A recent flyby by Cassini spacecraft offers opportunity to compare data collected 25 years apart near Saturn's largest moon

PASADENA — A recent flyby by the JPL-managed Cassini spacecraft has given scientists a unique opportunity to compare data collected 25 years apart near Saturn's largest moon, Titan, JPL said Tuesday.

Cassini flew within 6,240 miles of Titan shortly after noon yesterday, Pacific time, said Douglas Equils of the science planning team for Cassini. Its path took the craft through roughly the same region traveled by NASA's Voyager 1 in 1980.

Titan — which is larger than the planets Mercury and Pluto — is the only moon in the solar system known to have a dense atmosphere.

Equils said a comparison of data from the flybys by Voyager and Cassini is expected to show that Titan underwent an "atmospheric loss over the last 25 years."

Titan has a thicker atmosphere than Earth, but it also has less gravity and is "more subjected to thermal impacts on its surface, which cause hydrogen atoms to be lost in space," said Equils.

Yesterday's flyby was the 10th of 45 such maneuvers Cassini is scheduled to carry out near Titan.

Scientists consider the moon a frozen vault that could hold clues about the beginnings of Earth. Studying the moon is "one of the major goals of the Cassini-Huygens mission because it may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth," according to the JPL Web site.

Titan has a diameter of 3,200 miles, with a surface temperature of minus 290 Fahrenheit.

Launched Oct. 15, 1997, Cassini went into orbit around Saturn — the solar system's second-largest planet — June 30, 2004. The $3.3 billion Cassini- Huygens mission, which also involves the European and Italian space agencies, is expected to last four years. NASA is footing $2.6 billion of the bill.

The Huygens probe carried by Cassini landed on Titan in January, sending back stunning images of the moon's surface before it stopped transmitting data.


