secondary atmosphere

The secondary atmosphere refers to the atmosphere that developed after the initial, or primordial, gases were lost or failed to accumulate on a planet. This secondary atmosphere is formed through processes like outgassing from volcanic activity and the release of gases trapped within the planet's rocky materials during its formation.12

The composition of this secondary atmosphere differs from a primordial one. While a primordial atmosphere would contain all gases a planet could gravitationally retain, a secondary atmosphere is influenced by which volatile elements were incorporated into solid planetary materials. For instance, noble gases like argon are present in Earth's atmosphere primarily due to radioactive decay within rocks and subsequent outgassing, rather than direct capture from the primordial solar nebula.12

The evolution of a planet's atmosphere, including the formation of a secondary atmosphere, is influenced by factors such as the planet's mass, its distance from its star, and geological activity.3