Detecting a Difference in Clay Minerals at Two Gale Crater SitesData graphed here from the Chemistry and Camera (CheMin) instrument on NASA's Mars Curiosity rover show a difference between clay minerals in powder drilled from mudstone outcrops at two locations in Mars' Gale Crater: "Yellowknife Bay" and "Murray Buttes."
CheMin's X-ray diffraction analysis reveals information about the crystalline structure of minerals in the rock. The intensity peaks marked with dotted vertical lines in this chart indicate that the crystalline structure of the two sites' clay minerals differs. The difference can be tied to a compositional difference in the clay minerals, as depicted in a diagram at http://mars.nasa.gov/multimedia/images/?ImageID=8196.
The Yellowknife Bay site is on the floor of Gale Crater. The Murray Buttes site is on lower Mount Sharp, the layered mound in the center of the crater. A map at http://mars.nasa.gov/multimedia/images/?ImageID=8192 shows these locations.
Image Credit: NASA/JPL-Caltech