Troposphere: the lowest layer, where weather phenomena occur, extending roughly from the Earth's surface to about 12 kilometers. Stratosphere: located above the troposphere, extending to about 50 kilometers, containing the ozone layer which absorbs harmful ultraviolet radiation. Mesosphere: above the stratosphere, extending to about 80 kilometers, where meteors burn up. Thermosphere: located above the mesosphere, extending to about 800 kilometers, characterized by high temperatures due to solar radiation, and where the ionosphere is located. Exosphere: the outermost layer, extending into space, with very thin air, and where hydrogen and helium particles are widely dispersed.