NASA-International Space Station

The Huygens probe parachuted down to the surface of Saturn's haze-shrouded moon Titan accurately five years ago on Jan. 14, 2005, providing data that scientists on NASA's Cassini mission to Saturn are still building upon today.

"Huygens has gathered significant on-the-scene data on the atmosphere and surface of Titan, providing valuable ground truth to Cassini's ongoing investigations," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory.

The Huygens probe, built and managed by the European Space Agency, was bolted to Cassini and rode along during its practically seven-year journey to Saturn. Huygens' crash marked mankind's first and only effort to land a probe on another world in the outer solar system.

Huygens transmitted data for more than four hours, as it plunged through Titan's hazy atmosphere and landed near a region now called as Adiri. Atmospheric density measurements from Huygens have helped engineer’s process calculations for how low Cassini can fly through the moon's thick atmosphere.

Huygens captured the most consideration for providing the first view from inside Titan's atmosphere and on its surface. The pictures of drainage channels and pebble-sized ice blocks astonished scientists with the extent of the moon's similarity to Earth. They showed evidence of erosion from methane and ethane rain.

"It was eerie," said Jonathan Lunine, an interdisciplinary Cassini scientist at the University of Rome, Tor Vergata, and University of Arizona, Tucson, and was with the Huygens camera team five years ago as they combed through the imagery coming down. "We saw bright hills above a dark plain, a weird mixture of light and dark. It was like seeing a landscape out of Dante."

Combining these images with detections of methane and other gasses emanating from the surface, scientists came to believe Titan had a hydrologic cycle comparable to Earth's, though Titan's cycle depends on methane and ethane rather than water. Titan is the only other body in the solar system other than Earth supposed to have an active hydrologic cycle.

Huygens also gave scientists an occasion to make electric field measurements from the atmosphere and surface, revealing a signature consistent with a water-and-ammonia ocean under an icy crust.

While the Huygens probe itself remains inactive on the Titan surface, insights stimulated by the probe continue and ESA has convened a conference this week to extend the discussion, said Jean-Pierre Lebreton, Huygens Project Scientist for ESA.

"Huygens was an exclusive, once-in-a-lifetime mission," he said. "But we still have a lot to learn and I hope it will provide guidance for future missions to Titan."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter. Huygens data was sent to NASA's Cassini spacecraft, and was recorded and relayed to Earth by NASA's Deep Space Network. JPL also manages the Deep Space Network.