Re: What generates, or generated Titan's atmosphere?

Matt,

Your question is not as straightforward as you might think. Titan's atmosphere is still a topic astronomers are trying to explain and understand. It's not difficult for a planet or moon to obtain an atmosphere during the accretion stage of solar system formation, but it *is* difficult for the body to keep its atmosphere. Usually a celestial body needs to be considerably more massive and/or cooler than Titan to retain an atmosphere. But in fact, spectroscopy indicates that hydrogen still exists on Titan in non-negligible amounts. So what's going on?

Well, one of the theories was that Titan may have been "protected" from a certain type of atmospheric erosion (due to cometary impacts) because it is further out in the solar system. Other theories involve atmospheric gases being frozen/captured at some point in Titan's past and then outgassed at a later date to replenish the atmosphere. And yet other theories involve cryovolcanism to fuel the atmosphere of Titan. But though theories abound, we still don't know for certain how Titan got or how it retains its atmosphere.

The good news is that the Cassini-Huygens Mission to Saturn and Titan is on schedule and proceeding according to plan. The Cassini spacecraft is scheduled to reach Saturn in 2004 and then the Huygens probe will be released into the atmosphere of Titan. The Huygens probe has six instruments that will take measurements of the chemical composition and send back images. So come back in 2004 and perhaps we'll have a better answer to your question!

Keep asking good questions,
Amber

References:
http ://www.sciam.com/explorations/010697sagan/010697sagan1.html
http://ucsu.colorado .edu/~sbrooks/conclude.html
http://www.jpl.nasa.gov/cassini/
http://sci.esa.int/home/hu ygens/index.cfm