After spotting Pot of Gold, Spirit‘s handlers zoomed in for a closer look, revealing the crags and cracks caused by erosion. Scientists aren’t sure whether the erosion resulted from mechanical processesâ€the action of wind, sand or waterâ€or whether a chemical ate through the rock over time.
With its weight on its back four wheels, Spirit used one of its front wheels as a shovel, scuffing away at the soft dust of Gusev. This action uncovered salts that could have been left behind when saltwater percolated up from the ground and evaporated.
Spirit discovered this crusty rock, nicknamed Pot of Gold, poking up from the dust at the base of the Columbia Hills. The rock contains gray hematite, a mineral that forms in the presence of water. Scientists suspect that Pot of Gold might have rolled down from higher on the slope because it isn’t anchored in place.
The Journey Ahead
For Sojourner, the tiny robot that roamed Mars in 1997, the rocks here at the edge of the Bonneville Crater might have been insurmountable. Today’s larger, more advanced rovers can handle rougher terrain, but NASA engineers were still wary of sending Spirit on its trek to the Columbia Hills, seen here in the distance.