Despite the effects of a harsh Martian winter, JPL engineers are hoping to revive the Mars rover Spirit after losing contact with it on March 22.
Spirit became stuck 18 months ago in loose soil south of the planet's equator.
Unable to shift its solar panels to adapt to changing sunlight conditions, the rover entered a low-power mode that was intended to preserve vital functions but that prevented communication with Earth.
But now JPL has been sending signals into space to try to link up with Spirit as sunlight increases with the dawn of Martian spring. Seven years after its Jan. 4, 2004, arrival on the surface of Mars, Spirit's likelihood of returning to service remains unknown, said JPL rover engineer Bill Nelson.
In the best-case scenario, Spirit will have been able to preserve its mission clock, which provides the timekeeping needed to align with satellite-communication signals.
Just as likely, however, is that Spirit's clock has been reset, so engineers have begun broadcasting signals from Earth that override the clock and force a response.