Opportunity is inside ‘Marathon Valley’ on the west rim of Endeavour Crater. The rover is positioned on steep, north-facing slopes for improved solar array energy production.

The winter solstice occurred on Sol 4246 (Jan. 3, 2016), although solar insolation already started to improve. The near-term objective 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 4229 (Dec. 16, 2015), Opportunity bumped about 14 inches (35 centimeters) to set up for an extended in-situ (contact) science campaign through the holiday season. Over the holiday period, Opportunity proceeded to use the robotic arm to collect Microscopic Imager (MI) mosaics of the surface targets as well as place the Alpha Particle X-ray Spectrometer (APXS) for surface elemental analysis. Winter power levels and late Odyssey passes made planning difficult with some sols being used as recharge days.

On Sol 4234 (Dec. 22, 2015), Opportunity was able to use the RAT to brush the surface target ‘Pvt. John Potts.’ This was followed with more MI mosaics and APXS measurements. On Sol 4244 (Jan. 1, 2016), the RAT was used again, this time to grind (1 millimeter) into the surface target. More MI mosaics and APXS elemental analysis of the ground target followed.

As of Sol 4246 (Jan. 3, 2016), the solar array energy production was 449 watt-hours with an atmospheric opacity (Tau) of 0.414 and an improved solar array dust factor of 0.658.

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