Professor Friedemann Freund discusses how deep gases in the Earth may have helped to set the stage for the origin of life
Living on this beautiful planet of ours, we walk on solid ground made from rocks – rocks which, at their origin, once crystallized out of searing hot magmas. During crystallization, the minerals in those rocks picked up some of those gases that are dissolved in magmas, the same gases that spew out of volcanoes, when they erupt: carbon dioxide, water, nitrogen and sulfur compounds.
Isn’t it remarkable that the elements making up these common volcanic gases – Carbon, Hydrogen, Oxygen, Nitrogen and Sulfur, often called CHONS – are also the essential elements, on which Life is based?
Years back, in the 1980s, I started to study how these volcanic gases interact with magmatic minerals that can’t accommodate them, when they crystallize in their presence. To provide some context, I may add that the geoscience community at that time (and still today) likes to look at magmatic minerals more from the perspective of thermodynamic equilibrium, trying to determine which minerals form at which temperatures and pressures. I took a different approach: I tried to understand what the volcanic gases do – on the atomic level – when they get caught up in the unaccommodating host mineral structures and how they interact with the matrix oxygen anions.
I was in for a big surprise. It was well known already that minerals, which had gobbled up some of the magmatic gases such as water and carbon dioxide, tore these molecules apart and incorporated them as hydroxyl and carboxy anions. Nobody suspected however that, upon cooling to temperatures below thermodynamic equilibrium, the protons in the hydroxyls and the carbon in the carboxy anions would “steal” an electron from their associated oxygens. As a result, the protons become hydrogen and the carbon atoms become chemically reduced, “organic” carbon – just like that, by a purely physical process.
The follow-up steps were even more baffling: the back-and-forth shuffling of electrons causes the oxygen anions to change their valence from 2– to 1–, making them highly deformable and altering their bonding characteristics. This seemed to allow the chemically reduced carbon atoms to diffuse relatively easily, even when classical diffusion theory says that they should stay put. Consequently, the carbon atoms become unexpectedly mobile, even in dense mineral structures, squeezing from oxygen to oxygen, able to segregate to places, where other carbon atoms would also go. There carbon atoms tie carbon-carbon bonds. Hydrogen molecules join. Together they build, well inside the mineral matrices, polyatomic organic protomolecules. From the little we know so far, these CHONS protomolecules are not only complex, with molecular weights up to 600 atomic mass units, but also contain multiple functional carboxylic acid groups. Here and there, nitrogen and sulfur atoms are part of the mix, probably even phosphorus. When minerals weather at the surface of the Earth, these CHONS protomolecules will be released into the environment, producing complex CHONS molecules. This process must have gone on ever since planet Earth was very young. What better way than this to set the stage for the Origin of Life?
As so often in science, when something is discovered which seems to be fundamentally new, a torrent of disapproval arises among specialists, with many of them trying to prove that this cannot be true. The same happened to me in the 1980s, so much so that I retreated from this field altogether to let the controversy die down. Now is the time to start again.