'Incredibly exciting': NASA claims it's found the 'clearest sign' yet of past life on Mars

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."

Since arriving on Mars in 2021, Perseverance has been trundling across the 30-mile-wide (50 kilometers) Jezero crater, collecting dozens of rock samples for eventual return to Earth. Upon finding the leopard-spotted rock, scans by the rover's Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument showed that the specimen contained carbon-based molecules, alongside bands of reddish hematite that featured spots of iron and phosphate.

Related: Scientists find hint of hidden liquid water ocean deep below Mars' surface

"When the rover entered Bright Angel and started measuring the compositions of the local rocks, the team was immediately struck by how different they were from what we had seen before," study co-author Michael Tice, a geobiologist and astrobiologist at Texas A&M University, said in a statement. "They showed evidence of chemical cycling that organisms on Earth can take advantage of to produce energy. And when we looked even closer, we saw things that are easy to explain with early Martian life but very difficult to explain with only geological processes."

The additional discoveries announced by NASA today relate to clay-rich rock samples found at two sites, named Sapphire Canyon and Masonic Temple, containing vivianite, an iron-phosphate mineral, and greigite, a mineral containing iron sulfide.

These minerals may have formed from reactions between the mud and organic matter, according to the scientists. The minerals' distribution across the rocks appears to support this hypothesis.

"It's not just the minerals, it's how they are arranged in these structures that suggests that they formed through the redox cycling [in which bacteria are key players on Earth] of iron and sulfur," Tice said. "On Earth, things like these sometimes form in sediments where microbes are eating organic matter and 'breathing' rust and sulfate. Their presence on Mars raises the question: could similar processes have occurred there?"

Nonetheless, a definitive ruling over the biological or non-biological processes that created the patterns can only be made in labs on Earth, and whether Perseverence's precious cargo will be fetched for that analysis remains a contentious political question.

The European Space Agency (ESA) and NASA originally proposed the use of NASA’s Sample Retrieval Lander — a spacecraft carrying a small rocket — to collect the rover's samples by 2033 as a part of their Mars Sample Return mission. The rocket would then launch back into orbit with the samples.

But the mission, now significantly over budget and delayed, is facing cancellation from the Trump administration's planned budget cuts to NASA. Meanwhile, China has revealed its own plans for a Mars sample-return mission that could launch by 2028.

When pressed by reporters during a Q&A session following the announcement, Duffy was unable to confirm if or when the sample-return mission would happen, but he remained optimistic.

"The president loves space — he asked me about it," Duffy said. "I give him updates, how it's going, what we're doing, and he doesn't brush me off."

"If there was an issue with resources, I would go to him and I'm sure he would support us," he added.