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  • richardmitnick 3:44 pm on June 17, 2016 Permalink | Reply
    Tags: , , , UC Berkeley   

    From UC Berkeley: “Breakout: How black hole jets punch out of their galaxies” 

    UC Berkeley

    UC Berkeley

    June 16, 2016
    Robert Sanders

    A simulation of the powerful jets generated by supermassive black holes at the centers of the largest galaxies explains why some burst forth as bright beacons visible across the universe, while others fall apart and never pierce the halo of the galaxy.


    Access mp4 video here .
    New simulations of the jets produced by rotating supermassive black holes in the cores of galaxies show how, with enough power, the corkscrewing fields (white squiggles) can force their way through surrounding gas and drill out of the galaxy, channeling hot gas into the interstellar medium (top). Less powerful jets get stalled inside the galaxy, however, their magnetic fields breaking and dumping hot gas inside and heating up the galaxy. (Simulations by Alexander Tchekhovskoy, UC Berkeley, and Omer Bromberg, Hebrew University)

    4
    This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole’s event horizon, where no light can escape the massive object’s gravitational grip. The black hole’s powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as the stars skim by the black hole. Credit: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)

    About 10 percent of all galaxies with active nuclei — all presumed to have supermassive black holes within the central bulge — are observed to have jets of gas spurting in opposite directions from the core. The hot ionized gas is propelled by the twisting magnetic fields of the rotating black hole, which can be as large as several billion suns.

    A 40-year-old puzzle was why some jets are hefty and punch out of the galaxy into intergalactic space, while others are narrow and often fizzle out before reaching the edge of the galaxy. The answer could shed light on how galaxies and their central black holes evolve, since aborted jets are thought to roil the galaxy and slow star formation, while also slowing the infall of gas that has been feeding the voracious black hole. The model could also help astronomers understand other types of jets, such as those produced by individual stars, which we see as gamma-ray bursts or pulsars.

    “Whereas it was rather easy to reproduce the stable jets in simulations, it turned out to be an extreme challenge to explain what causes the jets to fall apart,” said University of California, Berkeley theoretical astrophysicist Alexander Tchekhovskoy, a NASA Einstein postdoctoral fellow, who led the project. “To explain why some jets are unstable, researchers had to resort to explanations such as red giant stars in the jets’ path loading the jets with too much gas and making them heavy and unstable so that the jets fall apart.”

    1
    This false-color image of the radio jet and lobes in the very bright radio galaxy Cygnus A is an example of the powerful jets that can be produced by supermassive black holes at the cores of large galaxies. (Image by R. Perley, C. Carilli & J. Dreher)

    By taking into account the magnetic fields that generate these jets, Tchekhovskoy and colleague Omer Bromberg, a former Lyman Spitzer Jr. postdoctoral fellow at Princeton University, discovered that magnetic instabilities in the jet determine their fate. If the jet is not powerful enough to penetrate the surrounding gas, the jet becomes narrow or collimated, a shape prone to kinking and breaking. When this happens, the hot ionized gas funneled through the magnetic field spews into the galaxy, inflating a hot bubble of gas that generally heats up the galaxy.

    Powerful jets, however, are broader and able to punch through the surrounding gas into the intergalactic medium. The determining factors are the power of the jet and how quickly the gas density drops off with distance, typically dependent on the mass and radius of the galaxy core.

    The simulation, which agrees well with observations, explains what has become known as the Fanaroff-Riley morphological dichotomy of jets, first pointed out by Bernie Fanaroff of South Africa and Julia Riley of the U.K. in 1974.

    “We have shown that a jet can fall apart without any external perturbation, just because of the physics of the jet,“ Tchekhovskoy said. He and Bromberg, who is currently at the Hebrew University of Jerusalem in Israel, will publish their simulations on June 17 in the journal Monthly Notices of the Royal Astronomical Society, a publication of Oxford University Press.

    Bendable drills

    The supermassive black hole in the bulging center of these massive galaxies is like a pitted olive spinning around an axle through the hole, Tchekhovskoy said. If you thread a strand of spaghetti through the hole, representing a magnetic field, then the spinning olive will coil the spaghetti like a spring. The spinning, coiled magnetic fields act like a flexible drill trying to penetrate the surrounding gas.

    3
    The black hole at the center of the galaxy M87 produced a weak jet that could not break out of the galaxy, as seen in this radio image from 1989. As in the new computer simulation, stalled jets dump hot gas into giant bubble-like structures that heat up the galaxy. These stalled jets may be part of the black hole feedback mechanism that periodically halts the inflow of gas that feeds the black hole. (VLA/NRAO/NSF image)

    The simulation, based solely on magnetic field interactions with ionized gas particles, shows that if the jet is not powerful enough to punch a hole through the surrounding gas, the magnetic drill bends and, due to the magnetic kink instability, breaks. An example of this type of jet can be seen in the galaxy M87, one of the closest such jets to Earth at a distance of about 50 million light-years, and has a central black hole equal to about 6 billion suns.

    “If I were to jump on top of a jet and fly with it, I would see the jet start to wiggle around because of a kink instability in the magnetic field,“ Tchekhovskoy said.“If this wiggling grows faster than it takes the gas to reach the tip, then the jet will fall apart. If the instability grows slower than it takes for gas to go from the base to the tip of the jet, then the jet will stay stable.“

    The jet in the galaxy Cygnus A, located about 600 million light-years from Earth, is an example of powerful jets punching through into intergalactic space.

    Tchekhovskoy argues that the unstable jets contribute to what is called black hole feedback, that is, a reaction from the material around the black hole that tends to slow its intake of gas and thus its growth. Unstable jets deposit a lot of energy within the galaxy that heats up the gas and prevents it from falling into the black hole. Jets and other processes effectively keep the sizes of supermassive black holes below about 10 billion solar masses, though UC Berkeley astronomers recently found black holes with masses near 21 billion solar masses.

    Presumably these jets start and stop, lasting perhaps 10-100 million years, as suggested by images of some galaxies showing more than one jet, one of them old and tattered. Evidently, black holes go through binging cycles, interrupted in part by the occasional unstable jet that essentialy takes away their food.

    The simulations were run on the Savio computer at UC Berkeley, Darter at the National Institute for Computational Sciences at the University of Tennesee, Knoxville, and Stampede, Maverick and Ranch computers at the Texas Advanced Computing Center at the University of Texas at Austin. The entire simulation took about 500 hours on 2,000 computer cores, the equivalent of 1 million hours on a standard laptop.

    The researchers are improving their simulation to incorporate the smaller effects of gravity, buoyancy and the thermal pressure of the interstellar and intergalactic media.

    The work was supported by NASA through Einstein Postdoctoral Fellowship grant number PF3-140115 awarded by the Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060, and the National Science Foundation through an XSEDE computational time allocation TG-AST100040.

    See the full article here .

    Please help promote STEM in your local schools.

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    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

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  • richardmitnick 8:57 am on February 13, 2016 Permalink | Reply
    Tags: , , , MyShake, UC Berkeley   

    From livescience: “‘MyShake’ App Turns Your Smartphone into Earthquake Detector” 

    Livescience

    February 12, 2016
    Mindy Weisberger

    Earthquake

    Seismologists and app developers are shaking things up with a new app that transforms smartphones into personal earthquake detectors.

    By tapping into a smartphone’s accelerometer — the motion-detection instrument — the free Android app, called MyShake, can pick up and interpret nearby quake activity, estimating the earthquake’s location and magnitude in real-time, and then relaying the information to a central database for seismologists to analyze.

    In time, an established network of users could enable MyShake to be used as an early- warning system, the researchers said.

    UC Berkeley MyShake
    MyShake network

    Crowdsourcing quakes

    Seismic networks worldwide detect earthquakes and convey quake data to scientists around the clock, providing a global picture of the tremors that are part of Earth’s ongoing dynamic processes. But there are areas where the network is thin, which means researchers are missing pieces in the seismic puzzle. However, “citizen- scientists” with smartphones could fill those gaps, according to Richard Allen, leader of the MyShake project and director of the Berkeley Seismological Laboratory in California.

    “As smartphones became more popular and it became easier to write software that would run on smartphones, we realized that we had the potential to use the accelerometer that runs in every smartphone to record earthquakes,” Allen told Live Science.

    How it works

    Accelerometers measure forces related to acceleration: vibration, tilt and movement, and also the static force of gravity’s pull. In smartphones, accelerometers detect changes in the device’s orientation, allowing the phone to know exactly which end is up and to adjust visual displays to correspond to the direction it’s facing.

    Fitness apps for smartphones use accelerometers to pinpoint specific changes in motion in order to calculate the number of steps you take, for example. And the MyShake app is designed to recognize when a smartphone’s accelerometer picks up the signature shaking of an earthquake, Allen said, which is different from other types of vibrating motion, or “everyday shaking.”

    In fact, the earthquake-detection engine in MyShake is designed to recognize an earthquake’s vibration profile much like a fitness app recognizes steps, according to Allen.

    “It’s about looking at the amplitude and the frequency content of the earthquake,” Allen said, “and it’s quite different from the amplitude and frequency content of most everyday shakes. It’s very low-frequency energy and the amplitude is not as big as the amplitude for most everyday activities.”

    In other words, the difference between the highs and lows of the motion generated by an earthquake are smaller than the range you’d find in other types of daily movement, he said.

    Quake, rattle and roll

    When a smartphone’s MyShake app detects an earthquake, it instantly sends an alert to a central processing site. A network detection algorithm is activated by incoming data from multiple phones in the same area, to “declare” an earthquake, identify its location and estimate its magnitude, Allen said.

    For now, the app will only collect and transmit data to the central processor. But the end goal, Allen said, is for future versions of the app to send warnings back to individual users.

    An iPhone version of the app will also be included in future plans for MyShake, according to Allen.For seismologists, the more data they can gather about earthquakes, the better, Allen said. A bigger data pool means an improved understanding of quake behavior, which could help experts design better early warning systems and safety protocols, things that are especially critical in urban areas prone to frequent quake activity. With 2.6 billion smartphones currently in circulation worldwide and an anticipated 6 billion by 2020, according to an Ericsson Mobility Report released in 2015, a global network of handheld seismic detectors could go a long way toward keeping people safe by improving quake preparation and response.

    The findings were published online today (Feb. 12) in the journal Science Advances, and the MyShake app is available for download at myshake.berkeley.edu.

    See the full article here .

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  • richardmitnick 5:32 pm on February 4, 2016 Permalink | Reply
    Tags: , Exoskeletal help for permanently injured people, UC Berkeley   

    From Berkeley: “A new-generation exoskeleton helps the paralyzed to walk” 

    UC Berkeley

    UC Berkeley

    February 3, 2016
    No writer credit found

    Until recently, being paralyzed from the waist down meant using a wheelchair to get around. And although daily life is more accessible to wheelchair users, they still face physical and social limitations. But UC Berkeley’s Robotics and Human Engineering Laboratory has been working to change that.

    The robotics lab, a team of graduate students led by mechanical engineering professor Homayoon Kazerooni, has been working for more than a decade to create robotic exoskeletons that allow those with limited mobility to walk again.

    New exoskeleton
    Steven Sanchez, who was paralyzed from the waist down after a BMX accident, wears SuitX’s Phoenix. “If I had this it would change a lot of things,” he says. (Photo courtesy of SuitX)

    This week, a new, lighter and more agile exoskeleton, for which the Kaz lab developed the original technology, was unveiled earlier this week: The Phoenix, by SuitX, a company that has spun off the robotics lab. Kazerooni is its founder and CEO.

    The Phoenix is lightweight, has two motors at the hips and electrically controlled tension settings that tighten when the wearer is standing and swing freely when they’re walking. Users can control the movement of each leg and walk up to 1.1 miles per hour by pushing buttons integrated into a pair of crutches. It’s powered for up to eight hours by a battery pack worn in a backpack.

    “We can’t really fix their disease,” says Kazerooni. “We can’t fix their injury. But what it would do is postpone the secondary injuries due to sitting. It gives a better quality of life.”

    Kazarooni and his team have developed a series of exoskeletons over the years. Their work in the field began in 2000 with a project funded by the Defense Advanced Research Projects Agency to create a device, now called the Berkeley Lower Extremity Exoskeleton (BLEEX), that could help people carry heavier loads for longer. At that time, Kazerooni also realized the potential use for exoskeletons in the medical field, particularly as an alternative to wheelchairs.

    The team began developing new devices to restore mobility for people who had become paraplegic.

    In 2011, they made the exoskeleton that helped Berkeley senior Austin Whitney, paralyzed from the waist down in a 2007 car accident, make an epic walk across the graduation stage to receive his diploma. Soon after, the Austin Project was created in honor of Whitney, with a goal of finding new technologies to create reliable, inexpensive exoskeleton systems for everyday personal use.

    Today, the Phoenix is one of the lightest and most accessible exoskeletons to hit the market. It can be adjusted to fit varied weights, heights and leg sizes and can be used for a range of mobility hindrances. And, although far from inexpensive at $40,000, it’s about the half the cost of other exoskeletons that help restore mobility.

    Read more about SuitX’s Phoenix suit in the MIT Technology Review.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

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  • richardmitnick 3:16 pm on January 20, 2016 Permalink | Reply
    Tags: , , , UC Berkeley   

    From Berkeley: “Advance improves cutting and pasting with CRISPR-Cas9 gene editing” 

    UC Berkeley

    UC Berkeley

    January 20, 2016
    Robert Sanders

    Temp 1
    A view of the Cas9 protein (red and blue) bound to a double strand of DNA (purple and grey). After both strands are cut, one DNA strand (purple dots) is free and able to bind with a piece of DNA to be inserted at the break.This behavior can be utilized to significantly boost the efficiency of gene editing. Image by Christopher Richardson, UC Berkeley, based on structure solved by Martin Jinek’s lab.

    UC Berkeley researchers have made a major improvement in CRISPR-Cas9 technology that achieves an unprecedented success rate of 60 percent when replacing a short stretch of DNA with another.

    The improved technique is especially useful when trying to repair genetic mutations that cause hereditary diseases, such as sickle cell disease or severe combined immune deficiency. The technique allows researchers to patch an abnormal section of DNA with the normal sequence and potentially correct the defect and is already working in cell culture to improve ongoing efforts to repair defective genes.

    “The exciting thing about CRISPR-Cas9 is the promise of fixing genes in place in our genome, but the efficiency for that can be very low,” said Jacob Corn, scientific director of the Innovative Genomics Initiative at UC Berkeley, a group that focuses on next-generation genome editing and gene regulation for lab and clinical application. “If you think of gene editing as a word processor, we know how to cut, but we need a more efficient way to paste and glue a new piece of DNA where we make the cut.”

    “In cases where you want to change very small regions of DNA, up to 30 base pairs, this technique would be extremely effective,” said first author Christopher Richardson, an IGI postdoc.

    Problems in short sections of DNA, including single base-pair mutations, are typical of many genetic diseases. Base pairs are the individual building blocks of DNA, strung end-to-end in a strand that coils around a complementary strand to make the well-known helical, double-stranded DNA molecule.

    Richardson, Corn and their IGI colleagues describe the new technique in the Jan. 21 issue of the journal Nature Biotechnology.

    Grabbing onto a loose strand

    Richardson invented the new approach after finding that the Cas9 protein, which does the actual DNA cutting, remains attached to the chromosome for up to six hours, long after it has sliced through the double-stranded DNA. Richardson looked closely at the Cas9 protein bound to the two strands of DNA and discovered that while the protein hangs onto three of the cut ends, one of the ends remains free.


    Jennifer Doudna explains how CRISPR-Cas9 edits genes. Video by Roxanne Makasdjian and Stephen McNally, UC Berkeley.
    Watch/download mp4 video here .

    When Cas9 cuts DNA, repair systems in the cell can grab a piece of complementary DNA, called a template, to repair the cut. Researchers can add templates containing changes that alter existing sequences in the genome — for example, correcting a disease-causing mutation.

    Richardson reasoned that bringing the substitute template directly to the site of the cut would improve the patching efficiency, and constructed a piece of DNA that matches the free DNA end and carries the genetic sequence to be inserted at the other end. The technique worked extremely well, allowing successful repair of a mutation with up to 60 percent efficiency.

    “Our data indicate that Cas9 breaks could be different at a molecular level from breaks generated by other targeted nucleases, such as TALENS and zinc-finger nucleases, which suggests that strategies like the ones we are using can give you more efficient repair of Cas9 breaks,” Richardson said.

    The researchers also showed that variants of the Cas9 protein that bind DNA but do not cut also can successfully paste a new DNA sequence at the binding site, possibly by forming a “bubble” structure on the target DNA that also acts to attract the repair template. Gene editing using Cas9 without genome cutting could be safer than typical gene editing by removing the danger of off-target cutting in the genome, Corn said.

    Co-authors with Richardson and Corn are IGI researchers Jordan Ray, Mark DeWitt and Gemma Curie. The work was funded by the Li Ka Shing Foundation.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

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  • richardmitnick 4:40 pm on December 23, 2015 Permalink | Reply
    Tags: , , UC Berkeley   

    From Berkeley: “Engineers demo first processor that uses light for ultrafast communications” 

    UC Berkeley

    UC Berkeley

    December 23, 2015
    Sarah Yang

    1
    The electronic-photonic processor chip communicates to the outside world directly using light, illustrated here. The photo shows the packaged microchip under illumination, revealing the chip’s primary features. (Image by Glenn J. Asakawa, University of Colorado, Glenn.Asakawa@colorado.edu)

    Engineers have successfully married electrons and photons within a single-chip microprocessor, a landmark development that opens the door to ultrafast, low-power data crunching.

    The researchers packed two processor cores with more than 70 million transistors and 850 photonic components onto a 3-by-6-millimeter chip. They fabricated the microprocessor in a foundry that mass-produces high-performance computer chips, proving that their design can be easily and quickly scaled up for commercial production.

    The new chip, described in a paper to be published Dec. 24 in the print issue of the journal Nature, marks the next step in the evolution of fiber optic communication technology by integrating into a microprocessor the photonic interconnects, or inputs and outputs (I/O), needed to talk to other chips.

    “This is a milestone. It’s the first processor that can use light to communicate with the external world,” said Vladimir Stojanović, an associate professor of electrical engineering and computer sciences at the University of California, Berkeley, who led the development of the chip. “No other processor has the photonic I/O in the chip.”

    Stojanović and fellow UC Berkeley professor Krste Asanović teamed up with Rajeev Ram at the Massachusetts Institute of Technology
    and Miloš Popović at the University of Colorado Boulder to develop the new microprocessor.

    “This is the first time we’ve put a system together at such scale, and have it actually do something useful, like run a program,” said Asanović, who helped develop the free and open architecture called RISC-V (reduced instruction set computer), used by the processor.

    Greater bandwidth with less power

    Compared with electrical wires, fiber optics support greater bandwidth, carrying more data at higher speeds over greater distances with less energy. While advances in optical communication technology have dramatically improved data transfers between computers, bringing photonics into the computer chips themselves had been difficult.

    2
    The electronic-photonic processor chip naturally illuminated by red and green bands of light. (Image by Glenn J. Asakawa, University of Colorado, Glenn.Asakawa@colorado.edu)

    That’s because no one until now had figured out how to integrate photonic devices into the same complex and expensive fabrication processes used to produce computer chips without changing the process itself. Doing so is key since it does not further increase the cost of the manufacturing or risk failure of the fabricated transistors.

    The researchers verified the functionality of the chip with the photonic interconnects by using it to run various computer programs, requiring it to send and receive instructions and data to and from memory. They showed that the chip had a bandwidth density of 300 gigabits per second per square millimeter, about 10 to 50 times greater than packaged electrical-only microprocessors currently on the market.

    The photonic I/O on the chip is also energy-efficient, using only 1.3 picojoules per bit, equivalent to consuming 1.3 watts of power to transmit a terabit of data per second. In the experiments, the data was sent to a receiver 10 meters away and back.

    “The advantage with optical is that with the same amount of power, you can go a few centimeters, a few meters or a few kilometers,” said study co-lead author Chen Sun, a recent UC Berkeley Ph.D. graduate from Stojanović’s lab at the Berkeley Wireless Research Center. “For high-speed electrical links, 1 meter is about the limit before you need repeaters to regenerate the electrical signal, and that quickly increases the amount of power needed. For an electrical signal to travel 1 kilometer, you’d need thousands of picojoules for each bit.”

    The achievement opens the door to a new era of bandwidth-hungry applications. One near-term application for this technology is to make data centers more green. According to the Natural Resources Defense Council, data centers consumed about 91 billion kilowatt-hours of electricity in 2013, about 2 percent of the total electricity consumed in the United States, and the appetite for power is growing exponentially.

    This research has already spun off two startups this year with applications in data centers in mind. SiFive is commercializing the RISC-V processors, while Ayar Labs is focusing on photonic interconnects. Earlier this year, Ayar Labs – under its previous company name of OptiBit – was awarded the MIT Clean Energy Prize. Ayar Labs is getting further traction through the CITRIS Foundry startup incubator at UC Berkeley.

    The advance is timely, coming as world leaders emerge from the COP21 United Nations climate talks with new pledges to limit global warming.

    Further down the road, this research could be used in applications such as LIDAR, the light radar technology used to guide self-driving vehicles and the eyes of a robot; brain ultrasound imaging; and new environmental biosensors.

    ‘Fiat lux’ on a chip

    The researchers came up with a number of key innovations to harness the power of light within the chip.

    3
    The illumination and camera create a rainbow-colored pattern across the electronic-photonic processor chip. (Image by Milos Popović, University of Colorado, milos.popovic@colorado.edu)

    Each of the key photonic I/O components – such as a ring modulator, photodetector and a vertical grating coupler – serves to control and guide the light waves on the chip, but the design had to conform to the constraints of a process originally thought to be hostile to photonic components. To enable light to move through the chip with minimal loss, for instance, the researchers used the silicon body of the transistor as a waveguide for the light. They did this by using available masks in the fabrication process to manipulate doping, the process used to form different parts of transistors.

    After getting the light onto the chip, the researchers needed to find a way to control it so that it can carry bits of data. They designed a silicon ring with p-n doped junction spokes next to the silicon waveguide to enable fast and low-energy modulation of light.

    Using the silicon-germanium parts of a modern transistor – an existing part of the semiconductor manufacturing process – to build a photodetector took advantage of germanium’s ability to absorb light and convert it into electricity.

    A vertical grating coupler that leverages existing poly-silicon and silicon layers in innovative ways was used to connect the chip to the external world, directing the light in the waveguide up and off the chip. The researchers integrated electronic components tightly with these photonic devices to enable stable operation in a hostile chip environment.

    The authors emphasized that these adaptations all worked within the parameters of existing microprocessor manufacturing systems, and that it will not be difficult to optimize the components to further improve their chip’s performance.

    Other co-lead authors on this paper are Mark Wade, Ph.D. student at the University of Colorado, Boulder; Yunsup Lee, a Ph.D. candidate at UC Berkeley; and Jason Orcutt, an MIT graduate who now works at the IBM Research Center in New York.

    The Defense Advanced Research Projects Agency (DARPA) helped support this work.

    See the full article here .

    Please help promote STEM in your local schools.

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    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

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  • richardmitnick 12:07 pm on December 20, 2015 Permalink | Reply
    Tags: , , UC Berkeley   

    From UC Berkeley: “Earth’s magnetic field could flip within a human lifetime” 2014 but very informative 

    UC Berkeley

    UC Berkeley

    October 14, 2014
    Robert Sanders

    Imagine the world waking up one morning to discover that all compasses pointed south instead of north.

    It’s not as bizarre as it sounds. Earth’s magnetic field has flipped – though not overnight – many times throughout the planet’s history. Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, but for incompletely known reasons it occasionally weakens and, presumably over a few thousand years, reverses direction.

    1
    Left to right, Biaggio Giaccio, Gianluca Sotilli, Courtney Sprain and Sebastien Nomade sitting next to an outcrop in the Sulmona basin of the Apennine Mountains that contains the Matuyama-Brunhes magnetic reversal. A layer of volcanic ash interbedded with the lake sediments can be seen above their heads. Sotilli and Sprain are pointing to the sediment layer in which the magnetic reversal occurred. (Photo by Paul Renne)

    Now, a new study by a team of scientists from Italy, France, Columbia University and the University of California, Berkeley, demonstrates that the last magnetic reversal 786,000 years ago actually happened very quickly, in less than 100 years – roughly a human lifetime.

    “It’s amazing how rapidly we see that reversal,” said UC Berkeley graduate student Courtney Sprain. “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

    Sprain and Paul Renne, director of the Berkeley Geochronology Center and a UC Berkeley professor-in- residence of earth and planetary science, are coauthors of the study, which will be published in the November issue of Geophysical Journal International and is now available online.

    Flip could affect electrical grid, cancer rates

    The discovery comes as new evidence indicates that the intensity of Earth’s magnetic field is decreasing 10 times faster than normal, leading some geophysicists to predict a reversal within a few thousand years.

    Though a magnetic reversal is a major planet-wide event driven by convection in Earth’s iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.

    And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates. The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.

    “We should be thinking more about what the biologic effects would be,” Renne said.

    Dating ash deposits from windward volcanoes

    The new finding is based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy. The lake sediments are interbedded with ash layers erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.

    2
    Leonardo Sagnotti, standing, and coauthor Giancarlo Scardia collecting a sample for paleomagnetic analysis.

    Italian researchers led by Leonardo Sagnotti of Rome’s National Institute of Geophysics and Volcanology measured the magnetic field directions frozen into the sediments as they accumulated at the bottom of the ancient lake.

    Sprain and Renne used argon-argon dating, a method widely used to determine the ages of rocks, whether they’re thousands or billions of years old, to determine the age of ash layers above and below the sediment layer recording the last reversal. These dates were confirmed by their colleague and former UC Berkeley postdoctoral fellow Sebastien Nomade of the Laboratory of Environmental and Climate Sciences in Gif-Sur-Yvette, France.

    Because the lake sediments were deposited at a high and steady rate over a 10,000-year period, the team was able to interpolate the date of the layer showing the magnetic reversal, called the Matuyama-Brunhes transition, at approximately 786,000 years ago. This date is far more precise than that from previous studies, which placed the reversal between 770,000 and 795,000 years ago.

    “What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years,” said Renne. “We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.”

    Unstable magnetic field preceded 180-degree flip

    Whether or not the new finding spells trouble for modern civilization, it likely will help researchers understand how and why Earth’s magnetic field episodically reverses polarity, Renne said.

    3
    The ‘north pole’ — that is, the direction of magnetic north — was reversed a million years ago. This map shows how, starting about 789,000 years ago, the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the pole somewhere in the Arctic. No image credit.

    The magnetic record the Italian-led team obtained shows that the sudden 180-degree flip of the field was preceded by a period of instability that spanned more than 6,000 years. The instability included two intervals of low magnetic field strength that lasted about 2,000 years each. Rapid changes in field orientations may have occurred within the first interval of low strength. The full magnetic polarity reversal – that is, the final and very rapid flip to what the field is today – happened toward the end of the most recent interval of low field strength.

    Renne is continuing his collaboration with the Italian-French team to correlate the lake record with past climate change.

    Renne and Sprain’s work at the Berkeley Geochronology Center was supported by the Ann and Gordon Getty Foundation.

    See the full article here .

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  • richardmitnick 6:55 pm on December 17, 2015 Permalink | Reply
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    From UC Berkeley: “Seeing Through the Big Data Fog” 

    UC Berkeley

    UC Berkeley

    December 14, 2015
    Wallace Ravven

    A neuroscientist studies how stress affects the brain’s ability to form new memories. Across the campus, another researcher looks for telltale signs of distant planets in a sliver of sky. What each of them seeks may lie hidden in an avalanche of data.

    1
    Joe Hellerstein and his students developed a new programming model for distributed computing which MIT Technology Review named one of the 10 technologies “most likely to change our world”.

    The same is true in industry, where data must be diced, sliced and analyzed to identify changes in customer behavior or the promise of new fabrication techniques.

    Working the data so that it can yield to analysis regularly runs into a bottleneck — a human bottleneck, says Berkeley computer science professor Joe Hellerstein.

    In 2011, Sean Kandel, a grad student working with Hellerstein and Stanford computer scientist Jeffrey Heer, interviewed three dozen analysts at 25 companies in different industries to ask them how they spend their time, what their “pain points” were, as Hellerstein says.

    “It became very clear that the task of wrangling data takes up the lion’s share of their time,” Hellerstein says. “People come at data differently. They name data differently, or it may be incomplete. You have to sort this out. You find oddball data, and you don’t know if it was input incorrectly or if it’s a meaningful outlier. All this precedes analysis. It’s very tedious.”

    Hellerstein, Heer and Kandel devised a software program to refine and speed the process. They called it, reasonably enough, Data Wrangler, and made it freely available online. Data Wrangler became the core of Trifacta, a startup they founded in 2012.

    Trifacta provides a platform to efficiently convert raw data into more structured formats for analysis. Its flagship product for data wrangling enables data analysts to easily transform data from messy traces of the real world into structured tables and charts that can reveal unsuspected patterns, or suggest new directions for analysis.

    Trifacta was quickly adopted by dozens of companies, from Linkedin to Lockheed Martin, and typically provides a major productivity gain.

    “What used to take weeks suddenly takes minutes”, Hellerstein says. “So you can experiment a great deal more with the data. This was far and away the most useful piece of research that I have been involved in.”

    In 2014, CRN, a high-profile communications technology magazine, placed Trifacta on its short list of The 10 Coolest Big Data Products.

    2
    Joe Hellerstein and his postdoc Eugene Wu worked on designing a high-level language for crafting interactive visualizations of data. Wu is now a professor at Columbia University. Photo: Peg Skorpinski

    GoPro, the company that makes wearable video recorders, was an early Trifacta client. On YouTube, GoPro videos run the gamut from a sky diver’s death-defying leap to Kama, the surfing pig. (He prefers three-to four-foot waves.)

    After sales of its recorders took off, GoPro moved into developing media software and other online services for customers. The company was soon inundated with coveted consumer data from devices, retail sales, social media and other sources.

    GoPro built a data science team, which brought in Trifacta to clean up the data and present it in an intuitive and accessible format, so the less techy business people could use it to tailor services to customers and offer new products.

    Hellerstein’s research also targets software developers who build Big Data systems — systems that may harness hundreds or thousands of computers to do their work. These “distributed computing” platforms, which also form the foundation of Cloud Computing, create major new hurdles for software engineering.

    Code for a single computer is an ordered list of instructions, and most programming languages were designed for simple, orderly computing on a single machine.

    With a distributed system, Hellerstein says, “If you force order, the machines spend all their time coordinating, and progress is limited by the slowest machine. Working around this with a traditional programming language is incredibly hard, and typically leads to all kinds of tricky bugs and design flaws.”

    With his students, he launched the BOOM (Berkeley Orders of Magnitude) project to develop a new programming model for distributed computers that helps programmers avoid specifying the steps of a computation in a particular order. Instead, it focuses on the information that the program must manage, and the way that information flows through machines and tasks.

    “The main result of the BOOM project is a ‘disorderly’ programming language called Bloom, which has enabled us to write complex distributed programs in simple, intuitive ways — with tens or hundreds of times less code than traditional languages,” Hellerstein says.

    In 2010, Bloom was recognized by MIT Technology Review as one of the 10 technologies “most likely to change our world.”

    Hellerstein has since used it in his courses on “Programming the Cloud” at Berkeley. It has been adopted by a number of research groups and forms the basis of a startup company in the Bay Area called Eve that Hellerstein advises.

    As he describes his work to ease data wrangling and speed cloud programming, Hellerstein turns a small metal hammer in his hands. “It’s true,” he says. “I do like to tinker.” Of course, he does way more than tinker. He’s developing better tools for the trade.

    See the full article here .

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  • richardmitnick 3:53 pm on December 1, 2015 Permalink | Reply
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    From Berkeley: “Exoplanet kicked into exile” 

    UC Berkeley

    UC Berkeley

    December 01, 2015
    Robert Sanders

    A planet discovered last year sitting at an unusually large distance from its star – 16 times farther than Pluto is from the sun – may have been kicked out of its birthplace close to the star in a process similar to what may have happened early in our own solar system’s history.

    1
    A wide-angle view of the star HD 106906 taken by the Hubble Space Telescope and a close-up view from the Gemini Planet Imager reveal a dynamically disturbed system of comets, suggesting a link between this and the unusually distant planet (upper right), 11 times the mass of Jupiter. Click image for hi-res versions & caption. Paul Kalas image, UC Berkeley.

    Images from the Gemini Planet Imager (GPI) in the Chilean Andes and the Hubble Space Telescope show that the star has a lopsided comet belt indicative of a very disturbed solar system, and hinting that the planet interactions that roiled the comets closer to the star might have sent the exoplanet into exile as well.

    NASA Hubble Telescope
    NASA/ESA Hubble

    The planet may even have its own ring of debris that it dragged along with it.

    “We think that the planet itself could have captured material from the comet belt, and that the planet is surrounded by a large dust ring or dust shroud,” said Paul Kalas, an adjunct professor of astronomy at the University of California, Berkeley. “We conducted three tests and found tentative evidence for a dust cloud, but the jury is still out.”

    “The measurements we made on the planet suggest it may be dustier than comparison objects, and we are making follow-up observations to check if the planet is really encircled by a disk – an exciting possibility,” added Abhi Rajan, a graduate student at Arizona State University who analyzed the planet images.

    Such planets are of interest because in its youth, our own solar system may have had planets that were kicked out of the local neighborhood and are no longer among of the eight planets we see today.

    “Is this a picture of our solar system when it was 13 million years old?” asks Kalas. “We know that our own belt of comets, the Kuiper belt, lost a large fraction of its mass as it evolved, but we don’t have a time machine to go back and see how it was decimated.

    3
    Known objects in the Kuiper belt beyond the orbit of Neptune. (Scale in AU; epoch as of January 2015.

    One of the ways, though, is to study these violent episodes of gravitational disturbance around other young stars that kick out many objects, including planets.”

    The disturbance could have been caused by a passing star that perturbed the inner planets, or a second massive planet in the system. The GPI team looked for another large planet closer to the star that may have interacted with the exoplanet, but found nothing outside of a Uranus-sized orbit.

    Kalas and Rajan will discuss the observations during a Google+ Hangout On Air at 7 a.m. Hawaii time (noon EST) on Dec. 1 during Extreme Solar Systems III, the third in a series of international meetings on exoplanets that this year takes place on the 20th anniversary of the discovery of the first exoplanet in 1995. Viewers without Google+ accounts may participate via YouTube.

    A paper about the results, with Kalas as lead author, was published in the The Astrophysical Journal on Nov. 20, 2015.

    Young, 13-million-year-old star

    The star, HD 106906, is located 300 light years away in the direction of the constellation Crux and is similar to the sun, but much younger: about 13 million years old, compared to our sun’s 4.5 billion years. Planets are thought to form early in a star’s history, however, and in 2014 a team led by Vanessa Bailey at the University of Arizona discovered a planet HD 106906 b around the star weighing a hefty 11 times Jupiter’s mass and located in the star’s distant suburbs, an astounding 650 AU from the star (one AU is the average distance between Earth and the sun, or 93 million miles).

    3
    The star HD 106906 and the planet HD 106906 b, with Neptune’s orbit for comparison

    3
    The Gemini Planet Imager mounted on the Gemini South telescope in Chile. Courtesy of Gemini Telescopes.

    Planets were not thought to form so far from their star and its surrounding protoplanetary disk, so some suggested that the planet formed much like a star, by condensing from its own swirling cloud of gas and dust. The GPI and Hubble discovery of a lopsided comet belt and possible ring around the planet points instead to a normal formation within the debris disk around the star, but a violent episode that forced it into a more distant orbit.

    Kalas and a multi-institutional team using GPI first targeted the star in search of other planets in May 2015 and discovered that it was surrounded by a ring of dusty material very close to the size of our own solar system’s Kuiper Belt. The emptiness of the central region – an area about 50 AU in radius, slightly larger than the region occupied by planets in our solar system – indicates that a planetary system has formed there, Kalas said.

    He immediately reanalyzed existing images of the star taken earlier by the Hubble Space Telescope and discovered that the ring of dusty material extended much farther away and was extremely lopsided. On the side facing the planet, the dusty material was vertically thin and spanned nearly the huge distance to the known planet, but on the opposite side the dusty material was vertically thick and truncated.

    “These discoveries suggest that the entire planetary system has been recently jostled by an unknown perturbation to its current asymmetric state,” he said. The planet is also unusual in that its orbit is possibly tilted 21 degrees away from the plane of the inner planetary system, whereas most planets typically lie close to a common plane.

    Kalas and collaborators hypothesized that the planet may have originated from a position closer to the comet belt, and may have captured dusty material that still orbits the planet. To test the hypothesis, they carefully analyzed the GPI and Hubble observations, revealing three properties about the planet consistent with a large dusty ring or shroud surrounding it. However, for each of the three properties, alternate explanations are possible.

    The investigators will be pursuing more sensitive observations with the Hubble Space Telescope to determine if HD 106906b is in fact one of the first exoplanets that resembles Saturn and its ring system.

    The inner belt of dust around the star has been confirmed by an independent team using the planet-finding instrument SPHERE on the ESO’s Very Large Telescope in Chile. The lopsided nature of the debris disk was not evident, however, until Kalas called up archival images from Hubble’s Advanced Camera for Surveys.

    The GPI Exoplanet Survey, operated by a team of astronomers at UC Berkeley and 23 other institutions, is targeting 600 young stars, all less than approximately 100 million years old, to understand how planetary systems evolve over time and what planetary dynamics could shape the final arrangement of planets like we see in our solar system today. GPI operates on the Gemini South telescope and provides extremely high-resolution, high-contrast direct imaging, integral field spectroscopy and polarimetry of exoplanets.

    Gemini South telescope
    Gemini South

    Among Kalas’s coauthors are UC Berkeley graduate student Jason Wang. The research was supported by the National Science Foundation and NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate.

    NASA NExSS bloc

    See the full article here .

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  • richardmitnick 2:02 pm on November 29, 2015 Permalink | Reply
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    From UC Berkeley: “CT scan of Earth links deep mantle plumes with volcanic hotspots” 

    UC Berkeley

    UC Berkeley

    September 2, 2015
    Robert Sanders

    University of California, Berkeley, seismologists have produced for the first time a sharp, three-dimensional scan of Earth’s interior that conclusively connects plumes of hot rock rising through the mantle with surface hotspots that generate volcanic island chains like Hawaii, Samoa and Iceland.

    Essentially a computed tomography, or CT scan, of Earth’s interior, the picture emerged from a supercomputer simulation at the Department of Energy’s National Energy Research Scientific Computing Center (NERSC) at the Lawrence Berkeley National Laboratory.


    Supercomputer simulation of plumes of hot rock rising through the mantle to the surface, where they generate volcanic eruptions that form island chains. Animation by Scott French, NERSC & Berkeley Lab; video by Roxanne Makasdjian and Stephen McNally, UC Berkeley.
    download mp4 video here.

    While medical CTs employ X-rays to probe the body, the scientists mapped mantle plumes by analyzing the paths of seismic waves bouncing around Earth’s interior after 273 strong earthquakes that shook the globe over the past 20 years.

    Previous attempts to image mantle plumes have detected pockets of hot rock rising in areas where plumes have been proposed, but it was unclear whether they were connected to volcanic hotspots at the surface or the roots of the plumes at the core mantle boundary 2,900 kilometers (1,800 miles) below the surface.

    The new, high-resolution map of the mantle — the hot rock below Earth’s crust but above the planet’s iron core — not only shows these connections for many hotspots on the planet, but reveals that below about 1,000 kilometers the plumes are between 600 and 1,000 kilometers across, up to five times wider than geophysicists thought. The plumes are likely at least 400 degrees Celsius hotter than surrounding rock.

    “No one has seen before these stark columnar objects that are contiguous all the way from the bottom of the mantle to the upper part of the mantle,” said first author Scott French, a computational scientist at NERSC who recently received his Ph.D. from UC Berkeley.

    Senior author Barbara Romanowicz, a UC Berkeley professor of earth and planetary science, noted that the connections between the lower-mantle plumes and the volcanic hotspots are not direct because the tops of the plumes spread out like the delta of a river as they merge with the less viscous upper mantle rock.

    “These columns are clearly separated in the lower mantle and they go all the way up to about 1,000 kilometers below the surface, but then they start to thin out in the upper part of the mantle, and they meander and deflect,” she said. “So while the tops of the plumes are associated with hotspot volcanoes, they are not always vertically under them.”

    Ancient anchors

    The new picture also shows that the bases of these plumes are anchored at the core-mantle boundary in two huge blobs of hot rock, each about 5,000 kilometers in diameter, that are likely denser than surrounding rock. Romanowicz estimates that those two anchors — directly opposite one another under Africa and the Pacific Ocean — have been in the same spots for 250 million years.

    2
    The 1,800-mile thick mantle under the Pacific Ocean contains rising plumes of hot rock that fan out at the surface to stationary hotspots, where they generate island chains as Earth’s crust moves due to plate tectonics. Scott French image.

    French and Romanowicz, who also is affiliated with the Institut de Physique du Globe and the Collège de France in Paris, will publish their findings in the Sept. 3 issue of the British journal Nature.

    The Earth is layered like an onion. An exterior crust contains the oceans and continents, while under the crust lies a thick mantle of hot but solid rock 2,900 kilometers thick. Below the mantle is the outer core, composed of liquid, molten iron and nickel, which envelopes an inner core of solid iron at the center of the planet.

    Heated by the hot core, the rock in the mantle rises and falls like water gently simmering in a pan, though this convection occurs much more slowly. Seismologists proposed some 30 years ago that stationary plumes of hot rock in the mantle occasionally punched through the crust to produce volcanoes, which, as the crust moved, generated island chains such as the Galapagos, Cape Verde and Canary islands.

    The Hawaiian Islands, for example, consist of 5 million-year-old Kauai to the west but increasingly younger islands to the east, because the Pacific Plate is moving westward. The newest eruption, Loihi, is still growing underwater east of the youngest island in the chain, Hawaii.

    Until now, evidence for the plume and hotspot theory had been circumstantial, and some seismologists argued instead that hotspots are very shallow pools of hot rock feeding magma chambers under volcanoes.

    Romanowicz, who uses seismic waves to study Earth’s interior, had previously worked with French, then a graduate student, on a tomographic model of the upper 800 kilometers of the mantle, which showed periodic hot and cold regions of rock underlying hotspot volcanoes. The new study completes that picture down to the core-mantle boundary.

    3
    Most of the known volcanic hotspots are linked to plumes of hot rock (red) rising from two spots on the boundary between the metal core and rocky mantle 1,800 miles below Earth’s surface.

    She noted that if higher temperature alone were responsible for the rising plumes, they would be only 100-200 kilometers wide, ballooning out only when they approach the surface. The fact that they appear to be five times wider in the lower mantle suggests that they also differ chemically from the surrounding cooler rock.

    This supports models where the material in the plume is a mixture of normal mantle rock and primordial rock from the dense rock anchoring the plume at the core-mantle boundary. In fact, lava emerging from hotspot volcanoes is known to differ chemically and isotopically from lava from other volcanoes, such as those erupting at subduction zones where Earth’s crust dives into the upper mantle.

    The supercomputer analysis did not detect plumes under all hotspot volcanoes, such as those in Yellowstone National Park. The plumes that feed them may be too thin to be detected given the computational limits of the global modeling technique, French said.

    Millions of hours of computer time

    To create a high-resolution CT of Earth, French used very accurate numerical simulations of how seismic waves travel through the mantle, and compared their predictions to the ground motion actually measured by detectors around the globe. Earlier attempts by other researchers often approximated the physics of wave propagation and focused mainly on the arrival times of only certain types of seismic waves, such as the P (pressure) and S (shear) waves, which travel at different speeds. French used numerical simulations to compute all components of the seismic waves, such as their scattering and diffraction, and tweaked the model repeatedly to fit recorded data using a method similar to statistical regression. The final computation required 3 million CPU hours on NERSC’s supercomputers, though parallel computing shrank this to a couple of weeks.

    Romanowicz hopes eventually to obtain higher resolution supercomputer images of Earth’s interior, perhaps by zooming in on specific areas, such as that under the Pacific Ocean, or by using new data.

    “Tomography is the most powerful method to get this information, but in the future it will be combined with very sensitive gravity measurements from satellites and maybe electromagnetic sounding, where people do conductivity measurements of the interior,” she said.

    This study was supported by the National Science Foundation (EAR-1417229) and the European Research Council. NERSC is supported by the U.S. Department of Energy Office of Science (DE-AC02-05CH11231).

    See the full article here .

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  • richardmitnick 10:36 pm on November 24, 2015 Permalink | Reply
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    From Berkeley: “Mars to lose its largest moon, but gain a ring” 

    UC Berkeley

    UC Berkeley

    November 23, 2015
    Robert Sanders

    1
    Mars could gain a ring in 10-20 million years when its moon Phobos is torn to shreds by Mars gravity. Image by Tushar Mittal using Celestia 2001-2010, Celestia Development Team.

    Mars’ largest moon, Phobos, is slowly falling toward the planet, but rather than smash into the surface, it likely will be shredded and the pieces strewn about the planet in a ring like the rings encircling Saturn, Jupiter, Uranus and Neptune.

    1
    Enhanced-color image of Phobos from the Mars Reconnaissance Orbiter with Stickney crater on the right

    NASA Mars Reconnaisence Orbiter
    Mars Reconnaissance Orbiter

    Though inevitable, the demise of Phobos is not imminent. It will probably happen in 20 to 40 million years, leaving a ring that will persist for anywhere from one million to 100 million years, according to two young earth scientists at the University of California, Berkeley.

    In a paper appearing online this week in Nature Geoscience, UC Berkeley postdoctoral fellow Benjamin Black and graduate student Tushar Mittal estimate the cohesiveness of Phobos and conclude that it is insufficient to resist the tidal forces that will pull it apart when it gets closer to Mars.

    Just as earth’s moon pulls on our planet in different directions, raising tides in the oceans, for example, so too Mars tugs differently on different parts of Phobos. As Phobos gets closer to the planet, the tugs are enough to actually pull the moon apart, the scientists say. This is because Phobos is highly fractured, with lots of pores and rubble. Dismembering it is analogous to pulling apart a granola bar, Black said, scattering crumbs and chunks everywhere.

    The resulting rubble from Phobos – rocks of various sizes and a lot of dust – would continue to orbit Mars and quickly distribute themselves around the planet in a ring.

    While the largest chunks would eventually spiral into the planet and collide at a grazing angle to produce egg-shaped craters, the majority of the debris would circle the planet for millions of years until these pieces, too, drop onto the planet in ‘moon’ showers, like meteor showers. Only Mars’ other moon, Deimos, would remain.

    Different moons, different fates

    Black and Mittal, both in UC Berkeley’s Department of Earth and Planetary Science, were drawn to the question of what might happen to Phobos because its fate is expected to be so different from that of most other moons in our solar system.

    “While our moon is moving away from earth at a few centimeters per year, Phobos is moving toward Mars at a few centimeters per year, so it is almost inevitable that it will either crash into Mars or break apart,” Black said. “One of our motivations for studying Phobos was as a test case to develop ideas of what processes a moon might undergo as it moves inward toward a planet.”

    Only one other moon in the solar system, Neptune’s largest moon, Triton, is known to be moving closer to its planet.

    Studying such moons is relevant to conditions in our early solar system, Mittal said, when it’s likely there were many more moons around the planets that have since disintegrated into rings – the suspected origins of the rings of the outer planets. Some studies estimate that during planet formation, 20-30 percent of planets acquire moons moving inward and destined for destruction, though they would have long since disappeared. Some of Mars’ several thousand elliptical craters may even have been formed by remnants of such moonlets crashing to the surface at a grazing angle.

    When tidal stresses overcome rock strength

    To estimate the strength of Phobos, Black and Mittal looked data from similarly fractured rocks on Earth and from meteorites that struck Earth and have a density and composition similar to Phobos. They also constrained the strength of Phobos based on results from simulations of the 10-kilometer diameter Stickney impact crater, which formed in the past when a rock rammed into Phobos without quite smashing the moon apart. That crater spans about one-sixth the circumference of Phobos and looks as if someone took a scoop out of the moon.

    3
    The Stickney crater at one end of Phobos was created by an impact that could have torn Phobos apart if the moon were less fractured and porous. NASA image, 2009.

    Once they determined when and how they expected tidal forces to tear Phobos apart, Mittal modeled the evolution of the ring, adapting techniques developed to understand Saturn’s rings.

    “If the moon broke apart at 1.2 Mars radii, about 680 kilometers above the surface, it would form a really narrow ring comparable in density to that of one of Saturn’s most massive rings,” Mittal said. “Over time it would spread out and get wider, reaching the top of the Martian atmosphere in a few million years, when it would start losing material because stuff would keep raining down on Mars.”

    If the moon breaks up farther from Mars, the ring could persist for 100 million years before raining down on Mars, they found.

    Mittal said it’s not clear whether the dust and debris rings would be visible from earth, since dust does not reflect much sunlight, whereas ice in the rings of the outer planets makes them easily visible. But Mars’ ring may reflect enough light to make Mars slightly brighter as seen from Earth, he said, and through a telescope the shadows of the rings might also be visible on the surface.

    “Standing on the surface of Mars a few tens of millions of years from now, it would be pretty spectacular to watch,” Black said.

    RELATED INFORMATION

    The demise of Phobos and development of a Martian ring system (Nature Geoscience)

    See the full article here .

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    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

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