The atmosphere of Mars is primarily composed of carbon dioxide (95%), molecular nitrogen (2.85%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases. The atmosphere of Mars is much thinner and colder than Earth's having a max density 20 g/m3 with a temperature generally below zero down to −60 °C. The average surface pressure is about 610 pascals (0.088 psi) which is 0.6% of the Earth's value.