JPL-Managed Curiosity Rover Reveals Clue to Mars’ Missing Carbonate Mystery

The discovery of a mineral called siderite at a site nicknamed “Ubajara” may help solve the mystery of what happened to the Red Planet’s carbon dioxide-rich atmosphere.

The discovery of a mineral called siderite at a site nicknamed “Ubajara” may help solve the mystery of what happened to the Red Planet’s carbon dioxide-rich atmosphere, according to new findings from the Curiosity Mars rover mission managed by NASA’s Jet Propulsion Laboratory in Pasadena.

Researchers have long theorized that Mars once had a thick, carbon dioxide-rich atmosphere and liquid water on its surface. According to this theory, the carbon dioxide and water should have reacted with Martian rocks to create substantial carbonate mineral deposits. However, until now, rover missions and near-infrared spectroscopy analysis from Mars-orbiting satellites hadn’t detected the predicted quantities of carbonate on the planet’s surface.

A study published in April in the journal Science reports that data from three of Curiosity’s drill sites revealed the presence of siderite, an iron carbonate mineral, within the sulfate-rich rocky layers of Mount Sharp in Mars’ Gale Crater.

“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 Benjamin Tutolo, assistant professor at the University of Calgary, Canada, and lead author of the paper.

To study the Martian chemical and mineral composition, Curiosity drills approximately 1.2-1.6 inches (3-4 centimeters) into the subsurface, then delivers the powdered rock samples to its Chemistry and Mineralogy (CheMin) instrument.

The instrument, developed at NASA’s Ames Research Center in California’s Silicon Valley, uses X-ray diffraction to analyze the samples. CheMin’s data was subsequently processed and analyzed by scientists at the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston.

“Drilling through the layered Martian surface is like going through a history book,” said Thomas Bristow, research scientist at NASA Ames and coauthor of the paper. “Just a few centimeters down gives us a good idea of the minerals that formed at or close to the surface around 3.5 billion years ago.”

The discovery of this carbonate mineral beneath the surface suggests that carbonates may be masked by other minerals in near-infrared satellite observations. If other sulfate-rich layers across Mars also contain carbonates, the amount of stored carbon dioxide would be a fraction of that needed in the ancient atmosphere to create conditions warm enough to support liquid water. The remainder could be hidden in other deposits or have been lost to space over time.

Future missions or analyses of other sulfate-rich areas on Mars could confirm these findings and help us better understand the planet’s early history and how it transformed as its atmosphere was lost.

Curiosity, part of NASA’s Mars Exploration Program, was built by JPL, which is managed by Caltech in Pasadena. JPL leads the mission on behalf of NASA’s Science Mission Directorate in Washington. The rover has been exploring Gale Crater since its landing in August 2012.

For more information on Curiosity, visit: https://science.nasa.gov/mission/msl-curiosity/