This is a guest post by Tim Cullen at Tall Bloke's Talk Shop – see http://tallbloke.wordpress.com/2013/05/09/tim-cullen-illumination-from-t… … professors Mark Smith and Horoshi Imanaka have published a paper available on the Geochemical Society web site and Tim Cullen has found it extremely useful as it illustrates photons are produced in the atmosphere. This idea was commonly regarded as cranky, he suggests, and ignored.
The Cassini spacecraft has sent back numerous images of the atmosphere of Titan and there are distinct differences to what is going on there to what is going on around the Earth. However, Titan has a methane rich atmosphere – and the Earth is thought to have a similar atmosphere in very early days. Hence, looking at Titan is useful in order to get an idea on what might have been going on above Earth millions of years ago – and some things may never have changed.