Transient reducing greenhouse warming on early Mars

By R. Wordsworth, Yulia N. Kalugina, S. Lokshtanov, A. Vigasin, Bethany L. Ehlmann, James W. Head III, C. Sanders, Huize Wang. 2016

196 citations recorded by the source corpus.

The evidence for abundant liquid water on early Mars despite the faint young Sun is a long‐standing problem in planetary research. Here we present new ab initio spectroscopic and line‐by‐line climate calculations of the warming potential of reduced atmospheres on early Mars. We show that the strength of both CO2–H2 and CO2–CH4 collision‐induced absorption (CIA) has previously been significantly underestimated. Contrary to previous expectations, methane could have acted as a powerful greenhouse gas on early Mars due to CO2–CH4 CIA in the critical 250–500 cm−1 spectral window region. In atmospheres of 0.5 bar CO2 or more, percent levels of H2 or CH4 raise annual mean surface temperatures by tens of degrees, with temperatures reaching 273 K for pressures of 1.25–2 bars and 2–10% of H2 and CH4. Methane and hydrogen produced following aqueous alteration of Mars' crust could have combined with volcanically outgassed CO2 to form transient atmospheres of this composition 4.5–3.5 Ga. Our results also suggest that inhabited exoplanets could retain surface liquid water at significant distances from their host stars.

Subfields: Astronomy and Astrophysics, Ecology

View Paper: https://www.semanticscholar.org/paper/a403e757866c684fe2d919d43dd555f15fc3aff2

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Citations in the corpus

The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up (2017, background): “…e.g., greenhouse warming due to elevated levels of atmospheric H2 (Stevenson 1999; Pierrehumbert & Gaidos 2011; Wordsworth & Pierrehumbert 2013; Wordsworth et al. 2017; Ramirez & Kaltenegger 2017), liquid water will freeze at the planet surface and life will be confined to volcanic or…”
Update of the HITRAN collision-induced absorption section (2019, unknown): “Also for this collisional pair, no experimental or theoretical line shapes are available, and we included the estimates of the model calculations of Wordsworth et al., 2017.”
How to Characterize Habitable Worlds and Signs of Life (2017, background): “…are not hydrogen dominated, foreign-broadening of hydrogen by the background atmosphere excites rototranslational bands within the hydrogen that promote significant absorption in spectral regions where CO2 and H2O absorb poorly, enhancing warming (Ramirez et al. 2014a,b, Wordsworth et al. 2017).”
Geologic Constraints on Early Mars Climate (2018, background): “• Most models assume ≳1 bar of CO2 to provide a baseline of greenhouse warming (e.g. Wordsworth et al. 2017).”