NASA Curiosity rover has uncovered compelling new evidence that ancient Mars may have once supported liquid water and possibly life, thanks to the discovery of a rare mineral in the planet rocky surface.
The mineral siderite an iron carbonate was found in rock samples collected in 2022 and 2023 from three locations inside Gale crater, a massive impact basin believed to have hosted a lake billions of years ago. Scientists say the presence of siderite suggests that Mars once had a dense, carbon dioxide-rich atmosphere, capable of warming the planet enough for water to exist on its surface.
This discovery helps solve a long-standing Martian mystery: if ancient Mars was warm and wet where did all the carbon dioxide go? According to scientists the carbon may have been trapped inside rocks as carbonate minerals like siderite. Until now, evidence of such carbonates on Mars had been surprisingly scarce, both in rover-based missions and from satellite surveys.
“These findings finally provide physical evidence that a major portion of Mars’ ancient carbon dioxide may be locked in its crust,” said Benjamin Tutolo, geochemist at the University of Calgary and lead author of the study published in Science. He added that this could explain why Mars transitioned from a habitable world to the cold, dry, and seemingly lifeless planet it is today.
Curiosity’s onboard tools analyzed the rocks and found that some samples contained up to 10.5% siderite by weight. This is a significant concentration, pointing to widespread deposits of carbonates across the planet’s surface. Since similar rocks have been observed elsewhere on Mars, researchers believe these mineral-rich formations could hold the key to understanding the planet’s climate history.
Planetary scientist Edwin Kite of the University of Chicago called the transformation of Mars “the largest-known environmental catastrophe,” and said that the new findings are a vital piece of the puzzle in uncovering where the planet’s once-thick atmosphere went.
Unlike Earth which recycles carbon dioxide through plate tectonics and volcanism Mars lacks such mechanisms. Instead, researchers now believe Mars’ carbon cycle was “imbalanced,” with more CO₂ being stored in rocks than released back into the atmosphere leading to a permanent cooling and the loss of its early habitability.
This discovery not only deepens our understanding of Mars’ past but also helps refine climate models that could inform future missions searching for signs of ancient life on the Red Planet.
