科技英语新闻：Mars rover Spirit ends mission

LOS ANGELES, May 25 (Xinhua) -- NASA project managers bade farewell to the Mars rover Spirit on Wednesday after sending a final set of commands to the stranded vehicle.

This marks the completion of one of the most successful missions of interplanetary exploration ever launched, NASA's Jet Propulsion Laboratory (JPL) said.

"Last night, just after midnight, the last recovery command was sent to Spirit," said John Callas, the Mars Exploration Rover Project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Los Angeles.

"It would be an understatement to say this was a significant moment. Since the last communication from Spirit on March 22, 2010, as she entered her fourth Martian winter, nothing has been heard from her."

NASA has tried in vain to regain communication with Spirit since it got stuck in sand about two years ago. The rover last communicated on March 22, 2010, as Martian winter approached and the rover's solar-energy supply declined.

NASA checked frequently in recent months for possible reawakening of Spirit as solar energy available to the rover increased during Martian spring, but to no avail.

A series of additional re-contact attempts ended on Wednesday, designed for various possible combinations of recoverable conditions, according to JPL.

"Our job was to wear these rovers out exploring, to leave no unutilized capability on the surface of Mars, and for Spirit, we have done that," said Callas.