Mired in dry quicksand, chilled to the bone by the martian winter, and silenced by its feeble wintertime supply of solar power, the Spirit rover should have, with luck, beamed its first radio message since 22 March back to Earth as spring breaks out. No such luck.
On 20 September, Mars rover team leader Steven Squyres of Cornell University said, "I firmly believe that in the next 4 to 6 weeks, we're going to hear from that vehicle." That was 8 weeks ago. And the weekly rover update has long included a comforting line about how the ascending springtime sun could be recharging Spirit's depleted batteries, producing an "increasing likelihood of hearing from Spirit in the period ahead." This week that line was dropped.
"There's a good possibility it died, and we'll never hear from it again," Squyres now says. Guaranteed 90 days of roving, Spirit spent 6 years roaming giant Gusev crater analyzing rocks and soil. Its early days were a bit of a bust, having targeted a lakebed that turned out to be a boring lava plain. But its long life let it rove into nearby hills where it discovered long-sought rocks rotted by martian water and even a long-dead Yellowstone-like fumarole.
But hope springs eternal when it comes to expensive NASA planetary missions. Squyres points to a plausible sort of rover failure that could be delaying the rover's awakening from its protective hibernation. With slowly increasing sunlight and a fortuitous wind to blow dust off the solar panels, Spirit might still pipe up, he says. "So we listen, [but] it could be a long wait."
If the mission has finally ended, NASA could save upward of $10 million a year in operating costs on the $470 million mission.