Serpentinites and the Origin of Life

April 17th, Jackson Sr. Center, 12:15 pm “Serpentinites and the Origin of Life” Presented by Dr. B. Ronald Frost Department of Geology and Geophysics University of Wyoming

One of the great mysteries in geology is “How did life begin”?  Darwin in a letter to a friend Joseph Hooker in 1871 postulated that life could have begun in a warm pond full of ammonia and phosphorous salts where proteins slowly developed.  The problem with this is that though the early atmosphere on Earth was reducing, the impact of light waves on Fe2+in the warm pond would convert it to Fe3+, making the pool too oxidizing for complex organic compounds to survive.  What’s more, without the ozone layer, the surface of the early Earth would have been bathed in UV radiation.  This means that the most likely locality for the origin of life is in submarine vents. The most reducing environment on Earth is found in the submarine vents emitting fluids that are associated with the formation of serpentinites.  Mantle rocks are rich in olivine (Mg,Fe)2SiO4, which is unstable in the presence of seawater. Hydration of olivine is commonly written as the reaction:

 2 Mg2SiO4+ 3 H2O = Mg3Si2O5(OH)4+ Mg(OH)3

                                         olivine        water       serpentine           brucite

Unfortunately the reaction isn’t this simple, partially because Fe is present and serpentinization produces magnetite by processes that are poorly known and still under dispute. One possibility si that Fe-brucite is not particularly stable and that it reacts to magnetite by the reaction:

3 Fe(OH)2  =  Fe3O4+  2 H2O  +  H2

                                               Fe in brucite  magnetite  water hydrogen

The production of magnetite during serpentinization explains why the fluids from some sea floor vents are so reducing that they contain hydrogen and methane.  In this environment, protected by kilometers of ocean water from the withering ultraviolet radiation that bathed the surface of the planet where life began.