Recently, the Curiosity rover measured total organic carbon, a necessary ingredient in the molecules of life, in Martian rocks for the first time. But it doesn’t prove that life ever existed on Mars, because carbon can also be produced by nonliving sources. Caves could also contain resources like water, reveal more about the history of a planet — and be havens for evidence of microbial life. But caves are dangerous — and since we’ve never peered inside a Martian cave, it’s difficult to know what to expect. ReachBot could also crawl inside of lunar caves that may serve as a resource for astronauts exploring the moon.