NASA’s Mars rover Perseverance has discovered rocks in an ancient dry river channel that could contain potential signs of past microscopic life, scientists reported Wednesday.
Researchers emphasized that detailed analysis of the samples collected by Perseverance—ideally in laboratories on Earth—is necessary before any conclusions can be drawn.
While noting that the findings “certainly are not the final answer,” NASA’s science mission chief, Nicky Fox, described the discovery as “the closest we’ve actually come to finding ancient life on Mars.”
Perseverance, which has been exploring the Martian surface since 2021, cannot detect life directly. The rover is equipped with a drill to collect rock samples and tubes to store them from locations considered most likely to have supported life billions of years ago. The samples are awaiting eventual return to Earth, although NASA is exploring faster and more cost-effective ways to achieve this.
Calling the discovery “exciting,” independent scientists Janice Bishop of the SETI Institute and Mario Parente of the University of Massachusetts Amherst cautioned that non-biological processes could also explain the findings.
Lead researcher Joel Hurowitz of Stony Brook University told The Associated Press, “All we can say is that one possible explanation is microbial life, but there could be other processes that created these features.” He added that the sample is the most compelling candidate so far in the rover’s search for signs of ancient life. The discovery was published in the journal Nature.
Collected last summer, the sample comes from reddish, clay-rich mudstones in Neretva Vallis, a river channel that once flowed into Jezero Crater. The sedimentary outcrop, known as the Bright Angel formation, was studied by Perseverance’s science instruments before the rover drilled into it.
In addition to organic carbon, a key building block of life, Hurowitz’s team found tiny mineral specks, nicknamed “poppy seeds” and “leopard spots,” enriched with iron phosphate and iron sulfide. On Earth, these compounds form when microorganisms consume organic material.
“There is no evidence of microbes on Mars today,” Bishop and Parente wrote in an accompanying editorial, “but if any had existed on ancient Mars, they might have produced sulfides by reducing sulfate minerals in a lake at Jezero Crater.”
Although there is no evidence of present-day Martian life, NASA has long targeted past watery environments on Mars that may have supported life billions of years ago.
Perseverance was launched in 2020, with initial plans to return samples to Earth by the early 2030s. However, the timeline has now been pushed into the 2040s due to rising costs, currently estimated at $11 billion.
Until the samples are transported back to Earth, scientists will rely on Earth-based experiments to study their potential for harboring ancient life, Hurowitz said. NASA acting Administrator Sean Duffy noted that budgets and timing will guide future efforts and suggested that advanced equipment might be sent to Mars to analyze the samples on-site. “All options are on the table,” he said.
Ten titanium sample tubes were previously deposited on the Martian surface as a backup to those aboard the rover, forming part of NASA’s ongoing but still uncertain sample return mission.