There's a chance that NASA's Kepler space telescope can recover from the malfunction that has halted its wildly successful search for alien planets, mission team members say.

The second of Kepler's four reaction wheels devices that allow the observatory to maintain its position in space has failed, depriving Kepler of the ability to lock precisely onto its 150,000-plus target stars, NASA oficials announced Wednesday (May 15).

But mission engineers are not conceding that Kepler's planet-hunting days have come to an end, vowing to try their best to recover the failed reaction wheels over the coming weeks. [Gallery: A World of Kepler Planets]

"I wouldn't call Kepler down and out just yet," NASA science chief John Grunsfeld told reporters Wednesday.

Balky reaction wheels

The Kepler spacecraft spots exoplanets by detecting the tiny brightness dips caused when they pass in front of their parent stars from the instrument's perspective.

The observatory needs three working reaction wheels to do such precision work. When Kepler launched in March 2009, it had four three for immediate use and one spare.

One of the wheels, known as number two, failed in July 2012, giving Kepler no margin for error. And the loss this week of another one (called number four) puts an end to the spacecraft's exoplanet hunt, unless a fix can be found.

Engineers have begun considering strategies for bringing the wheels back into service. They'll likely try a light touch at times and a brute-force approach at others, officials said.

"Like with any stuck wheel that you might be familiar with on the ground, we can try jiggling it," said Kepler deputy project manager Charlie Sobeck, of NASA's Ames Research Center in Moffett Field, Calif. "We can try commanding it back and forth in both directions. We can try forcing it through whatever the resistance is that's holding it up."

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Can NASA's Planet-Hunting Kepler Mission Be Saved?