XPost: sci.space.policy   
   From: henry@spsystems.net   
      
   In article <7L+C+NC9oiLAFwEA@merlyn.demon.co.uk>,   
   Dr John Stockton   wrote:   
   >>  A close encounter with a planet can split a rubble pile   
   >>into a pair of rubble piles, by tidal interaction.  (In fact, one of the   
   >>points offered in support of the rubble-pile hypothesis is precisely that   
   >>we see a suspiciously large number of double asteroids, which ought to be   
   >>fairly rare unless there is some specific mechanism that creates them.)   
   >   
   >Why a pair of rubble piles?  Half a rubble pile is still a rubble pile,   
   >and should itself be split (ignoring the presumably improbable case of   
   >an encounter virtually tangent to the Roche limit).   
      
   If memory serves -- I didn't pay close attention to the details -- the   
   two-way split of a rubble pile is a non-trivial interaction between tidal   
   forces and the rotation of the original rubble pile, and generally does   
   not involve further splitting of the resulting two piles.   
      
   Multi-way splits of fragile bodies are certainly possible, as witness SL9,   
   but they generally don't leave the fragments in orbit around each other.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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