An artist's rendition of the Huygens probe separating from the Cassini spacecraft. Cassini is in the top-center part of the image; Saturn is to the right; Huygens is center-left; and the moon Titan, Huygens' target, is shown in the lower-left of the scene.
Click on image for full size
Image courtesy NASA.

Huygens probe on its way to Titan
News story originally written on December 30, 2004

NASA's Cassini spacecraft, which is in orbit around Saturn, released the Huygens probe and sent it on its way to Saturn's largest moon, Titan. The probe, pushed away from the Cassini "mothership" on December 24, 2004 by springs, will coast through space for three weeks before starting a 2-1/2 hour descent through Titan's atmosphere on January 14, 2005. Huygens will then land on Titan and may continue to send data for up to 30 minutes after it touches down on the icy moon.

Cassini and Huygens were launched from Cape Canaveral, Florida on October 15, 1997. The Huygens probe, riding "piggyback" on Cassini, has been in "sleep" mode throughout most of the seven-year journey to Saturn. Huygens doesn't have a rocket engine to steer itself, so the probe had to be aimed correctly for its approach to Titan when Cassini released it. Cassini fired its engines three days after releasing the probe to change its course and avoid following Huygens on its plunge into Titan's atmosphere. Cassini will continue to orbit Saturn, studying the gas giant planet and its rings and moons, for at least four years.

Huygens, built and operated by the European Space Agency and named after the 17th century Dutch astronomer Christiaan Huygens, will be "awakened" by an automatic timer 45 minutes before the start of its descent to Titan. The probe will gather data and images as it descends on parachutes through Titan's thick atmosphere. Huygens will send the data to Cassini, which will then relay the information to scientists on Earth. Huygens will follow a pre-programmed, automated routine during its descent, for Saturn is quite far from Earth and radio signals will take more than an hour to reach us from Cassini at the time of the probe's descent. Cassini will disappear over the horizon as viewed from the Huygens landing site about 30 minutes after the probe touches down, so we will lose contact with Huygens then unless its batteries wear out sooner.

Titan is the only moon in our Solar System with a thick atmosphere. Although Titan is quite cold, the conditions on the moon may be similar to those on Earth early in our planet's history. Scientists are especially interested in the complex chemistry of Titan's atmosphere, which includes many organic compounds and may shed light on Earth's early chemistry before life arose on our home planet. We aren't yet sure what Titan's surface is like, so although Huygens might touch down on solid ground it is also possible it will splash down in a lake or sea of liquid ethane or methane or it might plunge into a pile of frozen methane snow!

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more


The Cassini probe began its journey to Saturn on October 15, 1997. It flew by Earth in August, 1999, before heading towards the distant planet. Cassini passed Jupiter in 2000 and then burned towards its...more

Cassini is Off!

Cassini has begun its 2.2 billion-mile journey to Saturn. Cassini was launched on a Titan rocket from Cape Canaveral Air Force Station early in the morning on October 15, 1997. The Cassini probe is one...more

A Rover on the Red Planet! Spirit Will Look at the Geology of Mars

NASA’s rover, named Spirit, has successfully landed and will soon be scouting the surface of Mars for interesting geology! Scientists are interested to know whether the depression where Spirit landed...more

Hubble Servicing Mission Canceled

On January 16, 2004, NASA Administrator Sean O'Keefe announced the cancellation of the final scheduled servicing mission to the Hubble Space Telescope (HST). The review board studying the Shuttle Columbia...more

Cassini approaches Saturn's Moon Phoebe

The Cassini spacecraft, en route to Saturn, will zoom past Saturn's odd moon Phoebe on June 11, 2004. Cassini will pass within 2,000 km (1,243 miles) of the moon's surface and should send back images with...more

Huygens probe on its way to Titan

NASA's Cassini spacecraft, which is in orbit around Saturn, released the Huygens probe and sent it on its way to Saturn's largest moon, Titan. The probe, pushed away from the Cassini "mothership"...more

Cassini Titan Flyby in October 2004

The robotic Cassini spacecraft flew by Saturn's moon Titan on October 26, 2004. Titan is Saturn's largest moon, and has the thickest atmosphere of any moon in our Solar System. Cassini captured what are...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA