Cassini Catches Meteors Hitting Saturn's Rings   
       
   April 29, 2013: NASA's Cassini spacecraft has provided the first direct   
   evidence of small meteoroids crashing into Saturn's rings and breaking into   
   streams of rubble.   
       
   These observations make Saturn's rings the only location besides Earth, the   
   moon and Jupiter where astronomers have been able to observe impacts as they   
   occur. The meteoroids Cassini detected range in size from about one-half inch   
   to several yards (1 centimeter to several meters). Scientists scrutinizing   
   images from the probe took years to distinguish tracks left by nine meteoroids   
   in 2005, 2009 and 2012. Details of the observations appear in a paper in the   
   Thursday, April 25 edition of Science.   
       
   http://tinyurl.com/bsulkgy   
       
   Five images of Saturn's rings, taken by NASA's Cassini spacecraft between 2009   
   and 2012, show clouds of material ejected from impacts of small objects into   
   the rings. Image credit: NASA/JPL-Caltech/Space Science Institute/Cornell   
       
   The solar system is full of small, speeding objects such as comet dust and   
   chips off asteroids. These objects frequently pummel planetary bodies.   
       
   "The new results imply the current-day impact rates for small particles at   
   Saturn are about the same as those at Earth -- two very different   
   neighborhoods in our solar system -- and this is exciting to see," said Linda   
   Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in   
   Pasadena, Calif. "It took Saturn's rings acting like a giant meteoroid   
   detector -- 100 times the surface area of the Earth -- and Cassini's long-term   
   tour of the Saturn system to address this question."   
       
   The Saturnian equinox in summer 2009 was an especially good time to see the   
   debris left by meteoroid impacts. The very shallow sun angle on the rings   
   caused the clouds of debris to look bright against the darkened rings in   
   pictures from Cassini's imaging science subsystem.   
       
   "We knew these little impacts were constantly occurring, but we didn't know   
   how big or how frequent they might be," said Matt Tiscareno, lead author of   
   the paper and a Cassini participating scientist at Cornell University in   
   Ithaca, N.Y. "Sunlight shining edge-on to the rings at the Saturnian equinox   
   acted like an anti-cloaking device, so these usually invisible features became   
   plain to see."   
       
   http://photojournal.jpl.nasa.gov/catalog/PIA14942   
       
   This illustration depicts the shearing of an initially circular cloud of   
   debris as a result of the particles in the cloud having differing orbital   
   speeds around Saturn. Image credit: NASA/Cornell Tiscareno and his colleagues   
   now think meteoroids of this size probably break up on a first encounter with   
   the rings, creating smaller, slower pieces that then enter into orbit around   
   Saturn. The impact into the rings of these secondary meteoroids creates clouds   
   of debris.  The tiny particles forming these clouds have a range of orbital   
   speeds around Saturn. As a result they are soon are pulled into diagonal,   
   extended bright streaks such as Cassini observed.   
       
   The finding could shed light on a long standing question: How old are Saturn's   
   rings?   
       
   "Saturn's rings are unusually bright and clean, leading some to suggest that   
   the rings are actually much younger than Saturn," said Jeff Cuzzi, a co-author   
   of the paper and a Cassini interdisciplinary scientist specializing in   
   planetary rings and dust at NASA's Ames Research Center in Moffett Field,   
   Calif.   
       
   Some estimates have even put the formation of Saturn's rings during the age of   
   dinosaurs on Earth.  That would make the rings very young compared to Saturn.   
       
   "To assess this dramatic claim, we must know more about the rate at which   
   outside material is bombarding the rings," continues Cuzzi. "This latest   
   analysis helps fill in that story with detection of impactors of a size that   
   we weren't previously able to detect directly."   
       
   For more information about Cassini and its mission, visit: http:   
   /www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .   
       
   Credits:   
       
    Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More information:   
       
   Cassini  -- mission home page   
       
   The Cassini-Huygens mission is a cooperative project of NASA, the European   
   Space Agency and the Italian Space Agency. JPL, a division of the California   
   Institute of Technology, Pasadena, manages the Cassini-Huygens mission for   
   NASA's Science Mission Directorate in Washington. The Cassini orbiter and its   
   two onboard cameras were designed, developed and assembled at JPL. The imaging   
   team consists of scientists from the United States, the United Kingdom, France   
   and Germany. The imaging operations center is based at the Space Science   
   Institute in Boulder, Colo.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.92   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)