The long-lived rover Spirit is stuck in the sand on Mars, and controllers at the Jet Propulsion Laboratory in La Canada Flintridge are scrambling to find a way to extricate the vehicle before it becomes entombed on the Red Planet.
"This is quite serious," said JPL's John Callas, the project manager for Spirit and its twin, Opportunity. "Spirit is in a very difficult situation. We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again."
The rover, which landed on Mars in 2004 for what was expected to be a three-month mission, was driving toward a pair of volcanic features named Von Braun and Goddard when it became ensnared in soft sand.
Over the last few days, controllers at JPL have tried everything they know to free the vehicle, but its wheels have sunk deeper into the sand.
Making the process more difficult is that only five of Spirit's six wheels are working because of a mechanical problem that occurred three years ago.
Callas said project scientists were concerned that efforts to free the rover might have dug it so deeply into the sand that its belly pan is resting on the Martian surface.
He said such a predicament would make it harder for the wheels to get the necessary traction to escape.
Callas said engineers had decided to stop trying to drive Spirit for now.
Instead, they will attempt to replicate the rover's plight in what is known as the "sandbox," a lab at JPL where scientists try to simulate conditions on Mars.
"We're looking at re-landscaping the sandbox to re-create the situation," Callas said. "We can't send anyone to Mars, so we're bringing Mars to Earth."
For Spirit, this is the latest in a season of problems. Earlier this year, it suffered a series of memory lapses that engineers have been trying to diagnose.
The only good news of late has been a series of sciroccos that cleaned the dusty surface of the rover's solar panels. So Spirit will have plenty of power available when, or should, engineers come up with a strategy to dig it out.
Callas said the situation, while difficult, might not be life-threatening to the rover. If it is unable to move, Spirit could still perform some science, at least until winter arrives, when the sun is low on the horizon. It just wouldn't be a rover anymore.
Whenever they die, Spirit and Opportunity will be regarded as among the most successful instruments NASA has built.
Besides outlasting every prediction for longevity, they have conducted numerous experiments that helped to clarify Mars' watery history. The rovers found that the Martian surface once had standing, shallow inland seas.
But they found no proof that water had been on the surface for billions of years.