Prebiotic chiral molecules created in interstellar dust and preserved in comets, comet dust, and meteorites: an exogenous source of life's origins

Interstellar dust grains have mantles of prebiotic organic molecules. A large fraction of the clouds of interstellar dust grains pass close enough to neutron stars for the circularly polarized ultraviolet radiation to produce a 10% or higher enantiomeric excess (e.e.) in the organic grain mantles. The time between such close passages is about ten times larger than the average lifetime of the molecular clouds so that most prestellar and protostellar clouds contain predominantly left or right handed prebiotic molecules; i.e., those clouds that collapse to form stars have probably passed by only one neutron star. Comets as agglomerated interstellar dust preserve the initial enantiomeric excess at least as well as meteorites which have been recently shown to have an e.e. of about 10%. Even if only 0.1% of the comet material survives as small comet dust particles that preserve their prebiotic molecules, there could be approximately 1025 chances for life to originate from one of these if it lands in water because of the special structure as well as composition of fluffy comet dust.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.