Posted: Thu, Mar 2, 2006, 7:09 AM ET (1209 GMT)
The methane detected in Titan's dense atmosphere was generated by three distinct outgassing episodes, scientists have concluded. In a paper published in the March 2 issue of the journal Nature, a group of planetary scientists in Arizona and France described their model to explain why Titan's atmosphere contains methane, a gas that breaks down in sunlight after tens of millions of years and thus must be continually replenished. Their models indicates there have been three times in the moon's history when the planet has released methane into the atmosphere: in the first billion years after its formation; two billion years ago, when its silicate core began to convect; and again starting 500 million years ago, when its icy crust began to convect and cool. This last episode, which is still in progress, will end in a few hundred million years, with no further episodes of methane outgassing before the sun enters its red giant phase and heats up the moon.

Related Links:

•  SPACE.com article
•  Univ. of Arizona press release
•  ESA press release