The rover's goal was to zigzag back and forth across a steep slope toward an outcrop nicknamed "Nevada," where scientists had hoped to do scientific analysis and collect high-resolution, panoramic images of the cliff face known as "Cape Verde."

It was not to be. On Opportunity's 1,600th Martian day (July 24, 2008) of exploration, the motor on the left front wheel suddenly drew an unexpectedly high level of current that exceeded the maximum limit.

The incident was unusual, and the rover immediately halted the drive. A similar event had occurred just prior to the failure of the right front wheel on Spirit, Opportunity's twin on the opposite side of Mars.

On Martian day, or sol, 1602 (July 26, 2008), rover engineers conducted tests of electrical resistance to determine if the motor on Opportunity's left front wheel had a short or an open circuit. They also steered the wheel and looked for unseen, natural obstructions near the wheel. Results from both tests indicated no problems.

Engineers next performed a more aggressive set of tests on sol 1604 (July 28, 2008) by commanding Opportunity to rotate the wheel using the motor that generated the anomaly. Again, test results showed no issues.

Engineers have not yet determined what caused the anomaly. Though the wheel appears to have gone back to functioning normally, the condition of its drive motor is uncertain. Because of concerns that the rover might not be able to get out of the crater using only five wheels should the left front wheel fail, team members have decided not to continue toward Nevada.

Instead, they plan to finish collecting images of Cape Verde from the rover's current position, then leave the crater as quickly as possible.

During the past week, Opportunity also took several panoramic-camera images of targets along the face of Cape Verde and completed two measurements of argon in the Martian aosphere using the alpha-particle X-ray spectrometer. Scientists use the measurements of changing argon levels to map seasonal air flows.

Otherwise, Opportunity is healthy and all subsystems are performing as expected. The latest available power readings from sol 1605 (July 29, 2008) showed power at 377 watt-hours (400 watt-hours would be enough energy to light a 100-watt bulb for four hours).

Sol-by-sol summary

In addition to making daily measurements of dust-related changes in visibility with the panoramic camera, Opportunity completed the following activities:

Sol 1600 (July 25, 2008): While driving toward Nevada, Opportunity's left front wheel drew unexpectedly high electrical current. Opportunity acquired images during and after the drive with the hazard-avoidance and navigation cameras. The rover relayed data to NASA's Odyssey orbiter for transmission to Earth.

Sol 1601: Opportunity acquired full-color images, using all 13 filters of the panoramic camera, of rock exposures dubbed "Playfair," "Eugene Smith," and "King."

Sol 1602: First thing in the morning, Opportunity acquired four, time-lapse, movie frames in search of clouds with the navigation camera. Opportunity conducted diagnostic tests of the left-front-wheel motor in search of electrical shorts or open circuits. The rover also steered the wheel and then acquired images in search of terrain obstructions with the hazard-avoidance and panoramic cameras. After sending data to Odyssey, the rover integrated measurements of aospheric argon using the alpha-particle X-ray spectrometer.

Sol 1603: Opportunity took images with the rear hazard-avoidance cameras and a 5-by-1 tier of images with the navigation camera.

Sol 1604: Upon awakening, Opportunity took thumbnail images of the sky for calibration purposes with the panoramic camera. Opportunity performed more diagnostic tests, rotating the left front wheel and taking images with the hazard-avoidance cameras. After sending data to Odyssey, the rover measured aospheric argon with the alpha-particle X-ray spectrometer.

Sol 1605: In the morning, Opportunity acquired panoramic-camera images of a rock exposure called "Bretz," acquired images with the rear hazard-avoidance cameras, and acquired a 3-by-1 tier and a 5-by-1 tier of images with the navigation camera. The rover acquired new, full-color, panoramic-camera images of Eugene Smith.

Sol 1606 (July 30, 2008): Opportunity took thumbnail images of the sky with the panoramic camera and monitored dust on the rover's mast. With the panoramic camera, the rover completed a sky survey and acquired overlapping, super-resolution images of a rock exposure known as "Siever" (the overlapping images compensate for dust on the camera lens). Opportunity took panoramic-camera images of an outcrop known as "McKee." Plans for the following morning called for the rover to survey the horizon and take spot images of the sky for calibration purposes with the panoramic camera.

Odometry: As of sol 1606 (July 30, 2008), Opportunity's total odometry was 11,726.21 meters (7.29 miles).

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