How long have viruses been around? No one knows. Ken Stedman, associate professor of biology at Portland State University and co-chair of the astrobiology Focus Group on Viruses, is working to change that. Stedman and his colleagues are trying to determine what kinds of biosignatures viruses leave behind in the environment. Their work could help astrobiologists understand the origin and evolution of viruses on Earth, and aid in identifying virus biosignatures on other worlds. The study was recently published in the journal Astrobiology.