Halos in Martian Sandstone

Pale zones called "halos" border bedrock fractures visible in this 2015 image from NASA's Curiosity Mars rover which has been darkened (a previously released image can be seen at PIA20268). Measurements overlaid on the image offer a sense of scale for the size of these fractures. The rover team determined that the halos are rich in silica, a clue to the duration of wet environmental conditions long ago. The location is on the lower slope of Mars' Mount Sharp. Curiosity's Navigation Camera (Navcam) acquired the component images of this mosaic on Aug. 23, 2015, during the 1.083rd Martian day, or sol, of the mission. The location is along the rover's path between "Marias Pass" and "Bridger Basin." In this region, the rover has found fracture zones to be associated with rock compositions enriched in silica, relative to surrounding bedrock. https://photojournal.jpl.nasa.gov/catalog/PIA21649