A whole-planet model of the Earth without life for terrestrial exoplanet studies

TL;DR

The paper tackles whether life is required to maintain habitable surface conditions and how to distinguish inhabited from merely habitable exoplanets. It introduces a coupled, one-dimensional core-mantle-crust-climate framework that evolves interior processes, geochemistry, atmosphere, and solar input from 50 Myr to 5 Gyr, calibrated to the pre-industrial Earth. The work achieves reproduction of 19 PIE observations within uncertainties after roughly 4.5 Gyr and generates realistic reflected-light spectra across the Habitable Worlds Observatory range to serve as abiotic baselines for biosignature interpretation. This whole-planet abiotic approach provides a robust baseline for interpreting HWO data and improves predictions of long-term habitability for Earth-like exoplanets without life.

Abstract

As the only known habitable (and inhabited) planet in the universe, Earth informs our search for life elsewhere. Future telescopes like the Habitable Worlds Observatory (HWO) will soon look for life on rocky worlds around Sun-like stars, so it is critical that we understand how to distinguish habitable planets from inhabited planets. However, it remains unknown if life is necessary to maintain a habitable planet, or how all of the components of an evolving planet impact habitability over time. To address these open questions, we present a coupled interior-atmosphere evolution model of the Earth without life from 50 Myr to 5 Gyr that reproduces 19 key observations of the pre-industrial Earth within measurement uncertainties after 4.5 Gyr. We also produce a reflected light spectrum covering the possible wavelength range of HWO. Our findings support the view that life is not required to maintain habitable surface conditions. The model presented here is apt for predicting the long-term habitability of Earth-like exoplanets via evolving bulk properties. By generating realistic reflected light spectra from evolved atmospheric states, this model represents significant progress towards whole-planet modeling, which may ultimately provide a robust abiotic baseline for interpreting biosignature observations with HWO.