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  • richardmitnick 7:42 am on March 25, 2017 Permalink | Reply
    Tags: Asteroids, , , ,   

    From Goddard: “OSIRIS-REx asteroid search tests instruments, science team” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    March 24, 2017
    Erin Morton
    morton@orex.lpl.arizona.edu
    University of Arizona, Tucson

    Nancy Neal Jones
    nancy.n.jones@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    1
    The path of the Main Belt asteroid 12 Victoria, as imaged by NASA’s OSIRIS-REx spacecraft on Feb. 11, 2017, during the mission’s Earth-Trojan Asteroid Search. This animation is made of a series of five images taken by the spacecraft’s MapCam camera that were then cropped and centered on Victoria. The images were taken about 51 minutes apart and each was exposed for 10 seconds. Credits: NASA/Goddard/University of Arizona


    OSIRIS-REx spacecraft

    During an almost two-week search, NASA’s OSIRIS-REx mission team activated the spacecraft’s MapCam imager and scanned part of the surrounding space for elusive Earth-Trojan asteroids — objects that scientists believe may exist in one of the stable regions that co-orbits the sun with Earth. Although no Earth-Trojans were discovered, the spacecraft’s camera operated flawlessly and demonstrated that it could image objects two magnitudes dimmer than originally expected.

    The spacecraft, currently on its outbound journey to the asteroid Bennu, flew through the center of Earth’s fourth Lagrangian area — a stable region 60 degrees in front of Earth in its orbit where scientists believe asteroids may be trapped, such as asteroid 2010 TK7 discovered by NASA’s Wide-field Infrared Survey Explorer (WISE) satellite in 2010. Though no new asteroids were discovered in the region that was scanned, the spacecraft’s cameras MapCam and PolyCam successfully acquired and imaged Jupiter and several of its moons, as well as Main Belt asteroids.

    “The Earth-Trojan Asteroid Search was a significant success for the OSIRIS-REx mission,” said OSIRIS-REx Principal Investigator Dante Lauretta of the University of Arizona, Tucson. “In this first practical exercise of the mission’s science operations, the mission team learned so much about this spacecraft’s capabilities and flight operations that we are now ahead of the game for when we get to Bennu.”

    The Earth Trojan survey was designed primarily as an exercise for the mission team to rehearse the hazard search the spacecraft will perform as it approaches its target asteroid Bennu. This search will allow the mission team to avoid any natural satellites that may exist around the asteroid as the spacecraft prepares to collect a sample to return to Earth in 2023 for scientific study.

    The spacecraft’s MapCam imager, in particular, performed much better than expected during the exercise. Based on the camera’s design specifications, the team anticipated detecting four Main Belt asteroids. In practice, however, the camera was able to detect moving asteroids two magnitudes fainter than expected and imaged a total of 17 Main Belt asteroids. This indicates that the mission will be able to detect possible hazards around Bennu earlier and from a much greater distance that originally planned, further reducing mission risk.

    Scientists are still analyzing the implications of the search’s results for the potential population of Earth-Trojan asteroids and will publish conclusions after a thorough study of mission data.

    NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s observation planning and processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for its Science Mission Directorate in Washington.

    For more information on OSIRIS-REx, visit:

    http://www.nasa.gov/osirisrex and http://www.asteroidmission.org

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA Goddard Campus
    NASA/Goddard Campus
    NASA

     
  • richardmitnick 10:29 am on March 1, 2017 Permalink | Reply
    Tags: Asteroids, , ,   

    From New Scientist: “If an asteroid hit London only 3% of deaths would be from impact” 

    NewScientist

    New Scientist

    24 February 2017
    Leah Crane

    1
    Chances are it won’t land anywhere near you. Getty

    Wind kills. The most casualties from an asteroid impact won’t come from the impact itself. The wind, pressure and heat caused by the crash are far more dangerous, no matter where the asteroid hits.

    Clemens Rumpf at the University of Southampton, UK, and his colleagues have calculated the mortality risk, should an asteroid hit a residential area. They considered asteroids that burn up completely, those that hit the ground, and those that strike in water. Surprisingly, the airborne side effects were the ones that cost the most lives.

    As an asteroid hurtles towards the ground, it deposits a huge amount of energy into the atmosphere, resulting in a powerful shockwave, tornado-like winds and a plume of fire trailing behind it. When it crashes down, it forms a crater, shaking the ground around the impact and hurling debris into the air.

    If the asteroid hits water (which is twice as likely as hitting land), it would create a tsunami, with waves reaching dozens of metres high. The farther from shore the impact is, the deeper the water and the taller the waves.

    Far-reaching effect

    In the past, people have shown that tsunamis posed the greatest risks from an asteroid impact, but the events are notoriously difficult to model. Rumpf and his colleagues have worked out that the continental shelf helps protect the shore by dissipating waves both at its steep edge and over its gentle beachward slope.

    “What sets tsunamis apart is that they’re really the most far-reaching effect of all the impact effects,” says Rumpf. A pressure wave or heat plume can’t travel very far, and craters only form right at the impact site, but tsunamis can traverse hundreds of kilometres of ocean to hit coastal communities.

    A tsunami caused by the impact of a 200-metre-wide asteroid 130 kilometres off the coast of Rio de Janeiro, for example, could cause more than 50,000 deaths, with 75 per cent of those being directly caused by the tsunami and the rest due to high winds.

    But an asteroid over or in a city would kill millions. Most of those deaths would be due to wind as well, even if the asteroid did crash to the ground instead of exploding in the air.

    For an airburst, about 15 per cent of casualties would come from heat. In a direct impact, the effects of gusting wind and surging temperatures are joined by pressure waves, which can rupture internal organs.

    Only about 3 per cent of casualties would be caused by the actual impact or the earthquakes and debris that result, says the team. The group plans to discuss the results with disaster managers to come up with suggestions for preparedness.

    Very rare events

    Luckily, large asteroids don’t hit Earth often: an impact by a 200-metre asteroid is expected only once every 40,000 years. And an asteroid could fall anywhere, and most of the planet’s surface is unpopulated.

    “Chances are that an asteroid hits the water, and even if it hits land it’s much more likely that it will hit away from populated regions,” says Rumpf. “These are very rare events, but with potentially high consequences.”

    In case you are starting to worry, there are lots of projects dedicated to planetary defence against asteroids: telescopes have spotted most of the big ones, and there are several potential ways to avoid an asteroid impact if we see it coming.
    “We are in the business of detecting asteroids well in advance of an impact, so this kind of work is only really important if we totally fail to do our jobs,” says Erik Christensen, director of the Catalina Sky Survey at the University of Arizona.

    Journal reference: arXiv:1702.05798

    See the full article here .

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  • richardmitnick 5:03 pm on February 16, 2017 Permalink | Reply
    Tags: Asteroids,   

    From Many Worlds: “Ceres, Asteroids And Us” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2017-02-16
    Marc Kaufman

    1
    Ceres Up Close. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    For most of us, asteroids exist primarily as a threat. An asteroid that landed around the Yucatan peninsula, after all, is generally considered to have set into motion the changes that resulted in the elimination of the dinosaurs.

    Other large in-coming asteroids laid waste to swaths of Siberia in 1908, dug the world’s largest crater (118 mile wide) in South Africa long ago, and formed the Chesapeake Bay a mere 35 million years past. And another large asteroid will almost certainly threaten Earth again some day.

    There is, however, a reverse and possibly life-enhancing side to the asteroid story, one that is becoming more clear and intriguing as we learn more about them where they live. Asteroids not only contain a lot of water — some of it possibly delivered long ago to a dry Earth — but they contain some pretty complex organic molecules, the building blocks of life.

    The latest chapter in the asteroid saga is being written about Ceres, the largest asteroid in the solar system and recently declared to also be a dwarf planet (like Pluto.)

    Using data from NASA’s Dawn spacecraft, a team led by the National Institute for Astrophysics in Rome and the University of California, Los Angeles identified a variety of complex organic compounds, amino acids and nucleobases — the kind that are the building blocks of life.

    NASA/Dawn Spacecraft
    NASA/Dawn Spacecraft

    The mission has also detected signs of a possible subsurface ocean as well as cryovolcanos, which spit out ice, water, methane and other gases instead of molten rock.

    “This discovery of a locally high concentration of organics is intriguing, with broad implications for the astrobiology community,” said Simone Marchi, a senior research scientist at Southwest Research Institute and one of the authors of the paper in Science. “Ceres has evidence of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and now organic materials.”

    He said that the organic-rich areas include carbonates and ammonia-based minerals, which are Ceres’ primary constituents. Their presence along with the organics makes it unlikely that the organics arrived via another asteroid.

    In an accompanying comment in the Feb. 16 edition of Science, Michael Küppers of the European Space Astronomy Center in Madrid makes the case that Ceres might be, or might once have been, habitable.

    The paper provides “the first observations of organic material on Ceres, confirming the presence of such material in the asteroid belt,” he writes. “Furthermore, because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself. It joins Mars and several satellites of the giant planets in the list of locations in the solar system that may harbor life.”

    2
    Illustration of the minor bodies in the inner part of the Solar System, including Jupiter trojans and the main asteroid belt. These objects are byproducts of planet formation and have key information about that process. Detecting them in extrasolar systems may help us to understand the early evolution of planetary systems. (NASA)

    Asteroids are as ancient as the solar system, some 4.6 billion years old. They are the leftovers from the planet formation process that took place in the disk around the very early sun — pieces of rock that didn’t become parts of planets or moons and weren’t otherwise smashed to bits.

    Both their age and their composition have made asteroids increasingly interesting to space scientists studying how the solar system came to look and behave as it does. The result has been a suite of missions to asteroids organized by NASA, the Japanese Aerospace Exploration Agency (JAXA), the European Space Agency, the Russian space agency Roskosmos, and the China National Space Administration.

    Many of the missions include substantial collaboration between different national space agencies. The Dawn effort has major European involvement and NASA’s OSIRIS-REx mission to the asteroid Bennu and the Japanese Hayabusa2 mission to Ryugu each have three principal investigators from the other agency.

    NASA OSIRIS-REx Spacecraft
    NASA OSIRIS-REx Spacecraft

    hayabasu2-spacecraft
    JAXA Hayabasu 2 spacecraft

    Both spacecraft are now on their way, will spend months on their destination asteroids, and are designed to bring home samples (in 2018 for Hayabusa2 and 2023 for OSIRIS-REx.)

    NASA also approved two additional asteroid missions earlier this year. The first mission, called Lucy, will study asteroids, known as Trojan asteroids, trapped by Jupiter’s gravity.

    The Psyche mission will explore a very large and rare object in the solar system’s asteroid belt — an asteroid made of metal. Scientists believe it might be the exposed core of a planet that lost its rocky outer layers from a series of violent collisions. Lucy is targeted for launch in 2021 and Psyche in 2023.

    Left NASA Lucy; right NASA PSYCHE. NASA
    Left NASA Lucy; right NASA PSYCHE

    Why so many asteroid missions?

    I put the question to Harold C. Connolly Jr. of Rowan University, mission sample scientist for OSIRIS-REx and a co-investigator for the mission. He answered by email from Japan, together with Shogo Tachibana of Hakkaido University, who is a principal investigator for Hayabusa2. Both are co-principal investigators for the others’ sample analysis efforts.

    “The science is really driving the interest,” they wrote. “There now exists broader understanding that asteroids are time capsules to the past and can help illuminate the origin of Earth-like planets and potentially even the materials and conditions that lead to the origin of life.

    “The target asteroids of both missions are a treasure box of the earliest time period of the solar system, with such riches as prebiotic compounds (precursors to life-building organics) preserved in them.”

    In Japan, the Hayabusa2 mission is also a follow-on to the hugely popular original Hayabusa mission, which returned with grains from the asteroid Itokawa in 2010. Despite enormous difficulties and the failure of its lander, the spacecraft brought back enough sample to tell scientists that the asteroid was four billion years old, at one time was exposed to temperatures of 800 degrees centigrade, and much more.

    Hayabusa inspired so much interest in Japan that it led to not only the follow-on mission but also three movies, including one with star actor Ken Watanabe.

    In a phone conversation, Küppers of the European Space Astronomy Center expanded on the scientific importance of asteroids.

    He said that Ceres research has already determined that asteroid most likely was formed further out in the solar system and then migrated in. This conclusion flows from the observed presence of geological features and minerals on the surface that require the presence of water to form. Closer-in asteroids are believed to have had any water baked out of them, strongly suggesting that Ceres was once further from the sun.

    That asteroidal (and cometary) water plays an important role in the history of Earth. “The oceans on Earth certainly could have been filled with water, and organic compounds, from asteroids like Ceres,” Küppers said. Different kinds of water have different isotopic signatures, and the water signature on Earth is very much like that detected in some asteroids and comets.

    The Dawn spacecraft has already visited the large asteroid Vesta on its mission, and found minerals formed in water, a geology with steep cliffs and landslides, and the presence of an enormous crater at one of the poles. For Vesta, as for Ceres, a primary goal of the Dawn mission is to map the asteroid in various ways and with substantial precision. The overall goal, however, is to explore the conditions and processes found worlds as old as the solar system.

    While Vesta is a described as a “protoplanet” because of its size, Ceres is considered a dwarf planet (as well as an asteroid) because it has sufficient mass and gravity to be rounded like a planet. Vesta, and the other asteroids, are not. Itokawa, below, is considerably smaller than Ceres or Vesta, and so has been rounded far less.

    3
    Ceres, the largest asteroid in the solar system, features areas with concentrations of shiny, white material. Scientists have described them as likely to be salts and ice. The dwarf planet contains about one third of the mass in the asteroid belt between Mars and Jupiter, yet it is still dwarfed in size by our moon. The more detailed images was taken by Dawn from 3,200 miles away. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    4
    NASA’s Dawn spacecraft captured this image of the asteroid Vesta while in orbit on July 18, 2011. The view looks across Vesta’s cratered and heavily-scarred south pole from a distance of about 6,500 miles. Vesta is the last remaining rocky protoplanet of the kind that formed the terrestrial planets. Numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vesta’s southern hemisphere. Debris from these events has fallen to Earth as meteorites which have been a rich source of information about Vesta. (NASA/JPL-Caltech/UCLA/MPS)

    What was planned to be the biggest NASA asteroid mission is the Asteroid Redirect Mission. It was proposed as the first robotic mission to visit a large near-Earth asteroid, to collect a multi-ton boulder from its surface, and to then redirect it into a stable orbit around the moon. Once in orbit around the moon, astronauts would explore it and return with samples in the 2020s.

    The proposed mission was driven by science, but also was part of NASA’s plan to advance the new technologies and spaceflight experience needed for a human mission to the Martian system in the 2030s. What’s more, some space scientists are concerned about the possibility of a large asteroid heading our way, and they want to develop techniques for just slightly changing an in-coming asteroid’s path so it would miss Earth.

    Many in Congress were never excited by the asteroid re-direct plan, and the future of the mission remains quite uncertain.

    But the part of the mission involved with learning more about asteroid pathways and how they might be changed is still, at least indirectly, alive.

    That’s because the asteroid Bennu, the destination for OSIRIS-REx, is one that often comes close to the Earth. (The acrony, by the way, stands for the Origins Spectral Interpretation Resource Identification Security Regolith Explorer.)

    As explained on the NASA OSIRIS-REx webside, “Bennu is a B-type asteroid with a ~500 meter diameter. It completes an orbit around the Sun every 436.604 days (1.2 years) and every 6 years comes very close to Earth, within 0.002 astronomical units (the term used to describe the distance from the sun to Earth.) These close encounters give Bennu a high probability of impacting Earth in the late 22nd century.”

    Some place that probability considerably lower, but it is nonetheless a sobering thought given the damage that asteroids have periodically inflicted on the Earth.

    See the full article here .

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    About Many Worlds

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

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

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

    About NExSS

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

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

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

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

     
  • richardmitnick 1:49 pm on February 11, 2017 Permalink | Reply
    Tags: Asteroids, Goldstone Antenna,   

    From JPL: “Asteroid Resembles Dungeons and Dragons Dice” 

    NASA JPL Banner

    JPL-Caltech

    Feb. 10, 2017
    DC Agle
    Jet Propulsion Laboratory, Pasadena, California
    818-393-9011
    agle@jpl.nasa.gov

    1
    This composite of 25 images of asteroid 2017 BQ6 was generated with radar data collected using NASA’s Goldstone Solar System Radar in California’s Mojave Desert.

    NASA DSCC Goldstone Antenna located in the Mojave Desert near Barstow in California, USA
    NASA DSCC Goldstone Antenna located in the Mojave Desert near Barstow in California, USA

    The images were gathered on Feb. 7, 2017, between 8:39 and 9:50 p.m. PST (11:39 p.m. EST and 12:50 a.m., Feb. 7), revealing an irregular, angular-appearing asteroid about 660 feet (200 meters) in size that rotates about once every three hours. The images have resolutions as fine as 12 feet (3.75 meters) per pixel. Credits: NASA/JPL-Caltech/GSSR

    Radar images of asteroid 2017 BQ6 were obtained on Feb. 6 and 7 with NASA’s 70-meter (230-foot) antenna at the Goldstone Deep Space Communications Complex in California. They reveal an irregular, angular-appearing asteroid about 660 feet (200 meters) in size that rotates about once every three hours. The images have resolutions as fine as 12 feet (3.75 meters) per pixel.

    “The radar images show relatively sharp corners, flat regions, concavities, and small bright spots that may be boulders,” said Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California, who leads the agency’s asteroid radar research program. “Asteroid 2017 BQ6 reminds me of the dice used when playing Dungeons and Dragons. It is certainly more angular than most near-Earth asteroids imaged by radar.”

    Asteroid 2017 BQ6 safely passed Earth on Feb. 6 at 10:36 p.m. PST (1:36 a.m. EST, Feb. 7) at about 6.6 times the distance between Earth and the moon (about 1.6 million miles, or 2.5 million kilometers). It was discovered on Jan. 26 by the NASA-funded Lincoln Near Earth Asteroid Research (LINEAR) Project, operated by MIT Lincoln Laboratory on the Air Force Space Command’s Space Surveillance Telescope at White Sands Missile Range, New Mexico.

    Radar has been used to observe hundreds of asteroids. When these small, natural remnants of the formation of the solar system pass relatively close to Earth, deep space radar is a powerful technique for studying their sizes, shapes, rotation, surface features, and roughness, and for more precise determination of their orbital path.

    NASA’s Jet Propulsion Laboratory, Pasadena, California, manages and operates NASA’s Deep Space Network, including the Goldstone Solar System Radar, and hosts the Center for Near-Earth Object Studies for NASA’s Near-Earth Object Observations Program within the agency’s Science Mission Directorate.

    JPL hosts the Center for Near-Earth Object Studies for NASA’s Near-Earth Object Observations Program within the agency’s Science Mission Directorate.

    More information about asteroids and near-Earth objects can be found at:

    http://cneos.jpl.nasa.gov

    http://www.jpl.nasa.gov/asteroidwatch

    For more information about NASA’s Planetary Defense Coordination Office, visit:

    http://www.nasa.gov/planetarydefense

    For asteroid and comet news and updates, follow AsteroidWatch on Twitter:

    twitter.com/AsteroidWatch

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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    NASA image

     
  • richardmitnick 8:30 am on January 25, 2017 Permalink | Reply
    Tags: Asteroids, , Atira asteroids, , , Gaia-606, Initial Data Processing (IDT) software   

    From ESA: “Gaia turns its eyes to asteroid hunting” 

    ESA Space For Europe Banner

    European Space Agency

    24 January 2017
    Paolo Tanga
    Observatoire de la Côte d’Azur, France
    Email: Paolo.Tanga@oca.eu

    Benoit Carry
    Observatoire de la Côte d’Azur, France
    Email: benoit.carry@oca.eu

    William Thuillot
    Observatoire de Paris, France
    Email: William.Thuillot@obspm.fr

    Timo Prusti
    Gaia Project Scientist
    Directorate of Science
    European Space Agency
    Email: timo.prusti@esa.int

    Whilst best known for its surveys of the stars and mapping the Milky Way in three dimensions, ESA’s Gaia has many more strings to its bow. Among them, its contribution to our understanding of the asteroids that litter the Solar System. Now, for the first time, Gaia is not only providing information crucial to understanding known asteroids, it has also started to look for new ones, previously unknown to astronomers.

    ESA/GAIA satellite
    ESA/GAIA satellite

    1
    Asteroid Gaia-606 on 26 October 2016. Credit: Observatoire de Haute-Provence & IMCCE

    Since it began scientific operations in 2014, Gaia has played an important role in understanding Solar System objects. This was never the main goal of Gaia – which is mapping about a billion stars, roughly 1% of the stellar population of our Galaxy – but it is a valuable side effect of its work. Gaia’s observations of known asteroids have already provided data used to characterise the orbits and physical properties of these rocky bodies more precisely than ever before.

    “All of the asteroids we studied up until now were already known to the astronomy community,” explains Paolo Tanga, Planetary Scientist at Observatoire de la Côte d’Azur, France, responsible for the processing of Solar System observations.

    These asteroids were identified as spots in the Gaia data that were present in one image and gone in one taken a short time later, suggesting they were in fact objects moving against the more distant stars.

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    Gaia’s asteroid detections. ESA/Gaia/DPAC/CU4, L. Galluccio, F. Mignard, P. Tanga (Observatoire de la Côte d’Azur)

    Once identified, moving objects found in the Gaia data are matched against known asteroid orbits to tell us which asteroid we are looking at. “Now,” continues Tanga, “for the first time, we are finding moving objects that can’t be matched to any catalogued star or asteroid.”

    The process of identifying asteroids in the Gaia data begins with a piece of code known as the Initial Data Processing (IDT) software – which was largely developed at the University of Barcelona and runs at the Data Processing Centre at the European Space Astronomy Centre (ESAC), ESA’s establishment in Spain.

    This software compares multiple measurements taken of the same area and singles out objects that are observed but cannot be found in previous observations of the area. These are likely not to be stars but, instead, Solar System objects moving across Gaia’s field of view. Once found, the outliers are processed by a software pipeline at the Centre National d’Etudes Spatiales (CNES) data centre in Toulouse, France, which is dedicated to Solar System objects. Here, the source is cross matched with all known minor bodies in the Solar System and if no match is found, then the source is either an entirely new asteroid, or one that has only been glimpsed before and has never had its orbit accurately characterised.

    Although tests have shown Gaia is very good at identifying asteroids, there have so far been significant barriers to discovering new ones. There are areas of the sky so crowded that it makes the IDT’s job of matching observations of the same star very difficult. When it fails to do so, large numbers of mismatches end up in the Solar System objects pipeline, contaminating the data with false asteroids and making it very difficult to discover new ones.

    “At the beginning, we were disappointed when we saw how cluttered the data were with mismatches,” explains Benoit Carry, Observatoire de la Côte d’Azur, France, who is in charge of selecting Gaia alert candidates. “But we have come up with ways to filter out these mismatches and they are working! Gaia has now found an asteroid barely observed before.”

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    Asteroid Gaia-606 on 26 October 2016. Credit: Observatoire de Haute-Provence & IMCCE

    The asteroid in question, nicknamed Gaia-606, was found in October 2016 when Gaia data showed a faint, moving source. Astronomers immediately got to work and were able to predict the new asteroid’s position as seen from the ground over a period of a few days. Then, at the Observatoire de Haute Provence (southern France), William Thuillot and his colleagues Vincent Robert and Nicolas Thouvenin (Observatoire de Paris/IMCCE) were able to point a telescope at the positions predicted and show this was indeed an asteroid that did not match the orbit of any previously catalogued Solar System object.

    However, despite not being present in any catalogue, a more detailed mapping of the new orbit has shown that some sparse observations of the object do already exist. This is not uncommon with new discoveries where, as with Gaia-606 (now renamed 2016 UV56), objects that first appear entirely new transpire to be re-sightings of objects whose previous observations were not sufficient to map their orbits.

    “This really was an asteroid not present in any catalogue, and that is an exciting find!” explains Thuillot. “So whilst we can’t claim this is the first true asteroid discovery from Gaia, it is clearly very close and shows how near we are to finding a never-before-seen Solar System object with Gaia.”

    4
    During the course of its five-year nominal mission Gaia is expected to observe several hundred thousand asteroids. Many of these will be in the main asteroid belt, located between Mars and Jupiter.

    One of the strengths of Gaia is that it will also observe regions that are not extensively observed by existing ground-based surveys – this gives it the potential to find asteroids in areas where others would not, or could not, look. Ground-based observations are made during the night when the angle between a source and the Sun is fairly large. Gaia can make observations at any time and hence observes objects much closer to the Sun. In particular, Gaia is ideally situated to probe the region between the Sun and Earth. This is where the Atira asteroids are found, orbiting inside Earth’s orbit. To date, only 16 of these asteroids have been discovered.

    The dashed lines indicate regions of the sky that are unobservable by Gaia. All other regions are accessible to Gaia, including swathes within Earth’s orbit.

    Gaia-606 was found in the main asteroid belt, which is not surprising given how many asteroids exist there. However, Gaia also provides data from swathes of the sky not extensively observed by existing ground-based surveys giving it the potential to find asteroids in areas where others would not look. One such area is a region close to the Sun as seen from Earth. Observations are made from the Earth during the night when the angle between any source and the Sun is fairly large, whilst Gaia can make observations at any time and so observe objects much closer to the Sun. This gives Gaia the exciting potential to observe asteroids that orbit within Earth’s orbit – these are known as Atira asteroids and only sixteen are currently known.

    Gaia also has the potential to make discoveries at high ecliptic latitudes. Not because ground-based surveys of Solar System objects cannot observe there, but because they tend not to. The vast majority of asteroids exist in the ecliptic plane and, as a result, it is here that most surveys concentrate their efforts. Gaia has no such prejudices and scans the entire sky, giving it the potential to discover new asteroids in the less crowded areas missed by other surveys.

    “Whilst Gaia’s primary role in Solar System science remains its ability to characterise the movement and physical properties of known asteroids, it has now shown that it can also play a role in finding new ones, adding to its ever expanding catalogue of Solar System objects,” concludes Tanga.

    About Gaia

    Gaia is an ESA mission to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its origin and evolution.

    The mission’s primary scientific product will be a catalogue with the positions, motions, brightnesses, and colours of the more than a billion surveyed stars. The first intermediate catalogue was released in September 2016. In the meantime, Gaia’s observing strategy, with repeated scans of the entire sky, is allowing the discovery and measurement of many transient events across the sky: among these are the detection of candidate asteroids which are subsequently observed by astronomers in the Gaia Follow-Up-Network. During the five-year nominal mission, Gaia is expected to observe about 350 000 asteroids of which a few thousand will be previously unknown.

    5
    Gaia Follow-Up Network for Solar System Objects. Credit: Google Earth

    The nature of the Gaia mission leads to the acquisition of an enormous quantity of complex, extremely precise data, and the data-processing challenge is a huge task in terms of expertise, effort and dedicated computing power. A large pan-European team of expert scientists and software developers, the Data Processing and Analysis Consortium (DPAC), located in and funded by many ESA member states, and with contributions from ESA, is responsible for the processing and validation of Gaia’s data, with the final objective of producing the Gaia Catalogue. Scientific exploitation of the data only takes place once the data are openly released to the community.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 7:35 am on January 7, 2017 Permalink | Reply
    Tags: Asteroids, , , , , Venus mission shelved   

    From Smithsonian: “NASA Just Announced Two New Missions, But Shelved Others” 

    smithsonian
    Smithsonian.com

    January 6, 2017
    Danny Lewis

    Though the new missions have exciting prospects, some scientists aren’t thrilled by the decision.

    This week, NASA announced two new missions set to explore asteroids in our solar system. During the 2020s, the space agency will launch two separate spacecraft to study a pair of asteroids. But while these missions could unveil new details about the origins of our cosmic neighborhood, the decision means that future missions to planets like Venus have been put on the backburner.

    In order to decide what missions to take up next, NASA put out a call for scientists to submit proposals to the Discovery Program. The program has spawned all sorts of missions exploring our solar system, including the Lunar Prospector, Kepler space telescope and the future Mars InSight lander. Now, NASA has announced its two latest winners: a pair of missions set to study two very different kinds of asteroids.

    NASA Mars Insight Lander
    “NASA Mars Insight Lander

    “These are true missions of discovery that integrate into NASA’s larger strategy of investigating how the solar system formed and evolved,” Jim Green, director of NASA’s Planetary Science division, says in a statement. “We’ve explored terrestrial planets, gas giants, and a range of other bodies orbiting the sun. Lucy will observe primitive remnants from farther out in the solar system, while Psyche will directly observe the interior of a planetary body.”

    While both missions are focused on asteroids, Lucy and Psyche are worlds apart. The Lucy mission is set to study multiple members of the Trojan asteroids—a swarm that orbits the gas giant Jupiter—in an effort to learn more about the materials that the outer planets are made from. Psyche, on the other hand, will travel to a 130-mile-wide asteroid that is almost entirely made of metal: a rarity that astronomers believe was once the core of a long-gone planet, Loren Grush reports for The Verge.

    Though these missions are intriguing, the decision to focus so much on asteroids is raising eyebrows among some scientists. Of the five finalists for this round of the Discovery Program, three were asteroid missions and two focused on the planet Venus. Some, however, thought NASA should be more interested in exploring the next planet over, Sarah Fecht reports for Popular Science.

    NASA also currently has two asteroid-focused missions in progress: the Dawn mission surrounding Ceres and the OSIRIS-REx mission en route to the asteroid Bennu. And the decision means it will be some time before Venus gets its time to shine.

    NASA/Dawn Spacecraft
    NASA/Dawn Spacecraft

    NASA OSIRIS-REx Spacecraft
    NASA OSIRIS-REx Spacecraft

    “I thought for sure they’d pick a Venus mission. I found it pretty surprising,” planetary scientist Mark Marley tells Fecht. “If we’re trying to understand atmospheres on exoplanets, we really need to understand as much as we can about our own Venus. It’s very hard to get exoplanet data, and it’s always lower quality than what you can get in the solar system.”

    Unlike Mars and the airless asteroids, Venus has a thick, protective atmosphere. As Kaplan reports, that makes the third planet from the sun a great candidate to learn more about how atmosphere works and how it could shelter organic molecules. The last time NASA sent an orbiter to Venus was in the 1970s.

    That doesn’t mean all hope is lost for those hoping to send a new spacecraft to visit Venus. NASA will be picking a new mission for its New Frontiers program in 2017, and officials have said that exploring Venus and Saturn are two of its top priorities for the bigger-budgeted division, Fecht reports. In the meantime, Lucy and Psyche are sure to reveal fascinating new information about the earliest days of our solar system.

    Left NASA Lucy; right NASA PSYCHE
    Left NASA Lucy; right NASA PSYCHE

    See the full article here .

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    Smithsonian magazine and Smithsonian.com place a Smithsonian lens on the world, looking at the topics and subject matters researched, studied and exhibited by the Smithsonian Institution — science, history, art, popular culture and innovation — and chronicling them every day for our diverse readership.

     
  • richardmitnick 5:44 am on December 6, 2016 Permalink | Reply
    Tags: Asteroid Ryugu, Asteroids, , , JAXA Hayabusa 2   

    From Seeker: “Quest to Reveal Asteroid’s Mysteries Before Japanese Spacecraft’s Visit” 

    Seeker bloc

    SEEKER

    Dec 5, 2016
    ELIZABETH HOWELL

    hayabasu2-spacecraft
    Artist’s concept of Hayabusa-2 approaching asteroid 162173 Ryugu (1999 JU3). Image Credit: JAXA

    A Japanese spacecraft is on its way to some daring work at an asteroid. Hayabusa 2 is expected to reach Asteroid Ryugu in June or July 2018 and will drop several tiny landers on to its surface. The spacecraft itself will scoop up a sample of asteroid material for return back to Earth, just as its predecessor Hayabusa did at asteroid Itokawa a decade ago.

    It’s clear that a lot of engineering and precision is needed to achieve these maneuvers, far from home and in a zone that doesn’t easily give second chances. So as Hayabusa 2 moves towards its target, astronomers on Earth are looking at Ryugu as much as they can to learn about its properties.

    “Before you can send an interplanetary mission to a small body, it is important to know its orbit with the best possible accuracy, but you also have to know the object’s properties,” said Thomas Mueller, co-investigator for Hayabusa’s thermal infrared imager instrument, in an email to Seeker. He is also leading the efforts to do a characterization of Ryugu before Hayabusa 2’s arrival.

    The latest research is based on analyzing results from the European Herschel Space Observatory (in April 2012) and the NASA Spitzer Space Telescope (between January and May 2013). The astronomers attempted to map the rotation of the object using its light curve (the change in light as seen from Earth), which in turn led to estimating its spin and surface composition. A paper based on the research was recently published on the prepublishing site arXiv, and has been accepted in the journal Astronomy & Astrophysics.

    ESA/Herschel
    ESA/Herschel spacecraft

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    2
    The shadow of Hayabusa, along with a target marker (circled, at left), is shown on asteroid Itokawa in November 2005. Credit: JAXA

    Mueller, who works with the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, has been interested in learning about small bodies in the solar system since his Ph.D. thesis, which he completed in 1997 — where he tried to apply infrared measurements of well-known targets to objects that were less well known, but still scientifically interesting. He’s been working to characterize Ryugu (in collaboration with the Japan Aerospace and Exploration Agency, or JAXA) since 2008.

    “Mission targets like Itokawa (Hayabusa mission in 2005) or Ryugu (Hayabusa-2 mission) always attracted my attention for many reasons,” Mueller added, providing a list: “(1) The possibility to compare my model predictions with ‘ground-truth’ at some point; (2) the relation to space projects (I worked in the European Space Agency for several years); (3) the connection between near-Earth objects and Earth (NEAs as a risk for Earth, but also as the origin of life, water and heavy element supply); (4) to find out more about the building blocks of the planets.”

    Specifically for Ryugu, Mueller says the latest research will help engineers adjust their instrument settings, do risk assessments and develop plans for what the spacecraft will do when it gets there. Some of the things they have covered include Ryugu’s estimated size, brightness (known as albedo), rotation period and spin axis, thermal properties and where grains of different sizes are distributed.

    But there are challenges with observing a small object from so far away. The new paper notes that because Ryugu is nearly spherical, it made it hard to get a light curve. So the astronomers combined radiometric and lightcurve inversion techniques to come up with an estimation of Ryugu’s physical and thermal properties.

    3
    A view of asteroid Itokawa based on data from the Hayabusa spacecraft. Credit: JAXA

    “In all our observations, we see Ryugu as a perfect point source (we cannot resolve the target from Earth distance),” Mueller added. “However, we are able to derive not only the size, shape, spin properties, but also things like the (most-likely) surface material (carbonaceous, complex organics?) or predominant grain sizes on the surface (1-10 mm).”

    He added that both Itokawa and Ryugu are “fantastic opportunities” to see how well models hold up against ground truth. The astronomers are lucky to have this opportunity, as only a fraction of small bodies are visited by spacecraft, he said.

    “Other experts in the field of small-body characterization/modelling will very likely pick up our published observations to make their own predictions,” he added. “It is very exciting for us to see who gets closest to the truth.”

    See the full article here .

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  • richardmitnick 12:19 pm on November 23, 2016 Permalink | Reply
    Tags: Asteroids, ,   

    From Rutgers: “Asteroid Impacts Could Create Habitats for Life” 

    Rutgers University
    Rutgers University

    11.23.16
    No writer credit

    An international team of 38 scientists, including Rutgers’ Sonia Tikoo, has shown how large asteroid impacts deform rocks and possibly create habitats for early life on Earth and elsewhere.

    Around 65 million years ago, a massive asteroid crashed into the Gulf of Mexico, causing an impact so huge that the blast and its aftermath wiped out about 75 percent of all life on Earth, including most of the dinosaurs. It’s known as the Chicxulub impact.

    2
    Split drill cores collected from the peak ring of Chicxulub crater. The left two cores consist of basement granite. The right two cores are impact melt rocks that were created by the heat associated with the impact. Photo: E. Le Ber

    In April and May, scientists on an offshore expedition drilled deep into part of the Chicxulub impact crater. Their mission was to retrieve samples from the rocky inner ridges of the crater – known as the “peak ring” – drilling about 1,600 to 4,380 feet below the modern-day sea floor to learn more about the ancient cataclysmic event.

    Now, the researchers have performed the first analysis of the core samples in a study published online today in the journal Science. They found that the impact deformed the peak ring rocks, making them more porous and less dense than models had predicted.

    “Chicxulub crater is the only crater on Earth that has such a well-preserved peak ring and since we can’t get samples of peak rings from other planets yet, it’s really our best window into understanding the formation of large impact basins anywhere in the solar system,” said Tikoo, an assistant professor in the Department of Earth and Planetary Sciences in the School of Arts and Sciences. “We really didn’t know the exact physical mechanisms behind how peak ring craters form until this study.”

    For more information, please contact science communicator Todd B. Bates at tbates@ucm.rutgers.edu or 848-932-0550.

    See the full article here .

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    Rutgers, The State University of New Jersey, is a leading national research university and the state’s preeminent, comprehensive public institution of higher education. Rutgers is dedicated to teaching that meets the highest standards of excellence; to conducting research that breaks new ground; and to providing services, solutions, and clinical care that help individuals and the local, national, and global communities where they live.

    Founded in 1766, Rutgers teaches across the full educational spectrum: preschool to precollege; undergraduate to graduate; postdoctoral fellowships to residencies; and continuing education for professional and personal advancement.

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  • richardmitnick 8:29 am on October 31, 2016 Permalink | Reply
    Tags: Asteroids, , , NASA's New 'Intruder Alert' System Spots An Incoming Asteroid   

    From NPR: “NASA’s New ‘Intruder Alert’ System Spots An Incoming Asteroid” 

    NPR

    National Public Radio (NPR)

    October 30, 2016
    Joe Palca

    1

    Asteroids regularly pass by Earth, as depicted here. A new NASA system called Scout aims to identify the ones that will come closest to the planet.
    P. Carril/ESA

    A large space rock is going to come fairly close to Earth later tonight. Fortunately, it’s not going to hit Earth, something astronomers are sure of thanks in part to a new tool NASA is developing for detecting potentially dangerous asteroids.

    The tool is a computer program called Scout, and it’s being tested at NASA Jet Propulsion Laboratory in Pasadena, Calif. Think of Scout as a celestial intruder alert system. It’s constantly scanning data from telescopes to see if there are any reports of so-called Near Earth Objects. If it finds one, it makes a quick calculation of whether Earth is at risk, and instructs other telescopes to make follow-up observations to see if any risk is real.

    NASA pays for several telescopes around the planet to scan the skies on a nightly basis, looking for these objects. “The NASA surveys are finding something like at least five asteroids every night,” says astronomer Paul Chodas of JPL.

    But then the trick is to figure out which new objects might hit Earth.

    “When a telescope first finds a moving object, all you know is it’s just a dot, moving on the sky,” says Chodas. “You have no information about how far away it is. “The more telescopes you get pointed at an object, the more data you get, and the more you’re sure you are how big it is and which way it’s headed. But sometimes you don’t have a lot of time to make those observations.

    “Objects can come close to the Earth shortly after discovery, sometimes one day, two days, even hours in some cases,” says JPL’s Davide Farnocchia. “The main goal of Scout is to speed up the confirmation process.”

    The rock whizzing past Earth tonight was discovered on the night of Oct. 25-26 by the NASA-funded Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) on Maui, Hawaii. Within a few hours, preliminary details about the object appeared on a Web page maintained by the Minor Planet Center at the Smithsonian Astrophysical Observatory. Scout did a quick analysis of the preliminary details and determined that the object was headed for Earth but would miss us by about 310,000 miles.


    Pannstars telescope, U Hawaii, Mauna Kea, Hawaii, USA. A telescope in Hawaii first spotted an errant rock headed toward Earth. The Scout program quickly flagged it for follow-up observations.

    Additional observations by three telescopes, one operated by the Steward Observatory, another called Spacewatch, and a third at the Tenagra Observatories, confirmed the object would miss Earth by a comfortable margin. Astronomers were also able to estimate the size of the object: somewhere between 5 meters and 25 meters across. In case you’re interested, full details about the object’s trajectory can be found here.

    U Arizona Steward Observatory Vatican Advanced Technology Telescope
    U Arizona Steward Observatory Vatican Advanced Technology Telescope

    2
    Spacewatch

    2
    Tenagra Observatory

    Scout is still in the testing phase. It should become fully operational later this year.

    Now Scout is mainly dealing with smallish, very nearby objects. Complementing Scout is another system that is already operational called Sentry.

    3
    NASA’s Other Asteroid Mission: Grab A Chunk And Put It In Orbit Around The Moon

    4
    Scientists in Michigan have found a new dwarf planet in our solar system. It’s about 330 miles across and some 8.5 billion miles from the sun. It takes 1,100 years to complete one orbit. But one of the most interesting things about the new object, known for the time being as 2014 UZ224, is the way astronomers found it. David Gerdes of the University of Michigan led the team that found the new dwarf planet. Gerdes describes himself as “an adult-onset astronomer,” having started his scientific career as a particle physicist.

    He helped develop a special camera called the Dark Energy Camera that the U.S. Department of Energy commissioned to make a map of distant galaxies.

    Fermilab DECam
    DEam built at FNAL

    The dwarf planet that Gerdes and his colleagues have found isn’t the first distant dwarf planet astronomers have found in recent years. Sedna, Eris and Makemake have all been discovered in the past decade or so. Add to that Pluto, which used to be a planet until it was demoted when the definition changed.

    Sentry’s job is to identify objects large enough to wipe out a major city that might hit Earth in the next hundred years. “Our goal right now is to find 90 percent of the 140-meter asteroids and larger,” says Chodas, but right now he estimates they’re able to find only 25 to 30 percent of the estimated population of objects that size.

    That number should get better when a new telescope being built in Chile called the Large Synoptic Survey Telescope [LSST] comes online. NASA is also considering a space telescope devoted to searching for asteroids.

    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC

    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST telescope, currently under construction at Cerro Pachón Chile

    OK, so let’s say you find one of these monster rocks heading for Earth. What then? Astronomer Ed Lu says there is something you can do. He’s CEO of an organization called B612. It’s devoted to dealing with asteroid threats.

    “If you know well in advance, and by well in advance I mean 10 years, 20 years, 30 years in advance, which is something we can do, ” says Lu, “then you can divert such an asteroid by just giving it a tiny nudge when it’s many billions of miles from hitting the Earth.”

    NASA and the European Space Agency are developing a mission to practice doing just that.

    6
    ESA/NASA DART

    Lu says in the past decade, people who should worry about such things have begun to make concrete plans for dealing with dangerous asteroids.

    “I believe in the next 10 to 15 years we’ll actually be at the point where we as humans can say, ‘Hey, we’re safe from this danger of large asteroids hitting the Earth,’ ” he says.

    In the meantime, we’ll just have to hope that luck is on our side.

    See the full article here.

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  • richardmitnick 9:44 am on August 5, 2016 Permalink | Reply
    Tags: , Asteroids, ,   

    From AAS NOVA: ” Images of an Activated Asteroid” 

    AASNOVA

    American Astronomical Society

    5 August 2016
    Susanna Kohler

    1
    Graphic (collage) showing relative sizes of possible target asteroids and other known asteroids. ESA

    In late April of this year, asteroid P/2016 G1 (PANSTARRS) was discovered streaking through space, a tail of dust extending behind it. What caused this asteroid’s dust activity?

    2
    Images of asteroid P/2016 G1 at three different times: late April, late May, and mid June. The arrow in the center panel points out an asymmetric feature that can be explained if the asteroid initially ejected material in a single direction, perhaps due to an impact. [Moreno et al. 2016]

    Asteroid or Comet?

    Asteroid P/2016 G1 is an interesting case: though it has the orbital elements of a main-belt asteroid — it orbits at just under three times the Earth–Sun distance, with an eccentricity of e ~ 0.21 — its appearance is closer to that of a comet, with a dust tail extending 20” behind it.

    To better understand the nature and cause of this unusual asteroid’s activity, a team led by Fernando Moreno (Institute of Astrophysics of Andalusia, in Spain) performed deep observations of P/2016 G1 shortly after its discovery. The team used the 10.4-meter Great Canary Telescope to image the asteroid over the span of roughly a month and a half.

    Gran Telescopio  Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain
    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain

    A Closer Look at P/2016 G1

    P/2016 G1 lies in the inner region of the main asteroid belt, so it is unlikely to have any ices that suddenly sublimated, causing the outburst. Instead, Moreno and collaborators suggest that the asteroid’s tail may have been caused by an impact that disrupted the parent body.

    To test this idea, the team used computer simulations to model their observations of P/2016 G1’s dust tail. Based on their models, they demonstrate that the asteroid was likely activated on February 10 2016 — roughly 350 days before it reached perihelion in its orbit — and its activity was a short-duration event, lasting only ~24 days. The team’s models indicate that over these 24 days, the asteroid lost around 20 million kilograms of dust, and at its maximum activity level, it was ejecting around 8 kg/s!

    4
    Comparison of the observation from late May (panel a) and two models: one in which the emission is all isotropic (panel b), and one in which the emission is initially directed (panel c). The second model better fits the observations. [Adapted from Moreno et al. 2016]

    Activation By Impact

    To reproduce the observed asymmetric features in the asteroid’s tail, Moreno and collaborators show that the ejected material could not have been completely isotropically emitted. Instead, the observations can be reproduced if the material was initially ejected all in the same direction (away from the Sun) at the time of the asteroid’s activation.

    These conclusions support the idea that the asteroid’s parent body was impacted by another object. The initial impact caused a large ejection of material, and the subsequent activity is due to the partial or total disruption of the asteroid as a result of the impact.

    To further test this model for P/2016 G1, the next step is to obtain higher-resolution and higher-sensitivity imaging (as could be provided by Hubble) of this unusual object. Such images would allow scientists to search for smaller fragments of the parent body that could remain near the dust tail.

    Citation

    F. Moreno et al 2016 ApJ 826 L22. doi:10.3847/2041-8205/826/2/L22

    See the full article here .

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