This image shows Rocks explored by the Rover.
Click on image for full size
Image from: NASA/JPL
Rock weathering on Mars
The rocks explored by the Mars Pathfinder's Rover are classified into two groups according to how they eroded. Rocks put in place as a result of an impact which forms a crater are usually much less eroded than rocks put in place by water.
For example,
Yogi was a bright rock and had many pits and holes. Barnacle Bill was a dark rock and not well eroded. This suggests that Barnacle Bill was put in place as a result of an impact.
By figuring out the conditions under which the rocks were deposited, scientists hope to learn where the rocks came from, and what happened to the Martian water.
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