Strange nodules of unusual minerals found on speckled rocks on Mars have offered more tantalizing clues that ancient life may have once thrived on the now-dead planet, NASA says.

NASA's Perseverance rover found one such arrow-shaped rock, nicknamed Cheyava Falls, in 2024 along the northern bank of Neretva Vallis, the dried-up remnants of an ancient river that once rushed into Mars' Jezero crater.

An initial analysis of the rock, which appeared in a lake bed formation known as Bright Angel, revealed it was crammed with organic compounds, had evidence that water once flowed through it, and contained flecks of leopard-like spots from chemical reactions that ancient microbes could have used for energy.

These features may result from non-biological processes occurring over millions of years. But now, in a new study published Sept. 10 in the journal Nature, NASA scientists have announced intriguing details about additional rock samples found at two nearby sites — and they say these clues bolster the case for past life on Mars.

"After a year of review, they have come back and they said, listen, we can't find another explanation," Acting NASA Administrator Sean Duffy, said during a news briefing following the announcement. "So this very well could be the clearest sign of life that we've ever found on Mars, which is incredibly exciting."