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Earths Primordial Environment



This is an artist's rendition of Earth's primordial environment and the beginnings of life.
Windows original
In the beginning, Earth had a hydrogen based atmosphere. Since molecules like methane and ammonia were included it must have been a pretty smelly place! In time, the early atmosphere of Earth changed from a hydrogen dominated one to one which contained lots of oxygen. Examples of those molecules include carbon dioxide, and water vapor. In its primordial state Earth's atmosphere resembled other primitive atmospheres.

Jupiter's atmosphere is an example of what such primitive atmospheres must have been like. This is because Jupiter is so big it has enough gravity to hang onto every molecule. So scientists think that Jupiter's atmosphere today is representative of the early atmospheres of the smaller planets.

Certain chemical reactions require energy to make them go. That energy can come from ultraviolet (UV) light or lightning which can link small molecules together to make larger ones. The Miller-Urey experiment showed that ultraviolet light plus lightning in a hydrogen-based atmosphere can produce interesting long chemicals which form the foundation of living cells.

Earth's early environment was conducive to this process because the early atmosphere did not provide protection from ultraviolet light. On Earth today, the ozone layer absorbs almost all but the longest wavelengths of UV. On the early Earth, there was little free oxygen, so UV from the sun fell directly onto the surface of the Earth.



Earths Primordial Environment



This is an artist's rendition of Earth's primordial environment and the beginnings of life.
Windows original
In the beginning, Earth had a hydrogen based atmosphere. Examples of molecules which were present include methane, CH4, hydrogen, H2, and ammonia, NH3. In time, the early atmosphere of Earth changed from a hydrogen dominated one to one which contained oxygen-rich molecules. Examples of those molecules include carbon dioxide, CO2, water vapor, H2O, and sulphur dioxide, SO2. In its early state, however, Earth's atmosphere resembled other primitive atmospheres. Jupiter's atmosphere is an example of what such primitive atmospheres must have been like. This is because, unlike smaller planets, Jupiter has such enormous gravity that it retains every molecule, and elements of the atmosphere cannot drift away as they do on other planets. Therefore scientists think that Jupiter's atmosphere today is representative of the ancient atmospheres of the smaller planets.

Certain chemical reactions require energy to make them go. That energy comes from ultraviolet (UV) light or lightning. Ultraviolet light and lightning can link small molecules together to make larger ones. The Miller-Urey experiment showed that ultraviolet light plus lightning in a hydrogen-based atmosphere can produce interesting chemicals which form the foundation of living cells.

Earth's early environment was friendly to this process because the early atmosphere did not provide protection from ultraviolet light. On Earth today, the ozone layer, O3 absorbs almost all but the longest wavelengths of UV. On the early Earth, there was little free oxygen, so UV from the sun fell directly onto the surface of the Earth.



Earths Primordial Environment


This is an artist's rendition of Earth's primordial environment and the beginnings of life.
Windows original
In the beginning, Earth had a hydrogen based atmosphere, one which contained molecules in which hydrogen was a dominant constituent. Examples of such molecules include methane, CH4, hydrogen, H2, and ammonia, NH3. Such an atmosphere is also called reducing, as opposed to oxidizing. An oxidizing atmosphere is one that contains molecules with oxygen as the dominant constituent. Examples of those molecules include carbon dioxide, CO2, water vapor, H2O, and sulphur dioxide, SO2. In time, the early atmosphere of Earth evolved from a primitive reducing atmosphere to an oxidizing atmosphere.

Jupiter's atmosphere of today is an example of what all the primitive atmospheres must have been like. This is because, unlike smaller planets with less mass, Jupiter has such enormous gravity that very little of its original atmosphere has escaped.

Certain chemical reactions require energy to make them go (endogenic). That energy comes from ultraviolet (UV) light. Electricity in the form of lightning also serves that purpose. The Miller-Urey experiment showed that ultraviolet light plus lightning in a reducing atmosphere can produce long molecule chains which form the foundation of living cells. Earth's early environment was conducive to this process because the early atmosphere did not provide protection from ultraviolet light. Ultraviolet light can link small molecules together to make larger ones. (On the other hand, some forms of ultraviolet light can break apart large molecules).

On Earth today, the ozone layer, O3 absorbs almost all but the longest wavelengths of UV. On the early Earth, there was little free oxygen, so UV from the sun fell directly onto the surface of the Earth.




Last modified December 17, 1998 by the Windows Team

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