Talk about vertigo! You've been dropped at the edge of a cliff, looking down for what seems to be miles! There's only one way to go from here: up! But it's going to be quite a climb, requiring all of the moutaineering skills you've ever heard of. The atmosphere here is very thin even at the mean surface level of this place; at altitude you'll never get a lungful. No matter, though, you could not breathe this atmosphere anyway, since it contains no oxygen; it's mostly carbon dioxide. You climb and climb; this mountain must be three times the height of Everest, and much broader at its base! There are clouds around you, and you can find water ice as well. When you try to melt it, however, it does not turn to liquid (it sublimes to gas). Oh well, just keep climbing. But what will you do when you get to the top