For the first time in its continuing mission to better understand the past habitability of the Red Planet, NASA's Mars rover Curiosity has detected a mineral drilled out of a Martian rock that matches orbital data from NASA's Mars Reconnaissance Orbiter (MRO).
Hematite, an iron-oxide mineral, was detected by the MRO's CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument in 2010 before Curiosity's 2012 landing site was selected. Inside Gale Crater, where mission scientists eventually decided to land Curiosity, hematite was detected, one of the reasons why the mission is studying the geology there.
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"This connects us with the mineral identifications from orbit, which can now help guide our investigations as we climb the slope and test hypotheses derived from the orbital mapping," said Curiosity Project Scientist John Grotzinger, of the California Institute of Technology (Caltech) in Pasadena, Calif.
The detection of hematite by Curiosity's on-board chemistry lab - the Chemistry and Mineralogy (CheMin) instrument - not only provides the "ground truth" by connecting orbital data with the mineralogy measured on the ground, it also provides a tool so we can better understand the environmental conditions - potentially habitable conditions - the hematite formed in.
"We've reached the part of the crater where we have the mineralogical information that was important in selection of Gale Crater as the landing site," said Ralph Milliken of Brown University, Providence, Rhode Island, and member of Curiosity's science team. "We're now on a path where the orbital data can help us predict what minerals we'll find and make good choices about where to drill. Analyses like these will help us place rover-scale observations into the broader geologic history of Gale that we see from orbital data."
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Hematite is formed when another mineral, magnetite, is exposed to oxidizing conditions. This happens when the mineral is exposed to Mars' atmosphere and water. Interestingly, this tiny CRISM sample contains magnetite, hematite and olivine in a range of oxidization states. This is suggestive of an oxidization gradient through the rock sample, a gradient that may have been used by hypothetical Mars microbes as an energy source.
This latest sample of rock was drilled from a location dubbed "Confidence Hills" at the base of Mount Sharp (a.k.a. Aeolis Mons) at an outcrop called "Pahrump Hills." The drilled rock dust was then dropped into CheMin, which uses X-ray diffraction to detect the chemical fingerprint of minerals locked in the rock.