Scientists have long suspected that ancient Mars supported a thick carbon dioxide atmosphere and liquid water on its surface. In 2011, NASA launched the Curiosity rover to explore Gale Crater on Mars, searching for evidence of these past environmental conditions.
New data collected and interpreted from the Curiosity rover, by Texas State University affiliates that are members of the Mars Science Laboratory (MSL) team located at NASA’s Johnson Space Center (JSC), provided evidence of an active carbon cycle on ancient Mars, an intriguing development that could be an important clue in determining whether the red planet was ever hospitable enough to support life.
Joanna Clark, Ph.D., Sarah Simpson, Ph.D., and Valerie Tu are grant specialists with TXST’s Office of Research and Sponsored Programs’ (ORSP) Johnson Space Center Astromaterials Research Exploration and Science division (ARES) (JETSII) program. They contributed to a multinational effort headed up by Benjamin Tutolo, Ph.D., an associate professor with the Department of Earth, Energy and Environment at the University of Calgary, and members of the Chemistry and Minerology (CheMin) X-ray diffraction (XRD) instrument team. The team’s findings, “Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars,” are published in the journal Science.
The team, working to understand climate transitions and habitability on ancient Mars, reveals that data from three of Curiosity’s drill sites had siderite, an iron carbonate material, within sulfate-rich layers of Mount Sharp in Gale Crater. The discovery of carbonate suggests that the ancient Martian atmosphere contained enough carbon dioxide to support liquid water on the planet’s surface. As the atmosphere thinned, chemical processes transformed the gaseous carbon dioxide into rock form. Additionally, the presence of iron oxyhydroxides in these deposits indicates that a partially closed carbon cycle returned some of the carbon dioxide bound in rocks back to the atmosphere.
Simpson and Tu are both collaborators on the CheMin XRD instrument team on the Curiosity rover. The X-ray diffractometer provides the mineralogy of drilled rock samples from the surface of Mars. Simpson’s role, as a planetary geologist, was to interpret the instrument data and help piece the data together with information from other instruments to understand how the rocks and minerals formed on Mars. This, in turn, can shed light on past conditions on the surface such as temperatures or whether water was present.
Tu, in addition to analyzing and interpreting the data, also performed mission operations for the CheMin instrument onboard Curiosity.
Clark is a member of the Sample Analysis at Mars (SAM) Science and Operations team. Curiosity’s SAM instrument suite measures the abundances and isotopic compositions of volatiles evolved during the heating of Martian surface materials and to sample directly from the atmosphere. SAM-Evolved Gas Analysis supports mineral detections by the CheMin instrument and can also infer the presence of amorphous phases or phases present at abundances below CheMin’s detection limit. She contributed interpretations of the mineralogy and chemistry of drilled samples from the SAM perspective, which can help researchers understand past mineral formation conditions such as water abundance.
