The spacecraft Cassini, after 13 years of studying Saturn, recently ended its mission by diving into the planet. The mission was designed to end this way so that there would be zero chance that the spacecraft will run into any of Saturn’s moons in decades to come, running the risk of contaminating them with Earth organisms. If the mission had continued, Cassini would have run out of fuel. At that point, it would have been controlled only by gravity; in the complex Saturnian system, it was impossible to completely rule out collisions with any of the moons somewhere down the road if Cassini were to continue to orbit the planet.
Planetary science fans can take heart in the fact that the data Cassini sent back will continue to provide new information for years to come. And science tourists can see a full-scale engineering model of the Cassini spacecraft and Huygens probe at the California Science Center in Los Angeles, where they’re on loan from NASA. (The Huygens probe, a project of the European Space Agency, was the smaller craft that visited Saturn’s moon Titan early in 2005.) The California Science Center also has an engineering model of the Viking lander, the space shuttle Endeavour, and other space-related exhibits.