[meteorite-list] Catalog of Known Near-Earth Asteroids Tops 15, 000
http://www.jpl.nasa.gov/news/news.php?feature=6664 Catalog of Known Near-Earth Asteroids Tops 15,000 Jet Propulsion Laboratory October 27, 2016 The number of discovered near-Earth asteroids (NEAs) now tops 15,000, with an average of 30 new discoveries added each week. This milestone marks a 50 percent increase in the number of known NEAs since 2013, when discoveries reached 10,000 in August of that year. Surveys funded by NASA's Near Earth Object (NEO) Observations Program (NEOs include both asteroids and comets) account for more than 95 percent of discoveries so far. The 15,000th near-Earth asteroid is designated 2016 TB57. It was discovered on Oct. 13 by observers at the Mount Lemmon Survey, an element of the NASA-funded Catalina Sky Survey in Tucson, Arizona. 2016 TB57 is a rather small asteroid -- about 50 to 115 feet (16 to 36 meters) in size -- that will come closest to Earth on Oct. 31 at just beyond five times the distance of the moon. It will safely pass Earth. A near-Earth asteroid is defined as one whose orbit periodically brings it within approximately 1.3 times Earth's average distance to the sun -- that is within 121 million miles (195 million kilometers) -- of the sun (Earth's average distance to the sun is about 93 million miles, or 150 million kilometers). This distance also then brings the asteroid within roughly 30 million miles (50 million kilometers) of Earth's orbit. Observers have already discovered more than 90 percent of the estimated population of the large NEOs -- those larger than 0.6 miles (one kilometer). "The rising rate of discovery is due to dedicated NEO surveys and upgraded telescopes coming online in recent years," said NASA's NEO Observations Program Manager Kelly Fast. "But while we're making great progress, we still have a long way to go." It is estimated by astronomers that only about 27 percent of the NEAs that are 460 feet (140 meters) and larger have been found to date. Congress directed NASA to find over 90 percent of objects this size and larger by the end of 2020. Currently, two NASA-funded NEO surveys -- the Catalina Sky Survey and the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) in Hawaii -- account for about 90 percent of new NEO discoveries. Both projects upgraded their telescopes in 2015, improving their discovery rates. A recent upgrade to one of the Catalina Sky Survey's telescopes resulted in a tripling of its average monthly NEO discovery rate. When the Pan-STARRS system increased the observing time it devoted to NEO searching to 90 percent, it increased its rate of discovery by a factor of three. Pan-STARRS also will add a second telescope to the hunt this fall. As more capable telescopes are deployed, the overall NEO survey effort will be able to find more objects as small as and smaller than 140 meters (460 feet). The NEO Observations Program is a primary element of NASA's Planetary Defense Coordination Office, which is responsible for finding, tracking and characterizing potentially hazardous NEOs, issuing warnings about possible impacts, and coordinating U.S. government planning for response to an actual impact threat. "While no known NEO currently poses a risk of impact with Earth over the next 100 years," says NASA Planetary Defense Officer Lindley Johnson, "we've found mostly the larger asteroids, and we have a lot more of the smaller but still potentially hazardous ones to find." For asteroid news and updates, follow AsteroidWatch on Twitter: http://www.twitter.com/AsteroidWatch News Media Contact DC Agle Jet Propulsion Laboratory, Pasadena, Calif. 818-393-9011 a...@jpl.nasa.gov Dwayne Brown / Laurie Cantillo NASA Headquarters, Washington 202-358-1726 / 202-358-1077 dwayne.c.br...@nasa.gov / laura.l.canti...@nasa.gov 2016-284 __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] Further Clues to Fate of Schiaparelli Mars Lander, Seen From Orbit
http://www.jpl.nasa.gov/news/news.php?feature=6663 Further Clues to Fate of Mars Lander, Seen From Orbit Jet Propulsion Laboratory October 27, 2016 The most powerful telescope orbiting Mars is providing new details of the scene near the Martian equator where Europe's Schiaparelli test lander hit the surface last week. An Oct. 25 observation using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows three impact locations within about 0.9 mile (1.5 kilometers) of each other. An annotated view is available online at http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA21131 The scene shown by HiRISE includes three locations where hardware reached the ground. A dark, roughly circular feature is interpreted as where the lander itself struck. A pattern of rays extending from the circle suggests that a shallow crater was excavated by the impact, as expected given the premature engine shutdown. About 0.8 mile (1.4 kilometers) eastward, an object with several bright spots surrounded by darkened ground is likely the heat shield. About 0.6 mile (0.9 kilometer) south of the lander impact site, two features side-by-side are interpreted as the spacecraft's parachute and the back shell to which the parachute was attached. Additional images to be taken from different angles are planned and will aid interpretation of these early results. The test lander is part of the European Space Agency's ExoMars 2016 mission, which placed the Trace Gas Orbiter into orbit around Mars on Oct. 19. The orbiter will investigate the atmosphere and surface of Mars and provide relay communications capability for landers and rovers on Mars. Data transmitted by Schiaparelli during its descent through Mars' atmosphere is enabling analysis of why the lander's thrusters switched off prematurely. The new HiRISE imaging provides additional information, with more detail than visible in an earlier view with the Context Camera (CTX) on the Mars Reconnaissance Orbiter. With HiRISE, CTX and four other instruments, the Mars Reconnaissance Orbiter has been investigating Mars since 2006. The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it. For additional information about the project, visit: http://mars.nasa.gov/mro News Media Contact Guy Webster Jet Propulsion Laboratory, Pasadena, Calif. 818-354-6278 guy.webs...@jpl.nasa.gov Markus Bauer European Space Agency, Villanueva de la Cañada, Spain 0031 61 594 3 954 markus.ba...@esa.int Dwayne Brown / Laurie Cantillo NASA Headquarters, Washington 202-358-1726 / 202-358-1077 dwayne.c.br...@nasa.gov / laura.l.canti...@nasa.gov 2016-283 __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] GRAIL Moon Mission Shares Insights into Giant Impacts
http://www.jpl.nasa.gov/news/news.php?feature=6662 NASA Moon Mission Shares Insights into Giant Impacts Jet Propulsion Laboratory October 27, 2016 Fast Facts: * Orientale basin is a giant, ringed impact crater on Earth's moon. * Until now, how impact craters with rings form had not been well understood. * Scientists have reconstructed Orientale's formation using data from NASA's GRAIL mission. New results from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission are providing insights into the huge impacts that dominated the early history of Earth's moon and other solid worlds, like Earth, Mars, and the satellites of the outer solar system. In two papers, published this week in the journal Science, researchers examine the origins of the moon's giant Orientale impact basin. The research helps clarify how the formation of Orientale, approximately 3.8 billion years ago, affected the moon's geology. Located along the moon's southwestern limb -- the left-hand edge as seen from Earth -- Orientale is the largest and best-preserved example of what's known as a "multi-ring basin." Impact craters larger than about 180 miles (300 kilometers) in diameter are referred to as basins. With increasing size, craters tend to have increasingly complex structures, often with multiple concentric, raised rings. Orientale is about 580 miles (930 kilometers) wide and has three distinct rings, which form a bullseye-like pattern. Multi-ring basins are observed on many of the rocky and icy worlds in our solar system, but until now scientists had not been able to agree on how their rings form. What they needed was more information about the crater's structure beneath the surface, which is precisely the sort of information contained in gravity science data collected during the GRAIL mission. The powerful impacts that created basins like Orientale played an important role in the early geologic history of our moon. They were extremely disruptive, world-altering events that caused substantial fracturing, melting and shaking of the young moon's crust. They also blasted out material that fell back to the surface, coating older features that were already there; scientists use this layering of ejected material to help determine the age of lunar features as they work to unravel the moon's complex history. The Importance of Orientale Because scientists realized that Orientale could be quite useful in understanding giant impacts, they gave special importance to observing its structure near the end of the GRAIL mission. The orbit of the mission's two probes was lowered so they passed less than 1.2 miles (2 kilometers) above the crater's mountainous rings. "No other planetary exploration mission has made gravity science observations this close to the moon. You could have waved to the twin spacecraft as they flew overhead if you stood at the ring's edge," said Sami Asmar, GRAIL project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. Of particular interest to researchers has been the size of the initial crater that formed during the Orientale impact. With smaller impacts, the initial crater is left behind, and many characteristics of the event can be inferred from the crater's size. Various past studies have suggested each of Orientale's three rings might be the remnant of the initial crater. In the first of the two new studies, scientists teased out the size of the transient crater from GRAIL's gravity field data. Their analysis shows that the initial crater was somewhere between the size of the basin's two innermost rings. "We've been able to show that none of the rings in Orientale basin represent the initial, transient crater," said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge, lead author of the first paper. "Instead, it appears that, in large impacts like the one that formed Orientale, the surface violently rebounds, obliterating signs of the initial impact." The analysis also shows that the impact excavated at least 816,000 cubic miles (3.4 million cubic kilometers) of material -- 153 times the combined volume of the Great Lakes. "Orientale has been an enigma since the first gravity observations of the moon, decades ago," said Greg Neumann, a co-author of the paper at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We are now able to resolve the individual crustal components of the bullseye gravity signature and correlate them with computer simulations of the formation of Orientale." Reproducing the Rings The second study describes how scientists successfully simulated the formation of Orientale to reproduce the crater's structure as observed by GRAIL. These simulations show, for the first time, how the rings of Orientale formed, which is likely similar for multi-ring basins in general. "Because our models show how the subsurface structure is formed, matching what
[meteorite-list] Water Detected on Largest Metallic Asteroid in Solar System (Psyche)
https://www.usgs.gov/news/water-detected-largest-metallic-asteroid-solar-system Water Detected on Largest Metallic Asteroid in Solar System USGS Release Date: October 20, 2016 Scientists have discovered possible evidence for water-rich minerals on the surface of the largest metallic asteroid in the solar system, according to a study by the U.S. Geological Survey and NASA. The asteroid, called Psyche, is 186 miles across and is made of almost pure nickel-iron metal. It is thought to be the remnant core of a planetary embryo that was mostly destroyed by impacts billions of years ago. Previous observations of Psyche had shown no evidence for water-rich minerals on its surface. However, new observations from the NASA Infrared Telescope Facility in Hawaii show evidence for water and/or hydroxyl on its surface. Results are published in The Astronomical Journal. While the source of these water molecules on Psyche remains a mystery, scientists propose a few possible mechanisms for their formation. It is possible that water-rich minerals detected on Psyche might have been delivered to its surface by carbonaceous asteroids that impacted Psyche in the distant past. "We think that Psyche may not be entirely exposed metallic core," says Driss Takir, lead author and scientist at the USGS Astrogeology Science Center in Flagstaff, Arizona. "What we see might instead have been a core-mantle boundary of a differentiated body that was disrupted via impacts. Solar radiation is another mechanism that can produce hydroxyl, which is a molecule consisting of one oxygen atom and one hydrogen atom, by interacting with the surface of Psyche." "This work underscores how much more we have to learn about asteroids," says Laszlo Kestay, Director of the USGS Astrogeology Science Center. "It will take more of this kind of careful work with telescopes on Earth, and spacecraft visiting asteroids, before we understand what treasures await us in space." Takir is a member of NASA's OSIRIS-REx mission and JAXA's Hayabusa 2 mission to collect carbonaceous samples from the water-rich asteroids, Bennu and Ryugu. "We are excited to continue studying Psyche, and other water-rich asteroids, to give us further insight into the distribution of potential resources in space," said Takir. This research on Psyche is funded by the USGS/NASA Eugene M. Shoemaker Fellowship, NASA Planetary Science Division Planetary Geology and Geophysics and Solar System Observations Programs. __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] Meteorite Picture of the Day
Today's Meteorite Picture of the Day: Twannberg Contributed by: Andreas Gren http://www.tucsonmeteorites.com/mpodmain.asp?DD=10/27/2016 __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
