Origin of Life -  
            Was it an astrobiological event  or chemical evolution ?
             Did Minerals play a Role in Chemical Evolution?

                    work of Robert Hazen at Carnegie Institute (Geophysical Lab)

Current Paradigm...  
     evidence favors a chemical evolutionary origin of life

         "simple chemical self-assembly has lead to self-replicating systems"

    Earth forms 4.5 billion years ago
            from 4.5 to 4.0 bya - Asteroids bombard & sterilize planet surface
            4.0 bya - first fossil evidence of microscopic life

    Initial event may have been evolution of Carbon based molecules
                ancient atmosphere (was reducing) with single carbon gases
                    carbon monoxide,  carbon dioxide,  methane

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1953 - Miller & Urey @ U Chicago
        recreate ancient atmosphere [ammonia, methane, water, & electricity]
        produce amino acids, which many assume can now link into complex polymers
                    rocky surfaces allow concentration via evaporations
       Origin of Life research is no longer philosophical, but rather experimental

 

1977 - discovery of deep hydrothermal vents
           suggests that origin of life organic reactions may have occurred in intense
                            heat & pressure of these vents

    Hazen's lab designed experiments to mimic high temp/pressure of hydrothermal vents
      & look at the role minerals may have played in producing self-replicating molecules

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  ROLE of MINERALS -
minerals (calcite, feldspar, magnetite, clay, etc...)
                                        may have fostered organic chemistry of early life.
  

    1998 - began in Robert Hazen's lab [Carnegie Institute, Washington]:
               showed that amino acids decompose at 200 oC under pressure,
               but when FeS (iron-sulfur) minerals are added, amino acids remain intact.
  

    the idea is one of SCAFFOLDING SUPPORT by the minerals...
        an easy way to assemble molecules in dilute solution is to concentrate the molecules
        on a flat surface, which is exactly what minerals may have helped provide:
         

            feldspar* - a mineral that houses microscopic pits that could shelter life's precursor
                            molecules from UV radiation and destruction...
                                       allows concentrating of components and greater chemical reactivity
     

            magnetite* (iron oxide) - triggers combination of nitrogen & hydrogen into
                                       ammonia (NH3), a reduction reaction essential for organic life
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            clay* - layered clays can trap organics [help concentrate them] between clay sheets;
                            held close together molecules can then form more complex molecules...
                     montmorillonite clays can sharply accelerate the formation of membranous fluid-filled sacs;
                              these vesicles can grow and undergo a simple form of division, giving them
                              properties akin to primitive cells & might be a mechanism that helped create
                              RNA molecules
enclosed in a membrane?
 

   Minerals may provide some possible answers to one chemical anomaly:
  

        the selection of only 1 specific optical isomer [ L-amino acids ] out of 2 (D & L) enantiomers*
        in the making of cellular proteins... today's proteins contain only L-amino acids.
  

        Miller's experiments produces 50-50 mix of the 2 isomers, the D & L amino acids...
  

        Could the Earth's minerals have help select one isomer over the other isomer?
                             calcite* - calcium carbonate mineral that attracts D & L- amino acids to
                                            different crystal faces, thus in the origin of life
                                            one amino acid isomer could have been selected over the other.
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Pre-Biotic Chemical Evolution   (current paradigm)
        origin of life was not a single event...
        it was most likely a gradual sequence of modest chemical compound formations,
                                     which added a degree of order and complexity to molecular structure.

            1st step - abiotic formation of building blocks...
                                     either ala...  Miller & Urey or hydrothermal vents or via 'space debris'
            2nd step - minerals provide structural basis for concentrating,
                                                     confining, ordering, & selecting molecules;
                                                     may have lead to first primitive self-replicating systems
           next step - competition for limited chemical resources leads to
                                                     MOLECULAR    NATURAL    SELECTION
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