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Oxygen evolution is the chemical process of generating elemental diatomic oxygen (O 2) by a chemical reaction, usually from water, the most abundant oxide compound in the universe. Oxygen evolution on Earth is effected by biotic oxygenic photosynthesis , photodissociation , hydroelectrolysis , and thermal decomposition of various oxides and ...
The influence of the evolution of life has to be taken into account rather soon in the history of the atmosphere because hints of earliest life forms appeared as early as 3.5 billion years ago. [48] How Earth at that time maintained a climate warm enough for liquid water and life, if the early Sun put out 30% lower solar radiance than today, is ...
The Great Oxygenation Event had the first major effect on the course of evolution. Due to the rapid buildup of oxygen in the atmosphere, the mostly anaerobic microbial biosphere that existed during the Archean eon was devastated, and only the aerobes that had antioxidant capabilities to neutralize oxygen thrived out in the open. [9]
The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, [2] was a time interval during the Earth's Paleoproterozoic era when the Earth's atmosphere and shallow seas first experienced a rise in the concentration of free oxygen. [3]
The modern atmosphere is oxidizing, due to the large volume of atmospheric O 2. In an oxidizing atmosphere, the majority of atoms that form atmospheric compounds (e.g. C) will be in an oxidized form (e.g. CO 2) instead of a reduced form (e.g. CH 4). In a reducing atmosphere, more species will be in their reduced, generally hydrogen-bearing forms.
The Earth's atmosphere, hydrosphere, and biosphere together hold less than 0.05% of the Earth's total mass of oxygen. Besides O 2 , additional oxygen atoms are present in various forms spread throughout the surface reservoirs in the molecules of biomass , H 2 O , CO 2 , HNO 3 , NO , NO 2 , CO , H 2 O 2 , O 3 , SO 2 , H 2 SO 4 , MgO , CaO ...
The composition of the Earth's atmosphere is different from the other planets because the various life processes that have transpired on the planet have introduced free molecular oxygen. [7] Much of Mercury's atmosphere has been blasted away by the solar wind. [8] The only moon that has retained a dense atmosphere is Titan.
The argon found in Earth's atmosphere is 99.6% 40 Ar; whereas the argon in the Sun – and presumably in the primordial material that condensed into the planets – is mostly 36 Ar, with less than 15% of 38 Ar. It follows that most of Earth's argon derives from potassium-40 that decayed into argon-40, which eventually escaped to the atmosphere.