SPACE 2006: Cassini Set to Visit Titan Monthly

By Irene Mona Klotz, Discovery News

Dec. 23, 2005— “Space 2006” is a series of articles highlighting key space programs and activities in the year ahead.

A year ago, the Cassini spacecraft zoomed toward Saturn’s enigmatic moon Titan and released a small probe. It parachuted through the moon’s thick atmosphere and landed on another world that had an oddly terrestrial feel.

The probe, called Huygens, found evidence of rain — though it was made of methane, not water — erosion, drainage channels, dry lake beds and volcanoes.

Like Earth, the surface of Titan appeared relatively free of impact craters, a sign that the moon’s surface was constantly being renewed by some global-wide phenomena.

By comparing the Huygens’ findings with Cassini’s aerial reconnaissance missions of Titan, scientists have begun piecing together a story of an exotic frozen world that seems to hold an organic brew and environmental conditions similar to primordial Earth’s.

“Titan can be looked at as an analog to Earth before life got started,” said Candice Hansen-Koharcheck, a Cassini science team manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Life has affected Earth. Once it gets hold, it changes the environment around it irreversibly.”

After skirting around Titan for much of 2005, Cassini will begin visiting the moon almost monthly for much of 2006. The new series of flybys, which begins Dec. 26, focuses on studies that examine Titan in a global context.

During Monday’s flyby, Cassini will closely match the perspective Voyager had of Titan when it flew by 25 years ago.

Scientists are curious to see how Saturn’s magnetic field, which drapes around Titan due to the moon’s ionized upper atmosphere, has changed during the passage of time, said Hansen-Koharcheck.

In addition to studies of magnetic fields and subatomic particles around Titan, scientists next year plan to use Cassini to measure atmospheric and temperature data down to the moon’s surface.

They also plan to use the spacecraft to gauge Titan’s gravity and to try to discern if the moon has a liquid layer buried beneath its frozen surface.

“If it has a liquid layer, it will flex differently and that will change Cassini’s orbit ever so slightly,” said Hansen-Koharcheck. “We would all sort of nod our heads if we saw evidence of a liquid layer. The puzzling thing is that so far, we have not discovered an internal magnetic field, which was the tipoff on Europa.”

Europa is a moon of Jupiter’s that scientists believe holds an underground ocean.

“If we do find liquid water, it may or may not be completely disconnected from what is going on the surface of Titan,” Hansen-Koharcheck said. “It could be like a layered cake and the liquids that are sculpting the surface are more like weather cycles.”

In addition to Cassini’s studies at Saturn, new robotic probes are scheduled to arrive at Mars in March and at Venus in April. NASA hopes to dispatch its first probe to Pluto, the only unexplored planet in the solar system, in January.

“It’s going to be a very exciting year,” said Colleen Hartman, NASA’s deputy associate administrator for science.

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