Atmosphere of Pluto by the spacecraft "New Horizons". The main component of the atmosphere of Pluto is nitrogen. Content of methane, according to measurements by "New Horizons", is 0.25%. For carbon monoxide, the Earth-based estimates are (2010) and (2015). Under influence of high-energy cosmic radiation, these gases react to form more complex compounds (not volatile at Pluto's surface temperatures), including ethane (CH), ethylene (CH), acetylene (CH), heavier hydrocarbons and nitriles and hydrogen cyanide (HCN) (amount of ethylene is about 0.0001%, and amount of acetylene is about 0.0003%). These compounds slowly precipitate on the surface. Probably, they also include tholins, which are responsible for
History of Earth it could be common in the universe." Photosynthetic organisms appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. Life remained mostly small and microscopic until about 580 million years ago, when complex multicellular life arose, developed over time, and culminated in the Cambrian Explosion about 541 million years ago. This sudden diversification of life forms produced most of the major phyla known today, and divided the Proterozoic Eon from the Cambrian Period of the Paleozoic Era. It is estimated that 99 percent of all species that ever lived on Earth, over five billion, have