A step forward in understanding how habitable ancient Mars was.
The recent discovery of evidence for carbonates beneath the surface of Mars points to a warmer and wetter environment in the planet’s past. What’s more, the presence of liquid water could mean the planet once hosted life.
A new study by James Wray at the Georgia Institute of Technology and Janice Bishop of the SETI Institute, as well as other collaborators, has found evidence for extensive buried deposits of iron- and calcium-rich carbonates.
“Identification of these ancient carbonates and clays on Mars represents a window into history when the climate on Mars was very different from the cold and dry desert of today,” said Bishop in a SETI press release.
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What happened to Mars’ water is highly debated since the planet is currently cold and dry, but scientists believe it once flowed because of the widespread geological features that hint to its ancient presence. And if water did, in fact, flow on the surface of Mars, the planet’s bedrock should be full of carbonates and clays, which would offer evidence that Mars could have had habitable environments.
However, researchers have struggled to find physical evidence for carbonate-rich bedrock.
But by focusing on Mars’ Huygens basin, where multiple impact craters have exposed ancient materials, carbonates were detected in this large region. According to study lead James Wray, “outcrops in the 450-km wide Huygens basin contain both clay minerals and iron- or calcium-rich carbonate-bearing rocks.”
The researchers identified these carbonates using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), which is located on the Mars Reconnaissance Orbiter. CRISM collects the spectral fingerprints (or signatures) of carbonates and other minerals through vibrational transitions of the molecules in their crystal structure. These transitions typically require energy, and that energy is emitted in the infrared region of the spectrum, which is detected by CRISM.
By pairing CRISM data with images from the High Resolution Imaging Science Experiment (HiRISE), the Context Camera (CTX) on the orbiter, as well as the Mars Orbiter Laser Altimeter (MOLA) on the Mars Global Surveyor, the team was able to gain valuable insights into the geologic features associated with carbonate-bearing rocks.
In fact, the researchers identified carbonate-bearing rocks in several sites across Mars, including the Lucaya crater, where 3.8 billion-year-old carbonates and clays were buried by as much as 3.1 miles (5 kilometers) of lava and caprock — a harder and more impermeable type of rock.
Bed forms overlie ancient layered, carbonate-rich material in the central pit of Lucaya crater, northwest Huygens basin, Mars. The image was taken by HiRISE. Photo Credit: NASA/JPL/University of Arizona
Although the distribution of carbonates is not fully known, and the early climate on the Red Planet is still debated, the study is definitely a step forward in understanding the potential habitability of ancient Mars.
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