Time is running out for NASA's stuck Mars rover Spirit as engineers prepare to make their final attempts to rescue the hard-luck robot from its Martian sand trap.
Spirit spun its wheels extremely slowly Tuesday in yet another attempt to extricate itself from the wheel-deep sand it has been stuck in since May 2009. Engineers are studying the results of that drive to decide which of the few remaining options to try next.
So far, nothing NASA has tried has worked to free Spirit.
"Earlier drives in the past two weeks using wheel wiggles and slow wheel rotation produced only negligible progress toward extricating Spirit," NASA officials said in an update.
Spirit and its robotic twin have been exploring different parts of Mars since January 2004 and far outlasted their initial 90-day life expectancy. Opportunity is working fine on the plains of Meridiani Planum and headed for a giant crater called Endeavour, but Spirit has seen better days.
The rover's wheels slipped into deep Martian sandon May 6, 2009 and have been stuck in place ever since. Spirit's robotic arm is too weak to push the rover up and out, and attempts to drive out have repeatedly failed, rover engineers have said.
Spirit's bum right-front wheel hasn't worked properly since mid-December (when engineers switched it back on for the first time since 2006) and the rover's right-rear wheel has been broken since November. That leaves the six-wheeled rover with only four working wheels, and only one operating wheel on the right side.
Engineers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., are now looking at their short list of options for rescuing Spirit.
Those options include driving Spirit backwards and using the robotic arm to sculpt the Martian sand directly in front of the rover's left front wheel – the only working wheel within reach. It could take several days to try either option, and time is short since winter is approaching on Mars.
The amount of power produced by Spirit's solar panels has been dropping each day as the Martian days, or sols, grow shorter in southern Mars.
"If NASA does determine that the rover will not be able to get away from its current location, some maneuvers to improve the tilt toward the winter sun might be attempted," mission managers said.