In a discovery that could reshape our understanding of Mars’ ancient climate, NASA’s Curiosity rover has uncovered fresh evidence that the Red Planet wasn’t always the cold, barren desert we see today. The rover has detected siderite—a rare iron carbonate mineral—in multiple rock samples from inside the Gale Crater, suggesting that Mars once had a much thicker carbon dioxide-rich atmosphere capable of sustaining bodies of liquid water.
Why is this important? Because siderite only forms in specific conditions—namely, in the presence of water and carbon dioxide. This means Mars may have once looked very different: warm, wet, and potentially teeming with microbial life.
The Curiosity rover, which has been exploring the surface of Mars since 2012, drilled into sedimentary rocks at three different locations in 2022 and 2023. These rocks are believed to be around 3.5 billion years old—dating back to a time when Gale Crater was likely home to a lake. The samples it returned contained up to 10.5% siderite by weight, a surprisingly high concentration and one that significantly strengthens the theory that Mars once had a much denser atmosphere.
“This is one of the most compelling pieces of evidence yet that Mars had the kind of climate needed to support liquid water on its surface,” said Dr. Benjamin Tutolo, a geochemist from the University of Calgary and the lead author of the new study published in Science. “And with water, there’s always the possibility of life.”
Read Also: China Launches World’s First Operational Thorium Nuclear Reactor, Thanks to ‘Strategic Stamina’
What makes this discovery even more fascinating is what it reveals about Mars’ carbon cycle. On Earth, carbon dioxide moves through the atmosphere, oceans, and rocks in a continuous loop—thanks in part to plate tectonics and volcanic activity. But Mars doesn’t have plate tectonics, and this new research suggests that much of the planet’s carbon dioxide may have become locked away in the rocks eons ago, never to return to the atmosphere.
“The Martian carbon cycle appears to have been fundamentally different from Earth’s,” said planetary scientist Dr. Edwin Kite, a co-author of the study. “It seems Mars stored up carbon in its crust but didn’t release much of it back into the air. That imbalance may explain why the planet eventually lost its ability to support life.”
Until now, one of the big mysteries about ancient Mars was the lack of widespread carbonate minerals on its surface. If the planet had a thick CO₂ atmosphere in the past, where did all that carbon go? Thanks to Curiosity’s new findings, we may finally be closing in on the answer.
The implications of this are huge—not just for understanding Mars’ past, but also for the future of planetary exploration. If siderite and other carbonate-rich rocks are common across the planet (as some satellite data suggests), future missions could target these deposits to learn more about Mars’ lost climate and even search for preserved signs of ancient microbial life.
This also adds fuel to the growing excitement around future Mars missions—including sample return programs and, eventually, human exploration. By studying these ancient rocks up close, we may unlock secrets not just about Mars, but about the history of habitability in our solar system.
As we continue to explore the Red Planet, one thing is becoming increasingly clear: Mars was not always as it is today. And somewhere in those layers of ancient rock, we may still find the story of life beyond Earth.
