Earth Planets Space, Vol. 60 (No. 1), pp. 75-82, 2008
M. B. Simakov
Group of Exobiology, Institute of Cytology RAS, Tikhoretsky Av., 4 St. Petersburg, 194064, Russia
(Received September 1, 2006; Revised November 19, 2007; Accepted November 23, 2007; Online published February 12, 2008)
It is now well-known that carbonaceous chondrites contain large quantities of prebiotic molecules, including amino acids, carbohydrates, and heterocyclic bases of nucleic acids. It has become evident that the chemical evolution proceeds under conditions of open space, which serves as a huge chemical reactor. The extraterrestrial origin of these prebiotic molecules has been established on the basis of diversity, molecular structure, and isotopic composition. The molecular composition of a meteorite's organics resembles abiotic processes governed by physico-chemical processes that occurred on the parent bodies, including asteroids. The synthesis of soluble compounds in carbonaceous chondrites consists of a multi-step process in which organic precursors were formed in the interstellar cloud, incorporated with many volatiles into icy planetesimals and, upon aqueous processing produced the variety of compounds which can form complexes under space energy sources. We show experimentally that the solid mixtures of biologically significant compounds (nucleosides and amino acids) produce more complex compounds when they are exposed to either vacuum UV photons or ionizing radiation.
Key words: Chemical evolution, abiogenic synthesis, amino acids, nucleotides.