Dr. Ben Tutolo, PhD, a geoscientist at the University of Calgary's Department of Earth, Energy and Environment, played a key role in the research. As a member of the Curiosity rover science team, Tutolo is focused on understanding the climatic shifts and habitability of early Mars.
The findings, published in Science, center on Curiosity's analysis of drill samples from Mount Sharp inside Gale Crater. The rover detected siderite, an iron carbonate, embedded within sulfate-rich rock layers at three separate sites. This mineral is believed to have formed under a carbon dioxide-heavy atmosphere, providing new support for theories that Mars once had a warmer and wetter climate.
"The discovery of large carbon deposits in Gale Crater represents both a surprising and important breakthrough in our understanding of the geologic and atmospheric evolution of Mars," said Tutolo.
Curiosity's exploration of these deposits had long been a target for NASA's Mars Science Laboratory mission. The presence of water-soluble salts in these layers, combined with the carbonates, adds to evidence of Mars' dramatic transition from a habitable environment to a cold, arid one.
Though scientists had previously theorized that carbonates would have formed under a thick, CO2-rich atmosphere, actual detections have been scarce until now. The discovery strengthens the case for a functioning carbon cycle in Mars' early history.
Since landing in 2012, Curiosity has traveled over 34 kilometers across the Martian surface. Its recent findings suggest that ancient Mars had enough atmospheric carbon dioxide to support stable liquid water. Over time, that carbon dioxide likely became locked in rock, gradually reducing the greenhouse effect and cooling the planet.
NASA believes further missions targeting sulfate-bearing terrains could validate the carbonate data and help reconstruct Mars' climatic past.
"It tells us that the planet was habitable and that the models for habitability are correct," Tutolo said. "The broader implications are the planet was habitable up until this time, but then, as the CO2 that had been warming the planet started to precipitate as siderite, it likely impacted Mars' ability to stay warm."
A key question emerging from the study is how much atmospheric CO2 ended up trapped in mineral form. This sequestration may have played a major role in the decline of planetary habitability.
Tutolo noted that the research also ties into his Earth-based studies, which explore carbon mineralization as a strategy to combat climate change.
"Learning about the mechanisms of making these minerals on Mars helps us to better understand how we can do it here," he explained. "Studying the collapse of Mars' warm and wet early days also tells us that habitability is a very fragile thing."
He emphasized the importance of small atmospheric changes, adding, "The most remarkable thing about Earth is that it's habitable and it has been for at least four billion years. Something happened to Mars that didn't happen to Earth."
Research Report:Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars
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