In the search for alien life, astrobiologists have turned over all sorts of rocks. For example, Mars has geological features that suggest it once had subsurface liquid water. Scientists have also eyed Jupiter’s moons Europa, Ganymede and Callisto as well as Saturn’s Titan and Enceladus as possible havens for life in their subsurface oceans. Now, University of Wisconsin–Madison planetary researcher Sanjay Limaye and colleagues are dusting off...
