Do ICE COMETS Vaporize in the Thermosphere?

Question

Can Massive Ice Comets vaporize in the thermosphere before reaching the lower layers of atmosphere.
If so, and that vaporized H20 condenses again to fall to the Earth's surface, would that rainfall , fall slower than the velocity it has when it was part of an Icy Comet that hit the thermosphere.
IN OTHER WORDS, would the rainfall cause less kinetic energy than if was still a solid material speeding to the Earth's surface.

Answer 1

Depending on the size, yes the comets begin to vaporize.

The thermosphere (literally "heat sphere") is the outer layer of the atmosphere, separated from the mesosphere by the mesopause. Within the thermosphere temperatures rise continually to well beyond 1000°C. The few molecules that are present in the thermosphere receive extraordinary amounts of energy from the Sun, causing the layer to warm to such high temperatures. Air temperature, however, is a measure of the kinetic energy of air molecules, not of the total energy stored by the air. Therefore, since the air is so thin within the thermosphere, such temperature values are not comparable to those of the troposphere or stratosphere. Although the measured temperature is very hot, the thermosphere would actually feel very cold to us because the total energy of only a few air molecules residing there would not be enough to transfer any appreciable heat to our skin.

The lower part of the thermosphere, from 80 to 550 km above the Earth's surface, contains the ionosphere. Beyond the ionosphere extending out to perhaps 10,000 km is the exosphere or outer thermosphere, which gradually merges into space.

Answer 2

For the same reason that metal doesn't. Ice is a solid, and as such the interactions between the molecules are pretty strong. They're packed tightly together, at least when compared to water or gas. So simple intermolecular forces are sufficient to keep the thing together. But when it comes down to it, comets *do* vaporize. As solar radiation heats up the surface of a comet so that the ice begins to melt, it vaporizes, creating the characteristic long tails occasionally visible from earth. But as space is rather cold, it requires an external heat source to melt the ice to the point that the water molecules are no longer tightly bonded to each other, and are blown away into space.