'Big Sky' and 'Greenhorn' drill holes and CheMin x-ray diffraction
The graph at right presents information from the Curiosity rover's onboard analysis of rock powder drilled from the "Big Sky" and "Greenhorn" target locations, shown at left. X-ray diffraction analysis of the Greenhorn sample inside the rover's Chemistry and Mineralogy (CheMin) instrument revealed an abundance of silica in the form of noncrystalline opal. The broad hump in the background of the X-ray diffraction pattern for Greenhorn, compared to Big Sky, is diagnostic of opal. The image of Big Sky at upper left was taken by the rover's Mars Hand Lens Imager (MAHLI) camera the day the hole was drilled, Sept. 29, 2015 (sol 1119). The Greenhorn hole was drilled, and the MAHLI image at lower left was taken, on Oct. 18, 2015 (sol 1137).