Engineers continue to have difficulty getting the rover to make significant progress toward a ridgeline destination due to high slippage that Spirit experiences on the sandy, sloped terrain. Spirit has been in roughly the same spot for the past 30 sols.

Since temporarily getting a potato-sized rock caught in the right rear wheel on sol 339, engineers have been careful to monitor the slip as Spirit drives. If the wheels slip too much, engineers stop the drive to avoid the possibility of picking up another rock as Spirit spins and digs with its wheels.

The opacity of the sky - or how much light does not shine through the atmosphere - has been higher than normal in the past week due to local dust disturbances.

Higher opacity means less energy for the solar-powered rover. However, despite the recent increase in opacity, Spirit has had adequate energy (with a safe margin) to continue normal operations.

The rover's power bus return is a collection of wires designed to carry current back to the rover power source (battery or solar array). Electrical current between Spirit's chassis and the power bus return changed on sol 342 from zero volts to 0.1 volts.

The small change in voltage coincided with powering of heater circuits on the instrument deployment device (or rover arm). This confirms that there is a short (unexpected metal-to-metal contact) between the power bus return and the chassis, as had been suspected since October.

The short is somewhere on the return side of the rover arm heater circuits. The presence of this short does not affect daily operations. It does, however, take away one layer of protection should Spirit have a short to the chassis somewhere else on Spirit.

Sol Summaries:

On sol 353, Spirit continued inspecting the rock "Champagne" and performed a Moessbauer spectrometer integration on two Champagne targets.

On sol 354, Spirit used its rock abrasion tool to brush the dust off a target on Champagne, then used the microscopic imager and the alpha particle X-ray spectrometer to analyze the dust-free spot.

On sol 355, Spirit used the rock abrasion tool to grind into Champagne, then placed the alpha particle X-ray spectrometer in the hole for an overnight observation.

On sol 356, Spirit continued using its alpha particle X-ray spectrometer on the hole drilled by the rock abrasion tool hole.

On sol 357, Spirit changed tools to the Moessbauer spectrometer and placed it in the rock abrasion tool hole for a long integration.

On sol 358, Spirit took microscopic images of the rock abrasion tool hole, then stowed the rover arm. Engineers then attempted a short drive that would have allowed Spirit to image the rock abrasion tool hole from a distance. The drive did not reach the intended position because of slippage.

Sol 359 was a "restricted" sol, meaning that engineers had to plan this sol without knowing the results of the sol 358 sequence. Consequently, it was a relatively simple day that included routine atmospheric science and miniature thermal emission spectrometer observations. Sol 359 ended on Jan. 6.

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