It's also worth considering that these are hypothesised alien cells, whichmay or may not even play by our known rules... ie. DNA. And I believe that the reproduction temperatures in air are higher than those in water... So when coming through the atmosphere higher temperatures could be survived and reproduced within. And that point about physics is quite valid, especially if the Meteorite broke up high in our atmosphere the frictional force would be minute if you assume a low entrance velocity, and the cells encountered high flying water vapour clouds.
But you've got to think how cool would it be to work on it though???
