[troutman]

Originally Posted by Barnes

Is a methane atmosphere that unusual? I was pretty sure that they had found evidence of extra solar planets with atmospheres similar to Titan. If it can happen in our solar system it probably is not the unusual?

Correct (March 2008):

http://www.scientificamerican.com/ar...asolar-methane

Astronomers report they have detected methane for the first time in the atmosphere of a planet outside our solar system. The finding comes from extrasolar planet HD 189733 b, a gaseous "hot Jupiter" locked in a tight orbit around a star 63 light-years away.

The observations "decisively show that methane is present in addition to water," writes the research team from NASA's Jet Propulsion Laboratory in Pasadena, Calif., and University College London. Members of the same team reported last year that they had identified water vapor in the atmosphere of HD 189733 b.

Although Earthlings may associate methane with gassy cows, it is a common and perfectly nonbiological constituent of other atmospheres in the solar system, including those of Mars and Titan as well as the gas giants Jupiter, Saturn, Uranus and Neptune. Researchers believe that methane and water would also be common components of planetary atmospheres outside of the solar system.