The focus of our work is to determine the constraints placed by atmosphere-water-rock interactions on the environmental conditions for self-assembly of the molecular building blocks of the earliest like-like entities, “protocells.” 

We have addressed the problem that modern geochemical concentrations of total dissolved phosphate (P_T) and Mg²⁺ are much lower than those are required for non-enzyamtic (prebiotic) RNA synthesis, while Mg² and Ca²⁺ concentrations are too high for membrane stability, so how did life emerge on early Earth? 

We used a geochemical thermodynamic modeling approach, to show that a single, globally-occurring geological process of komatiite rock weathering and evaporation of the resulting solutions under specific partial pressures of atmospheric CO₂ (P_CO2) can quantitatively provide the P_T, Mg²⁺ and Ca²⁺ concentrations required for nucleotide synthesis, RNA polymerization and protocell-membrane stability. 

Conversely, the biologically-required concentrations of P_T, Mg²⁺ and Ca²⁺ place constraints on the P_CO2 levels on early Earth compared to previous estimates ranging over five orders of magnitude. Using these environmental constraints on Mg²⁺ and Ca²⁺ concentrations, we examined the stability and evolution of simple protocell membranes from pure single chain amphiphile (SCA) compositions through mixed SCA-phospholipid (PL) to pure PL compositions found in modern cells. 

We showed that, rather than acting being toxic, the divalent cations promoted evolution of the membranes towards more modern compositions. We also found that RNA oligomer synthesis is possible even at much lower concentrations of Mg²⁺ than previously reported, well within the concentration range constrained by the atmosphere-water-rock interactions. 

Thus, we have used a geochemical modeling approach to create the components of a simple protocell under geochemically plausible conditions.