The right front wheel previously had an episode of balkiness but this week the motor that turns the wheel stopped working, the space agency's Jet Propulsion Laboratory said in a statement.
"It is not drawing any current at all," Jacob Matijevic, rover engineering team chief, said in the statement.
Spirit and its twin, Opportunity, landed on opposite sides of the Red Planet in January 2004 and have long outlasted missions originally planned to span 90 Martian days, which are a different length than Earth days.
Spirit's new wheel problem occurred this week during the rover's 779th Martian day.
Saturday, March 18, 2006
Spirit wheel not working
One of the rovers wheel is stuck. The other five wheels are working though, dragging Spirit along up a crater slope. (HT KFWB/LATIMES here.