NASA has deactivated the Stardust spacecraft two weeks after it jettisoned a space capsule to Earth with the first comet dust samples.
Putting the mothership to indefinite sleep gives the space agency the option to reuse it for future missions, said Tom Morgan, Stardust program executive at NASA headquarters in Washington.
The 100-pound capsule parachuted to the remote Utah salt flats on Jan. 15 after a seven-year voyage to collect microscopic debris from comet Wild 2 and interstellar dust streaming through space.
"Stardust has performed flawlessly these last seven years ... and deserves a rest for a while," mission project manager Tom Duxbury said in a statement.
The $212 million project is managed by the Jet Propulsion Laboratory in Pasadena.
On Sunday, engineers powered down all of Stardust's systems except for its solar panels and receiver antenna. The move was necessary to maintain the spacecraft's health and save fuel for possible missions in the future.
The mothership, which has traveled nearly 3 billion miles, remains in permanent orbit around the sun. The next time it flies by Earth will be on Jan. 14, 2009.
Stardust's successful return with the comet cargo was a relief to NASA, which suffered a setback in 2004 when its Genesis space probe slammed into the same desert after its parachutes failed to open.
The return samples were recently flown to a laboratory at the Johnson Space Center in Houston where scientists unlocked the canister containing the particles.
A preliminary investigation revealed that the Stardust capsule trapped thousands of cosmic debris samples, exceeding scientists' expectations. Most of the particles were tinier than the width of a human hair, but a surprising number of particles were visible to the naked eye.
NASA scientists spent the past two weeks analyzing the cosmic grains under a microscope. The next step is to ship the samples to 150 scientists worldwide for further investigation.
The comet and interstellar dust particles are believed to have originated at the fringes of the solar system about 4.5 billion years ago. Some samples are thought to be older than the sun and studying them could shed light on the origins of the solar system.