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
Atmosphere of Venus water on the surface. At some point in the evolution of Venus, a runaway greenhouse effect occurred, leading to the current greenhouse-dominated atmosphere. The timing of this transition from Earthlike to Venuslike is not known, but is estimated to have occurred around 4 billion years ago. The runaway greenhouse effect may have been caused by the evaporation of the surface water and the rise of the levels of greenhouse gases that followed. Venus's atmosphere has therefore received a great deal of attention from those studying climate change on Earth. There are no geologic forms on the planet to suggest the