"The photostability of amino acids in space." P. Ehrenfreund (Sackler Laboratory for Astrophysics, Leiden Observatory) and M. P. Bernstein, J.P. Dworkin S. A. Sandford, and L. J. Allamandola. Submitted to Ap.J. (2000)

Abstract:

Organic compounds observed in the interstellar medium (ISM) and in solar system objects are of particular importance for revealing the chemistry which may have led to life's origin. Among these compounds, amino acids may have played a crucial role, since they are basic components of proteins, essentialconstituents of all organisms. We present laboratory studies testing thestability of amino acids against ultraviolet (UV) photolysis. Two biological and two non-biological amino acids have been irradiated in frozen Ar, N₂, and H₂O to simulate conditions in the interstellar gas and on interstellar grains. The experimental results indicate that amino acids in the gas phase will likely be destroyed during the lifetime of a typical interstellar cloud. In regions with relatively low UV radiation, amino acids might be present as transient gas phase species. Their survival in interstellar icy grain mantles and the surface layers of comets and planets, is strongly limited in the presence of UV irradiation. The rate of destruction is rather insensitive to the amino acid structure and to the ice matrix. We consider the implications of these results for the survival, and transfer of amino acids in space environments, and thus their possible availability for prebiotic chemistry.