Earth's Moon. It's even bigger than Mercury and Pluto. The only moon larger is Jupiter's moon, Ganymede.
There is something special about Titan. Titan is the only moon in the solar system with a significant atmosphere. Titan's atmosphere is made mostly of nitrogen. Earth's atmosphere is also mostly nitrogen. Titan's atmosphere is more like Earth's atmosphere than any other planet or moon in the solar system.
The surface of Titan is covered with an orange smog. The smog is caused by ultraviolet radiation from the Sun. The radiation breaks down methane in the atmosphere. This creates smog. The smog forms a deep blanket high in Titan's atmosphere. Smog molecules also
