[John Galt's cousin]

I recall from high school chemistry or physics that the boiling point of water gets lower with decreasing pressure. I don't understand how water could remain liquid, or ice could remain solid, in the vacuum of outer space.

Wouldn’t the water all boil off, similar to being "freeze dried"?

Can anyone explain the phenomenon?

Thanks

[inquest]

You're right that water can't remain liquid in the vacuum of space. When they refer to water in this article, they almost have to mean the general chemical sense (H₂O molecules).

As for ice being able to remain solid, you'll note that that your information only refers to the boiling point - that is, the conversion from liquid to gas. The conversion from solid to anything else is a separate issue.

It's pretty much true of all substances that the boiling point will decrease as pressure goes down. But that doesn't mean these substances can't exist as solids. They all certainly can. Solids are held together by electrostatic forces between molecules. They generally don't need outside pressure for that. It's a bit different for liquids, because with them, the molecules aren't held in place. Instead, they slip and slide all around each other. So that usually means that some outside force has to hold them together to prevent them from dispersing into a gas.