The suggested accumulation of complex but photostable π-systems in the UV-illuminated
environments is in agreement with the presence of polycyclic aromatic
hydrocarbons in meteorites [194,286], as well as with the reported synthesis of
nucleotides from simpler precursors at the outer surfaces of Russian spacecraft
[287]. Generally, one would expect that complex organic compounds would
break into pieces in outer space. This is not the case; instead, the “pieces” join
together at surfaces to build complex aromatic π-systems that apparently are more
stable than simpler compounds against diverse types of cosmic radiation.