The ambitious Cassini orbiter and Huygens lander mission achieved the first landing of a probe on another planet’s moon. For more than 11 years, Cassini has orbited the ringed planet, taking photos and making observations that have greatly expanded our understanding of the Saturnian system.
As of Oct. 28, 2015, Cassini has completed 220 orbits of Saturn. Cassini’s path is often adjusted to allow the probe to make close flybys of Saturn’s satellites. Since 2004, Cassini has made 147 of these so-called “targeted” flybys, including 114 of Titan. Cassini has also made 604 “untargeted” flybys, or flybys that do not require a rocket engine burn.
In 2005, the Huygens lander revealed the surface of Titan is a wasteland of water ice and frozen hydrocarbons (photo, right). Despite Titan’s lack of liquid water, some scientists believe the moon may support life, now or in the distant future when the sun’s heat increases.
Cassini photos revealed massive plumes of water ice spewing from cracks in the surface of Saturn’s moon Enceladus. Recently, researchers discovered that Enceladus has a giant world-circling subsurface ocean beneath its icy crust. The presence of massive quantities of water makes Enceladus a prime target in the search for other life in the solar system.
Far from being a dead boulder field in the sky of Saturn, Cassini has discovered that the ring system is a chaotic, ever-changing system and a laboratory for studying how small bodies collide to form larger moons.
Despite an average surface temperature of minus 290 degrees Fahrenheit (minus 179 degrees Celsius), Saturn’s moon Titan turns out to have quite a bit in common with Earth. Both worlds have rain, rivers, lakes and seas – of liquid methane, not water.
The action of flowing liquid carves the surface of Titan, allowing the formation of bodies of standing liquid. This makes Earth and TItan two of only a very few such worlds in the solar system.
Titan’s smoggy atmosphere is filled with some of the most chemically complex organic molecules in the solar system.
For more than 300 years, astronomers have known that Iapetus has a strange surface, with one hemisphere jet black and the other bright white. Cassini’s observations proved that Iapetus sweeps up dark, reddish dust in its path as it orbits Saturn. The darkened hemisphere absorbs solar energy and becomes warmer, while the snow-white, trailing hemisphere remains cooler.
One of Saturn’s remaining mysteries is a well-defined, hexagonal jet stream at the north pole of the planet. In the remaining years of Cassini’s mission, scientists hope to learn more about the hexagon’s properties.
