Traces of past life may have been found in Mars' 'leopard-print' rocks

These mudstones, discovered in a dusty riverbed by NASA's Perseverance Rover, are covered in intriguing markings that scientists call "leopard spots" and "poppy seeds."

Researchers believe these features may contain minerals formed by chemical reactions that could be associated with ancient Martian microbes.

It's possible the minerals formed through natural geological processes, but the findings are considered significant enough to meet NASA's definition of a "potential biosignature."

THESE ROCKS WILL BE BROUGHT TO THE WORLD AND STUDIED

This means that further research is needed to understand whether the minerals are of biological origin.

"We've never seen anything like this before, so this is a huge breakthrough," says Prof. Sanjeev Gupta, a planetary scientist at Imperial College London and one of the authors of the study published in the journal Nature.

"If we saw such features on Earth, they could be explained by biological processes – by microbes. So we're not saying 'we've found life,' but we are saying we need to pursue it."

The only way to definitively know if the minerals were actually produced by microbes is to bring them back to Earth and study them. A proposed Mars sampling mission by NASA and the European Space Agency (ESA) faces a highly uncertain future.

The US space agency's science budget is being hit by major cuts proposed in President Trump's 2026 budget plan, and this mission is among the projects slated for cancellation.

Mars is a cold, arid desert, but billions of years ago, it had a thick atmosphere and water, making it a promising environment for searching for past life. The Perseverance rover, which landed on Mars in 2021, was sent to search for biological traces. For four years, it has been exploring Jezero Crater, a former lake with a river flowing into it.

Last year, the Perseverance Rover found these leopard-print rocks at the bottom of a river-carved canyon in an area called the Bright Angel Formation. These rocks, approximately 3.5 billion years old, are composed of mudstone, a fine-grained rock composed of clays.

"As soon as we saw the rocks, we realized there was an interesting chemical process going on here, so we were very excited," says Joel Hurowitz, a Perseverance mission scientist at Stony Brook University in New York and lead author of the paper.

The rover's onboard laboratory instruments analyzed the mineral composition of the rocks. This data was sent back to Earth and analyzed by scientists.

Dr. Hurowitz explains these findings:

"Our findings show that a series of chemical reactions occur within the mud that settles to the bottom of a lake. These reactions appear to occur through the combination of the mud itself and organic matter; these two components react to create new minerals."

When similar conditions exist on Earth, such mineral formations are often caused by microbes.

"One possible scenario that could explain how these traits arose involves microbes," Dr. Hurowitz says. "This may be the strongest potential biomarker detection we've had to date."

Scientists have studied how minerals can form without microbes and have determined that natural geological processes can also lead to chemical reactions.

This would require high temperatures, but the rocks don't appear to have been heated. "We found some problems with non-biological pathways, but we can't completely rule them out," Dr. Hurowitz says.

While exploring Mars, Perseverance collected samples of the Bright Angel Formation, including these rocks. These will be placed in capsules and deposited on the Martian surface to await a return mission.

NASA has such a plan, but its future is uncertain due to budget cuts, while China is working on a sample-return mission that could launch in 2028.

While scientists wait for the verdict to be finalized, they eagerly await the opportunity to study these rocks on Earth.

"We need to bring these samples back to Earth," says Prof. Gupta.

"To have real confidence, most scientists will want to see and study these rocks on Earth. This is one of our top priority samples to bring back."