Earth Without Life 2: A Global Network Model of Abiotic Phosphorus Cycling on Earth Through Time

Abstract

Phosphorus (P) is a crucial structural and bioenergetic component of living systems. P cycles through terrestrial geochemical reservoirs via complex physical and chemical processes. Terrestrial life has altered the fluxes between these reservoirs as it evolved, thus it is of interest to explore planetary P flux evolution in the absence of biology. This is especially true since environmental P availability may have influenced the emergence of life on Earth, and affected life’s ability to alter other geochemical cycles, and these processes may be common to other planets. Geochemical P fluxes likely change as planets evolve, and element cycling models that take those changes into account can provide insights on how P fluxes evolve abiotically. There is considerable uncertainty in many aspects of modern and historical global P cycling, including Earth’s initial P endowment and distribution after differentiation and how P interactions between reservoirs and fluxes have evolved over time. We present here a user-configurable dynamical box model for Earth’s abiological P evolution. This model suggests that in the absence of biology, long term planetary geochemical cycling on planets similar to Earth tend to bring P to surface reservoirs, while biology tends to move P to subductable marine reservoirs.