Comet Storm in a Nearby Star System   
       
   Oct. 19, 2011: NASA's Spitzer Space Telescope has detected signs of icy bodies   
   raining down in an alien solar system. The downpour resembles our own solar   
   system several billion years ago during a period known as the "Late Heavy   
   Bombardment," which may have brought water and other life-forming ingredients   
   to Earth.   
       
   "We believe we have direct evidence for an ongoing Late Heavy Bombardment in   
   the nearby star system Eta Corvi, occurring about the same time as in our   
   solar system," said Carey Lisse, senior research scientist at the Johns   
   Hopkins University Applied Physics Laboratory in Laurel, Md., and lead author   
   of a paper detailing the findings to appear in the Astrophysical Journal.   
       
   An artist's concept of a comet storm around Eta Corvi. Image credit:   
   NASA/JPL-Caltech   
       
   http://www.nasa.gov/mission_pages/spitzer/multimedia/pia14739.html   
       
   During the Late Heavy Bombardment, comets and other frosty objects from the   
   outer solar system pummeled the inner planets. The barrage scarred our Moon   
   and produced large amounts of dust.   
       
   Spitzer has spotted a band of dust around Eta Corvi that strongly matches the   
   contents of an obliterated giant comet, probably destroyed by a collision with   
   a planet or some other large body. The dust is located close enough to Eta   
   Corvi that Earth-like worlds could exist in the collision zone, suggesting   
   that planets like our own might be involved. The Eta Corvi system is   
   approximately one billion years old, which researchers think is about the   
   right age for such a hailstorm.   
       
   Astronomers used Spitzer's infrared detectors to analyze the light coming from   
   the dust around Eta Corvi. Curiously, the light signature emitted by the dust   
   around Eta Corvi resembles the Almahata Sitta meteorite, which fell to Earth   
   in fragments across Sudan in 2008. The similarities between the meteorite and   
   the object obliterated in Eta Corvi imply a common birthplace in their   
   respective solar systems.   
       
   A second, more massive ring of colder dust located at the far edge of the Eta   
   Corvi system seems like the proper environment for a reservoir of cometary   
   bodies. This bright ring, discovered in 2005, matches the size of a similar   
   region in our own solar system, known as the Kuiper Belt, where icy and rocky   
   leftovers from planet formation linger. The comets of Eta Corvi and the   
   Almahata Sitta meteorite may have each originated in the Kuiper Belts of their   
   respective star systems.   
       
   About 4 billion years ago, not long after our solar system formed, scientists   
   think the Kuiper Belt was disturbed by a migration of Jupiter and Saturn. This   
   jarring shift in the solar system's gravitational balance scattered the icy   
   bodies in the Kuiper Belt, flinging the vast majority into interstellar space   
   and producing cold dust in the belt. Some Kuiper Belt objects, however, were   
   set on inward paths that crossed the orbits of Earth and other rocky planets.   
       
   The resulting bombardment of comets lasted until 3.8 billion years ago. After   
   comets hit the side of the Moon that faces Earth, magma seeped out of the   
   lunar crust, eventually cooling into dark "seas." Everyone has seen them:   
   Those seas form the distinctive face of the "Man in the Moon." Comets also   
   struck Earth or incinerated in the atmosphere, and are thought to have   
   deposited water and carbon on our planet. This period of impacts might have   
   helped life form by delivering its crucial ingredients.   
       
   "We think the Eta Corvi system should be studied in detail to learn more about   
   the rain of impacting comets and other objects that may have started life on   
   our own planet," Lisse said.   
       
   For more information about Spitzer and Eta Corvi, visit   
       
   http://spitzer.caltech.edu/   
       
   and   
       
   http://www.nasa.gov/spitzer.edu   
       
       
   Production Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Eta Corvi is an F-type star some 30% more massive than the sun and 59 light   
   years from Earth   
       
   Credits: NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the   
   Spitzer mission for the agency's Science Mission Directorate in Washington.   
   Science operations are conducted at the Spitzer Science Center at the   
   California Institute of Technology in Pasadena. Caltech manages JPL for NASA.     
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)