What Probes Have Been Sent to Saturn?

Known since ancient times, Saturn is over 885 million miles from the sun and reveals sparse details about its atmosphere, ring system and satellites through ground-based telescopes. Beginning in 1979, four space probes (plus a lander on its moon Titan) have expanded our knowledge. The latest probe, Cassini is still orbiting the planet as of May 2009.

Pioneer 11

In 1979, after flying past Jupiter, Pioneer 11 became the first space probe to reach Saturn, passing to within 13,000 miles. It discovered two small moons and an additional ring, and mapped the planet's magnetic field and magnetosphere. The spacecraft continued beyond the solar system carrying a plaque showing a man, a woman and Earth's location in the galaxy, in case it is ever found by aliens.

Voyager 1

Voyager 1 reached Saturn in 1980 and discovered that its upper atmosphere was mostly hydrogen and about seven percent helium, with winds of nearly 1,100 miles a second (blowing mostly eastward). The spacecraft also discovered five new moons and two shepherding satellites that keep the F ring intact. Voyager 1 is currently leaving the solar system at 3.5 Astronomical Units per year, northward relative to the orbital plane.

Voyager 2

Launched with its sister ship in 1977, Voyager 2 did not reach Saturn until 1981 but also carries a golden phonograph record showing the sounds and pictures of Earth. By sending a radio beam through the upper atmosphere, the spacecraft discovered a minimum temperature of --312 degrees Fahrenheit and air pressure of 70 millibars (compared to Earth's surface pressure of 1000 millibars). It left the solar system in 2007.

Cassini

In 2004, Cassini became the first spacecraft to orbit Saturn for several years. Its close-up views of the rings show a jumble of small moons and particles forming waves and jets. It also discovered that plumes of ice shooting from the moon Enceladus contain organic compounds. Having completed its initial four-year mission, the spacecraft is now observing seasonal variations as the planet enters its equinox.

Huygens

As part of the Cassini mission, Huygens became the first spacecraft to land in the outer solar system by parachuting onto the surface of Titan. Though designed to float, it landed on solid ground after taking high-altitude pictures of what looked like rivers draining into a shoreline. Before dying on the surface, it showed a temperature of --291 degrees Fahrenheit and pebble-sized rocks and ice in an orange haze.