<P> The atmosphere of Venus is composed of 96.5% carbon dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur dioxide . The amount of nitrogen in the atmosphere is relatively small compared to the amount of carbon dioxide, but because the atmosphere is so much thicker than that on Earth, its total nitrogen content is roughly four times higher than Earth's, even though on Earth nitrogen makes up about 78% of the atmosphere . </P> <P> The atmosphere contains a range of interesting compounds in small quantities, including some based on hydrogen, such as hydrogen chloride (HCl) and hydrogen fluoride (HF). There is carbon monoxide, water vapour and atomic oxygen as well . Hydrogen is in relatively short supply in the Venusian atmosphere . A large amount of the planet's hydrogen is theorised to have been lost to space, with the remainder being mostly bound up in sulfuric acid (H SO) and hydrogen sulfide (H S). The loss of significant amounts of hydrogen is proven by a very high D--H ratio measured in the Venusian atmosphere . The ratio is about 0.015--0.025, which is 100--150 times higher than the terrestrial value of 1.6 × 10 . According to some measurements, in the upper atmosphere of Venus D / H ratio is 1.5 higher than in the bulk atmosphere . </P> <P> The atmosphere is divided into a number of sections depending on altitude . The densest part of the atmosphere, the troposphere, begins at the surface and extends upwards to 65 km . At the furnace - like surface the winds are slow, but at the top of the troposphere the temperature and pressure reaches Earth - like levels and clouds pick up speed to 100 m / s . </P> <P> The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found 900 m (3,000 ft) below the surface of the ocean . The atmosphere has a mass of 4.8 × 10 kg, about 93 times the mass of the Earth's total atmosphere . The density of the air at the surface is 67 kg / m, which is 6.5% that of liquid water on Earth . The pressure found on Venus's surface is high enough that the carbon dioxide is technically no longer a gas, but a supercritical fluid . This supercritical carbon dioxide forms a kind of sea that covers the entire surface of Venus . This sea of supercritical carbon dioxide transfers heat very efficiently, buffering the temperature changes between night and day (which last 56 terrestrial days). </P>

Why is there so little wind on the surface of venus
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