qWhen the Earth was formed 4.6
billion years ago, Earth’s atmosphere was probably mostly hydrogen
(H) and helium (He) plus hydrogen compounds, such as methane
(CH4) and ammonia (NH3).
èThose gases eventually
escaped to the space.
è
qThe release of
gases from rock through volcanic eruption (so-called outgassing) was
the principal source of atmospheric gases.
èThe primeval
atmosphere produced by the outgassing was mostly carbon dioxide (CO2) with some
Nitrogen (N2) and water vapor (H2O), and trace
amounts of other gases.