The Brief Rocks found on Mars may provide the strongest evidence yet of past life on the Red Planet, but more testing is needed to back up those findings. NASA’s Perseverance Mars rover has discovered rocks in a dry river bed that could have signs of ancient microscopic life. FILE - NASA's Perseverance Mars rover takes a selfie (NASA)The findings appeared in the journal Nature. How does the Mars Perseverance rover work? The backstory:Roaming Mars since 2021, the rover cannot directly detect life.