Moving outward from Mars to Jupiter. The Galileo Spacecraft is set to be destroyed later this month to avoid crashing into Europa once it runs out of fuel. Europa is possibly the best chance for alien life in our solar system, and it is feared that Galileo could still carry microbial life from Earth that would contaminate any ecosystem that the Jovian moon might harbor. Here is a great article detailing the life of Galileo (the spacecraft, not the man).