NASA’s Perseverance Rover has uncovered unusual rocks on Mars that could represent the strongest evidence yet of potential ancient life on the Red Planet.

The rover discovered mudstones in a dried-up Martian riverbed, marked with distinctive features nicknamed “leopard spots” and “poppy seeds.” Scientists believe these formations contain minerals created by chemical reactions that may have been linked to microbial activity billions of years ago.

While the minerals could also be explained by purely geological processes, the findings are significant enough to qualify as “potential biosignatures” under NASA’s criteria. This means the rocks warrant further study to determine whether their origins were biological.

“We’ve not had something like this before, so I think that’s the big deal,” said Prof. Sanjeev Gupta, planetary scientist at Imperial College London and co-author of a study published in Nature. “If you saw these features on Earth, you could explain them by biology. We’re not saying we’ve found life, but it gives us something real to chase.”

Dr. Nicola Fox, NASA’s Associate Administrator for Science, added: “It’s like seeing a leftover fossil. Maybe it was a leftover meal, maybe it was excreted—and that’s what we’re seeing here.”

The discovery deepens the excitement around Perseverance’s mission, which is also collecting samples for eventual return to Earth. If confirmed, these leopard-spot rocks could mark one of the most compelling signs yet that Mars once hosted microbial life.