Curiosity rover reveals ancient carbon cycle on Mars

NASA’s Curiosity rover has uncovered compelling evidence of an ancient carbon cycle on Mars, marking a significant step forward in the quest to determine whether the red planet could have once supported life.

The findings, recently published in the journal Science, stem from data collected by Curiosity from three different drill sites within Gale Crater on the Red Planet. Researchers discovered siderite, an iron carbonate mineral, embedded within sulfate-rich layers of Mount Sharp—a major geological feature inside the crater. These carbonate deposits are crucial indicators of past atmospheric and geologic conditions.

Dr. Ben Tutolo, associate professor in the Department of Earth, Energy and Environment at the University of Calgary, is a participating scientist on NASA’s Mars Science Laboratory Curiosity Rover team and the lead author of the study. He emphasised the significance of the discovery, describing it as a "surprising and important breakthrough" in understanding Mars' atmospheric evolution and its potential for habitability.

According to Tutolo, reaching these carbonate-rich rock layers had long been a goal of the Mars Science Laboratory mission. The presence of highly soluble salts in these rocks—and similar deposits found across Mars—has previously been linked to the planet’s transition from a once warm and wet environment to its current cold, arid state. The identification of siderite strengthens the case that Mars once had a thicker, carbon dioxide-rich atmosphere that could support liquid water on the surface.

Carbonates are thought to form when carbon dioxide from the atmosphere reacts with minerals in water, which means their presence points to a more hospitable Martian past. However, until now, sedimentary carbonate had only been sparsely identified on Mars, leaving major questions about the planet’s atmospheric history unanswered.

Curiosity, which landed on Mars on August 5, 2012, has now traveled over 34 kilometers across the Martian terrain, steadily gathering data to help scientists reconstruct the planet’s complex geological timeline. The rover’s exploration of Gale Crater has been particularly fruitful, revealing a variety of sedimentary rock layers that record the environmental shifts Mars has undergone.

NASA believes that the discovery of these carbon deposits could be just the beginning. Future missions, especially those that target other sulfate-rich regions on the planet, may provide additional confirmation of this ancient carbon cycle and yield deeper insights into how Mars lost its atmosphere over time.

Understanding whether Mars once had a stable carbon cycle is key to assessing its potential to have supported microbial life. With each new discovery, Curiosity is helping to unravel the mysteries of Mars’ transformation from a potentially life-friendly planet to the barren world we see today.

By Nazrin Sadigova