This is one of many possibilities. It is also possible that if there is any life on Mars, it could have gotten there from Earth by the same meteoritic impact and hitch hiking process. Some people still think it is possible that much of the organic processing happened off-Earth, and this could include even the partial assembly of DNA material, although I find this hard to believe. Planetary surfaces are far more stable and hospitable places for stitching together large molecules than the surfaces of dust grains, small asteroids and comets.