NASA’s Mars Exploration Rover Spirit acquired this mosaic on the mission’s 1,202nd Martian day, or sol (May 21, 2007), while investigating the area east of the elevated plateau known as “Home Plate” in the “Columbia Hills.” The mosaic shows an area of disturbed soil, nicknamed “Gertrude Weise” by scientists, made by Spirit's stuck right front wheel.
The trench exposed a patch of nearly pure silica, with the composition of opal. It could have come from either a hot-spring environment or an environment called a fumarole, in which acidic, volcanic steam rises through cracks. Either way, its formation involved water, and on Earth, both of these types of settings teem with microbial life.
The image is presented here as a vertical projection, as if looking straight down, and in false color, which brings out subtle color differences.