Well? what do you think it is?
Both pictures show the same object, but from different angels.
Edit: Sorry! A little more info would be helpful, huh? The bottom image is from Sol 65 of Spirit's approach to Bonneville. The one here is from Sol 66 on the rim of the crater "Bonneville". Both pics can be found on the JPL Rover website under the Raw images, front nav cam... Again, sorry.