Did NASA discover evidence of life on Mars and then misplace it for almost 25 years? A University of Southern California scientist argues that is just what happened and that once-lost data collected by the 1975 Viking probes suggest the existence of Martian microbes. The significance of that finding was overlooked — along with the data itself — after NASA concluded that its experiments showed only signs of chemical activity on the surface of the “Red Planet,” said Joseph Miller, a USC neurobiologist. But a careful reexamination of a fragment of the recovered NASA record showed a surprising pattern: gas released by the Martian soil and tracked by Viking followed the same kind of rhythms followed by all Earth-bound organisms from humans to fruit flies in a cycle akin to feeding and respiration by colonies of microbes.