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.