科技英语新闻：Mars rover Spirit ends mission

With the completion of Spirit's mission, NASA will have to transition the Mars Exploration Rover Project to a single-rover operation focused on Spirit's still-active twin, Opportunity.

Spirit operated for more than six years after landing in January 2004 for what was planned as a three-month mission. Its twin, Opportunity, landed on the other side of the planet three weeks after Spirit.

Despite being stuck, the rover performed beyond expectations. It returned more than 124,000 images, ground the surfaces off 15 rock targets and scoured 92 targets with a brush to prepare the targets for inspection with spectrometers and a microscopic imager.

"What's really important is not only how long Spirit worked or how far Spirit drove, but also how much exploration and scientific discovery Spirit accomplished," Callas said.

Spirit started out with some problems in its electronic memory, but detected evidence of water-altered rocks and carbonates -- both building blocks of life -- on what scientists call the Gusev site.

But the rover found evidence that Mars was once like Earth, with water and hot springs. Concentrated deposits of silica led the project's principal investigator to conclude that steam vents or hot springs once existed at a site known as Home Plate. Such an environment could have supported microbial life.

After its first year on Mars, the rover lost the use of one of six wheels while scrambling over a hilly area, but continued to send data back to Earth for years. It logged 4.8 miles (about 7.7 km) over the Martian surface -- about a dozen times farther than it was expected to go.

Opportunity is still working. It has logged 12 miles (19.2 km), collected more than 130,000 images and is headed toward a crater called Endeavour.

NASA is currently preparing for the launch of another Mars rover Curiosity.

"We're now transitioning assets to support the November launch of our next generation Mars rover, Curiosity," said Dave Lavery, NASA's program executive for solar system exploration.