why is there less oxygen in space than there is on earth?? x

Question: why is there less oxygen in space than there is on earth?? x
- Keywords:
  earth,
  oxygen,
  space
Asked by howestwh to Ian on 20 Jun 2011.
- Ian van der Linde answered on 20 Jun 2011:
  
  Planets are able to hold an atmosphere in place because they have a large mass mass that exerts a strong gravitational pull.

Question: why is there less oxygen in space than there is on earth?? x