SciFri producer Christie Taylor spoke with Sarah Stewart Johnson, author of this spring’s Book Club choice, whose work explores how to detect evidence for past or present life, especially those we might find off-world. We talked about planetary geology, what it's like to work on rovers before they set out into space and after they reach Mars, and the process of writing about another planet—and we’ll took your questions. --- This is a recording of an online event as part of our #SciFriBookClub series, where attendees can hear from experts about a topic related to our Book Club pick. Listeners chat with fellow attendees, ask questions to our guests via chat, and could be selected to ask their question live—just like our call-in show!