n.
Largest moon of Saturn .
Titan is the only satellite in the solar system known to have clouds and a dense atmosphere. It is believed to make one rotation for each revolution, always keeping the same hemisphere toward Saturn. With a diameter of 3,200 mi (5,150 km), Titan is, after Jupiter's Ganymede, the largest moon in the solar system. Its density implies that its interior is a mixture of rocky and icy materials, the latter probably including solid ammonia and methane as well as solid water. Its atmosphere is mainly nitrogen. It was once proposed that an ocean of liquid methane and ethane covered much of the surface, but Earth-based radar observations indicate that the surface is generally solid.