NASA said Spirit’s other four wheels all drove forward in the most recent attempt to extricate Spirit from the sand trap but that positive note was tempered by the fact that while Sprit moved forward, it also dug in a little further. According to NASA, the rover moved 2 millimeters (0.08 inch) forward and 4 millimeters (0.16 inch) downward. That ratio of forward to downward movement is well below what would be necessary over longer distance for extrication, NASA noted.

Spirit has been stuck in a place NASA calls "Troy" since April 23 when the rover's wheels broke through a crust on the surface that was covering brightly-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap.

Even in the best of conditions, moving the stuck rover could take weeks.

Still there is little doubt the highly successful rover might be on its last legs regardless of the approaching winter. NASA said in February, it will assess Mars missions, including Spirit, for their potential science versus costs to determine how to distribute limited resources.