What if "sky ice" is the result of the oxygen in our atmosphere rising to the limit of what the earth's heat can reach and then a layer freezes like a bubble. It would create a thin, flexible blue layer that would disappear when heated. This layer would remain very thin since earth's gravity would pull it inward if it grew too heavy, which would cause the inside to melt as it approached the heat radiating from the surface.

So our sky would appear blue, our atmosphere would stay sealed off from escaping into space, and a spacecraft trying to re-enter would hit the resistance of the bubble until the friction melts a hole through which they could pass.

If there were sufficient cold present at the surface in Antarctica for some reason, that's where the bubble could be anchored, as a thick layer of sky ice could form with the ground to support it.

So then we would have a round earth (which fits with observable phenomenon) AND a huge coverup surrounding the ice wall in Antarctica.