WASHINGTON — Scientists have found potential evidence of past life on Mars in a rock sample collected by a NASA rover, even as the agency’s budget proposal would cancel plans to return those samples to Earth.
At a Sept. 10 press conference, NASA officials and scientists discussed a paper published in Nature about a rock sample named Sapphire Canyon, collected by the Perseverance rover last year. The sample, taken from a larger rock called Cheyava Falls, stood out because of dark spots in the rock.
“These textural features told us that something really interesting has happened in these rocks, some set of chemical reactions occurred at the time they were being deposited,” said Joel Hurowitz, a planetary scientist at Stony Brook University and lead author of the paper.
Detailed examination by two Perseverance instruments — a spectrometer called SHERLOC and an X-ray instrument called PIXL — showed organic matter in the sedimentary rock, created when water flowed on the Martian surface early in the planet’s history. The dark “leopard spots” contained iron, phosphorus and sulfur consistent with minerals known as vivianite and greigite.
“When we see features like this in sediment on Earth, these minerals are often the byproduct of microbial metabolisms that are consuming organic matter and making these minerals as the result of these reactions,” Hurowitz said.
Agency leaders called the finding the strongest evidence yet that Mars once hosted primitive life. “This finding by our incredible Perseverance rover is the closest we’ve actually come to discovering ancient life on Mars,” said Nicky Fox, NASA associate administrator for science, stressing it does not mean life exists on Mars today.
“A year ago, we thought we found what we believe to be signs of microbial life on Mars, so we put it out to our scientific friends to pressure test it, analyze it,” said Sean Duffy, NASA’s acting administrator. “After a year of review, they have come back and they said, ‘Listen, we can’t find another explanation.’”
Hurowitz, though, said there are alternative, nonbiological explanations that can’t be ruled out. Greigite, for example, could be created in the rock it was heated. “It would basically cook those ingredients to produce that new mineral phase,” he said.
He said the scientific team found no signs the rock had been heated in that way, but urged further lab experiments to test biological and nonbiological scenarios.
Mars Sample Return option
There is little more Perseverance can do to analyze the rock. “We’re pretty close to the limits of what the rover can do on the surface in terms of making progress on that particular question,” said Katie Stack Morgan, project scientist for Perseverance.
That was by design, she said, since Perseverance was intended to use those instruments to choose the most scientifically promising samples for later return to Earth, where they could be analyzed in much greater detail.
But the future of the Mars Sample Return program is uncertain. After years of cost and schedule overruns, NASA announced in January it would study two lower-cost approaches to bring samples back as soon as 2035.
NASA’s 2026 budget proposal, however, would cancel the program entirely. “NASA plans to terminate the Mars Sample Return Program given that current architecture options remain unaffordable. The project will halt formulation activities and begin termination of all procurements,” the budget document states.
Duffy, asked about the status of MSR at the briefing, said he was open to other ways to bring back Perseverance’s samples. “We’re looking at how we get this sample back,” he said. “We believe there is a better way to do this, a faster way to get these samples back.”
He offered no other details about this alternative, including technical approach, cost or schedule. “That is the analysis that we’ve gone through: can we do it faster, can we do it cheaper. And we think we can, and that’s why we’re not going to take them back on Percy. We’ll actually go to a different way to bring it back.”
NASA’s previous plans for MSR did not, as Duffy claimed, involve bringing back the entire Perseverance rover, nicknamed Percy. Instead, another lander would collect the samples gathered by the rover and launch them into orbit, where a European spacecraft would capture them and bring them to Earth.
The briefing, announced Sept. 8, was originally billed as a teleconference but changed at the last minute to a video broadcast. It started more than 15 minutes late with Duffy and several other participants huddled around a podium rather than sitting on stage as is the case for typical NASA briefings. It also featured odd errors, with one speaker stating that the Milky Way is 100 billion light-years across — it is instead 100,000 light-years across — and another stating that a Mars rock was 350 billion years old, 25 times the estimated age of the universe.
The budget proposal under debate in Congress would not only cancel MSR but also shut down existing Mars missions such as the 2001 Mars Odyssey and MAVEN orbiters. It also cuts Perseverance’s operating budget by nearly 25%.
“Science isn’t going away at NASA. We are leaning into the science because we need it to make sure that we are successful on our missions to the moon and Mars,” Duffy said. “I’ve been given an ask for spending a little less money. I think we can do that. I know we can do that.”
That “ask,” apparently referring to the administration’s proposal, would reduce overall NASA funding by about 25% and science programs by nearly 50%. Duffy said he is willing to seek more money if necessary.
“I’ve told the team at NASA, if we don’t have the resources for the right missions or the right people, I will go to the president, I’ll go to Congress, I’ll ask for more money,” he said. “But I feel pretty confident that with the money that we’ve been given in the president’s budget we can accomplish our mission.”