I did find a reference to exterior ice on a history.nasa.gov site! The ice did not persist. I find it quite plausible that some exhaust from the hydrogen/oxygen S-4 stage got inside the shroud and frosted onto the cold surfaces. Shroud off, and ... ice slowly goes away. remaining residue ... rocket exhaust contains ... rocket, after all.
033:17:54 Conrad: Say, you know, yesterday we talked to you about this stuff that's all over the windows, and on Dick's rendezvous window - window 2 - We've got some kind of a white deposit that's like a - I don't know, it's like an ash and it's not flush on it, it's built up in little humps and tabs of it sticking out, especially in the upper right-hand corner. What we'd like to do is photograph this for you. We don't have much to do right now. We thought we'd photograph these windows and thought maybe you'd come up with some recommended settings and everything. Seems to me I remember somewhere we had those procedures for photographing windows back in D or something because they were bad.
033:18:43 Carr: Roger, Pete. We'll get somebody going on that right away.
033:18:48 Conrad: We expect this stuff will be long gone after re-entry.
033:18:53 Carr: Roger. We've been kind of dying to ask you too about the ice situation. How long did it take that to sublime off?
033:19:01 Conrad: Well, now, that's a funny thing. The ice was sublimed off, but it's left a white deposit all along the perimeter of the number 1 window, that - that's on the black surface of the outside of that window, and it's up along the side of the window too. It's similar to the same stuff that's on the rendezvous window. Now, the ice that was on the inside of the outer pane in the number 1 window - that's sublimated, too, since we started PTC. We have a - a fine deposit of water droplet; whatever was in the water - has adhered to the window and that's all in streaks and dots and splatters, so we kind of think some of this may have come when - when the tower was jettisoned; we're not sure, and I guess what we want to do is try and photograph this as best we can for you to see -because I haven't heard [garble] before either.
033:20:05 Carr: Roger, Pete. How long did it take for that outer layer of ice on window 1 to sublime? How long was it before it was gone?
033:20:16 Conrad: Yes, it didn't go until we were finally asleep last night or - we stopped looking at it. It was still there, I think, when we went to bed last night.
033:20:26 Carr: Roger.
