XPost: sci.space.tech   
      
   On Mon, 10 Nov 2003 12:01:58 -0700, Hop David   
    wrote:   
      
   >In _Entering Space_ Robert Zubrin mentions that it would take only a   
   >small amount of Delta V to send Kuiper Belt Objects down to Mars. He   
   >believes comets striking Mars would thicken the atmosphere and raise the   
   >temperature. (I also seem to recall Kim Stanley Robinson using this idea   
   >in his Mars trilogy)   
   >   
   >But now in John S. Lewis' _Rain of Iron and Ice_ I read about   
   >atmospheric erosion  by meteorites. Most the atmosphere the other side   
   >of a tangent plane touching the Martian sphere at point of impact is   
   >sent into space.   
   >   
   >So would comets add or subtract to Mars' atmosphere?   
      
   Depends on their size and impact velocity.   
      
   >By my calculations KBOs sent on a Hohmann transfer orbit to Mars would   
   >come into Mars orbit at about 9 km/sec. Mars gravity would add another   
   >5. So I believe a KBO would hit Mars at around 14 km/sec.   
      
   It would be easy to avoid the atmosphere losses and large-scale   
   areophysical effects resulting from a straight-in impact of a large   
   body by arranging a suitable pre-impact with a much smaller body to   
   disrupt the main incoming body.  Such a pre-impact would convert the   
   incoming into an expanding sphere of rapidly declining average   
   density, spreading the impact out over an entire hemisphere and a much   
   longer period of time.  Even objects as large as peta-ton class could   
   probably be "soft-landed" on Mars using this technique, avoiding the   
   significant atmosphere losses and awkward long-term areophysical   
   consequences of large straight-in impacts.   
      
   -- Roy L   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)