LOS ANGELES -- Spirit, the robot geologist that captivated the world with its work on Mars before getting stuck in a sand trap, is about to meet its end after six productive years.
Spirit has been incommunicado for more than a year despite daily calls by NASA. The cause of Spirit's silence may never be known, but it's likely the bitter Martian winter damaged its electronics, preventing the six-wheel rover from waking up.
The space agency tried every trick to listen for Spirit to no avail. Project manager John Callas of NASA's Jet Propulsion Laboratory said the last commands were to be sent up Wednesday. Though orbiting spacecraft will continue to listen through the end of May, chances are slim that Spirit will respond.
"Spirit went into a deep sleep," said Callas, who said the rover will be remembered for demystifying Mars to the masses.
When the rover team gets together this summer, David Lavery of NASA headquarters said the mood would likely be that of an Irish wake rather than funeral.
"We drove it until its wheels came off," he said. "We never expected that that would be the way that we'd finish up with this project."
The solar-powered Spirit and its twin Opportunity parachuted to opposite ends of the Martian southern hemisphere in January 2004 for what was supposed to be a three-month mission.
The golf cart-size rovers were an instant hit with the public who followed the rovers' every move as they rolled across the Martian plains and stopped to drill into rocks.
Their greatest achievement was uncovering geologic evidence that Mars, now dry and dusty, was far more tropical billions of years ago. The red planet was toastier and wetter, conditions that suggest the ancient environment could have been favorable for microbial life.