Possible Seismic Activity on Asteroid 2012 DA14   
       
   Feb. 14, 2013:  For eons, Earth has felt the tremors of asteroids striking our   
   planet. From the extinction of the dinosaurs 65 million years ago to the   
   felled forests around Tunguska in 1908, the space rocks keep coming.   
       
   This week, Earth strikes back. When asteroid 2014 DA14 makes a record close   
   approach to our planet on Feb. 15th, the space rock could be the one feeling   
   tremors.   
       
   New research by Richard Binzel, a professor of planetary science at MIT,   
   suggests that many near-Earth asteroids experience a seismic jolt when they   
   pass too close to our planet's gravitational field.   
       
   "We are going to be looking closely for evidence of seismic activity on 2014   
   DA14 as it passes by," says Binzel. "This is the first case of an object   
   coming close enough to experience quakes AND where we have enough notice to   
   plan observations."   
       
   http://www.youtube.com/watch?v=GwidzVHvbGI   
       
   A ScienceCast video previews the close flyby of asteroid 2012 DA14. Play it   
   Binzel first began to entertain the idea of asteroid-quakes a few years ago   
   when he was pondering a mystery about near-Earth asteroids:   
       
   "As asteroids move through space, they slowly turn dark-red.  This phenomenon,   
   called 'space weathering', is caused by long exposure to cosmic rays and solar   
   radiation. For decades, however, we have known about a handful of small   
   asteroids that looked [light and fresh]; they were not space weathered."   
       
   How did this group of space rocks avoid space weathering?    To solve the   
   mystery, Binzel and colleagues calculated the asteroids' orbits and found a   
   telling clue: They all had very close encounters with Earth in the past   
   million years.   
       
   "We believe they were 'shaken up' by their encounters with Earth," he says.   
   "Gravitational forces during the flybys can stretch, rattle, and torque these   
   asteroids, causing dark, space-weathered material on the surface to be   
   overturned, revealing the fresh stuff underneath."   
       
   There is no Richter Scale for asteroids.  Instead, Binzel expresses the force   
   of the quakes in units of gravitational acceleration, or gees.  1 g = the   
   acceleration due to gravity on Earth's surface. "These asteroids experience   
   [seismic activity] in the milli- to micro-g range," he says. "That might not   
   sound like much, but remember these are small bodies. Gravity is not very   
   strong, so just a little shaking or stretching goes a long way."   
       
   http://echo.jpl.nasa.gov/   
       
   NASA's 70-meter diameter Goldstone radar will be observing 2012 DA14. [more]     
   Binzel imagines what an astronaut floating alongside such an asteroid might   
   see: "The surface could slowly sway or rock by a few centimeters. Other things   
   to look for would be puffs of asteroid-dust rising from the surface and gentle   
   avalanches on the steepest slopes of craters." In rare cases, "rubble pile"   
   asteroids might break apart during the encounter and then re-form as Earth   
   recedes into the distance.   
       
   On February 15th, 2012 DA14 will thread the gap between Earth and the belt of   
   geosynchronous satellites that orbits our planet.  At closest approach, the   
   50-meter space rock will be just 17,200 miles above Earth's surface, a prime   
   target for radars and telescopes.   
       
   MIT postdoc Nick Moskovitz, who works with Binzel, is coordinating   
   observations with worldwide observatories to pin down the color, spin, shape,   
   and reflectivity of the asteroid as it passes by.  Changes in any of these   
   quantities might be a sign of a quake.  Participating telescopes include La   
   Palma in the Canary Islands, the Siding Spring and Perth observatories in   
   Australia, Mt John in New Zealand, Mt Canopus in Tasmania, WISE in Israel, and   
   the Clay Center Massachusetts.   
       
   Also, NASA's Goldstone radar will be pinging 2012 DA14.  The radar data can be   
   used to create 3D movies showing the space rock from all sides. Goldstone   
   might be the first to capture an asteroid-quake in action.   
       
   "We stand to learn a lot from the observations," says Binzel.   
       
   Let the flyby begin.   
       
   For more information about 2012 DA14 and other asteroids of interest, visit   
   NASA's Near-Earth Object Program web site: http://neo.jpl.nasa.gov   
       
       
   Author: Dr. Tony Phillips |Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.9   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)