After a year of fruitlessly trying to communicate with Spirit, one of two rovers on the surface of Mars, NASA scientists have finally decided to let it rest in peace. They plan to send their last commands to the rover a little after midnight Wednesday.
Spirit, which landed on Mars in January 2004, has been stuck in Martian sand for two years and has been silent for more than a year, despite regular attempts by NASA scientists to contact it.
Along with its twin rover Opportunity, which landed on the opposite side of the planet, it was sent to explore the Martian landscape for about three months. Yet although they were not built to survive the planet's harsh winters, the two have far outlived their life expectancies and their mission has proven wildly successful, sending back strong evidence, for example, that water once shaped Mars' surface.
Spirit, in the planet's southern hemisphere, had it much harder than Opportunity. The beginning of the end came when a front wheel broke in 2006. Scientists controlling the rovers from the Jet Propulsion Laboratory in La Cañada Flintridge learned to drive the vehicle backward — they even used the tracks left by the broken wheel to observe what materials lay just beneath the planet's surface.
But that asset turned into a liability in 2009, when the malfunctioning wheel broke through the thin Martian crust as Spirit was moving toward a pair of volcanic features. The rover became stuck in the sand, and attempts to maneuver it out caused another wheel to fail.
With no solar power to keep it heated during the brutal winter season, Spirit fell into hibernation. It went silent on March 22, 2010. NASA officials had hoped to make contact with it after the seasons grew favorable, but have heard nothing.
Opportunity continues to send back scientific data as it crosses the Martian surface toward the crater Endeavour. But things won't be quite the same without Spirit, scientists on the mission said.
"We have developed a strong emotional attachment to both of these rovers," John Callas, project manager for the rover program at JPL, said in a Tuesday news conference announcing the decision. "They are just the cutest darn things out in the solar system."