DOI: 10.1051/orvie/2009001 The terrestrial craddle of life

Abstract. The Miller and Urey experiment in which amino acids were produced by electrical discharges in an atmosphere of water, methane, and ammonia was dismissed as being inconsistent with the secondary origin and the oxidizing character of the atmosphere. Since then, it has been found that simple geochemical arguments favor a dry accretion of the Earth and late delivery of water from the outer Solar System forming the primordial hydrosphere. This ocean of water must have interacted with the underlying terrestrial magma ocean, the existence of which is now well documented by evidence from the extinct radioactivity of 146Sm (T1/2 = 103 Ma) in Archean rocks. Water-hot rock interaction, with its hallmark reaction of serpentinization, produced enormous amounts of H2, which interacted with nitrogen and carbon dioxide to form CH4 and NH3. From this follows that the Miller and Urey experiment should be reinstated as the main template of the origin of life. Sustainable life needs nutrients that can be steadily resupplied, most notably phosphate for which mid-ocean ridges act as a sink. In the modern world, phosphate is brought to the ocean by the erosion of continents, which are the hallmark of plate tectonics. On Earth