How was oxygen introduced into Earth's atmosphere?

Answer 1

Oxygen was not necessarilly "introduced" to the Earth. Many people have a hard time understanding that the ozone layer that surrounds the Earth is not "holding in" our breathable atmosphere.

Air is our atmosphere. Air has "weight", believe it or not. The Earth has "gravity". Air acts much like water in that respect, atmosphere will be "pulled" to the Earth by gravity.

It is believed that the chemical reactions on the Earth, like magma from volcanoes, has created a lot of carbon dioxide. Thus life forms as plants grew. As we all know, plants live on carbon dioxide and it grew and encouraged growth of other life forms. Other life forms produced more chemical reactions and by-products such as carbon dioxide, and nitrogen when the life form died and decomposed. Thus creating our atmosphere.

There is also the concept that the Big Bang scattered the components necessary for the planets in the system and that the Earth "accumulated" it while revolving aroudn the Sun. This is very plausible considering there is a lot of ice in outer space and when it impacts a surface, like the Earth, the ice melts and creates water, which is made of hydrogen and oxygen. Remember also that life "came from the pre-historic oceans as we know it".

So, long story short, oxygen was not necessarilly "introduced" to the Earth as much as it was "produced" also.

Answer 2

Plant photosynthesis mainly and indirectly from the splitting of water molecules in the air by lightening and possibly by cosmic rays from the sun splitting water molecules into hydrogen and oxygen as well (which helps create the ozone layer), but mainly it's plants that do it converting carbon dioxide into carbon (sugars) for them and oxygen expelled out.

Answer 3

photosynthesis