NASA Science Fleet Prepares for Mars Comet   
       
   Oct. 9, 2014: NASA's extensive fleet of science assets, particularly those   
   orbiting and roving Mars, have front row seats to image and study a   
   once-in-a-lifetime comet flyby on Sunday, Oct. 19.   
       
   Comet C/2013 A1, also known as comet Siding Spring, will pass within about   
   87,000 miles (139,500 kilometers) of the Red Planet -- less than half the   
   distance between Earth and our moon and less than one-tenth the distance of   
   any known comet flyby of Earth.   
       
   https://www.youtube.com/watch?v=2R4yj7DtQbM   
   Image Credit: NASA   
       
   Siding Spring's nucleus will come closest to Mars around 2:27 p.m. EDT,   
   hurtling at about 126,000 mph (56 kilometers per second). This proximity will   
   provide an unprecedented opportunity for researchers to gather data on both   
   the comet and its effect on the Martian atmosphere.   
       
   "This is a cosmic science gift that could potentially keep on giving, and the   
   agency's diverse science missions will be in full receive mode," said John   
   Grunsfeld, astronaut and associate administrator for NASA's Science Mission   
   Directorate in Washington. "This particular comet has never before entered the   
   inner solar system, so it will provide a fresh source of clues to our solar   
   system's earliest days."   
       
   Siding Spring came from the Oort Cloud, a spherical region of space   
   surrounding our sun and occupying space at a distance between 5,000 and   
   100,000 astronomical units.  It is a giant swarm of icy objects believed to be   
   material left over from the formation of the solar system.   
       
   Siding Spring will be the first comet from the Oort Cloud to be studied up   
   close by spacecraft, giving scientists an invaluable opportunity to learn more   
   about the materials, including water and carbon compounds, that existed during   
   the formation of the solar system 4.6 billion years ago.   
       
   Some of the best and most revealing images and science data will come from   
   assets orbiting and roving the surface of Mars. In preparation for the comet   
   flyby, NASA maneuvered its Mars Odyssey orbiter, Mars Reconnaissance Orbiter   
   (MRO), and the newest member of the Mars fleet, Mars Atmosphere and Volatile   
   EvolutioN (MAVEN), in order to reduce the risk of impact with high-velocity   
   dust particles coming off the comet.   
       
   http://www.nasa.gov/sites/default/files/thumbnails/image/14-282.jpg   
       
   Click to see the ScienceCast video: Colliding Atmospheres: Mars vs. Comet   
   Siding SpringThe period of greatest risk to orbiting spacecraft will start   
   about 90 minutes after the closest approach of the comet's nucleus and will   
   last about 20 minutes, when Mars will come closest to the center of the   
   widening trail of dust flying from the comet's nucleus.   
       
   "The hazard is not an impact of the comet nucleus itself, but the trail of   
   debris coming from it. Using constraints provided by Earth-based observations,   
   the modeling results indicate that the hazard is not as great as first   
   anticipated. Mars will be right at the edge of the debris cloud, so it might   
   encounter some of the particles -- or it might not," said Rich Zurek, chief   
   scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory   
   (JPL) in Pasadena, California.   
       
   The atmosphere of Mars, though much thinner that Earth's, will shield NASA   
   Mars rovers Opportunity and Curiosity from comet dust, if any reaches the   
   planet. Both rovers are scheduled to make observations of the comet.   
       
   NASA's Mars orbiters will gather information before, during and after the   
   flyby about the size, rotation and activity of the comet's nucleus, the   
   variability and gas composition of the coma around the nucleus, and the size   
   and distribution of dust particles in the comet's tail.   
       
   Observations of the Martian atmosphere are designed to check for possible   
   meteor trails, changes in distribution of neutral and charged particles, and   
   effects of the comet on air temperature and clouds. MAVEN will have a   
   particularly good opportunity to study the comet, and how its tenuous   
   atmosphere, or coma, interacts with Mars' upper atmosphere.   
       
   Earth-based and space telescopes, including NASA's iconic Hubble Space   
   Telescope, also will be in position to observe the unique celestial object.   
   The agency's astrophysics space observatories -- Kepler, Swift, Spitzer,   
   Chandra -- and the ground-based Infrared Telescope Facility on Mauna Kea,   
   Hawaii -- also will be tracking the event.   
       
   NASA's asteroid hunter, the Near-Earth Object Wide-field Infrared Survey   
   Explorer (NEOWISE), has been imaging, and will continue to image, the comet as   
   part of its operations. And the agency's two Heliophysics spacecraft, Solar   
   TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics   
   Observatory (SOHO), also will image the comet. The agency's Balloon   
   Observation Platform for Planetary Science (BOPPS), a sub-orbital   
   balloon-carried telescope, already has provided observations of the comet in   
   the lead-up to the close encounter with Mars.   
       
   Images and updates will be posted online before and after the comet flyby.   
   Several pre-flyby images of Siding Spring, as well as information about the   
   comet and NASA's planned observations of the event, are available online at   
   http://mars.nasa.gov/comets/sidingspring   
       
   Credits:   
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More information:   
       
   Colliding Atmospheres: Mars vs. Comet Siding Spring -- from Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)