I noticed the Ammonia thing. It is weird though, because most theorize that if silicon based life exists, it does at very high temperatures. Ammonia heavy atmospheres (at least close to ground level) usually occur around colder planets. Of course, Ancients are not your average lifeform by any standards.

Here's a couple interesting links that came up in similar discussions:

www.extrasolar.net/speculations.html

www.daviddarling.info/enc..._life.html