Over the Fourth of July weekend, Spirit completed a robotic-arm campaign which had some surprising results.
It turned out that targets at "Independence Rock" seem to have less iron than expected. This result prompted the science team to take a closer look.
On sol 536 (July 6), because the grinding teeth on the rock abrasion tool are worn, the rover team decided to remove some of the surface area by scuffing it with the front left wheel.
The scuff worked as follows:
