Micrometeorite

This is an electron microscope image of a micrometeorite:
 
  http://www.freemars.org/jeff2/umeteor.jpg
 
I think I found the image on a NASA site a few years ago.
 
Can anyone explain why it is ovoid?
 
  -- Jeff, in Minneapolis
 
Subtract 1 from my e-mail address above for my real address.
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