Spacecraft Landed in Mud on Saturn Moon

By MELISSA EDDY | Associated Press Writer

8:53 PM EST, January 18, 2005

FRANKFURT, Germany - A European spacecraft that landed on Saturn's largest moon Titan twisted and spun as it tumbled to the muddy surface, scientists said Tuesday, revealing animated pictures of the final stage of its descent.

The latest images underline the belief that the Huygens probe landed at the shoreline of what appears to be a large body of liquid when it came to rest Friday after a seven-year voyage from Earth.

Scientists at the European Space Agency are scrambling to determine the exact spot where the probe came to rest on Titan's mysterious, frozen surface.

One photo released Tuesday showed a large body of liquid -- possibly liquid methane -- jutting into what appeared to be rough, frozen terrain, with the probe appearing to be just a few yards from the shoreline.

Another series of photos showed how Titan's hazy atmosphere gave way to a more solid but clearly varied surface as the spacecraft tumbled and spun toward its final resting place.

"There wasn't even a glitch at impact. That landing was a lot friendlier than we had anticipated," said Charles See, a scientist who has been studying the images.

In addition to the soft landing, material that appears to have accumulated on the camera lens in the final images suggests the weight of the 705-pound probe may have pulled it into the muddy surface.

About 30 scientists are working to recreate the probe's descent to try to determine wind speeds and the chemical makeup of Titan's atmosphere.

The Cassini mother ship carried Huygens into space and ejected it Dec. 25. The orbiter also played a key role in picking up the probe's transmission and relaying the telemetry to NASA, which passed the data on to ESA.

Scientists said Tuesday they were surprised the probe rocked so much during its descent, tilting at least 10-20 degrees in the high-altitude haze.

"The ride was bumpier than we thought it would be," said Marty Tomasko, of the Lunar and Planetary Laboratory at the University of Arizona in Tucson, who heads the imaging team.

Huygens, named after Titan's discoverer, the 17th century Dutch astronomer Christiaan Huygens, carried instruments to explore Titan's atmosphere. It will take years for scientists to fully process the information collected during the probe's 2 1/2-hour descent.

Titan is the only moon in the solar system known to have a significant atmosphere. Rich in nitrogen and containing about 6 percent methane, its atmosphere is believed to be 1 1/2 times thicker than Earth's.