Scientists working with NASA's Mars Exploration Rover Spirit decided to examine this rock, dubbed "Wishstone," based on data from the miniature thermal emission spectrometer. That instrument's data indicated that the mineralogy of the rocks in this area is different from that of rocks encountered either on the plains of Gusev Crater or in bedrock outcrops examined so far in the "Columbia Hills" inside the crater. Spirit used its rock abrasion tool first to scour a patch of the rock's surface with a wire brush, then to grind away the surface to reveal interior material. Placement of the rover's alpha particle X-ray spectrometer on the exposed circle of interior material revealed that the rock is rich in phosphorus. Spirit used its panoramic camera during the rover's 342nd martian day, or sol, (Dec. 18, 2004) to take the three individual images that were combined to produce this false-color view emphasizing the freshly ground dust around the hole cut by the rock abrasion tool.
Unusually Rich in Phosophorus
The graph in figure 1 compares the elemental makeup of a rock dubbed "Wishstone" with the average composition of rocks that Spirit examined on the western spur of the "Columbia Hills." Wishstone lies farther into the hills than that spur. It is richer in phosphorus than any other Mars rock ever examined. Scientists plan to examine other rocks near Wishstone to help explain the significance of the high phosphorus concentration. The vertical scale is the ratio of the concentration of an element in the hills rocks to the concentration of the same element in a typical volcanic rock from the plains that Spirit crossed to reach the hills.