Unfortunately, due to the steep slopes and lack of traction when driving in this terrain, the rover experienced up to 50 percent slip during parts of its traverse. It ended up more than 50 centimeters (about 20 inches) downslope from the planned final position.

This left the rover close to the edge of its safe terrain zone.

For sol 205, the team shifted its objective from Shag to another target, "Auk," on the other side of Ellesmere. Auk, though farther from the rover's current position, was of higher scientific priority, in safer terrain, and more accessible to the rover arm.

To avoid the significant slip observed during turns in place, the traverse was planned as a tight-radius turn covering 1.6 meters (5.2 feet). Mindful of the uncertainties inherent in navigating in this terrain, planners designed the traverse to cover only a portion of the total distance to Auk.

This proved to be prudent, since the rover again ended up slipping more than 50 percent during most of its drive, with little progress away from dangerous terrain.

On the bright side, analysis of the drive indicated that the rover was getting better traction during its last moves.

On sol 206 the rover was commanded to perform a drive to turn away from its cross-slope orientation and move upslope toward Auk. The drive succeeded.

After the slips of the sol 205 traverse, this traverse managed nearly all of the desired yaw response to get the rover pointed uphill and then found good traction to deliver the rover more than a meter (3.3 feet) farther upslope.

Serendipitously, the rock directly in front of the rover at the end of the drive proved to be so interesting to the science team that efforts were redirected to study it. The rock was dubbed "Escher."

On sol 207 the team entered restricted planning. This happens when the timing of the rover's sol on Mars and our day in the California time zone get out of sync due to the nearly 40-minute difference in length of Earth days and Mars sols.

The afternoon downlink arrives at JPL too late in the day to plan the next sol unless the team works through the night.

Instead of staying up all night, the team plans with restrictions that forbid rover movement or arm activity on a sol immediately following a sol on which the rover has moved.

This gives additional time for the data to become available so that planners can use up-to-date knowledge about the rover's position and orientation.

So, rather than any driving on sol 207, Opportunity conducted remote-sensing work, including atmospheric observations and panoramic camera imaging of several features.

For sol 208, which ended on Aug. 25, Opportunity drove again. It bumped forward to put Escher well within the arm's work volume.

The sol also included panoramic camera imaging of Escher and of a trench created by Opportunity's prior wheel movements in the vicinity. Opportunity slept deeply on the night of sol 208 for the second night in a row.

The purpose of successive deep sleeps was to align the deep-sleep nights with poorer overnight Mars Odyssey passes, leaving the rover ready to take advantage of higher-volume passes on alternate nights.

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