Atmosphere of Earth the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around . Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earth's atmosphere and its processes is called atmospheric science (aerology). Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around
Nu Earth Souther forces arrive to recapture the trenches. Nu Earth Nu-Earth is the name of a fictional planet near two suns and a wormhole that is the main setting for the Rogue Trooper fictional universe. Due to its strategic importance the Southers and the Norts are fighting over the planet. This perpetual war has seen the use of just about every weapon of mass destruction, which made the planet's atmosphere toxic. Most life forms became extinct or mutated, and all inhabitants must wear protective chem-suits at all times. Because of this the Souther scientists were instructed to start the G.I. program