text: There is a layer, called the heterosphere, in which the earth's atmosphere has varying composition. As the altitude increases, the atmosphere is dominated successively by helium, molecular hydrogen, and atomic hydrogen. The precise altitude of the heterosphere and the layers it contains varies significantly with temperature. The heterosphere generally extends from about 55 miles altitude right up to the edge of outer space. Surely you don't want somebody to figure out the changes in gravity over that entire range.