The atmosphere of Venus is mostly composed of carbon dioxide, which makes up 96.5% of the atmosphere. Nitrogen is the second most abundant gas, making up less than 3.5% of the atmosphere. The atmosphere is also composed of trace amounts of other gases, including sulfur dioxide, argon, carbon monoxide, helium, oxygen, neon, and water vapor. The clouds in the atmosphere of Venus are composed of sulfuric acid. The atmospheric pressure at the surface of Venus is about 92 times that of Earth, which is similar to the pressure found 900 meters below the surface of the ocean. The air at the surface of Venus is so dense that by mass, the small traces of nitrogen are four times the amount found on Earth, although nitrogen makes up more than three-fourths of the terrestrial atmosphere. The density of the air at the surface is 65 kg/m3, which is 6.5% that of liquid water on Earth.