this should clear things up. This is made possible by bad astronomy.com, under the mission to mars review.
Bad: It becomes clear that Blake will die, and no one can save him. He knows his wife will try, even though it might kill her too. To save her, he kills himself by taking his helmet off. Instantly, he freezes, and his face becomes distorted and icky.
Good: Again, he wouldn't freeze that fast. The human body holds a lot of heat, and it would take a long time to freeze. Have you ever found yourself literally freezing solid when you go outside on a winter's day? No, of course not. Yet losing heat by transferring it to cold air is far faster than doing so by simply radiating it away, as you would in space. If it takes a long time in frigid air, it would take even longer in frigid space.
His face would not get icky, either; at least, not right away. There is no air in space. Despite what movies like ``Outland'' would have you believe, you wouldn't explode if exposed to space. The air would rush out of your lungs explosively, which could damage your lungs and throat. But your skin and vascular system would contain your blood fairly well, protecting it against the vacuum, so your blood would not boil. After a long time, the cells would freeze, and the expanding ice crystals (water expands when it freezes) would rupture the cells, making you look a pretty good mess. But that would take hours, or longer, not seconds. Oddly though, a human can survive several seconds of pure vacuum. ``2001: A Space Odyssey'' had a scene like this; the astronaut had to go from his pod to the airlock without his helmet. I don't think he would look as nicely coiffed after the incident as he did in the movie, but the scene was largely accurate. Ironically, as Arthur C. Clarke has pointed out, in Earth orbit, your biggest problem is sunburn! Exposure to the UV light of the Sun would fry your skin in minutes, giving you a very bad sunburn. I'd be satisfied to live with that, given the alternative! For more info about what happens when a human is exposed to a vacuum, read the Imagine the Universe! website. They have real-life examples discussed too. Very cool.
Note (April 11, 2000): Shame on me. I originally said your blood would boil on this page. I was confused about something I had read quite some time ago. Several Bad Readers wrote in saying I was a wrong, and they were right! I also wasn't clear on why your cells would rupture, so I made that more specific in the text above. Also (added June 6, 2001) I said originally that the Sun would give you sunburn in seconds, but I think that is too fast; it would take a few minutes. I have no references for this, just a logical guess. If anyone knows any better, let me know!