Discolored Fracture Zones in Martian SandstonePale zones called "halos" border bedrock fractures visible in this 2015 image from NASA's Curiosity Mars rover. 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.
Image Credit: NASA/JPL-Caltech