Which moon has a thick atmosphere?

Titan's atmosphere is made mostly of nitrogen, like Earth's, with a few per cent methane. The air pressure at its surface is about 1.5 times that at sea level on Earth, and an orange haze of organic chemicals hides the surface from view. Titan is so cold, about −179°C, that methane and ethane fall as rain and collect in rivers, lakes and seas. The European Space Agency's Huygens probe landed on Titan on 14 January 2005, the most distant landing ever made on another world. Titan is larger than the planet Mercury and is the second-largest moon in the solar system after Jupiter's Ganymede.