http://arxiv.org/abs/2012.00819
In the conventional habitable zone (HZ) concept, a CO${2}$-H$_2$O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO${2}$ partial pressure (pCO${2}$) 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 pCO${2}$ 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 CO$_2$ outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO$_2$ with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO$_2$ in the HZ and show that it could be detected from at least 83 ($2{\sigma}$) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.
O. Lehmer, D. Catling and J. Krissansen-Totton
Thu, 3 Dec 20
75/81
Comments: Published 12/1/2020 in Nature Communications. The supplemental data and code referenced in this work are available from the Nature Communications website (see DOI below) or by email from the authors