Stardust and comets

The NASA Stardust mission to comet 81P/Wild-2 returned to Earth in January 2006 carrying captured cometary dust grains. Analysis of these grains is permitting an extensive study of cometary composition to be carried out. This includes identifying both the mineral and organic content of the captured material. Based on this, the picture emerges of a comet whose component materials have a diverse origin and which has not undergone any extensive aqueous alteration, has a nitrogen rich organic history, may contain amines and at least 1 amino acid and has organics which in some respects resemble interplanetary dust particles and meteorites, in others resemble one and not the other, and in yet others are distinct from both. In terms of astrobiology, comets as a source of organic materials for the inner Solar System clearly have a role to play, but this cannot be fully assessed based on the history of just one comet nucleus. Nevertheless, the positive identification of a range of organic materials in this comet significantly moves forward the discussion of organic materials and comets.