Titan
has an atmosphere. This can be seen faintly in the image on the left as
an outline, and more clearly in the following image
taken by Voyager looking back at Titan and showing sunlight scattering in the atmosphere. The
atmosphere of Titan has several layers of haze. It has a pressure
at the surface of 1.6 times that of Earth, and is made up primarily of
nitrogen, with about a 1% concentration of methane.
The
temperature on the surface is very cold, about -180 degrees Celsius.
The atmosphere is extremely opaque because of thick smog that appears to
result from sunlight interacting with hydrocarbons, much as smog forms
on the Earth. The clouds are probably composed of liquid nitrogen and methane drops, and it is speculated that Titan may be coverered with hydrocarbon lakes or oceans (specifically, methane and ethane). Although many of the organic chemicals thought to have been the precursors to life on Earth are present on Titan, it appears to be too cold for life as we know it to have evolved there. Here is a movie of infra-red images of Titan made with the Hubble Space Telescape. The structure shown in this animation represents heat variations in the atmosphere and surface of Titan.
