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A high obliquity would probably result in dramatic changes in the climate and may destroy the planet's habitability. [41] When the axial tilt of the Earth exceeds 54°, the yearly insolation at the equator is less than that at the poles. The planet could remain at an obliquity of 60° to 90° for periods as long as 10 million years.
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]
Nuclear war is an often-predicted cause of the extinction of humankind. [1]Human extinction or omnicide is the hypothetical end of the human species, either by population decline due to extraneous natural causes, such as an asteroid impact or large-scale volcanism, or via anthropogenic destruction (self-extinction).
[109] [110] [111] A 1997 assessment states that over a third of Earth's land has been modified by humans, that atmospheric carbon dioxide has increased around 30 percent, that humans are the dominant source of nitrogen fixation, that humans control most of the Earth's accessible surface fresh water, and that species extinction rates may be over ...
An important Earth example was the production of molecular oxygen gas (O 2) by ancient cyanobacteria, and eventually photosynthesizing plants, leading to a radical change in the composition of Earth's atmosphere. This environmental change is called the Great Oxidation Event. This oxygen proved fundamental to the respiration of
Earth also emits radiation back into space, but at longer wavelengths that humans cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. [ 41 ] [ 42 ] In May 2017, glints of light, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in ...
Exoplanet K2-18 b sits in the habitable zone of its parent star and has several key molecules needed in the formation of life.
A nearby gamma-ray burst (less than 6000 light-years away) would be powerful enough to destroy the Earth's ozone layer, leaving organisms vulnerable to ultraviolet radiation from the Sun. [158] Gamma ray bursts are fairly rare, occurring only a few times in a given galaxy per million years. [159]