The Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover analyzes Martian rocks, soils and dust at scales of less than 0.04 inch (1 millimeter). This diagram shows how materials analyzed by ChemCam during the first 100 Martian days of the mission (Aug. 5, 2012, to Nov. 16, 2013) differed with regard to hydrogen content (horizontal axis) and alkali (vertical axis).
Rocks analyzed in Gale Crater during that period show a variety of compositions, as reflected here on the alkali axis. These rocks are all characterized by a low signal for hydrogen. Soils, on the other hand, are characterized by a dynamic range in both alkali and hydrogen content. Cluster analysis of the ChemCam data set has revealed the presence of two soil components and a mechanical mixing line between them. One of the two soil components is coarse-grained soils (high alkali, low hydrogen), which are very likely made of rock fragments deposited as part of an alluvial fan from Peace Vallis on the north rim of Gale Crater. The other is finer particles with low alkali and high hydrogen, which are typically found in aeolian (wind-related) bedforms, such as the "Rocknest" deposit of windblown dusty sand where Curiosity scooped up samples for analysis by laboratory instruments. The composition of dust measured by ChemCam is similar to that of a low-alkali portion of the fine soils.
ChemCam observes spectral characteristics of dust on every first shot at any target analyzed on Mars.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Mars Science Laboratory Project and the mission's Curiosity rover for NASA's Science Mission Directorate in Washington. The rover was designed and assembled at JPL, a division of the California Institute of Technology in Pasadena.
More information about Curiosity is online at http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/.