This collage shows the variety of soils found at landing sites on Mars. The elemental composition of the typical, reddish soils were investigated by NASA's Viking, Pathfinder and Mars Exploration Rover missions, and now with the Curiosity rover, using X-ray spectroscopy. The investigations found similar soil at all landing sites. In addition, the soil was usually unchanged over the traverse across the Martian terrain made by both Mars Exploration Rovers.
The Mars Exploration Rover Spirit's landing region in Gusev Crater is seen in both pictures at top; Viking's landing site is shown at lower left; and a close-up of Curiosity's Gale Crater soil target called "Portage" is at lower right.
In Gusev Crater, several white subsurface deposits were excavated with Spirit’s wheels and found to be either silica-rich or hydrated ferric sulfates.
Image credit: NASA/JPL-Caltech