NASA’s Curiosity rover has made a major discovery that could help explain what happened to Mars’ ancient atmosphere—and why the planet became so dry and lifeless.
For years, scientists have believed that early Mars had a thick carbon dioxide (CO₂) atmosphere and flowing liquid water on its surface.
Under those conditions, the CO₂ in the air and water should have reacted with Martian rocks to form a type of mineral called carbonate.
But surprisingly, until now, scientists hadn’t found enough carbonate on Mars to support that theory.
That mystery may now be solved, thanks to new findings published in Science.
Using data from three drill sites on Mount Sharp in Gale Crater, researchers discovered a specific kind of carbonate called siderite, which contains iron.
The mineral was found in sulfate-rich rock layers and appears to have formed near the surface about 3.5 billion years ago.
This is the first solid mineral evidence showing that Mars once had a thick CO₂ atmosphere, strong enough to keep the planet warm and allow water to exist on the surface.
That’s a big deal, because water is essential for life as we know it—and understanding Mars’ watery past helps scientists figure out if life could have once existed there.
Dr. Edwin Kite, a researcher from the University of Chicago and one of the study’s authors, says the discovery also sheds light on why Earth and Mars, which were once similar, ended up on such different paths. Earth has remained habitable for billions of years, while Mars became cold and barren.
To make this discovery, NASA’s Curiosity rover drilled small holes into the Martian surface—about 1 to 1.5 inches deep—and collected powdered rock samples. These were then analyzed inside the rover using an instrument called CheMin, which uses X-rays to identify minerals.
“Drilling into the surface is like reading pages in Mars’ history book,” said NASA scientist Thomas Bristow, another author of the study. Just a few centimeters down, scientists can see what conditions were like billions of years ago.
Previously, researchers used infrared satellites to search for carbonates from orbit, but those tools couldn’t detect minerals that are hidden beneath other materials. That’s likely why the carbonate minerals remained undetected until Curiosity physically drilled into the rocks.
Lead author Dr. Benjamin Tutolo from the University of Calgary called the discovery “both surprising and important,” as it offers a clearer picture of how Mars’ atmosphere may have slowly turned into rock over time.
These new insights could guide future missions looking for similar rock layers elsewhere on Mars, giving scientists more clues about the planet’s ancient climate and the chances it may once have supported life.
