Titan
NASA / JPL / SSI
This image of the Saturn moon Titan was taken by the Cassini spacecraft earlier this month during a flyby.
updated 12/25/2004 12:13:49 AM ET 2004-12-25T05:13:49

The international Cassini spacecraft launched a probe Friday on a three-week free-fall toward Saturn’s mysterious moon Titan, where it will plunge into the hazy atmosphere and descend by parachute while its science instruments and cameras make observations.

The European Space Agency’s Huygens probe is equipped with instruments to sample the chemistry of the planet-size moon’s thick atmosphere, and may reveal whether it actually has lakes or seas of liquid methane and ethane that have been theorized by scientists.

A signal confirming release of the probe was received at NASA’s Jet Propulsion Laboratory at 7:24 p.m. PST. The actual event occurred earlier, but it took more than an hour for radio signals to cross the hundreds of millions of miles between Saturn and Earth.

Smiles broke out in the JPL control room where many members of the mission staff wore red and white Santa hats.

The aim had to be good because Huygens has no maneuvering system to adjust its own course, and it was designed to remain dormant until just before hitting Titan’s atmosphere Jan. 14.

“This was a big one partly because we had to do this right or no mission at all,” said David Southwood, the ESA science program director. “But there’s still a lot to come. We’ve got a hell of a long way to go.”

Slideshow: Best of Cassini

No problems reported
A detailed analysis of data from the release was under way, but there were no indications of any problems, said Earl Maize, the Cassini deputy program manager at JPL.

“We are quite confident we had a very clean release,” he said.

Cassini was equipped with springs to gently push the 705-pound probe away at a rate of one foot per second and impart a stabilizing spin of seven revolutions per minute. Next week Cassini will make a course change to avoid following Huygens into Titan’s atmosphere.

Huygens was designed for only a brief mission. After entering the atmosphere it will deploy a huge parachute that will allow it to make a 2½-hour descent while radioing findings back to Cassini.

After touching down at 15 mph, it may continue sending data for up to 30 minutes, when either its battery fails or Cassini vanishes over Titan’s horizon.

Cassini will later turn its antenna toward Earth and send the data back to NASA’s Deep Space Network and on to an ESA operations center in Darmstadt, Germany.

Titan is a key target of Cassini’s $3.3 billion mission to study the Saturn system, which includes its spectacular rings and numerous moons. Scientists believe Titan may have organic — meaning carbon-based — compounds similar those that existed on the early Earth.

Titan's surface a mystery
Bigger than the planets Mercury and Pluto, Titan is the only moon in the solar system known to have a significant atmosphere. Rich with nitrogen and containing about 6 percent methane, the atmosphere is 1½ times thicker than Earth’s.

With the Saturn system averaging about 890 million miles from the sun, Titan has a surface temperature of minus 290 degrees Fahrenheit.

That surface continues to puzzle scientists despite close flybys in which Cassini’s cameras have tried to peer through Titan’s smog-like haze.

Imaging scientists have discerned distinct dark and light-colored areas, sometimes toying with such words as “islands” to describe features, but conceding they have yet to find a specific type of reflection that would indicate areas of liquid.

The Cassini mission is a joint project of NASA, ESA and the Italian space agency. Cassini was launched from Cape Canaveral, Fla., on Oct. 15, 1997, and arrived at Saturn in June.

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