From Stargate Wiki
- "And poisonous. .13% molecular oxygen. 95% carbon dioxide with a hint of argon.
Oooh, nasty planet."
- — Hunter Riley and Ronald Greer
Argon (Chemical symbol Ar) is a noble gas on the periodic table with an atomic mass 39.938 u. It is poisonous to many organisms. The Hoth planet had a portion of argon in its atmosphere, in part making the planet uninhabitable for humans. (SGU: "Water")