On the Role of 40K in the Origin of Terrestrial Life

Abstract

The abundance and biological role of potassium suggest that its unstable nuclide was present in all stages of terrestrial biogenesis. With its enhanced isotopic ratio in the Archean eon, (Formula presented.) K may have contributed to the special, perhaps unique, biogenetic conditions that were present in the primitive Earth. Compared to the U and Th radionuclides, (Formula presented.) K has a less disruptive radiochemical impact, which may drive a moderate, but persistent evolution of the structural and functional properties of proto-biological molecules. In the main (Formula presented.) -decay route of (Formula presented.) K, the radiation dose generated by an Archean solution with potassium ions can be larger than the present background radiation on Earth by one to two orders of magnitude. Estimates of the rates of organic molecules indirectly affected by (Formula presented.) decays are provided for two schematic models of the propagation of secondary events in the solvent of prebiotic solutions. The left-handed (Formula presented.) particles emitted by (Formula presented.) K are the best candidates to trigger an enantiomeric excess of L-type amino acids via weak nuclear forces in the primitive Earth. The concentration-dependent radiation dose of (Formula presented.) K fits well in dry–wet scenarios of life’s origins and should be considered in realistic simulations of prebiotic chemical pathways.