'Incredibly exciting': NASA claims to have found 'clearest sign' of past life on Mars

A selfie taken by NASA's Perseverance rover on Mars. (Photo: NASA)

Strange clusters of unusual minerals found on patchy rocks on Mars provide even more intriguing clues that ancient life may have once thrived on the now-dead planet, NASA scientists say.

In 2024, NASA's Perseverance rover discovered one such arrow-shaped rock, dubbed Čejava Falls, along the northern shore of the Neretva Valley, the dried-up remains of an ancient river that once flowed into Mars' Jezero Crater.

Initial analysis of the rock, found in a lake formation known as Bright Angel, found it to be rich in organic compounds, has evidence that water once flowed through it, and contains patches of leopard-like spots left over from chemical reactions that ancient microbes could have used for energy.

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These features could be the result of nonbiological processes that have been going on for millions of years. But now, in a new study published Sept. 10 in the journal Nature, NASA scientists have provided intriguing details about additional rock samples found at two nearby sites — clues they say bolster the case for past life on Mars.

“After a year of research, they came back and said, look, we can't find any other explanation,” NASA acting administrator Sean Duffy said at a press conference after the announcement. “So this could very well be the clearest sign of life we've ever found on Mars, and that's incredibly exciting.”

Since arriving on Mars in 2021, Perseverance has been cruising the 50-kilometer-wide Jezero Crater, collecting dozens of rock samples for eventual return to Earth. After finding a rock with leopard-like spots, scans by the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument revealed that the sample contained carbon-based molecules, as well as bands of reddish hematite flecked with iron and phosphate.

“When the rover arrived at Bright Angel and started measuring the composition of the rocks there, the team was immediately struck by how different they were from anything we’d seen before,” said study co-author Michael Tice, a geobiologist and astrobiologist at Texas A&M University. “They showed evidence of a chemical cycle that organisms on Earth can use to produce energy. And when we looked even closer, we saw things that are easy to explain by early Martian life, but very difficult to explain by geologic processes alone.”

The photograph of Cheyava Fallas shows white marks that may be traces of ancient microbial activity.

Additional discoveries announced today by NASA involve clay-rich rock samples found at two sites called Sapphire Canyon and Masonic Temple that contain vivianite, an iron phosphate mineral, and greigite, an iron sulfide mineral.

Scientists believe that these minerals may have formed as a result of reactions between mud and organic matter. The distribution of minerals in the rocks seems to support this hypothesis.

“It’s not just the minerals, but the way they’re organized in these structures that suggests they formed through the redox cycling [in which bacteria play a key role on Earth] of iron and sulfur,” Tice said. “On Earth, similar structures sometimes form in sediments where microbes feed on organic matter and ‘breathe’ rust and sulfates. Their presence on Mars raises the question: Could similar processes have occurred there?”

However, a final decision on whether the patterns were created by biological or non-biological processes can only be made in laboratories on Earth, and whether Perseverence's precious cargo will be delivered for this analysis remains a contentious political issue.

The European Space Agency (ESA) and NASA originally proposed using NASA's Sample Retrieval Lander, a spacecraft with a small rocket, to collect samples from the rover by 2033 as part of the Mars Sample Return mission. The rocket would then return to orbit with the samples.