How do we know that the early earths atmosphere was made up of hydrogen and hellium before?
The early atmosphere contained a lot of water vapour; until the earth cooled enough for the oceans to form. Then the atmosphere consisted mainly of nitrogen (which is relatively inert) with minor amounts of carbon dioxide, hydrogen sulphide and maybe methane. There is still some disagreement as to the exact composition of the early atmosphere; and research is still going on. However; there is one startling fact that most researchers agree on: the early atmosphere was totally lacking in oxygen. Oxygen is far too reactive for it to be present in the early atmosphere; so where did it come from? The answer is that the earliest life forms (sulphide consuming and photosynthetic bacteria and algae) gave off oxygen as a waste product of their metabolism (such life forms can still be seen today as ‘blue-green algae’, and stromatolites). Over millions of years, enough oxygen was produced for other life forms to develop. There is very strong evidence to support this theory: there are certain rock
