Opportunity is inside "Marathon Valley" on the west rim of Endeavour Crater. The rover is positioned on steep slopes for improved solar array energy production. The near-term object is to position the rover to be able to grind a high-value surface target with the Rock Abrasion Tool (RAT).

This target may hold some of the clues as to the origin of the clay spectral signature detected in Marathon Valley.

On Sol 4222 (Dec. 9, 2015), Opportunity bumped back about 12 feet (3.65 meters) to set up for an approach to this target on a very steep slope.

On the next sol, the rover bumped forward about 28 inches (70 centimeters), but because of the steep slopes the drive stopped as wheel currents exceeded protective set points for this steep terrain.

A second attempt was made on the next sol to approach this same target. Again the steep terrain caused the drive to stop after only 3.6 feet (1.1 meters) of wheel motion. Slips as high as 50 percent (not uncommon for this steep terrain) were seen on the last drive step.

The rover used the next sol to perform a robotic arm salute to allow unobstructed imagery in front of the rover.

Then on Sol 4227 (Dec. 14, 2015), Opportunity backed down slope about 10 feet (3 meters), collecting both pre-drive and post-drive imagery.

On the next sol, the rover drove about 14 feet (4.4 meters) to approach the target from a more lateral direction. An approach bump is planned for the next sol.

As of Sol 4221 (Dec. 8, 2015), the solar array energy production was 407 watt-hours with an atmospheric opacity (Tau) of 0.438 and an improved solar array dust factor of 0.660.

Total odometry is 26.50 miles (42.65 kilometers), more than a marathon.