On Sol 105, Opportunity acquired a series of microscopic images of Lion Stone and the surrounding soil. The stone has become a science target owing to its darker color compared to the surrounding area--a feature that hints at a different chemical composition or mechanism of formation.

The rover then went on to collect a short M�ssbauer integration on the rock during the day, performed a tool change to the alpha particle X-ray spectrometer in late afternoon, and acquired that integration in the early morning of Sol 106. That sol also included additional microscopic images and a successful "bump" maneuver to reposition the rover so the top of Lion Stone was in position for the rock abrasion tool on Sol 107.

Remote sensing was also acquired during the two sols, including panoramic camera images of the heatshield that protected Opportunity during its toasty trip through the martian atmosphere. The heatshield impacted approximately 250 meters (about 820 feet) south of Endurance Crater.

Plans for Sol 107 are to perform a rock abrasion tool grind on Lion Stone with subsequent microscopic images and alpha particle X-ray spectrometer overnight integration. The tentative plan for Sol 108 is to leave Lion Stone and begin traverse to observation position 2 on the southeastern rim of Endurance Crater.

Several days ago, the rover was commanded to go into its first 'deep sleep', a potentially risky maneuver that it might not fully awaken from. Deep sleep refers to a power-conserving mode which particularly renders thermal control 'off' during the very cold martian night. Opportunity however successfully awakened on sol 102. This set of activities was initiated to conserve the energy that is being used by the instrument arm's stuck-on heater switch.

During deep sleep, rover planners power off the main electronics at night and open the switches that supply battery power to the main power bus, and in turn nearly all the secondary electronics. In particular this removes power input to the Rover Power Distribution Unit, which normally supplies power to the stuck-on heater.

With the Rover Power Distribution Unit input turned off, the heater cannot burn any energy either. In the morning, when the sun strikes the solar panel array, the Battery Control Board resets and connects the batteries to the main power bus again. At this time, the stuck-on heater again draws power, but this will only be for a few hours in the morning instead of all night.

The most vulnerable instrument to the cold martian nights is the miniature thermal emission spectrometer. With a cutoff of the power electronics, its heater cannot keep it warm overnight. Data returned on sol 102 showed the temperature reached -46 degrees Celsius (-50.8 degrees Fahrenheit), a bit warmer than the spectrometer's lowest proven temperature for functionality, -50 degrees Celsius (-58 degrees Fahrenheit).

All systems are healthy and Opportunity's batteries are near a full state of charge.

Opportunity won't be heading into Endurance Crater any time soon. The rover will spend the next few weeks traversing the rim of the crater, collecting extensive sets of Pancam images and Mini-TES spectra from at least two additional vantage points, and perhaps examining a few interesting rocks it encounters along the way. Only after this survey is complete will mission planners decide whether - and when - to send the rover into the crater.

That decision is a complex one, which must weigh the potential scientific gain of entering the crater against the potential risk of doing so. Even if the rover driving team decides that it is safe to send Opportunity in to Endurance Crater, they may not be equally confident that they can get it back out. By studying the interior of the crater from different angles and different vantage points around the rim, MER mission planners will be able to weigh the options.

Related Links
Mars Rovers at JPL
Mars Rovers at Cornell

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