for National Geographic News
If all goes according to plan, Huygens will parachute through Titan's hazy atmosphere tomorrow. The 8.9-foot-wide (2.7-meter-wide), 703- pound (319-kilogram) probe should land somewhere just south of the moon's equator.
Scientists from around the world have been waiting for years for the moment when Huygens sends back to Earth images and readings from Saturn's mysterious moon's atmosphere.
The Cassini spacecraft jettisoned Huygens on Christmas Day, sending the probe on its merry way to Titan.
Huygens spent the last seven years bolted to the Cassini spacecraft, which arrived at Saturn July 1, 2004, for a four-year mission to study the planet, its rings, and its icy moons.
At 3:24 GMT on December 25 (10:24 p.m. ET on December 24) confirmation was received on Earth that all had gone according to plan: Cassini had fired bolts and sent Huygens on a collision course with Titan, the second largest moon in the solar system. Twelve hours later the orbiter sent one last image of Huygens to Eartha tiny receding point of light which gives scientists confidence that the probe is indeed on the right trajectory for its landing on January 14.
"We've always known these dates, but they've always seemed infinitely far away in the distance. It really is quite unreal they're now actually here," said John Zarnecki, a space scientist at The Open University in Milton Keynes, England. Zarnecki is the principal investigator for Huygens's surface science package.
The probe's two-and-a-half-hour descent through Titan's atmosphere is anticipated to be a highlight of the international Cassini-Huygens Mission, which is managed jointly by the ESA, the Italian Space Agency, and NASA.
Titan's atmosphere is composed of nitrogen, methane, and other organic compounds. Scientists believe the chemistry is similar to that of Earth's about 4 billion years ago, before life evolved on our planet.
Data gleaned from the suite of robotic instruments on Huygens may shed light on how chemistry that predates life works in a "cold, waterless environment and tell us clues on how life started on Earth," Lebreton, the Huygens project scientist, said.
Hidden beneath a hazy atmosphere, the surface of Titan remains a great mystery. Scientists have long speculated that the moon may be covered in icy mountains and seas of liquid methane, but no one really knows.
Zarnecki, the Open University space scientist, noted that recent images of the moon taken by cameras aboard Cassini that can see through the lunar haze have only added to the mystery.
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