NASA Rover Discovers Siderite on Mars: New Clues About Red Planet’s Warm and Wet Ancient Past

Siderite is a type of iron carbonate mineral. On Earth, such minerals typically form in warm, watery environments where carbon dioxide interacts with iron-rich sediments. Its detection on Mars strongly implies similar ancient conditions.

According to the study, "One of the longstanding mysteries in the study of Martian planetary evolution and habitability is: if large amounts of carbon dioxide were required to warm the planet and stabilize liquid water, why are there so few detections of carbonate minerals on the Martian surface?" said University of Calgary geochemist Benjamin Tutolo, who led the research.

The Curiosity Rover’s Findings in Gale Crater

Drilling into Ancient Sediments

NASA's six-wheeled Curiosity rover, about the size of a car, collected rock samples from three separate sites within Gale Crater—a vast impact basin featuring a central mountain—during its missions in 2022 and 2023.

These samples, drilled 1.2 to 1.6 inches (3-4 centimeters) into the Martian surface, were found to contain up to 10.5% siderite by weight, marking one of the most significant mineralogical discoveries on Mars to date.

Reconstructing Mars’ Ancient Climate

The Role of Carbon Dioxide in Warming Mars

Carbon dioxide acts as a primary greenhouse gas on Earth and other planets like Mars and Venus. Its presence in a dense Martian atmosphere would have created a greenhouse effect, raising surface temperatures enough to allow liquid water to exist.

Until now, little direct evidence existed that CO₂ was ever abundant in the Martian atmosphere. However, scientists hypothesize that “when the atmosphere – for reasons not fully understood – evolved from thick and rich in carbon dioxide to thin and starved of this gas, the carbon through geochemical processes became entombed in rocks in the planet’s crust as a carbonate mineral.”

The new Curiosity data strongly supports this theory.

Was Mars Ever Habitable?

Signs Point to Ancient Lakes and Rivers

The sedimentary rocks analyzed by Curiosity, primarily consisting of sandstones and mudstones, are thought to have formed approximately 3.5 billion years ago, during a time when Gale Crater is believed to have contained a lake.

These findings align with long-standing theories that Mars once had oceans, lakes, and river systems, providing potential habitats for microbial life.

According to planetary scientist Edwin Kite, a co-author of the study, "The shift of Mars’ surface from more habitable in the past, to apparently sterile today, is the largest-known environmental catastrophe."

Mars' Carbon Cycle: A Geological Mystery

Mars Vs. Earth – A Carbon Story

On Earth, the carbon cycle is largely regulated by plate tectonics, volcanic eruptions, and ocean absorption. However, Mars lacks plate tectonics, which means once carbon was sequestered into rocks, there was no geological mechanism to release it back into the atmosphere.

As Tutolo explains, “The important feature of the ancient Martian carbon cycle that we outline in this study is that it was imbalanced. In other words, substantially more carbon dioxide seems to have been sequestered into the rocks than was subsequently released back into the atmosphere.”

This imbalance may have played a key role in Mars’ transition from a warm, wet planet to the cold, dry desert we see today.

Broader Implications and Future Exploration

The detection of siderite suggests that similar carbonate-rich rocks may be present across Mars, meaning the Curiosity findings could be the tip of the iceberg. These results open new possibilities for understanding how Mars lost its habitability and could guide future missions, including sample return efforts and even potential human exploration.

As researchers refine climate evolution models, the newly discovered mineral deposits will play a critical role in rewriting our understanding of Mars' geological and atmospheric history.

Conclusion: Uncovering Mars’ Mysterious Past, One Rock at a Time

The discovery of siderite in the Gale Crater by NASA’s Curiosity rover adds a vital new chapter to our understanding of Mars' evolutionary history. These iron carbonate minerals not only hint at a time when the Red Planet had a dense carbon dioxide-rich atmosphere but also strengthen the argument that it once harbored lakes, rivers, and possibly even microbial life.

This breakthrough helps resolve a long-standing mystery in planetary science — the apparent absence of widespread carbonate minerals on Mars despite models predicting their presence.

With up to 10.5% siderite found in rock samples and similar sedimentary rocks observed across the planet, scientists now believe that vast reserves of carbon dioxide could be trapped beneath Mars' crust.

This shifts the focus toward understanding how Mars lost its habitability and what role this imbalanced carbon cycle played in the planet's transformation from warm and wet to cold and arid.

The Curiosity rover's findings not only deepen our knowledge of Mars’ climate history but also guide future missions in the search for life beyond Earth. As we continue to unlock secrets buried in Martian rock, each revelation brings humanity a step closer to answering the ultimate question: Was Mars ever alive?