XPost: sci.military.moderated   
   From: pfaustin@bellsouth.net   
      
   "Ian Stirling"  wrote in message   
   news:HoY5c.24159$Y%6.2399514@wards.force9.net...   
   > In sci.space.tech Roger Moore  wrote:   
   > > "Ami Silberman"  writes:   
   > >   
   > >>There are no moon sized asteroids.   
   > >   
   > > Only because anything that big in orbit around the sun is called a   
   planet   
   > > rather than an asteroid.  I'll agree, though, that it would be very   
   > > difficult for something the size of the moon to hide well enough that we   
   > > wouldn't see it until it was just 25 years away.  FWIW, NASA has just   
   > > announced the discovery of a new object in the Kupier belt that is   
   > > estimated to be significantly smaller than the moon and several times   
   > > further away than Pluto.  I'd expect that we would have caught anything   
   > > bigger and closer than that already.   
   >   
   > Things can have been further away than pluto for the entire history   
   > of photographic astronamy, and still have periapsis closer in.   
   > It's not inconcievable that something large could have a very long period   
   > and interact with Pluto/Uranus to turn it into a large impactor with only   
   > a few years warning.   
   > Vanishingly unlikely, yes.   
   >   
   > Have there been any proposals to stare at Uranus/Pluto/Jupiter/Saturn   
   > looking for gravitational interactions?   
      
   It's not even necessary. Go look at the images of Shoemaker-Levy's impact(s)   
   on Jupiter. A long period comet can easily put paid for us. After all, the   
   dinosaurs remember...   
      
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