TITLE:
From Where Did the Water Come That Filled the Earth’s Oceans? A Widely Overlooked Redox Reaction
AUTHORS:
Friedemann T. Freund, Minoru M. Freund
KEYWORDS:
Redox Conversion, Hydroxyls, Peroxy, Water, Earth’s Upper Mantle
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.6 No.4,
March
26,
2015
ABSTRACT: Though
two-thirds of Earth’s surface is covered by oceans, measurements of hydroxyl concentrations
in upper mantle minerals, specifically in olivine, reportedly provide
surprisingly low values. This has been interpreted to mean that there is little
dissolved H2O in the Earth’s mantle. By inference, when Earth
formed, there might not have been able enough water to fill the oceans through
volcanic degassing. It has therefore been proposed that the missing water was
delivered to Earth from space, through comets and other impacting bodies.
However, the reported low hydroxyl concentrations in olivine and similar mineralsis
probably based on a profound misunderstanding of a solid state reaction that
converts hydroxyls into something more difficult to detect. There is indeed a
redox reaction that converts, during cooling, solute hydroxyls in the matrix of
minerals into peroxy plus H2. This widely overlooked redox conversion
takes place under thermodynamic non-equilibrium conditions. Its significance is
that any mineral and any rock available for collection at the Earth surface has
gone through a process that causes hydroxyls, the telltale sign of dissolved H2O,
to change into peroxyplusH2. The H2 molecules are diffusively
mobile and may leave even structurally dense mineral grains. The remaining peroxy thus become the memory of the “true” solute H2O
content, besides a few residual hydroxyls. Though first described over 30 years
ago, this redox conversion has been largely ignored. As a result it is unknown
how much H2O is contained in the Earth’s upper mantle but it is
certainly much more than has been assumed until now on the basis of analysis of
residual hydroxyls.