Adenine, cytosine, guanine, thymine and uracil. Those are the five 'primary nucleobases', the 'letters' (A, C, G, T, and U) whose multiple combinations make up the instruction book of life. The first four molecules 'write' our DNA, while the last (uracil) is only present in RNA, where it replaces thymine.
For decades, astronomers have toyed with the idea of panspermia, the theory that life, or at least its essential elements, did not originate on Earth but arrived on our planet aboard meteorites. And although scientists have already found numerous organic compounds and molecules in these space rocks, until now they had only managed to identify... See more