This graphic shows proportions of minerals identified in mudstone exposures at the "Yellowknife Bay" location where NASA's Curiosity Mars rover first analyzed bedrock, in 2013, and at the "Murray Buttes" area investigated in 2016.

Minerals were identified by X-ray diffraction analysis of sample powder from the rocks. The samples were acquired by drilling and delivered to the Chemistry and Mineralogy (CheMin) instrument inside the rover.

Two key differences in the Murray Buttes mudstone include hematite rather than magnetite, and far less abundance of crystalline mafic minerals, compared to the Yellowknife Bay mudstone composition. Hematite and magnetite are both iron oxide minerals, with hematite as a more oxidized one. That difference could result from the Murray Buttes mudstone layer experiencing more weathering than the Yellowknife Bay mudstone. More weathering could also account for the lower abundance of crystalline mafics, which are volcanic-origin minerals such as pyroxene and olivine.

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 PIA21144 shows these locations.

Presented at the 2016 AGU Fall Meeting on Dec. 13. in San Francisco, CA.

NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington.

For more information about Curiosity, visit http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl.