NASA's Perseverance rover has found rocks in a dry river channel on Mars that may indicate signs of ancient microscopic life. Scientists reported these findings on Wednesday, emphasizing the need for further analysis of the samples, ideally in laboratories on Earth, before drawing any definitive conclusions.

Since its landing in 2021, the Perseverance rover has been exploring Jezero Crater, an area believed to have once contained water. The rover is equipped with a drill to collect rock samples and store them in tubes for future retrieval. Currently, plans to bring these samples back to Earth are on hold as NASA seeks more cost-effective and efficient options.

Lead researcher Joel Hurowitz from Stony Brook University described the discovery as exciting but cautioned against jumping to conclusions. "That’s part of the reason why we can’t go so far as to say, ‘A-ha, this is proof positive of life,’" he said. He noted that while microbial life is one possible explanation for the features observed, other non-biological processes could also account for them.

The sample in question, collected last summer, comes from reddish, clay-rich mudstones in Neretva Vallis, a river channel that once flowed into Jezero Crater. This area, known as the Bright Angel formation, was analyzed by the rover's scientific instruments before the drilling took place. The team discovered organic carbon, a fundamental building block of life, along with tiny specks enriched with iron phosphate and iron sulfide. These compounds are typically produced when microorganisms consume organic matter on Earth.

Hurowitz stated that this sample is the most compelling candidate yet in the search for signs of ancient life on Mars. The rover has now collected 30 samples, with plans to gather six more. He expressed hope that future research could conclusively demonstrate whether these features were formed by living organisms on Mars billions of years ago. "It would be amazing to be able to demonstrate conclusively that these features were formed by something that was alive on another planet billions of years ago, right?" Hurowitz said.

However, he also acknowledged the challenges ahead. The timeline for returning the samples to Earth has shifted from the early 2030s to the 2040s due to rising costs, which have ballooned to $11 billion. Until the samples can be retrieved by robotic spacecraft or astronauts, scientists will rely on Earth-based experiments to assess the potential for ancient Martian life.

In an editorial accompanying the findings, scientists Janice Bishop and Mario Parente noted that while there is no evidence of current microbial life on Mars, ancient microbes could have interacted with minerals in lakes like those in Jezero Crater. They stated, "If any had been present on ancient Mars, they too might have reduced sulfate minerals to form sulfides in such a lake."

The findings were published in the journal Nature, marking a significant step in the ongoing exploration of Mars and the search for life beyond Earth.