At 9:08 P.M. EST December 24, NASA’s Cassini spacecraft launched the European Space Agency’s Huygens probe on the final leg of its 7-year, 2.25-billion-mile journey. Cassini has been orbiting Saturn for the past 6 months, sending back marvelous photographs and other data about the planet, its rings, and its family of moons. Until now, Huygens had yet to do anything. Its sole purpose is to dive through the thick, hazy atmosphere of Saturn’s giant moon, Titan. If the mission is a success, scientists will get their first close look at this enigmatic moon’s atmosphere and surface.
When Huygens reaches Titan, instruments will study the atmosphere’s temperature, pressure, density, wind speed, and composition during an expected 2.5-hour-long descent. Shortly before Huygens reaches Titan’s surface, a camera will photograph the area around the landing site. Huygens should hit the surface at about 10 miles per hour and could survive for half an hour before its battery dies. A suite of instruments will determine the physical properties of the surface — whether the probe lands on solid ground or in a hydrocarbon lake.
The year in astronomy: a deeper look
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Titan in a test tube