Have viruses been around since life first appeared on Earth? A census of all the current living organisms would show that viruses outnumber everything else 10 to one. Whether this was true long ago is uncertain.

To learn about the history of viruses, researchers supported by the NASA Astrobiology Institute are exploring whether salt beds and hot springs preserve viral biosignatures. High-silica hydrothermal ecosystems and evaporative brines are known to be good places to search for microbe remains. Could the same be true for viruses?