  What constitutes a habitable planet is a frontier to be explored and requires
pushing the boundaries of our terracentric viewpoint for what we deem to be a
habitable environment. Despite Venus' 700 K surface temperature being too hot
for any plausible solvent and most organic covalent chemistry, Venus'
cloud-filled atmosphere layers at 48 to 60 km above the surface hold the main
requirements for life: suitable temperatures for covalent bonds; an energy
source (sunlight); and a liquid solvent. Yet, the Venus clouds are widely
thought to be incapable of supporting life because the droplets are composed of
concentrated liquid sulfuric acid-an aggressive solvent that is assumed to
rapidly destroy most biochemicals of life on Earth. Recent work, however,
demonstrates that a rich organic chemistry can evolve from simple precursor
molecules seeded into concentrated sulfuric acid, a result that is corroborated
by domain knowledge in industry that such chemistry leads to complex molecules,
including aromatics. We aim to expand the set of molecules known to be stable
in concentrated sulfuric acid. Here, we show that nucleic acid bases adenine,
cytosine, guanine, thymine, and uracil, as well as 2,6-diaminopurine and the
"core" nucleic acid bases purine and pyrimidine, are stable in sulfuric acid in
the Venus cloud temperature and sulfuric acid concentration range, using UV
spectroscopy and combinations of 1D and 2D 1H 13C 15N NMR spectroscopy. The
stability of nucleic acid bases in concentrated sulfuric acid advances the idea
that chemistry to support life may exist in the Venus cloud particle
environment.
