Early Earth / UV Radiation / Life ???

[juantonwan]

During the early stages of earth there was no O2 atmospheric oxygen, no living things, no photosynthesis, no ozone layer etc. I have been reading that this would have allowed pure UV radiation to penetrate deep onto earth.

 

How would this have affected the creation of adenine, amino acids etc. and the first single celled organisms?

 

Would they have had to been sheltered in a cave?

 

Could the UV radiation penetrate the surface of the earth? Could it penetrate down to the bottom of the ocean?

[Moontanman]

No, UV cannot penetrate deep into the Earth or to the bottom of the oceans. UV of sterilizing wave lengths is stopped in just a few feet of water and just millimeters of soil and or rocks.

[juantonwan]

No, UV cannot penetrate deep into the Earth or to the bottom of the oceans. UV of sterilizing wave lengths is stopped in just a few feet of water and just millimeters of soil and or rocks.

 

I see. And would this be any different with less of an ozone layer or an early earth atmosphere; or is the environment not relevant and that is just the properties of UV?

[Moontanman]

I see. And would this be any different with less of an ozone layer or an early earth atmosphere; or is the environment not relevant and that is just the properties of UV?

 

It's just the properties of UV, in space even a grain of sand is enough to protect spores from being killed by UV.

[Mr Skeptic]

The early atmosphere was a reducing atmosphere with no oxygen nor ozone. While we didn't have an ozone layer, life required a barrier of a few feet of water to block out the UV. With the advent of photosynthesis, we got an oxygen atmosphere. The oxygen killed off a lot of life and also had other effects (eg very little iron could dissolve in the ocean anymore), but some oxygen got converted to ozone in the upper atmosphere due to sunlight. The ozone then shielded life from UV, so that life could live on the surface.