The Science of The Callisto Incident
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Biochemists now believe that before the DNA-dominated life we now know, we once lived in an RNA world [G.F. Joyce, Nature 338, 217 (1989)]. But this doesn't solve the mystery of where life came from: there had to be a precursor to RNA, and one possibility is PNA: peptide nucleic acid -- although no one knows for sure (there are several guesses out there). [C. Bohler, P.E. Neilsen, and L.E. Orgel, Nature 376, 578 (1995); A.W. Schwartz, Planet Space. Sci. 43, 161 (1995)] In the future setting of this story, I presume that PNA is known to be the RNA-precursor, but there are still some remaining unknowns concerning the ultimate origins of life.