These images and overlay bar charts from the Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover indicate where some high-potassium material is localized within mineral veins at "Garden City."

The two images are from ChemCam's Remote Micro-Imager. Each covers an area just over an inch wide (scale bars are in millimeters) in veins at the Garden City site on lower Mount Sharp. The overlay charts show comparisons of potassium (blue) and iron (red) in the mineral veins' compositions determined by reading the spectra of light induced by zapping points in each area with ChemCam's laser.

Mineral veins such as these form where fluids move through fractured rocks, depositing minerals in the fractures and affecting chemistry of the surrounding rock. The thin layer of dark fracture-filling material in the image on the right contains much more potassium than the other local material on the left, indicating either different fluid compositions or local variations in the rock.

The image on the left was taken on April 4, 2015, during the 946th Martian day, or sol, of Curiosity's work on Mars. The image on the right was taken on Sol 936, on March 25, 2015.

A broader view of the prominent mineral veins at Garden City is at PIA19161.

ChemCam is one of 10 instruments in Curiosity's science payload. The U.S. Department of Energy's Los Alamos National Laboratory, in Los Alamos, New Mexico, developed ChemCam in partnership with scientists and engineers funded by the French national space agency (CNES), the University of Toulouse and the French national research agency (CNRS). More information about ChemCam is available at http://www.msl-chemcam.com.

More information about Curiosity is online at http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/.