Titan is a place where methane and ethane rain from the sky and have a hydrologic cycle like the kind we’ve only ever seen before with water on Earth. These organics form rivers and flow into seas, carrying sediment with them. This mission will be going to the equatorial desert to understand that sediment.
Titan, like Europa, is an icy ocean moon. Titan is even larger, though. While Europa’s ocean is measured to have about twice the liquid volume of all of the earth’s oceans combined, Titan’s ocean (which possibly has significant quantities of ammonia and organics and alcohols mixed in) has five times the liquid volume of all of the earth’s oceans combined.
Sitting atop this ocean is a thick icy crust, upon which is a surface that looks more earth-like than any other planetoid surface in our solar system. Although it looks earth-like, the chemistry is in fact fundamentally different. It is based around organic solvents instead of water as the dominant driver of weather and erosion. The water on titan is stored in the bedrock!
And the sediment on top? Well, titan’s atmosphere is 5% methane. That methane gets hit by UV light and turns into more complex organics. Titan’s atmosphere is also rich in nitrogen and carbon monoxide, which add Nitrogen and Oxygen to these complex organics. These organics sediment out and coat the surface. Around the equator, they blow into large dunes in a desert biome. Precipitation falls and erodes the tar-covered landscape. These complex organics get mixed together as sediment in the rivers and dumped into the beds of the polar lakes and seas.
Dragonfly isn’t going to the seas. Too dangerous for the first mission here. We don’t know what we’ll find, and it’s hard to communicate with earth, and there is complex weather and clouds called the “polar hood” that might interfere. Dragonfly is going to the desert, to observe the complex organics falling from the sky and gathering on the ground to be blown into dunes. These are the ingredients that will get mixed together in the seas. There is also a cool crater there that calculations suggest melted the H2O bedrock and created a water-filled pool for the organics that has long-since frozen over. However, calculations suggest that this liquid water pool full of organics may have stayed partially liquid for hundreds of thousands of years in the subsurface. This is a location where we can study: “what happens if you take a bunch of complex organics and add water?” How far along the path to life could they get before the snapshot was frozen?