Ocean-atmosphere paradox

Oxygen is the most abundant element on the earth s surface it occurs both as the free element and combined in innumerable compounds, and comprises 23% of the atmosphere by weight, 46% of the lithosphere and more than 85% of the hydrosphere ( 85.8% of the oceans and 88.81% of pure water). It is also, perhaps paradoxically, by far the most abundant element on the surface of the moon where, on average, 3 out of every 5 atoms are oxygen (44.6% by weight). 

As we have seen (Chapter 6), Mars is rich in iron peroxides but their abundance in Martian soils tells us nothing about how quickly they were formed on the early Earth. While they were almost certainly formed on Earth (which is, after all, closer to the Sun, and so more drenched in ultraviolet rays), the abundance of hydrogen peroxide on Earth would have depended on its rate of formation and destruction — and these in turn are dependent on atmospheric and oceanic conditions. While the existence of catalase implies that hydrogen peroxide was indeed abundant, the story is suggestive but far from conclusive. Luckily, there are other ways to answer the question, and they not only support the notion that photosynthesis evolved in response to oxidative stress, but they also explain a few other long-standing paradoxes. 

Pavlov A A, Pavlov AK, Kasting JF (1999) Irradiated interplanetary dust particles as a possible solution for the deuterium/hydrogen paradox of Earth s oceans. J Geophys Res 104 30725-30728 Pepin RO (1989) On the relationship between early solar activity and the evolution of terrestrial planet atmospheres. In The Formation and Evolution of Planetary Systems. Weaver HA, Danly L (eds) Space Tel Sci Inst Symp Series 3, Cambridge University Press, New York p 55-74 Pepin RO (1991) On the origin and early evolution of terrestrial planet atmospheres and meteoritic volatiles. Icams 92 2-79... 

---