Early Earth Atmosphere

by DC-Corona
Early Earth Atmosphere

Earth is thought to have had a thin atmosphere composed primarily of
helium and hydrogen gases. The Earth’s gravity could not hold these
light gases and they easily escaped into outer space. Today, H2 and He
are of low abundance in our atmosphere. For the next several million
years, volcanic out gassing began to create a thicker atmosphere
composed of a wide variety of gases that were part of the original
volatile inventory when the Earth formed.
Some of the gases that were released were probably similar to
those created by modern volcanic eruptions. It is thought that greater
than 85% of this atmosphere was produced by the early catastrophic
degassing that also contributed to the formation of the oceans ,the rest
through “continual degassing”.
The early atmosphere would have been reducing containing
constituents such as sulphur dioxide and hydrogen sulphide produced
by volcanic outgassing .Carbon dioxide and carbon monoxide would
have been outgassed and produced from cometary impacts between
impactors and the atmosphere. Methane would have been produced
by degassing in the early stages and maybe augmented by microbial
The atmosphere would have been contained nitrogen gas up to a bar
similar to a present day levels, and derivatives of atmospheric gases
such as nitrogen oxides, produced by lightning and impacts. Ammonia
would have been present from primordial outgassing, production at
hydrothermal vents and the reaction of nitrogen oxides with reduced
iron in the oceans, although its lifetime in the atmosphere is short .It

could have persisted for a longtime if the atmosphere had hydrocarbon
haze layer that would have protected it from destruction by UV
radiation.Hydrogen would have been outgassed,eventually being lost to
space in addition to the hydrogen produced by the photolysis of
water.The oxygen so produced would have reacted in the atmosphere
with reduced gases or with surface minerals to form oxidized
compounds .As the environment became more oxidized, CO2 would
have dominated over reduced gases and the atmosphere would have
become only weakly reducing. Thoughout the Hadean this CO2 might
have been consumed in carbonatisation reactions with volcanic rocks .
According to human standards, our early atmosphere was very
poisonous. It contained almost no oxygen.
Evidence suggest that the surface became suitable for life soon after
the accretion of the planet, frustrated by the Moon-forming impact and
early bombardment .The early Earth had some characteristics very
different from today. High impact flux, an anoxic atmospheric
composition very different from today.
By this we are now in a position to examine how was early earth
atmosphere .

By – Pratyush Sarin (Dccorona`s Writer)

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