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LIFE could have started from a mix of just two amino acids dropped on the
planet from comets, say Jeffrey Bada from Scripps Institution of Oceanography,
San Diego, and his colleagues. They studied the meteorites Orgueil and Ivuna and
found just two amino acids, b-alanine and glycine. Unlike other amino acids,
these two are most likely to be made inside a comet. They also happen to be just
the two amino acids needed to make peptide nucleic acid, a possible precursor to
DNA (Proceedings of the National Academy of Sciences, vol 98, p
2138).