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

Straightforward, what created the substantial atmosphere on Saturn's moon Titan?
I know the air is flooded with organic chemicals that, when exposed to 
sunlight, create a substance much like smog.  What is the source of all this 
organic chemistry?
I know that finding life there is, at best, a longshot, and that the atmosphere 
probably isn't being produced by volcanism and breathing creatures as it is 
here.
Thank you for your time...
-Matt

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