The usual cadre of scientists who disproved previous findings are stumped
If you were ever wondering where you'd be when NASA announced peer-reviewed evidence hinting at extraterrestrial life - long dead, if it existed at all - look around, because this is it.
Let's qualify this discovery: The evidence is contained in a rock that's around 140 million miles away and has only been studied via photograph or the instruments on NASA's Perseverance rover. NASA's scientists aren't 100 percent sure what they've found is evidence of biological life. But so far, no simple abiotic explanation fits all the data.
"In the past we thought we found signs of life, and when we put [our findings] out to the scientific community they would come back and say, well, listen - there are different explanations," US Transportation Secretary and acting NASA Administrator Sean Duffy said at a press conference on Wednesday.
"A year ago we found what we believe to be signs of microbial life on Mars' surface," Duffy added, referring to the rock that's the subject of the latest discovery. "After a year of review [the scientific community] has come back and said it can't find another explanation."
NASA Science Mission Directorate associate administrator Nicola "Nicky" Fox likewise described the finding as "the closest we've come to actually discovering ancient life on Mars" at today's press conference - but she wanted to make clear it's not First Contact quite yet.
"This is a signature - a leftover sign - not life itself," Fox added. "It's the equivalent to seeing leftover fossils from a meal excreted by a microbe."
A 3.5 billion-year-old meal at that, and there's no sign of the microbes themselves - just their poo. Still, scientists have spent the last year trying to prove this wasn't a sign of life and have come up with nothing - and that's something.
NASA's Perseverance Rover collected the sample, called "Sapphire Canyon", in July 2024. It came from the rocky outcroppings of Neretva Vallis, a region near the Jezero Crater believed to have once been a river. Perseverance has spent its entire Martian life in the area around Jezero, which NASA believes was a lake in Mars' ancient past.
Early indicators from the larger vein-filled rock that Sapphire Canyon was cut from, known as Cheyava Falls, suggested it was a good contender for a "potential biosignature," NASA said in an April video.
As detailed in the paper published on Wednesday about the findings, the potential biosignatures can be found in two features on Sapphire Canyon: small dark spots dubbed "poppy seeds" and larger dark rings called "leopard spots."
Stony Brook University planetary scientist Joel Hurowitz, lead author on the paper and deputy principal investigator on Perseverance's PIXL instrument, explained at the press conference that analysis of those spots contained a "smoking gun for the presence of organic matter" in the form of G-band signals that suggest the presence of organic carbon.
The mud of the rock itself, Hurowitz explained, is rich in iron and a pair of related minerals: one made up of iron phosphate, likely vivianite, and an iron sulfide combo known as greigite, both of which form in the presence of organic material.
"These combinations of mud and organic matter [on Earth] are often the byproduct of microbial life consuming minerals," Hurowitz said. But he noted there are also ways those minerals can form without the involvement of biological life.
Greigite, for example, can be formed when a rock containing iron and sulfur is "cooked" at high heat - but there's no evidence that was the case at this point, Hurowitz said.
"We looked in as much detail as we possibly could to find signs the rocks were cooked, but we couldn't make that determination," Hurowitz said on the conference call. "It doesn't look like they've been heated to that level."
The same goes for other avenues NASA and its peer reviewers explored to explain the finding without biology - in short, none fit cleanly. To quote every single official on the call, this is a very "exciting" discovery.
Perseverance project scientist Katie Stack Morgan was pretty clear on what needs to come next if we're to determine whether the Sapphire Canyon sample is actual evidence of long-extinct life on Mars or not: Humans need to get their hands on it somehow.
"We threw the entire rover science payload at this rock," Stack Morgan said on the call. "We're close to the limits of what [Perseverance] can do - and that's by design."
Stack Morgan shared the sentiment that the results thus far are exciting, but she said Perseverance was designed with the endangered Mars Sample Return mission as a key part of its exploratory function: Get us some initial "wow" moments that we could further explain once the samples come back to Earth.
The MSR mission has been struggling for years with being over budget, too technologically complex, and much delayed. That hasn't stopped the scientific community and scientists from publicly urging the government not to cancel the endeavor.
The mission remains at risk of being cut entirely in next year's NASA budget. Duffy wasn't exactly direct when asked whether this discovery would prompt the administration to reprioritize the sample return mission.
The acting administrator was asked several times about MSR, and only said that he wanted the program to continue, albeit in a more efficient, cost-effective manner than it's operated to this point.
"We're in another space race and I want to make sure we're making the right decisions," Duffy said. "Continuing with missions that can't meet budget and timing would be foolish on my part."
Nonetheless, "we're looking at how to get the samples back," Duffy said - so not all hope is lost at this point. "We believe there is a faster way to do this," the acting admin added.
It might just take a lot longer to get human hands on those samples to prove whether they contain signs of life, as Duffy reiterated that the Trump administration's space priority is on human exploration, not just robots.
"We don't want to just bring samples back from Mars - we want to send boots to the Moon and Mars," Duffy asserted. "Maybe we'll send equipment to test this sample to Mars itself."
That might not happen anytime soon, so for now we'll have to be content with what little evidence we have.
Meanwhile, as the US government dithers over cost, China's plans to launch its own Mars Sample Return mission were moved up two years to 2028, with plans to return red planet rocks to Earth by 2031.
In other words, there's a distinct possibility the US could lose that new space race
"We lead and we're going to continue to lead," Duffy proclaimed at the press conference. That's true for now - but those space laurels won't stay fresh forever. ®