Astrobiology Workshop, Macquarie University July 12-13 2001

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Prebiotic Molecules in the Interstellar Medium

Maria Hunt (University of New South Wales)

It is presumed that life on Earth originated from an initial reservoir of simpler prebiotic organic material such as amino acids, fatty acids and sugars. What is not clear is whether this initial reservoir originated on the early Earth, in comets or in the ISM. The ratios of the stable isotopes of C, N, S and O in organic molecules can be used as both a biosignature and to differentiate the extraterrestrial from a terrestrial origin of organic material when such mat erial is found in comets, meteorites or on a planetary surface (Engel and Macko 1988). The isotope ratios investigated in comets and meteorites to date give ratios that are quite different from Solar System ratios, and in the case of one comet are similar to those found in the ISM. The stable isotope ratios in complex organic molecules in the ISM differ from the elemental isotope ratios and may be correlated with the complexity of the molecule. ISM ratios in simpler molecules such as HCN and CS have been studied extensively, however it is the values for the more complex molecules that is significant for comparison with organic material found within the Solar System. A study of the stable isotope ratios in more complex organic molecules (e.g. CH3C2H) is now being undertaken with the Mopra Radio Telescope to provide a statistical database of the stable isotope ratios of C, N, S and O in these more complex molecules.

Engel, M.H. & Macko, S.A., 1998. Proc SPIE, 3441, 190.