Spirit is currently straddling the edge of a 26-foot wide crater that has been filled with a deposits created long ago by a steam or hot water environment. The deposits have formed distinct layers, each with their own composition and tint. The layers are capped by a crusty soil. It is this soil that Spirit’s wheels broke through, getting mired in a layer of slippery sand. After a few attempts to get Spirit out in the subsequent days, the rover began sinking deeper in the sand trap.

Researchers expect the extraction process to be long and the outcome uncertain based on tests here on Earth this spring that simulated conditions at the Martian site. Engineers plan to continue escape efforts until early 2010.

"This is going to be a lengthy process, and there's a high probability attempts to free Spirit will not be successful," said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington. "Mobility on Mars is challenging, and whatever the outcome, lessons from the work to free Spirit will enhance our knowledge about how to analyze Martian terrain and drive future Mars rovers…Spirit has provided outstanding scientific discoveries and shown us astounding vistas during its long life on Mars, which is more than 22 times longer than its designed life."

Despite being trapped, Spirit has been helping NASA find out more about Mars. Using a robotic arm and camera mast, the rover has augmented earlier discoveries it made indicating ancient Mars had hot springs or steam vents, possible habitats for life. Even if the escape attempts fail, Spirit might still produce new scientific findings about Mars.

"The soft materials churned up by Spirit's wheels have the highest sulfur content measured on Mars," said Ray Arvidson a scientist at Washington University in St. Louis and deputy principal investigator for the science payloads on Spirit and Opportunity. "We're taking advantage of its fixed location to conduct detailed measurements of these interesting materials."

Spirit and its twin rover Opportunity landed on Mars in January 2004. They have explored Mars for five years, far surpassing their original 90-day mission. Opportunity currently is driving toward a large crater called Endeavor.

For updates about Spirit's progress, visit http://www.nasa.gov/rovers

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