From the May 2003 issue

Piercing Titan’s haze

The Huygens probe will plunge into an alien atmosphere that may resemble that of early Earth.
By | Published: May 6, 2003
Titan's Haze
Methane and complex carbon molecules make up roughly 5 percent of Titan’s atmosphere. The other 95 percent is nitrogen. Titan’s haze merges with a darker “hood” or cloud layer over the north pole.
Aptly named, Titan is not only Saturn’s largest satellite, but also the second-largest satellite in the solar system. In addition, it is the only moon known to have a dense atmosphere. With that thick atmosphere, Titan’s surface has remained hidden from view, even during the fly-bys of Voyager 1 and 2, though the latter brought some clarity to the photochemistry of Titan’s all-enshrouding haze.

Though primarily comprised of nitrogen, Titan’s atmosphere holds a good amount of methane, as opposed to the carbon dioxide of Earth’s atmosphere. Scientists theorize that atmospheric conditions on the moon are similar to those of primeval Earth. Since methane converts to hydrogen cyanide when combined with nitrogen, the building blocks of life are present, even if prohibited from taking the next step — becoming life — due to the extremely cold temperatures on the moon.

A great deal of intellectual light will be cast into this hazy fog come December 2004 when the Huygens probe will be released by the Cassini spacecraft in a 22-day arc towards Titan. The European Space Agency (ESA) launched Cassini and Huygens from Earth in 1997, and the mission is taking a tour of the heavens, with Saturn as its final destination.

Plunging into Titan's Atmosphere
This painting shows the Huygens probe descending through some high clouds in Titan’s murky atmosphere.
In January 2005, the Huygens probe will parachute to Titan’s surface, taking atmospheric readings during its 2.5-hour descent. Looking like a futuristic shellfish, the probe has a casing designed to protect its delicate instrumentation from the extremes of descending into Titan’s atmosphere — a rush that could soar in temperature to 1,700 degrees Celsius (3,000 degrees Fahrenheit) in less than a minute. The probe may transmit additional surface data for 30 minutes, should it land safely.

Information from Huygens will be relayed to Earth via the Cassini orbiter. This less adventurous spacecraft will orbit Saturn, studying the planet and its moons, for at least four years. The Cassini-Huygens mission is a joint project of NASA’s Jet Propulsion Laboratory, the European Space Agency, and the Italian Space Agency.