If it had 200 nucleotides you'd know for sure it's a contamination. RNA isn't very stable (in our conditions, I have no idea how it does at 3 Kelvin, blasted with radiation for a million years...)
instead, better to take tardigrades, induce tun state, embed that in rock, and let that float around for a while. They have pretty much everything needed to survive including safe storage for DNA, DNA repair enzymes, redundant DNA, radiation-resistant exterior, etc.