, the Moon speeds up, causing it to move away from Earth.

    Collecting data from the network of five retroreflectors over the course of several decades also has allowed planetary scientists to probe the Moon’s interior by measuring how the Moon “wobbles” on its axis.

    Some of those wobbles are caused by the Moon’s elliptical orbit, but others are produced by motions within the Moon itself. Measurements of that interior “sloshing” revealed that the Moon has a liquid outer core that’s about 700 kilometers in diameter, roughly 20% of the Moon’s overall diameter.

    “Everybody came in thinking, ‘we really know the Moon,’ but we didn’t,” says Peter Shelus, a research scientist at the University of Texas at Austin, which conducted lunar laser-ranging operations for more than 40 years. “We didn’t know the lunar rotation as well as we thought. As we got more data, though, everything fell into place, and the rotation rate allowed us to probe the interior.”

    When the lunar laser-ranging experiment was conceived in the early 1960s, however, learning about the Moon itself was a secondary goal. The primary goal was to study gravity. And so far, laser ranging has confirmed Isaac Newton’s gravitational constant to the highest precision yet seen and confirmed other tenets of gravitational theory, including the equivalence principle, which says that gravitational energy should behave like other forms of energy and mass.

    “What we’re after, the flagship science, is the strong equivalence principle,” says Murphy. “By, quote, dropping Earth and the Moon toward the Sun, we can use the Earth-Moon separation as a way to explore whether two bodies are pulled toward the Sun differently. That’s a foundational tenet of general relativity, and it would be very important if we saw a violation there.”

    So far, the lunar laser-ranging experiment has confirmed relativity’s predictions about the equivalence principle to the highest precision yet seen—within the experiment’s margin of error, Earth and the Moon “fall” toward the Sun at the same rate.

    “There’s Still Work to Do”

    Despite the experiment’s success, Murphy says he’s “disappointed” in the results to date.

    “We’ve managed to produce measurements we’re all confident in at the millimeter level of accuracy, but the model that it takes to extract science from this result has been slow to catch up. So we haven’t yet seen the order-of-magnitude level of improvement that we hoped for in those tests. We’ve seen maybe a factor-of-2 level of improvement, but that’s not very satisfying.”

    James Williams, a senior research scientist at NASA’s Jet Propulsion Laboratory and another pioneer in the lunar-ranging field, agrees that there’s work to do to improve our understanding of the results.

    “We’ve measured the Earth-Moon acceleration toward the Sun to 1.5 parts in 1013, which is a very, very sensitive test. It limits certain gravitational theories,” Williams says. “But there’s stuff in the model and in the data that we still don’t understand. There’s still work to do.”

    While the models catch up, the observational side of the project could stand some improvement as well, scientists say.

    The Lunokhod reflectors, for example, can be used only around sunrise and sunset; thermal problems scuttle observations at other points in the lunar cycle. The Apollo reflectors are degrading, probably because micrometeorite impacts on the surface are splashing dust onto the corner cubes. All of the current retroreflectors are placed near or north of the equator, leaving the southern half of the lunar globe uncovered. And current ranging is so precise that the orientation of the retroreflectors can cause a problem: As the laser bounces off opposite corners of an array, it can increase uncertainty in the measurements by a few centimeters.

    Currie has proposed sending new reflectors to the Moon using a new corner cube design.

    “We’ve been working on a 100-millimeter glass reflector that’s basically a scaled-up version of the Apollo reflectors,” he says. “You don’t have to worry whether a returned photon came from the near corner or the far corner of an array. We think that’ll improve the accuracy of a shot by a factor of a hundred. We’ve had to solve some thermal issues with the reflectors and the frame, but we can put together a package that can fly.”

    Currie’s group has submitted proposals to NASA to strap one of the new modules on an upcoming lunar mission and has signed an agreement with Moon Express, a company vying to launch a lander.

    “If you’re going to the Moon, these are almost no-brainer accompaniments,” says Murphy. “Their success is almost guaranteed; they require no power, they’ll work for decades and decades….It’s a low-cost, high-reward investment, which is why it was included on the initial Apollo mission.”

    It’s an investment that’s still paying dividends 50 years later.

    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.

     
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