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Planets and moons


The globe of Titan with its thick, orange atmosphereThe globe of Titan with its thick, orange atmosphere Titan, Saturn’s largest moon, with a diameter of 5150 kilometres (3200 miles), is the second largest moon in the Solar System. Half as big again as Earth’s Moon, it is larger than the planet Mercury. It is the only moon known to have a thick atmosphere, almost entirely composed of nitrogen. Titan’s atmosphere is so thick, and its gravity so low, that humans could fly through it by flapping “wings” attached to their arms. The atmosphere contains small amounts of hydrocarbons, forming a haze. This reflects sunlight back to space, making the Titan's surface colder than the upper atmosphere.


A view of Titan's internal layersA view of Titan's internal layers Titan is the only other world apart from Earth where areas of surface liquid exist. The liquid is not water, however, but methane—a gas on Earth but which exists in a liquid state in Titan's -170°C (-275°F) temperatures. There are even methane clouds, rain and snow. Titan is thought to have an internal liquid layer between its crust and core made of liquid water and ammonia, which, along with methane, erupts at the surface through crustal cracks. Scientists think it is just possible there may be some kind of living things inhabiting this layer. 

Titan was discovered in 1655, by the Dutch astronomer Christiaan Huygens, after whom the 2002 lander was named.

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