Suppose when the earth took the rigid shape before forming the environment upon it, do you think that the longterm consistent journey of solar winds on earth carried "oxygen" from sun over here.
Or, the evolution of earth and all other things formed here at the same time, earth formation+environment formation both things are equally formed !
Or the environment was ready here and later earth formed ! and later "ozone" formed !
I think "Mission-Genesis" has proved that the travelling solar wind on earth having ample oxygen.
Or the sun rays are doing everytime bifercation of water to retain the oxygen on earth, but what before the sea(s) on earth !
So what assumption can we draw !