Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept.
Where this comes from
- Record sourced from PubMed, PMID 33262334.
- Also identified by DOI 10.1038/s41467-020-19896-2 and PMC identifier 7708846.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
In the conventional habitable zone (HZ) concept, a CO<sub>2</sub>-H<sub>2</sub>O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO<sub>2</sub> partial pressure (pCO<sub>2</sub>) 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<sub>2</sub> 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<sub>2</sub> outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO<sub>2</sub> with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO<sub>2</sub> 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.