NASA’s Perseverance rover has bagged its first hint of ancient microbes on Mars.

“We’re not able to say that this is a sign of life,” says Perseverance deputy project scientist Katie Stack Morgan of NASA’s Jet Propulsion Lab in Pasadena, Calif.  “But this is the most compelling sample we’ve found yet.”

The rover drilled up the sample on July 21 from a reddish rock, dubbed Cheyava Falls after a feature at the Grand Canyon. It is the first piece of Mars that Perseverance has examined that contains organic molecules, the building blocks of life, project scientist Ken Farley of Caltech reported July 25 at the 10th International Conference on Mars in Pasadena.