Siderite Discovery Reveals Ancient Mars Was Warm and Wet

A new study based on data from NASA’s Curiosity rover has provided compelling evidence that Mars once hosted a warmer, wetter climate—conditions that may have supported life.

Siderite Detected in Gale Crater Samples

A mineral called siderite, identified in rock samples collected by NASA’s Curiosity rover between 2022 and 2023, offers strong indications of Mars’ ancient climate. The samples were taken from three locations inside Gale Crater, a site believed to have once held a large lake.

The discovery marks one of the most significant mineral findings to date on Mars. Siderite, an iron carbonate, typically forms in environments rich in carbon dioxide and liquid water—conditions that no longer exist on the planet.

Carbon Storage in Martian Rocks

According to researchers, the presence of siderite suggests that Mars once had a thicker atmosphere, rich in carbon dioxide. This greenhouse gas would have warmed the surface, allowing liquid water to exist.

• Up to 10.5% siderite by weight was found in the samples.
• This mineral likely formed when carbon dioxide from the atmosphere was absorbed and chemically locked into the Martian crust.
• The process mirrors Earth’s carbon cycle, but Mars lacks plate tectonics to recycle carbon.

A Long-Standing Mystery Addressed

Scientists have long questioned why carbonate minerals—expected to be abundant if Mars once had a warm, CO₂-rich atmosphere—are rarely detected on the surface. This discovery provides a possible explanation: the carbon may have been stored in the crust rather than remaining in the atmosphere.

“This is a major clue in solving the mystery of Mars’ lost atmosphere,” said Dr. Benjamin Tutolo, lead author of the study and geochemist at the University of Calgary.

Implications for Mars’ Climate History

The sedimentary rocks in Gale Crater are estimated to be 3.5 billion years old, dating back to when the crater likely held a lake. These formations suggest a period when Mars was more habitable than it is today.

• Ancient river channels and lakebeds have been observed on Mars, supporting the theory of a wetter past.
• The decline in atmospheric CO₂ may have led to the planet’s dramatic environmental transformation.

Understanding Mars’ Carbon Cycle

Unlike Earth, where carbon is continually cycled through volcanic activity and plate tectonics, Mars’ carbon system appears to have been one-way. Once sequestered into rocks, the carbon did not return to the atmosphere.

“Mars’ carbon cycle was imbalanced. More carbon dioxide was stored than released,” said Tutolo.

This imbalance may have played a key role in the loss of Mars’ habitability.

Conclusion

NASA’s Curiosity rover has offered vital new insights into Mars’ climate evolution. The detection of siderite not only strengthens the theory that Mars was once warm and wet, but also redefines our understanding of the planet’s ancient carbon cycle.

As planetary scientists continue to explore the Red Planet, findings like this bring us one step closer to understanding whether life ever existed on Mars.