A weak signal was last heard from Pathfinder on October 8, and efforts since then to raise the spacecraft have failed. Engineers believe that the spacecraft's battery ran out, resetting electronics within the lander and causing it to lose track of time. Cold temperatures from the onset of Martian winter may have also contributed to the problem. Pathfinder team members hoped to hear from the spacecraft again to discover the fate of its rover, Sojourner. The rover was programmed to return to the lander and circle it if it did not receive communications from ground controllers after several days.
Engineers believe the rover eventually failed, because of mechanical problems or a loss of power.