The European-made space probe Huygens took off Saturday for a historic up-close encounter with Titan, the only celestial body of the Solar system with an atmosphere resembling that of Earth.
An illustration shows Huygens approaching the reddish Titan moon
The probe successfully detached from the Cassini (US spacecraft) orbiter," Rosemary Sullivant, a spokeswoman for the Jet Propulsion Laboratory in Pasadena, California, told AFP in a brief telephone interview.
An ultraviolet image from the Cassini spacecraft in orbit around Saturn
"They received the signal, I think, at 7:24 (0324 GMT Saturday) this evening Pacific time," she said. "All systems performed as expected, and no problems were reported."
The mission may help prove, or disprove, a long-held theory that Titan may even have rain as well as lakes and rivers, albeit containing unknown muddy substances and not water.
A dream come true
It will take Huygens 20 days to reach Titan. The European probe is scheduled to arrive at its destination on January 14.
At separation time, specially designed springs gently pushed Huygens away from Cassini onto a ballistic four-million-kilometer (about 2.5-million-mile) path toward Titan, officials said.
"We wish to congratulate our European partners as their journey begins and wish them well on their descent to Titan," Robert Mitchell, NASA's Cassini program manager, said in a statement. "We are very excited to see the probe off and to have accomplished this part of our job."
David Southwood, director for science at the European Space Agency, thanked his American colleagues for their assistance in the project and expressed confidence in continued fruitful cooperation between the two sides.
"Now all our hopes and expectations are focused on getting the first in-situ data from a new world we've been dreaming of exploring for decades," Southwood said.
US and Europe working in tandem
A European Space Agency graphic Grafik shows the planned seperation of Huygens, left, from the Cassini-Orbiter
The European probe will remain dormant until the on-board timer wakes it up shortly before it reaches Titan's upper atmosphere. Then it will begin a dramatic plunge through Titan's murky atmosphere, tasting the chemical makeup and composition as it descends, with the help of parachutes, to touch down on the moon's surface.
The data gathered during this descent, which is expected to take two and a half hours, will be transmitted from the probe to the Cassini orbiter. Cassini, in turn, is scheduled to perform Monday a deflection maneuver to keep it from following Huygens into Titan's atmosphere.
The move will also help establish the required geometry between the probe and the orbiter for radio communications during the European probe's descent.
Then the US orbiter will point its antenna to Earth and relay the data through the US National Aeronautics and Space Administration to the European Space Agency's operations center in Darmstadt, Germany.
A step closer to solving mystery
Huygens will be the first human-made object to explore up-close the unique environment of Titan, whose chemistry is assumed to be very similar to that existed on early Earth before life formed.
This image shows Saturn's moon Titan taken by the Cassini spacecraft as it approached Titan for its second close encounter with this intriguing moon.
Titan, the largest of Saturn's satellites, has intrigued astronomers for a long time. Its atmosphere, like that of Earth, is composed mostly of nitrogen, yet appears to have few clouds. However it contains significant quantities of aerosols and organic compounds, including methane and ethane.
At minus 180 C (-365 F), the temperature on Titan's surface is too cold for liquid water, and the atmospheric pressure is 1.6 times greater than that on Earth. This pressure, scientists believe, is likely creating conditions for complex chemical reactions between methane, ethane, ammonia and ice in its atmosphere resulting in eruptions, condensation and precipitation.
Some even suspect there could be lakes, rivers and even seas on Titan made up of liquids and muddy substances of yet to be determined nature.