A sample obtained by NASA’s Perseverance rover of reddish rock formed billions of years ago from sediment on the bottom of a lake contains potential signs of ancient microbial life on Mars, according to scientists, though the minerals spotted in the sample also can form through nonbiological processes.

The discovery by the six-wheeled rover in Jezero Crater represents one of the best pieces of evidence to date about the possibility that Earth’s planetary neighbor once harbored life.