The fate of water on Mars has been hotly debated by scientists because the planet is currently dry and cold, in contrast to the widespread fluvial features that carve much of the planet’s surface. Scientists believe that if water did once flow on the surface of Mars, the planet’s bedrock should be full of carbonates and clays. Such minerals could provide further evidence that Mars once hosted habitable environments with liquid water. Researchers have struggled to find physical evidence for carbonate-rich bedrock, which may have formed when paleoatmospheric carbon dioxide was trapped in ancient surface waters.
A new study by Wray et al. provides evidence for widespread buried deposits of Fe- and Ca-rich carbonates on Mars. The researchers, supported by the SETI Institute NASA Astrobiology Institute (NAI) team, identified carbonates on the planet using data from CRISM and HiRISE on the Mars Reconnaissance Orbiter.
“Outcrops in the 450-km wide Huygens basin contain both iron- and calcium-rich carbonate-bearing rocks” according to study lead Dr. James Wray of Georgia Tech and NAI team Co-Investigator. The Huygens basin is an ideal site to investigate carbonates because multiple impact craters and troughs expose ancient, subsurface materials where carbonates are detected across a broad region. The study highlights evidence of carbonate-bearing rocks in multiple sites across the Red Planet, including Lucaya crater, where the ancient 3.8 Ga year old carbonates and clays were buried by as much as 5 km of lava and caprock. Study co-author Dr. Janice Bishop of the SETI Institute and also a NAI Co-Investigator says that “identification of these ancient carbonates and clays on Mars represents a window into the past when the climate on Mars was very different from the cold and dry desert of today”. The extent of the global distribution of Martian carbonates is not yet resolved and the early climate on Mars remains under debate. However, this study moves us forward in our understanding of potential Martian habitability.
Aeolian bed forms overlie ancient layered, ridged carbonate-rich outcrop exposed in the central pit of Lucaya crater, northwest Huygens basin, Mars. The image was taken by the High Resolution Imaging Science Experiment (HiRISE) instrument aboard the Mars Reconnaissance Orbiter. Credit: NASA/JPL/University of Arizona.