By Deborah Halber News Office Researchers at MIT and two European institutions reported in the March 25 issue of Nature that the atmosphere is more like a Napoleon pastry than a four-layer cake. The atmosphere is divided into four major layers related to differences in the temperature gradient. The thick troposphere, closest to Earth, where the temperature decreases with increasing altitude, is thought to be well-mixed.
Weather happens and planes fly in the troposphere.
Above that is the stratosphere, where the ozone layer absorbs harmful solar rays. The mesosphere, between 50 and 80 kilometers altitude, is where meteors burn up. The thermosphere is where the space shuttle orbits. The layers described in the study are within the troposphere, between a half and 1.3 kilometers thick and at an average altitude between 5.5 and 6.6 kilometers. One can classify the layers into types by whether a layer has an excess or deficit of the trace gases, which also then gives clues about the origin of the layers, Professor Newell said.