Ozone depletion as the International Day for the Preservation of the Ozone Layer, or "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987. Ozone depletion Ozone depletion describes two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events. The main
Atmosphere of Mars slowly decreased to very low concentrations, with no layer detectable above 35 km. The reporting scientists think that the observed polar ozone layers are the result of the same atmospheric circulation pattern that creates a distinct oxygen emission identified in the polar night and also present in Earth's atmosphere. This circulation takes the form of a huge Hadley cell in which warmer air rises and travels toward the south pole before cooling and sinking at higher latitudes. Mars is on a quite elliptical orbit and has a large axial tilt, which causes extreme seasonal variations in temperature amongst the northern