NASA's Kepler space telescope has come to the end of its mission to hunt for Earth-like planets in the galaxy.
Now NASA is on the hunt to figure out what scientific research Kepler can do in its current condition.
NASA scientists announced this afternoon that the spacecraft's two broken wheels can't be fixed well enough for Kepler to continue its primary mission of finding Earth-like planets outside this solar system that are capable of supporting life.
In July, one of the four wheels that control the space telescope's orientation in space stopped working. A second wheel had stopped working in May 2012. The space telescope needs at least three working wheels to be stable enough to do its work.
NASA got the two problematic wheels working, but a test last week showed there now is friction when those two wheels turn. If the friction doesn't remain at a constant level, the wheels are unusable.
"Kepler's primary mission requires three working wheels," said Paul Hertz, director of NASA's astrophysics division, during a press conference. "We have spent hundreds of hours on this.... We do not believe we can recover three-wheel operations for Kepler's original science mission."
Launched in 2009, Kepler completed its primary mission last November and began what scientists hoped would be a four-year extended mission.
While Kepler will no longer search for exoplanets, that doesn't mean the research won't continue.
William Borucki, the Kepler mission's principal science investigator, said Kepler has sent back enough data to keep scientists busy for another two to three years.
"The Kepler mission has been spectacularly successful," Borucki said. "With the completion of Kepler observations, we know the universe is full of Earth-like planets.... The most exciting discoveries are going to come in the next few years as we analyze this data."
He added that he expects that within two years, scientists should be able to answer the question of whether Earth is unique or a common kind of planet in our galaxy.
"We won't be able to explore as much as we'd all like. There is some regret about that," said Borucki. "I'm actually delighted with what we have accomplished. I feel like I'm standing at the bottom of the ocean and I'm covered with an ocean full of data."
As scientists work their way through the data Kepler already has sent, other NASA scientists will begin the process of figuring out what Kepler's next mission will be.
Suspecting that Kepler wouldn't be repaired, NASA recently issued a call for white papers on alternative scientific projects that a limited space telescope could work on.
Charles Sobeck, engineer and deputy project manager of NASA's Kepler mission, said in a recent interview with Computerworld that he hopes the scientific community will come up with some intriguing goals for Kepler.
"We're looking for ideas for science you might do with the Kepler mission that you might not be able to easily do from the ground," he said. "Maybe it could be used to find near-Earth asteroids, giving us a different perspective than we get from the ground."
Borucki said that he expects that Kepler could be used to search for asteroids, comets or supernovas.
"We have no way of knowing yet which of these missions would be practical," he added.
Other than the malfunctioning wheels, Kepler appears to be in solid working order, according to Sobeck. "Something might fail," he said, "but there's nothing on the horizon that looks like it's marginally degrading."
Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter, at @sgaudin, and on Google+, or subscribe to Sharon's RSS feed . Her email address is email@example.com.