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Cassini makes first flyby of Titan

The Cassini spacecraft on Tuesday cruised to within 1192km of Titan, Saturn's planet-size moon, for the first close encounter with it. The moon, long an enigma wrapped in smog, has been described by one scientist as the "largest unexplored surface in the solar system."

Scientists and flight controllers here at NASA's Jet Propulsion Laboratory had to wait hours to learn if the mission was a success. While Cassini's cameras, radar system and other instruments were surveying the moon, as planned, its antenna was facing Titan and unable to communicate with Earth.

Late Tuesday evening, radio transmission from the spacecraft confirmed that the flyby was successful and pictures of Titan were being received.

Mission officials had said they had reason to be optimistic.

Earl Maize, the deputy program manager, noted that the spacecraft and all systems were "in perfect shape" before the encounter. A rocket maneuver over the weekend had put Cassini on course to give scientists a revealing look at the moon's surface while passing safely above the outer fringe of its dense atmosphere.

The moment of closest approach to Titan presumably occurred at 12:44am Taiwan time.

The first detailed exploration of Titan is perhaps the most eagerly anticipated goal of the US$3.2 billion Cassini mission. The robotic spacecraft began orbiting Saturn on June 30.

Titan, larger than the planets Mercury and Pluto and second in size only to Jupiter's giant satellite Ganymede, is a bitterly cold world -- minus 144? C -- but with an active carbon-based chemistry that creates the thick smog and may shed light on conditions that contributed to the origin of life on Earth.

Tobias Owen, a planetary scientist at the University of Hawaii at Manoa, called Titan, with a diameter of 5120km, the largest unexplored surface in the solar system. And a strange landscape it may be: ridges and deep cracks, stretches of ice and tar, pools of liquid hydrocarbons, perhaps resembling, in Owen's description, "a frozen chocolate sundae."

"We're not expecting to find life -- it's too cold -- but we are expecting to find prebiotic chemistry like that in the very earliest days of Earth," Owen said.

Titan is also intriguing because it is the only moon in the solar system with a substantial atmosphere and its main constituent is nitrogen, as is Earth's. Owen said that Titan may prove to be a natural laboratory for studying the origin of Earth's own atmosphere.

Torrence Johnson of the Jet Propulsion Laboratory, a member of the imaging team, said scientists did not know what they would find. "I'm expecting to be pleasantly bewildered," Johnson said, adding the findings would probably challenge preconceptions and provoke "lively debate among scientists."
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