NASA's Curiosity rover uncovers a 3.5 billion-year-old secret hiding beneath its surface-- Here's what it is

Scientists might finally have solid evidence that the Red Planet once had the ingredients necessary for life. After years of exploration, NASA’s Curiosity rover has finally unearthed a crucial piece of the Martian puzzle: traces of a long-lost carbon cycle preserved in ancient rocks.

The breakthrough study, led by Dr. Benjamin Tutolo, an associate professor at the University of Calgary, was published in the journal Science on April 12, 2025.
Within sulfate-rich sedimentary rocks on Mount Sharp in Gale Crater, the team reportedly found abundant siderite, a type of iron carbonate mineral.

According to the paper, this finding marks the first definitive evidence that Mars had a thick, carbon dioxide-rich atmosphere billions of years ago, and enough warmth to sustain liquid water on its surface.


"The discovery of abundant siderite in Gale Crater represents both a surprising and important breakthrough in our understanding of the geologic and atmospheric evolution of Mars," said Dr. Tutolo in a NASA press release.

Carbon cycle on Mars
For decades, planetary scientists have theorised that Mars’ early carbon dioxide and water should have chemically interacted with rocks to form carbonate minerals. This evidence remained elusive despite numerous missions until Curiosity’s latest drill campaign.

Using its onboard CheMin (Chemistry and Mineralogy) instrument, the rover extracted powdered samples from three to four centimetres beneath the Martian surface. They identified siderite within rock layers that date back approximately 3.5 billion years, when Mars likely had rivers, lakes, and possibly even a climate conducive to microbial life.

Carbon, the backbone of organic life, also serves a vital function in climate regulation. On Earth, it’s the reason our planet remains warm and habitable. On ancient Mars, that same carbon, originally in the form of atmospheric CO₂, may have slowly become trapped in rock formations as siderite, robbing the planet of its greenhouse effect.


"The broader implications are that the planet was habitable until this time," said Dr. Tutolo. "But then, as the CO₂ that had been warming the planet started to precipitate as siderite, it likely impacted Mars’ ability to stay warm."

The formation of siderite points to what scientists call the "great drying"—a dramatic planetary climate shift in which Mars transitioned from a warm, wet environment to the frozen desert we see today. The newly discovered carbonates offer a record of that transition- the time when the planet lost its carbon or potentially life.

This transformation, now etched into Martian stone, provides researchers with a rare chance to understand the conditions that make or break planetary habitability. It also offers a stark contrast to Earth, where the carbon cycle continues to balance atmospheric temperatures over billions of years.



Since landing in 2012, Curiosity has travelled over 20 miles across Gale Crater, systematically analysing soil, rocks, and atmosphere in search of clues about Mars’ past. Every drill, sample, and scan helps piece together the story of a planet that may once have looked a lot like early Earth.

While the siderite discovery doesn’t confirm that life ever existed on Mars, it confirms that the planet once had the necessary ingredients—water, carbon, and warmth—for life to flourish.“This doesn’t mean we’ve found life,” NASA scientist Ashwin Vasavada, the Indian-origin project scientist for the Curiosity mission, emphasised in an earlier update. “But it does mean we’ve found the conditions that could have supported it.”