Moderate and high-temperature metamorphic conditions produced diverse phosphorous species for the origin of life

Low solubility and low reactivity towards organic compounds make phosphorus a problematic element for the origin and early evolution of life. Reduced and polymerized phosphorus species are more bioavailable and may resolve these issues, but widespread formation pathways for these species are not well understood. Here we show, using experiments and thermodynamic modelling, that diverse polyphosphates (straight-chains with up to five and cyclophosphates with three and four phosphate molecules) and reduced phosphite can form under ferruginous anhydrous conditions at 80-700 °C. We find that hydrogen and temperature enhance phosphite production while polyphosphate formation maximizes at moderate temperatures (175-200 °C). Chromite and Nickel-bearing minerals enhance phosphate polymerization and reduction whereas magnetite inhibits them. These findings expand on previous investigations of thermally induced changes in phosphorus-speciation and show that these reactions may be widespread in nature. Metamorphism of ferruginous sediments, serpentinization, as well as subaerial lakes exposed to volcanic heating could potentially produce a wealth of polyphosphates along with phosphite on the early Earth. Later, these species may have participated in prebiotic phosphorylation reactions upon liberation by subsequent fluid infiltration. Our results thus offer a more widespread pathway for the generation of reactive phosphorus for the origin of life.