NASA says it has found "the clearest sign" of ancient life on Mars.

Barcelona"This exciting discovery is the closest we've come to discovering ancient life on Mars and answering one of humanity's deepest questions: Are we truly alone in the universe?" said NASA's Chief Scientist, Nicola Fox, on Wednesday. The representative of the US space agency enthusiastically outlined the results of the analysis of the samples taken by the rover. Perseverance collected last year on the red planet, in an area where a river flowed 3.8 billion years ago and emptied into a lake. The minerals found by the "six-wheeled geologist" then opened a window of optimism about the possibility of proving that microbial life could have existed outside of Earth billions of years ago. "And after a year of review, scientists told us, 'We can't find any other explanation,'" said NASA Director Sean Duffy.

Since 2020 Perseverance scours Mars' Jezero Crater for signs of ancient life. Now, NASA scientists have reported that the sediments found hide "strange" mineral nodules whose chemical history suggests they could have formed through prebiotic or microbial chemical processes—processes linked to life. The samples, analyzed by an international team of scientists with the participation of the Center for Astrobiology (INTA-CSIC), the University of Valladolid (UVA), and the CSIC Institute of Geosciences, contain small nodules of clay minerals enriched with iron phosphate and iron sulfide, carbon-associated compounds that are the basis of life. They are, according to NASA, "the clearest sign" of ancient life on Mars.

According to the team, these processes took place after the sediments were deposited in the lake and under low-temperature conditions, making these "extraordinary samples" potential biosignatures; That is, traces of ancient chemical processes that could have been the basis for the emergence of life on Mars, but which need further investigation. "The identification of a potential biosignature on the Red Planet is a groundbreaking discovery that will enhance our understanding of Mars," said Duffy. "It's a sort of residual signal. It's not life itself, and it certainly could have been ancient life. And that would be something that existed millions of years ago, nothing that's still present," Fox said at a press conference detailing the results of the research, which was published Wednesday. Nature. For this reason, the study's authors are cautious, warning that the very evidence that these rocks could have been formed by microbes billions of years ago, when Neretva Vallis contained water, could be the result of abiotic geological processes and therefore unrelated to life.

The challenge of bringing samples back to Earth

To confirm this and determine whether the red planet once hosted life, it is essential to bring samples of the Perseverance on Earth and study them in detail. The rover found the samples in July 2024 while exploring the Bright Angel Formation, a set of rock outcrops on the northern and southern edges of Neretva Vallis. NASA scientist Katie Scott Morgan said they chose this location "because it's among the oldest terrain on Mars, versus some of the oldest rocks anywhere in the polar system."

The rover's suite of science instruments found that the sedimentary rocks in this formation are composed of clay and silt, which, on Earth, are excellent preservatives of past microbial life. They're also rich in organic carbon, sulfur, oxidized iron (rust), and phosphorus. "The combination of chemical compounds we found in the Bright Angel Formation could have been an abundant energy source for microbial metabolisms," says Perseverance scientist Joel Hurowitz of Stony Brook University and lead author of the paper. However, he points out that all these chemical signatures didn't mean per se that there was a potential biosignature. "We needed to analyze what this data could mean," he says.

The Martian rock where these samples were identified is shaped like an arrowhead and has spots similar to leopard fur. NASA claims they are traces of both chemical reactions consistent with how microorganisms obtain energy and the presence of water, necessary for life. However, representatives from the space agency clarified that verifying whether it is a sign of life "requires more work and study," and therefore emphasized the importance of returning the samples to Earth for further study. This request clashes with some recent decisions by the US government, as President Donald Trump plans to reduce NASA's budget and abandon the return to Earth of many samples from space missions.