Opportunity is inside "Marathon Valley" on the west rim of Endeavour Crater.

The rover is positioned on a steep slope with an approximately 19-degree northerly tilt for improved solar array energy production.

On Sol 4215 (Dec. 2, 2015), the robotic arm was used to collect imaging of the Rock Abrasion Tool (RAT) bit.

That imagery will allow the assessment of remaining grind bit life before the next RAT grind. Also, with the robotic arm out of the way, unobstructed Panoramic Camera (Pancam) images of the surface target, "Pvt. Hugh McNeal" were taken.

Finally, the Alpha Particle X-ray Spectrometer (APXS) was placed on the surface target by the robotic arm for the next sol's integration. More Pancam imagery was collected over subsequent sols.

On Sol 4219 (Dec. 6, 2015), the RAT was used to brush the surface target and then the APXS was placed, slight offset, on the surface target.

On Sol 4220 (Dec. 7, 2015), another tuck of the robotic arm was done to allow unobstructed images of the surface to be taken. Then, the Microscopic Imager (MI) was used to collect a detailed surface mosaic, followed by the placement of the APXS for a short integration.

On the next sol, another MI mosaic was collected and more color Pancam panoramas were taken.

As of Sol 4221 (Dec. 8, 2015), the solar array energy production was 419 watt-hours with an atmospheric opacity (Tau) of 0.430 and an improved solar array dust factor of 0.660.

Total odometry is 26.49 miles (42.63 kilometers), more than a marathon.