Washington: A new study has tried to find an explanation to the decreasing density of Mars’ atmosphere.
Scientists have theorized for decades about the whereabouts of Mars’ ‘missing’ carbon.
If deeply buried carbonate layers are found to be widespread, they would help answer questions about the disappearance of most of ancient Mars’ atmosphere, which is deduced to have been thick and mostly carbon dioxide.
“We’re looking at a pretty lucky location in terms of exposing something that was deep beneath the surface,” said planetary scientist James Wray of Cornell University, Ithaca, N.Y.
Huygens crater, a basin 467 kilometers (290 miles) in diameter in the southern highlands of Mars, had already hoisted material from far underground, and then the rim of Huygens, containing the lifted material, was drilled into by a smaller, unnamed cratering event.
Observations in the high-resolution mode of the Compact Reconnaissance
Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter show spectral characteristics of calcium or iron carbonate at this site.
The occurrence of this type of carbonate in association with the largest impact features suggests that it was buried by a few kilometers (or miles) of younger rocks, possibly including volcanic flows and fragmented material ejected from other, nearby impacts.
Carbonates found in rocks elsewhere on Mars, from orbit and by NASA’s
Spirit rover, are rich in magnesium. Those could form from reaction of
volcanic deposits with moisture, Wray said.
“The broader compositional range we’re seeing that includes iron-rich and calcium-rich carbonates couldn’t form as easily from just a little bit of water reacting with igneous rocks. Calcium carbonate is what you typically find on Earth’s ocean and lake floors.”
“A dramatic change in atmospheric density remains one of the most intriguing possibilities about early Mars,” said Mars Reconnaissance
Orbiter Project Scientist Richard Zurek, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
“Increasing evidence for liquid water on the surface of ancient Mars for extended periods continues to suggest that the atmosphere used to be much thicker.”
NASA will launch the Mars Atmosphere and Volatile Evolution Mission (MAVEN) in 2013 to investigate processes that could have stripped the gas from the top of the atmosphere into interplanetary space.
Meanwhile, CRISM and other instruments now in orbit continue to look for evidence that some of the carbon dioxide in that ancient atmosphere was removed, in the presence of liquid water, by formation of carbonate minerals now buried far beneath the present surface.