On January 14, 2005, Huygens lander, after releasing from the main Cassini spacecraft, landed in the soft wet riverbed on Titan surface. Then we for the first time have a glance behind thick orange cloud layer covering the biggest Saturn's satellite. This is no doubt one of main milestones in space exploration. I remember that day - I had to wait until 2 a.m., until images from Titan surface appeared.
First close Titan flyby was made by Voyager-1 spacecraft in 1981, but all its sensors were able to see - orange disk without any details.
Lander designers had absolutely no information about surface conditions - there was common opinion that all surface is covered by ocean from liquid hydrocarbons, so lander was made floating. But finally Huygens landed on hard, but wet surface. Now, after 12 year of observations we know that all seas and lakes of Titan are in polar areas, while Hyugens landed near to equator.
This video from JPL, compiled from Huygens images during 2,5 hours decent, shows what happened this day 12 years ago.
Unfortunately, 2017 is the final year of Cassini mission: on Sept 15, it will dive into Saturn atmosphere and burn there - here is why.
It is very disappointing that next mission to Saturn, Titan and Enceladus (TSSM) was canceled in favor of equally ambitious Laplace mission to Jupiter and its moons with subsurface liquid water oceans. However there is encouraging notion that TSSM may be revived with use of US heavy SLS rocket and corresponding funding.