Atmosphere of Mars and southern hemispheres. Mars's temperature difference greatly influences the amount of water vapor in the atmosphere, because warmer air can contain more moisture. This, in turn, affects the production of ozone-destroying hydrogen radicals. In early 2016, Stratospheric Observatory for Infrared Astronomy (SOFIA) detected atomic oxygen in the atmosphere of Mars. This was the first time in forty years it was detected, the last time being the Viking and Mariner missions in the 1970s. Molecular nitrogen (N) is present in the atmosphere at 1.9%. Measurements by various robotic missions, and analyses of Martian meteorites, show that the atmosphere is enriched in
Atmosphere of Mars exceeds that of the triple point of water () in the lowest elevations; at higher elevations water can exist only in solid or vapor form. Annual mean temperatures at the surface are currently < , significantly lower than that needed to sustain liquid water. However, early in its history Mars may have had conditions more conducive to retaining liquid water at the surface. In 2013, a team of scientists proposed that Mars once had "oxygen-rich" atmosphere billions of years ago. Possible causes for the atmospheric escape of a previously thicker Martian atmosphere include: Atmosphere of Mars The atmosphere of the