Xanthine molecule (3,7-dihydro-purine-2,6-dione, CsH4N4O2) is an intermediate in nucleic acid degradation from the dcamination of guanine, and also a compound present in the ancient solar system and that is found in high concentrations in extraterrestrial meteorites.The self-assembly of xanthine molecules on inorganic surfaces is therefore of interest for the study of biochemical processes, and it may also be relevant to the fundamental understanding of prebiotic biosynthesis.