ABSTRACT
We initially classify planetary atmospheres by a single bulk parameter, their mass, or equivalently by a measurable magnitude-the pressure they exert at their base (de˜ned by a surface or a deep interior level in the ¥uid giants). The “surface pressure” is the weight of the mass column per unit surface (Ps = Mg/S; strictly in the Cartesian coordinate system). Accordingly, the atmospheres of the solar system planets and satellites can be divided into the following types: (1) thin atmospheres (Ps < 10−5 bar): Mercury, Moon, Galilean satellites (Io, Europa, Ganymede, and Callisto), Enceladus, Triton, and Pluto; (2) intermediate atmospheres (Ps = 7 × 10−3 to 90 bar): Venus, Earth, Mars, and Titan; and (3) massive and deep atmospheres (Ps > kbar-Mbar): Jupiter, Saturn, Uranus, and Neptune. The atmospheres originate with the planet or satellite and evolve, changing their mass and properties as they interact with their boundaries (the surface and the outer space). This chapter deals with the basics of the origin and evolutionary processes of the atmospheres of planets and satellites in the solar system. We do not intend to be exhaustive in details, but we will describe the fundamental, common processes affecting their lifetime on a long-term basis.
