Hello All!   
      
   Evidence Mounts for Ice in Shackleton Crater    
      
   June 21, 2012: According to data from NASA's Lunar Reconnaissance Orbiter   
   (LRO), ice may make up as much as 22 percent of the surface material in   
   Shackleton crater at the Moon's south pole.   
      
   The huge crater, named after the Antarctic explorer Ernest Shackleton, is two   
   miles deep and more than 12 miles wide. The small tilt of the lunar spin axis   
   means Shackleton's interior is permanently dark and very cold..  Researchers   
   have long thought that ice might collect  there.   
      
   When a team of NASA and university scientists used LRO's laser altimeter to   
   examine the floor of Shackleton crater, they found it to be brighter than the   
   floors of other nearby craters around the South Pole. This is consistent with   
   the presence of small amounts of reflective ice preserved by cold and   
   darkness. The findings are published in today's edition of the journal Nature.    
      
   http://science.nasa.gov/media/medialibrary/2012/06/21/media.mp4   
      
   This visualization, created using Lunar Reconnaissance Orbiter laser altimeter   
   data, offers a view of Shackleton Crater located in the south pole of the   
   moon. Play it   
      
   In addition to the possible evidence of ice, the group's map of Shackleton   
   revealed a remarkably preserved crater that has remained relatively unscathed   
   since its formation more than three billion years ago. The crater's floor is   
   itself pocked with several small craters, which may have formed as part of the   
   collision that created Shackleton.   
      
   "The crater's interior is extremely rugged," said Maria Zuber, the team's lead   
   investigator from the Massachusetts Institute of Technology in Cambridge in   
   Mass. "It would not be easy to crawl around in there."    
      
   http://www.nasa.gov/images/content/656996main_shackleton-interior-rgb.jpg   
      
   In this laser elevation map of Shackleton crater, false colors indicate   
   height, with blue lowest and red highest. Credit: NASA/Zuber, M.T. et al.,   
   Nature, 2012 While the crater's floor was relatively bright, Zuber and her   
   colleagues observed that its walls were even brighter. The finding was at   
   first puzzling. Scientists had thought that if ice were anywhere in a crater,   
   it would be on the floor, where no direct sunlight penetrates. The upper walls   
   of Shackleton crater are occasionally illuminated, which could evaporate any   
   ice that accumulates.    
      
   "The brightness measurements have been puzzling us since two summers ago,"   
   said Gregory Neumann of NASA's Goddard Space Flight Center in Greenbelt, Md.,   
   a co-author on the paper.   
      
   A theory offered by the team to explain the puzzle is that "moonquakes"--   
   seismic shaking brought on by meteorite impacts or gravitational tides from   
   Earth -- may have caused Shackleton's walls to slough off older, darker soil,   
   revealing newer, brighter soil underneath. Zuber's team's ultra-   
   igh-resolution map provides strong evidence for ice on both the crater's floor   
   and walls.   
      
   "There may be multiple explanations for the observed brightness throughout the   
   crater," said Zuber. "For example, newer material may be exposed along its   
   walls, while ice may be mixed in with its floor."   
      
   For more information on LRO and the Lunar Orbiter Laser Altimeter, visit:   
   http://lunar.gsfc.nasa.gov   
      
      
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
      
   More Information    
   The initial primary objective of LRO was to conduct investigations that   
   prepare for future lunar exploration. Launched in June 2009, LRO completed its   
   primary exploration mission and is now in its primary science mission. LRO was   
   built and is managed by Goddard. This research was supported by NASA's Human   
   Exploration and Operations Mission Directorate and Science Mission Directorate   
   at the agency's headquarters in Washington.   
      
   The spacecraft mapped Shackleton crater with unprecedented detail, using a   
   laser to illuminate the crater's interior and measure its albedo or natural   
   reflectance. The laser light measures to a depth comparable to its wavelength,   
   or about a micron. That represents a millionth of a meter, or less than one   
   ten-thousandth of an inch. The team also used the instrument to map the relief   
   of the crater's terrain based on the time it took for laser light to bounce   
   back from the moon's surface. The longer it took, the lower the terrain's   
   elevation.   
       
      
   Regards,   
      
   Roger    
   --- timEd/386 1.10.y2k+   
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