Oxygen, essential to our existence, took nearly a billion years to appear in significant quantities on Earth, despite the presence of microorganisms capable of producing it. This delay in our planet's ...

Holland, H. D., in The Origin and Evolution of Atmospheres and Oceans (edit. by Brancazio, P. J., and Cameron, A. G. W.), 86 (John Wiley and Sons, New York, 1964).

ONE of the unsolved questions of geophysics is whether the earth's atmosphere is mainly primitive, or whether its constituents have for the most part been evolved from the interior of the earth since ...