Life on Earth - Conditions of Early Earth

This module looks at the development of life on Earth and the conditions that may have spawned  life.  To do this we need to see what the initial conditions of life on Earth were like.

4.5 billion years ago to 3.8 billion years ago.

At this time the Earth has no liquid water, and no stable crust.  The planet was still subject to heavy asteroid bombardment.  Because of the heat on the surface, any gases present would have escaped into space.  


3.8 - 3.45 billion years ago

By this time the Earth had cooled to the point where stable crust had formed and the temperature had cooled to the point that liquid water covered most of the surface of the planet.  Volcanic activity was still violent and frequent, but the gases being released from them were beginning to create an atmosphere.

This atmosphere was thought to be rich in methane, ammonia, carbon dioxide, carbon monoxide and possibly cyanide.  No free oxygen was present at this stage.  Hydrogen may have been formed from the spitting of water by UV radiation but the oxygen would have reacted quickly.  The lack of oxygen makes this atmosphere anoxic.

A number of small volcanic island were thought to have been forming at this time.  At the edges there may have been hot mud springs.  These springs may have been the place where life arose.  But before life can start, the complex molecules for life need to be created.  This is a topic for another post.