History of Earth the third atmosphere, rich in oxygen, emerged when bacteria began to produce oxygen about 2.8 Ga. In early models for the formation of the atmosphere and ocean, the second atmosphere was formed by outgassing of volatiles from the Earth's interior. Now it is considered likely that many of the volatiles were delivered during accretion by a process known as "impact degassing" in which incoming bodies vaporize on impact. The ocean and atmosphere would, therefore, have started to form even as the Earth formed. The new atmosphere probably contained water vapor, carbon dioxide, nitrogen, and smaller amounts of other gases. Planetesimals
Atmosphere of Jupiter is commonly treated as the base of the troposphere. In scientific literature, the 1 bar pressure level is usually chosen as a zero point for altitudes—a "surface" of Jupiter. As with Earth, the top atmospheric layer, the exosphere, does not have a well defined upper boundary. The density gradually decreases until it smoothly transitions into the interplanetary medium approximately 5,000 km above the "surface". The vertical temperature gradients in the Jovian atmosphere are similar to those of the atmosphere of Earth. The temperature of the troposphere decreases with height until it reaches a minimum at the tropopause, which is the