Titan And The Huygens Probe
Titan is the only moon in the solar system with a dense atmosphere similar to the early Earth. Here is an awesome BBC documentary looking at Titan and the Huygens mission.
Huygens was an atmospheric entry probe carried to Titan as part of the Cassini-Huygens mission. The probe was supplied by the ESA and named after the Dutch 17th century astronomer Christian Huygens.
It touched down on land, although the possibility that it would touch down in a sea or ocean, so this was also taken into account in its construction and design. Huygens was designed to gather information for a few hours in the atmosphere while it descended, and hopefully for a short time at the surface. It carried on sending data for about an hour and a half after touchdown. It remains the most distant landing of any spacecraft.