Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

Owen R Lehmer; David C Catling; Joshua Krissansen-Totton

doi:10.1038/s41467-020-19896-2

Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

Nat Commun. 2020 Dec 1;11(1):6153. doi: 10.1038/s41467-020-19896-2.

Authors

Owen R Lehmer^{1

2

3}, David C Catling^{4

5}, Joshua Krissansen-Totton^{5

6}

Affiliations

¹ MS 239-4, Space Science Division, NASA Ames Research Center, Moffett Field, CA, 94035, USA. owen.r.lehmer@nasa.gov.
² Department of Earth and Space Sciences/Astrobiology Program, University of Washington, Box 351310, Seattle, WA, 98195, USA. owen.r.lehmer@nasa.gov.
³ Virtual Planetary Laboratory at the University of Washington, Seattle, WA, 98195, USA. owen.r.lehmer@nasa.gov.
⁴ Department of Earth and Space Sciences/Astrobiology Program, University of Washington, Box 351310, Seattle, WA, 98195, USA.
⁵ Virtual Planetary Laboratory at the University of Washington, Seattle, WA, 98195, USA.
⁶ Department of Astronomy and Astrophysics, MS UCO/Lick Observatory, 1156 High Street, Santa Cruz, CA, 95064, USA.

Abstract

In the conventional habitable zone (HZ) concept, a CO₂-H₂O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO₂ partial pressure (pCO₂) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO₂ and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO₂ outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO₂ with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO₂ in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.