Spirit became stuck in soft soil at Troy on Mars. The rover was resting on a patch of loose, weakly cohesive material on the west side of a feature called Home Plate.
The trouble began on May 1, 2009, after Spirit had already far exceeded its planned 90-sol mission. Its wheels sank into the soil, which concealed iron(III) sulfate, including the mineral jarosite. Because that material offered very little traction, attempts to drive out repeatedly failed.
NASA spent roughly eight months testing escape strategies with rover replicas and computer models on Earth. In January 2010, engineers concluded that Spirit was probably irrecoverably stuck and converted it into a stationary science platform. “Troy” is the location name, while Home Plate is the nearby geological feature—an easy distinction to miss. Spirit later fell silent in March 2010, and NASA ended recovery efforts in 2011.