[meteorite-list] Frosty Cold Nights Year-Round on Mars May Stir Dust
http://www.jpl.nasa.gov/news/news.php?feature=6564 Frosty Cold Nights Year-Round on Mars May Stir Dust Jet Propulsion Laboratory July 8, 2016 Some dusty parts of Mars get as cold at night year-round as the planet's poles do in winter, even regions near the equator in summer, according to new NASA findings based on Mars Reconnaissance Orbiter observations. The surface in these regions becomes so frigid overnight that an extremely thin layer of carbon dioxide frost appears to form. The frost then vaporizes in the morning. Enough dust covers these regions that their heat-holding capacity is low and so the daily temperature swing is large. Daily volatilization of frost crystals that form among the dust grains may help keep the dust fluffy and so sustain this deep overnight chill. Carbon dioxide is the main ingredient of Mars' atmosphere. The planet also has large reserves of frozen carbon dioxide buried in the polar ice caps. Seasonal buildup and thawing of carbon dioxide frost at high latitudes on Mars have been studied for years and linked to strange phenomena such as geyser-like eruptions and groove-cutting ice sleds. Here's what's new knowledge: the presence and extent of transient overnight carbon dioxide frosts, even at middle and low latitudes. Infrared-wavelength observations of dust-covered regions by the Mars Climate Sounder instrument on NASA's Mars Reconnaisance Orbiter not only indicate cold-enough nighttime surface temperatures for carbon dioxide frost to form, they also detect a spectrum signature at night consistent with a trace of frost. "The temperature gets so low, you start freezing the atmosphere onto the surface," said Sylvain Piqueux of NASA's Jet Propulsion Laboratory, Pasadena, California, lead author of a report on these findings published online by the Journal of Geophysical Research: Planets. "Once you reach that temperature, you don't get colder, you just accumulate more frost. So even on the polar caps, the surface temperature isn't any colder than what these lower-latitude regions get to overnight." Three middle- and low-latitude areas in the Tharsis, Arabia and Elysium regions of Mars have nightly temperatures cold enough for carbon dioxide frost year-round or nearly year-round. Each of the three is bigger than Texas. All three are dust-covered to the extent that surface temperatures change much quicker than in areas with exposed-bedrock surfaces. Piqueux said, "These same regions that are coldest at night are the warmest during the day. It has to do with the nature of the material -- it's so fluffy. Think of when you're at the beach on a summer afternoon, where you step on the fine grain sand. You almost burn your foot, it's so hot at the surface, but just below the surface it's not as hot, and if you touch a boulder, it doesn't feel as hot. Then it's the opposite at night: The surface of the sand cools off quickly, while the boulder stays warm." Unlike the polar regions, at lower latitudes the atmosphere is warmer than the ground at night. A critical step in understanding just how cold the ground in these areas gets at night was correcting observations of the planet's surface for slightly warmer atmospheric temperatures. Temperatures are determined from orbit by analyzing the infrared radiation oserved at the top of the atmosphere; this includes radiation from both the ground and the atmosphere. The Mars Climate Sounder instrument, by observing both sideways toward the horizon from orbit and downward, can record infrared emissions from a cross-section of the atmosphere, as well as from the planet's surface. Analysis then reveals the true -- colder -- ground temperature. The same instrument also provides readings at multiple infrared wavelengths, yielding results consistent with the presence of microscopic-scale carbon dioxide frost crystals forming a layer no thicker than a few sheets of paper. "If at night you form little frost crystals between the grains of dust on the surface, pushing the grains apart, then the frost crystal becomes a little puff of air in the morning, that might be helping to maintain the fluffiness of the surface," Piqueux said. "You prevent the cementation of grains, the locking together of grains into a more consolidated surface. It's a self-maintaining process: Where you keep the soil fluffy, you maintain the conditions to form frost at night." "A cycle of carbon dioxide frost that happens every night could be related to other active processes on Mars," said Rich Zurek, JPL's chief Mars scientist. "This agitation of the soil would affect surface physical properties and could have implications for erosive processes and for the exchange of water vapor between the atmosphere and surface." Many streaks on Martian slopes appear to be slides of dry material, with no liquid involved. The lubrication effect of carbon dioxide frost thawing directly into gas has been linked to such slides
[meteorite-list] Dawn Maps Ceres Craters Where Ice Can Accumulate
http://www.jpl.nasa.gov/news/news.php?feature=6560 Dawn Maps Ceres Craters Where Ice Can Accumulate Jet Propulsion Laboraotry July 8, 2016 Scientists with NASA's Dawn mission have identified permanently shadowed regions on the dwarf planet Ceres. Most of these areas likely have been cold enough to trap water ice for a billion years, suggesting that ice deposits could exist there now. "The conditions on Ceres are right for accumulating deposits of water ice," said Norbert Schorghofer, a Dawn guest investigator at the University of Hawaii at Manoa. "Ceres has just enough mass to hold on to water molecules, and the permanently shadowed regions we identified are extremely cold -- colder than most that exist on the moon or Mercury." Permanently shadowed regions do not receive direct sunlight. They are typically located on the crater floor or along a section of the crater wall facing toward the pole. The regions still receive indirect sunlight, but if the temperature stays below about minus 240 degrees Fahrenheit (minus 151 degrees Celsius), the permanently shadowed area is a cold trap -- a good place for water ice to accumulate and remain stable. Cold traps were predicted for Ceres but had not been identified until now. In this study, Schorghofer and colleagues studied Ceres' northern hemisphere, which was better illuminated than the south. Images from Dawn's cameras were combined to yield the dwarf planet's shape, showing craters, plains and other features in three dimensions. Using this input, a sophisticated computer model developed at NASA's Goddard Space Flight Center, Greenbelt, Maryland, was used to determine which areas receive direct sunlight, how much solar radiation reaches the surface, and how the conditions change over the course of a year on Ceres. The researchers found dozens of sizeable permanently shadowed regions across the northern hemisphere. The largest one is inside a 10-mile-wide (16-kilometer) crater located less than 40 miles (65 kilometers) from the north pole. Taken together, Ceres' permanently shadowed regions occupy about 695 square miles (1,800 square kilometers). This is a small fraction of the landscape -- much less than 1 percent of the surface area of the northern hemisphere. The team expects the permanently shadowed regions on Ceres to be colder than those on Mercury or the moon. That's because Ceres is quite far from the sun, and the shadowed parts of its craters receive little indirect radiation. "On Ceres, these regions act as cold traps down to relatively low latitudes," said Erwan Mazarico, a Dawn guest investigator at Goddard. "On the moon and Mercury, only the permanently shadowed regions very close to the poles get cold enough for ice to be stable on the surface." The situation on Ceres is more similar to that on Mercury than the moon. On Mercury, permanently shadowed regions account for roughly the same fraction of the northern hemisphere. The trapping efficiency -- the ability to accumulate water ice -- is also comparable. By the team's calculations, about 1 out of every 1,000 water molecules generated on the surface of Ceres will end up in a cold trap during a year on Ceres (1,682 days). That's enough to build up thin but detectable ice deposits over 100,000 years or so. "While cold traps may provide surface deposits of water ice as have been seen at the moon and Mercury, Ceres may have been formed with a relatively greater reservoir of water," said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles. "Some observations indicate Ceres may be a volatile-rich world that is not dependent on current-day external sources." The findings are available online in the journal Geophysical Research Letters. Dawn's mission is managed by NASA's Jet Propulsion Laboratory for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit: http://dawn.jpl.nasa.gov/mission More information about Dawn is available at the following sites: http://dawn.jpl.nasa.gov http://www.nasa.gov/dawn News Media Contact Elizabeth Landau Jet Propulsion Laboratory, Pasadena, Calif. 818-354-6425 elizabeth.lan...@jpl.nasa.gov Written by Elizabeth Zubritsky NASA's Goddard Space Flight Center 2016-180 __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing
[meteorite-list] Mars Canyons Study Adds Clues about Possible Water
http://www.jpl.nasa.gov/news/news.php?feature=6562 Mars Canyons Study Adds Clues about Possible Water Jet Propulsion Laboratory July 7, 2016 Fast Facts: * Big canyons on Mars hold thousands of seasonal dark streaks examined in a new study of such features, which might be signs of liquid water. * The seasonal streaks at many locations are unlikely to result from underground water reaching the surface. * Salts drawing water vapor from the atmosphere might be a key mechanism in how these streaks form, but puzzles and other possibilities remain. Puzzles persist about possible water at seasonally dark streaks on Martian slopes, according to a new study of thousands of such features in the Red Planet's largest canyon system. The study published today investigated thousands of these warm-season features in the Valles Marineris region near Mars' equator. Some of the sites displaying the seasonal flows are canyon ridges and isolated peaks, ground shapes that make it hard to explain the streaks as resulting from underground water directly reaching the surface. It is highly unlikely that shallow ground ice would be present as a source for seasonal melting, given the warm temperatures in the equatorial canyons. Water pulled from the atmosphere by salts, or mechanisms with no flowing water involved, remain possible explanations for the features at these sites. What are RSL? These features are called recurring slope lineae, or RSL, a mouthful chosen to describe them without implying how they form. Since their discovery in 2011, Martian RSL have become one of the hottest topics in planetary exploration, the strongest evidence for any liquid water on the surface of modern Mars, even if transient. They appear as dark lines extending downslope during a warm season, then fading away during colder parts of the year, then repeating the progression in a following year. Water, in the form of hydrated salts, was confirmed at some RSL sites last year, including in Valles Marineris. Research results published today present many findings from detailed observation of 41 RSL sites in central and eastern portions of Valles Marineris, the largest canyon system in the solar system. Each site is defined as the size of a single image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter: about 3.4 miles by 8 miles (5.4 by 12 kilometers). The number of individual lineae (flows) in each site ranges from a few to more than 1,000. Densest Population of RSL "There are so many of them, it's hard to keep track," said Matthew Chojnacki of the University of Arizona's Lunar and Planetary Laboratory, Tucson, and lead author of today's report in the Journal of Geophysical Research: Planets. "The occurrence of recurring slope lineae in these canyons is much more widespread than previously recognized. As far as we can tell, this is the densest population of them on the planet, so if they are indeed associated with contemporary aqueous activity, that makes this canyon system an even more interesting area than it is just from the spectacular geology alone." The possibility of liquid water at or near the surface of Mars carries major ramifications for investigating whether life exists on Mars, since all known life relies on liquid water. Either liquid or frozen water near the surface could become an important resource for humans on Mars. Fresh crater impacts and other data have revealed water ice close to the surface at many locations in middle and high latitudes of Mars. If RSL are indicators of water, they extend possible water-access sites to low latitudes. If water is involved in forming RSL, what is the mechanism? Seeking an answer, Chojnacki and five co-authors examined the geological context of canyonland RSL sites and also calculated how much water would need to be present if the streaks are due to liquid water seeping through a thin surface layer to darken the ground. Many of the sites where RSL were previously identified are on inner walls of impact craters. At that type of site, a conceivable explanation could be that an extensive underground layer holding water was punctured by the crater-forming impact long ago and still feeds warm-season flows. No such underground layer fits the ridge or peak shapes at several of the RSL sites in the new study. Salt Connection Another possible mechanism previously proposed for RSL is that some types of salts so strongly pull water vapor out of the Martian atmosphere that liquid brine forms at the ground surface. The new study bolsters the link between RSL and salts. Some sites bear bright, persistent streaks near the dark, seasonal ones. The bright streaks might result from salt left behind after evaporation of brine. "There are problems with the mechanism of pulling water from the atmosphere, too," Chojnacki said. If it is seeping water that darkens RSL, the amount of liquid
[meteorite-list] Ad: Johnstown and Bishopville USA FALLS!
Hi all, Just finished up a trade with Arizona State University and came away with some cool specimens. Johnstown (Dio) a 1924 Colorado fall http://www.ebay.com/sch/m.html?_odkw=&_ssn=mr-meteorite=222180776963&_osacat=0=STRK%3AMESELX%3AIT&_from=R40&_trksid=p2046732.m570.l1313.TR12.TRC2.A0.H0.XJohnstown.TRS0&_nkw=Johnstown&_sacat=0 and Bishopville (Aubrite) a 1843 South Carolina fall. http://www.ebay.com/sch/m.html?_odkw=Johnstown&_ssn=mr-meteorite=222180776963&_osacat=0=STRK%3AMESELX%3AIT&_from=R40&_trksid=p2046732.m570.l1313.TR0.TRC0.H0.Xbishopville.TRS0&_nkw=bishopville&_sacat=0 About half of the Johnstown specimens have crust and all the Bishopville have crust that varies in color from whitish to jet black - a product of the low metal content. Of course, these specimens come with an ASU label but also have an added bit of provenance. You’ll notice in the photos that the card has the description written on the front and on the back is the deaccession date as well as the signature of ASU Collections Manager, Dr. Laurence Garvie. Also, each specimen has a best offer option! -- Rock On! Ruben Garcia http://www.MrMeteorite.com __ 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
Re: [meteorite-list] Home World
Very cool, thanks for sharing! Roman Jirasek From: Sterling K. Webb via Meteorite-list Sent: Friday, July 08, 2016 1:25 AM To: meteorite-list@meteoritecentral.com Subject: [meteorite-list] Home World List, We're all familiar with the famous "blue marble" photo of the Earth supposedy taken by Apollo. (It was actually patched together for use as a publicity shot.) But, there is (now) a true "blue marble" camera that photographs the Earth from a million miles out, the Earth Polychromatic Imaging Camera, or EPIC. There's a large archive of photos there to flip through, a movie of our endlessly fascinating planet. http://epic.gsfc.nasa.gov/ I love to watch the home world from orbit... and it's much cheaper than the ticket to orbit. Sterling Webb __ 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 __ 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] AD-ebay auctions ending Sat July 9
Aloha Meteorite lovers, Big Kahuna is offering some interplanetary interlopers on eBay in auctions that begin ending tomorrow, Saturday, July 9 at 9:00am Pacific / 12:00pm Eastern / 5:00pm London / 7:00pm Helsinki / 12:00am Singapore. FREE Worldwide shipping on select meteorites. Lunar meteorites NWA 4734 Lunar 0.02g fragment, bid at $1 - http://tinyurl.com/h7c2bjf NWA 8682 Lunar 0.18g full slice, bid at $12.50 - http://tinyurl.com/jsh87x4 NWA 8783 Lunar 0.54g endcut, bid at $66 - http://tinyurl.com/j7yq6l3 NWA 10609 Lunar 0.07g slice, bid at $1 - http://tinyurl.com/jkg2gbv NWA 10678 Lunar 0.05g slice, bid at $1 - http://tinyurl.com/zww3vjc Dho 007 4.01g full slice, bid at $10 - http://tinyurl.com/hzzbqaf Holbrook L/LL6 0.45g perfect pea, bid @ $3.25 - http://tinyurl.com/hgffkwx Mundrabilla IAB 74.32g Stunning Showpiece - http://tinyurl.com/zztfr9v Peekskill H6 0.14g slice of car hitter - http://tinyurl.com/znp2aar Tatahouine Dio 1.70g The Green Meteorite - http://tinyurl.com/hsdg57t NWA 2086 CV3 0.43g CRAZY CAI, AOAs - http://tinyurl.com/hlb5pbp NWA 10265 Lod 1.97g slice, bid at $34 - http://tinyurl.com/gwjq7uh NWA 10580 CO3 1.68g full slice, bid at $7.50 - http://tinyurl.com/jhhgsjv NWA x HED 1.19g slice, bid at $1.25 - http://tinyurl.com/zztudof And many more: http://www.ebay.com/sch/fujmon/m.html Gary Fujihara Big Kahuna Meteorites Inc. PO Box 4175, Hilo, HI 96720 (808) 640-9161 http://bigkahuna-meteorites.com/ http://www.ebay.com/sch/fujmon/m.html __ 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] Home World
List, We're all familiar with the famous "blue marble" photo of the Earth supposedy taken by Apollo. (It was actually patched together for use as a publicity shot.) But, there is (now) a true "blue marble" camera that photographs the Earth from a million miles out, the Earth Polychromatic Imaging Camera, or EPIC. There's a large archive of photos there to flip through, a movie of our endlessly fascinating planet. http://epic.gsfc.nasa.gov/ I love to watch the home world from orbit... and it's much cheaper than the ticket to orbit. Sterling Webb __ 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: NWA 859 (Taza) Contributed by: Tomasz Jakubowski http://www.tucsonmeteorites.com/mpodmain.asp?DD=07/08/2016 __ 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
