Which moon is the only satellite in our solar system to possess a dense atmosphere?

The story behind the answer

Titan is the only moon with a truly dense atmosphere—thicker than Earth’s and mostly nitrogen with methane clouds and a photochemical haze. At its surface, the pressure is about 1.5 times Earth’s. By contrast, Europa, Callisto, and Miranda have only tenuous exospheres, far too thin to be called atmospheres.

Cassini-Huygens revealed rivers, dunes, and lakes of liquid methane and ethane on Titan in 2005, making it a prime analog for early Earth’s atmospheric chemistry—just much colder. This thick blanket both hides and shapes Titan’s surface. Memory tip: “Titan has a Titanic atmosphere.” If a moon has weather, rain, and lakes, think Titan.