outhouse
Atheistically
Ok but would love to hear how they were involved.
Well the first forms of photosynthesis would not have produced oxygen and would have been able to withstand the sun for obvious reasons.
correct
The atmosphere - origin and structure
Photochemical dissociation - breakup of water molecules by ultraviolet
- Produced O2 levels approx. 1-2% current levels
- At these levels O3 (Ozone) can form to shield Earth surface from UV