Opportunity is within 'Marathon Valley' on the west rim of Endeavour Crater conducting a walk-about survey for clay minerals.

The rover's current location within Marathon Valley with its high walls to the north and west presents a challenge for low-elevation Ultra-High-Frequency (UHF) relay passes to the west. On Sol 4141 (Sept. 17, 2015), no data were received as the orbiter's flight path was below the elevation on the valley ridgeline.

On that sol, the rover did successfully perform an in-situ science campaign on the surface target, 'Pvt. George Gibson' that included a Microscopic Imager (MI) mosaic and the placement of the Alpha Particle X-ray Spectrometer (APXS). Some of those data were received on subsequent sols. On Sol 4144 (Sept. 20, 2015), another MI mosaic was taken and the robotic armed stowed for a future drive.

Once again, the high ridgeline of the valley obscured the low-elevation pass on Sol 4145 (Sept. 21, 2015), and little data were received.

On Sol 4146 (Sept. 22, 2015), Opportunity was configured from RAM-only operation to Flash as a planned test of the non-volatile storage system. The drive on that sol completed successfully, but an amnesia event with Flash prevented a return of drive-related data on that sol. Those data are expected to be received on subsequent sols. The plan forward is to continue to operate in Flash for one week in order to gain information and statistics on the state of the Flash storage system.

As of Sol 4146 (Sept. 22, 2015), the solar array energy production was 335 watt-hours with an atmospheric opacity (Tau) of 0.539 and a solar array dust factor of 0.569.

Total odometry is (26.43 miles) 42.53 kilometers, more than a marathon.