POLLUTION OR JUST EVOLUTION
The atmosphere on Earth has evolved during its last 4.5 billion years
of existence. The early Earth was probably an accretion of cool
particles, possibly composed of compounds of silicon, iron, and
magnesium. The particles compacted and eventually produced heat
internally. The early atmosphere may have been hydrogen and helium, but
it would have been lost quickly into outer space. Therefore, the Earth
was devoid of an atmosphere.
The early Earth had no oceans. Life was not even a possibility. The
rocks on Earth have only witnessed the last 3.5 billion years, so we can
only speculate on the early atmosphere.
The beginning of a permanent atmosphere would have formed by
outgassing of volcanoes. This refers to the release of gases trapped in
the interior of the early Earth. The oceans may have started to form
about 1.5 billion years after the formation of the Earth. The early
atmosphere was not preserved. Gases produced were probably similar to
those created by modern volcanoes (H2O, CO2, SO2,
CO, S2, Cl2, N2, H2) and NH3
(ammonia) and CH4 (methane).