Atmosphere

An atmosphere was a gaseous envelope surrounding planets, such as Sol 3.
 * Sol 3 had an atmosphere of 80% oxygen and 20% carbon dioxide
 * New Earth had the same atmosphere as Sol 3, its predecessor. (DW:[[New Earth])
 * The Tenth Sontaran Battle Fleet made Luke Rattigan develop the ATMOS in peoples cars, across the entire planet Earth, this was part of their plan to poison Earths atmosphere with clone feed, so Earth could become the new clone world for the Sontaran species, The Doctor later cleared the atmosphere, saving the planet. (DW:The Sontaran Stratagem, DW:The Poison Sky).
 * Alfava Metraxis had a breathable atmosphere. (DW:Time of Angels)