Organic Chemistry in Far-From-Equilibrium, High Energy Environments: Habitability and Life’s Origins

The free energy sources of a given planet or moon that can shape its propensity to originate or support life are multifaceted. As a starting point, typical bond dissociation energies for geologic and atmospheric materials range from about 1-15 eV, which correspond to photon wavelengths covering visible light as well as adjacent portions of the infrared and ultraviolet. We may reasonably expect that chemical cycling sufficient to generate and maintain redox gradients that can support biochemistry ought to be driven by energy sources equal to or greater than this range. Energy sources that greatly exceed this range yield interesting organic synthesis results, but also typically contribute a smaller overall fraction of the energy and power budgets of most rocky bodies. This talk will be an exploration of the demonstrated effects that such far-from-equilibrium energy sources may impart on organic synthesis occurring on rocky bodies. Recent findings have demonstrated that γ radiolysis of aqueous solutions of simple, single-carbon organics can drive the synthesis of higher mass organics such as glycolaldehyde and cyanamide, while also generating intermediates at a variety of redox states. Despite a bewildering array of possible reaction permutations between initial compounds and intermediates, there are relatively few detectable outputs of this system, and those that are observed are additionally associated with the assembly of even more complicated but key biological molecules such as ribonucleotides. The network of organic compounds generated via radiolysis itself is unique, and bears many attributes associated with life such as a heterogeneous connectivity distribution and numerous, interwoven sets of chemical cycles. The conclusion is that far-from-equilibrium sources of energy, regardless of their relative contribution to a body’s energy budget, can generate robust means of potentially initiating and sustaining life.