Opportunity is exploring the south side of 'Marathon Valle' located on the rim of Endeavour crater. The rover is up on the slopes of 'Knudsen Ridge'.

The objective is to identify specific outcrops for evidence of clay minerals. Opportunity recently backed down off of some of the steepest slopes of the mission and has begun the move to new locations to the southwest.

Supporting Navigation Camera (Navcam) and Panoramic Camera (Pancam) images were collected on Sols 4318 and 4319 (March 17 and March 18, 2016), to identify future targets and drive paths.

On Sol 4320 (March 19, 2016), the rover drove about 31 feet (9.5 meters) to the southwest towards areas of putative phyllosilicate clays. Again, supporting Navcam and Pancam panoramas were collected after the drive to set up for the next drive.

On Sol 4323 (March 22, 2016), Opportunity headed due west about 41 feet (12.5 meters). An atmospheric argon measurement with the Alpha Particle X-ray Spectrometer (APXS) was sequenced for that evening.

earlier report
Rover Goes Back Downhill
Previously during sols 4311-4316, Opportunity was exploring within 'Marathon Valley' on the rim of Endeavour crater. The rover is up on the slopes of 'Knudsen Ridge.'

The primary objective is to examine specific outcrop types for evidence of clay minerals. The current objective had been to reach the surface science target 'Pvt. Joseph Whitehouse' (named after a member of the Corps of Discovery).

However, with slopes in excess of 30 degrees and some gravel terrain under the wheels, Opportunity was unable to reach the intended target.

On Sol 4311 (March 10, 2016), the rover made only 3.5 inches (9 centimeters) of progress after almost 66 feet (20 meters) of commanded wheel motion. This was the third attempt to reach this very interesting target.

In the end, the team decided to abandon this target and back away. On Sol 4313 (March 12, 2016), the rover backed down from this target with a 7-foot (2-meter) drive.

Documentary imagery in both Navigation Cameras (Navcams) and Panoramic Cameras (Pancams) where collected. An overnight Alpha Particle X-ray Spectrometer (APXS) measure of atmospheric argon was also collected.

More readouts of Flash memory were performed. On Sol 4316 (March 15, 2016), the rover moved further downhill, driving about 22 feet (6.7 meters) north to set up for a longer drive towards the next science target along Knudsen Ridge.

As of Sol 4323 (March 22, 2016), the solar array energy production was 576 watt-hours with an atmospheric opacity (Tau) of 0.423 and an improved solar array dust factor of 0.764.

Total odometry is 26.53 miles (42.69 kilometers), more than a marathon.