Advanced Intermediate Beginner Home

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.


Credits Settings Sponsorship Membership Contact us About the site Site map Help Myths People News Arts, books and film Images and multimedia Tours Life Geology Physics Space weather Space Missions Solar system Astronomy and the Universe Shop for science stuff Games Ask a scientist Journal Comets Dwarfs Neptune Uranus Saturn Jupiter Asteroids Mars Earth Venus Mercury Sun Teacher resources Kids Space Search Home



Last modified December 17, 1998 by the Windows Team

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). ©1995-1999, 2000 The Regents of the University of Michigan; ©2000-05 University Corporation for Atmospheric Research. All Rights Reserved. Site policies and disclaimer