In 2025, detailed analysis of rocks collected by NASA's Perseverance rover has uncovered tantalising clues suggesting past microbial life on Mars. Features like 'leopard spots' and greenish mineral nodules resemble those linked to microbes on Earth. However, confirming these signs requires returning the samples to Earth, a mission now at risk of cancellation.
NASA's Perseverance rover, which began collecting samples last year, has provided some of the most promising evidence yet for ancient life on Mars. Scientists examining the rocks identified tiny splotches, known as 'leopard spots', measuring just millimetres across and surrounded by a dark ring. These resemble fossilised microbial structures observed on Earth.
A team led by Joel Hurowitz at Stony Brook University in New York conducted further tests on these spots, detecting forms of iron and sulphur typically produced by microbial chemical reactions. Hanna Sizemore at the Planetary Science Institute in Arizona praised the findings, stating, “I find it much more promising [an indication of life] than anything I’ve seen in the last 20 years.” She added, “I am more enthusiastic about these findings than any of those [previous hints like methane variations or meteorite structures]. That was all at the wrong physical scale.” The spots, she noted, match the scale expected for microbial activity.
Perseverance also discovered small greenish nodules of minerals, which on Earth are often associated with microbial life. Andrew Steele at Carnegie Science in Washington DC, who helped define the rover's scientific objectives, remarked, “It was always obvious that life there isn’t obvious. It’s not herds of wildebeests sweeping majestically across the plain.” He emphasised the need for advanced instruments to detect subtle signs.
While the rover's tools offer valuable insights, definitive proof demands laboratory analysis on Earth. Perseverance has cached the samples for a future retrieval mission. Steele underscored their importance: “These samples represent the best chance that we have of a next step in the analysis of whether there is [or has been] life on Mars – we just have to bring them back.”
Yet, the Mars Sample Return project faces cancellation under the Trump administration's proposed 2026 NASA budget. Sizemore warned, “We keep making so much progress, but our big picture of Martian habitability keeps not moving. We’re right on the edge – we cannot dismiss it and we cannot prove it. It’s only missions on the ground that will change that.” This uncertainty leaves the potential discovery in limbo.