It's important to remember...
Temperature doesn't mean the same things as it does in a thicker atmosphere. I remember as a kid learning that the temperature in the very upper reaches of the atmosphere (effectively in space) were over a thousand degrees, yet nothing sitting there would burn up. The molecules are moving fast, but there are very few of them.
"Room temperature" in a near-vacuum isn't enough to give you open-air liquid water. Frost can form directly from vapor, and back directly to vapor it will go, like dry ice.