NASA has announced a plan to extricate its rover Spirit, which has been stuck in a Martian sand trap since April. The space agency will begin transmitting commands to the exploration robot on Monday. Based on tests conducted on Earth this spring that simulated conditions at the Martian site, researchers do not expect the effort to be quick or easy. “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. “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,” McCuistion said. “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.”