Plunging Into Saturn's Moon

Jan. 14, 2015

Ten years ago, on Jan. 14, 2005, the first man-made object touched down on an alien world in the outer solar system. To this day, it remains the only one. After a seven-year journey to Saturn, the European probe Huygens detached from NASA's Cassini spacecraft and embarked on a 21-day solo cruise toward Titan, a haze-shrouded moon orbiting Saturn.

Plunging into Titan's atmosphere, the probe survived the hazardous 2 1/2-hour descent to touch down safely on Titan's frozen surface. During descent, a suite of cameras and spectrometers aboard recorded the first detailed images of the moon's surface enshrouded in a thick atmosphere of nitrogen laced with methane and tarlike hydrocarbons.

To highlight the 10th anniversary of the Huygens landing, the European Space Agency has published a movie showing the landing in more detail than ever. Erich Karkoschka, a senior staff scientist in the University of Arizona's Lunar and Planetary Laboratory, who was a member of the descent imager instrument team during the Cassini/Huygens mission, produced the animation.

"Huygens took about 300 images on the descent," Karkoschka said. "All the image files combined were about two megabytes, less than one image you would take today with your digital point-and-shoot camera. That was the upper limit of data Huygens could uplink to the orbiting Cassini spacecraft, which would then send them to Earth."

Karkoschka said each image had to be compressed to the average size of a plain-text email message to meet the requirement.

"For this animation, I tried to get rid of the compression artifacts as best as possible, and then I arranged the images together in a mosaic. Once that was done, I could make a movie together of what Huygens saw during its descent."

As the probe hurtled toward the moon's surface, dangling from a parachute and snapping pictures, it spun around its axis, completing 10 turns per minute at one time, then slowing down as it approached the frozen surface.

Just before touching down, Huygens rotated very slowly, turning once every minute, all the while scanning the surroundings with electronic eyes arranged in different viewing perspectives. Karkoschka's movie ends showing the probe from an imaginary bird's-eye view, in the actual location where it is today, long after its batteries have drained, a silent visitor sent from a tiny blue world 746 million miles away.  

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