<P> Several natural satellites in the Solar System have atmospheres and are subject to atmospheric loss processes . They typically have no magnetic fields of their own, but orbit planets with powerful magnetic fields . Many of these moons lie within the magnetic fields generated by the planets and are less likely to undergo sputtering and pick - up . The shape of the bow shock, however, allows for some moons, such as Titan, to pass through the bow shock when their orbits take them between the Sun and their primary . Titan spends roughly half of its transit time outside of the bow - shock and being subjected to unimpeded solar winds . The kinetic energy gained from pick - up and sputtering associated with the solar winds increases thermal escape throughout the transit of Titan, causing neutral hydrogen to escape . The escaped hydrogen maintains an orbit following in the wake of Titan, creating a neutral hydrogen torus around Saturn . Io, in its transit around Jupiter, encounters a plasma cloud . Interaction with the plasma cloud induces sputtering, kicking off sodium particles . The interaction produces a stationary banana - shaped charged sodium cloud along a part of the orbit of Io . </P> <P> The impact of a large meteoroid can lead to the loss of atmosphere . If a collision is energetic enough, it is possible for ejecta, including atmospheric molecules, to reach escape velocity . Just one impact such as the Chicxulub event does not lead to a significant loss, but the terrestrial planets went through enough impacts when they were forming for this to matter . </P> <P> Sequestration is not a form of escape from the planet, but a loss of molecules from the atmosphere and into the planet . It occurs on Earth when water vapor condenses to form rain or glacial ice . It also occurs on Earth when carbon dioxide is sequestered in sediments, or cycled through the oceans . The dry ice caps on Mars are also an example of sequestration . </P> <P> One mechanism for sequestration is chemical; for example, most of the carbon dioxide of the Earth's original atmosphere has been chemically sequestered into carbonate rock . Very likely a similar process has occurred on Mars . Oxygen can be sequestered by oxidation of rocks; for example, by increasing the oxidation states of ferric rocks from Fe to Fe . Gases can also be sequestered by adsorption, where fine particles in the regolith capture gas which adheres to the surface particles . </P>

Earth’s original atmosphere escaped into space because