From Doug’s fevered 7th grade imagination comes today’s breakfast brain teaser. If there was a snowflake in high Earth orbit and gravity drew it down to the ground through the atmosphere, would it melt? Hmmm… there’s something to take your mind off your waffles.

His thinking was mostly around whether the very small mass of the flake would generate enough frictional heat on re-entry to cause it to melt, or if it would float gently all the way down like it does from the clouds. But there are several more fundamental questions that we had to deal with.

First, could a snowflake form in space? I think the answer is maybe. Snowflakes require nucleation sites meaning that water alone won’t do. Small particles of dust would be required as well. In deep space this might be a problem, but in high orbit, there should be ample detritus. But there are still the near-zero atmospheric pressure and the stupidly sub-zero temperatures involved. At those pressures, liquid water is not stable, and there will be a tendency for solid ice to sublimate directly to water vapor. I think on the sunny side of earth, this is exactly what we’d see, similar to how vapor trails exist on the sun-side of comets. On the dark side of Earth, I think it would be too cold to get flake-like crystals. After all, crystal structure is highly temperature dependent. I think you’d just get ice. Could there be a sweet spot near the terminus line where there is just enough heat to get you a flake? Maybe. But ice would not reform as a flake. It would sublimate in the coming sun. It would have to be the sun to dark transition that caused water vapor to condense to flake crystals around nucleates. This seems an unlikely confluence of conditions, but maybe.

His next idea was that maybe you could form a flake on the space station and shove it out an air lock. I think you could certainly form snow inside a space station. However, I think the transition to space is where the trouble is. Sudden vacuum would certainly cause the ice to sublimate. But could you vent the air lock slow enough to preserve the flake? Maybe. It would need to be done on the dark side. But maybe.

So under some stupidly ideal conditions, maybe you could get a flake in orbit. But I think keeping its flake-like consistency would be near impossible. The slightest bit of added energy would cause it to sublimate to vapor, especially given the enormous surface area of a flake. That energy could come from atmospheric friction, sunlight, or most anything else. The chances it would reach stabilizing pressures before it encountered that energy seem vanishingly small.

And then the bus came. So that was my hypothesis. I also encouraged him to ask his science teacher. He seemed to like that idea, so we’ll see if the teacher has a different take. If you have other ideas or think of factors I haven’t considered, feel free to post them.

… or just roll your eyes.