3D modelling of the early Martian Climate under a denser CO2 atmosphere: Temperatures and CO2 ice clouds.

By Francois Forget, R. Wordsworth, Ehouarn Millour, Jean-Baptiste Madeleine, L. Kerber, J. Leconte, E. Marcq, R. Haberle. 2012

319 citations recorded by the source corpus.

On the basis of geological evidence, it is often stated that the early martian climate was warm enough for liquid water to flow on the surface thanks to the greenhouse effect of a thick atmosphere. We present 3D global climate simulations of the early martian climate performed assuming a faint young Sun and a CO2 atmosphere with surface pressure between 0.1 and 7 bars. The model includes a detailed radiative transfer model using revised CO2 gas collision induced absorption properties, and a parameterisation of the CO2 ice cloud microphysical and radiative properties. A wide range of possible climates is explored using various values of obliquities, orbital parameters, cloud microphysic parameters, atmospheric dust loading, and surface properties. Unlike on present day Mars, for pressures higher than a fraction of a bar, surface temperatures vary with altitude because of the adiabatic cooling and warming of the atmosphere when it moves vertically. In most simulations, CO2 ice clouds cover a major part of the planet. Previous studies had suggested that they could have warmed the planet thanks to their scattering greenhouse effect. However, even assuming parameters that maximize this effect, it does not exceed +15 K. Combined with the revised CO2 spectroscopy and the impact of surface CO2 ice on the planetary albedo, we find that a CO2 atmosphere could not have raised the annual mean temperature above 0 C anywhere on the planet. The collapse of the atmosphere into permanent CO2 ice caps is predicted for pressures higher than 3 bar, or conversely at pressure lower than 1 bar if the obliquity is low enough. Summertime diurnal mean surface temperatures above 0 C (a condition which could have allowed rivers and lakes to form) are predicted for obliquity larger than 40 at high latitudes but not in locations where most valley networks or layered sedimentary units are observed. In the absence of other warming mechanisms, our climate model results are thus consistent with a cold early Mars scenario in which nonclimatic mechanisms must occur to explain the evidence for liquid water. In a companion paper by Wordsworth et al. we simulate the hydrological cycle on such a planet and discuss how this could have happened in more detail.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/b60fa34b24aa460999d51bc3625f0912f9f5948b

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Citations in the corpus

3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability (2013, methodology): “This quantity, which represents the number density per unit mass of activated cloud condensation nuclei, is assumed to be uniform throughout the atmosphere (Forget et al. 2013).”
HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS (2014, background): “Several other recent studies used 3D global circulation models (GCMs) to study the po- tential habitability of specific systems (Wordsworth et al. 2010; Forget et al. 2013).”
Origin and evolution of the atmospheres of early Venus, Earth and Mars (2018, background): “…2012; Rodriguez et al. 2015; Iijima et al. 2017; Palumbo and Head III 2018), available greenhouse gases (i.e., CO2, CH4, H2, etc.) (Kasting 1991; Forget et al. 2013; Ramirez et al. 2014; Wordsworth et al. 2013; Kerber et al. 2015; Wordsworth 2016b; Fairén 2017; Iijima et al. 2017) and the Sun’s…”
The Climate of Early Mars (2016, methodology): “This conclusion, which was reached by Kasting using a one-dimensional clear-sky radiativeconvective climate model, has recently been confirmed by three-dimensional climate models that include cloud effects (Forget et al. 2013; Wordsworth et al. 2013).”
Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets (2017, background): “Planet h is not suitable for surface liquid water, whatever the thickness of the CO2 atmosphere is, and even when maximizing the radiative effect of CO2 ice clouds (parameterized following Forget et al. 2013).”
Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model (2015, background): “This causes the equatorial highlands to be among the coldest regions of the Martian surface, leading to enhanced stability of snow deposits there (the ‘icy highlands’ effect [Wordsworth et al., 2013]).”
Global modelling of the early Martian climate under a denser CO2 atmosphere: Water cycle and ice evolution (2012, background): “In a companion paper [Forget et al., 2012], we describe the climate under dry (pure CO2) conditions.”
Geologic Constraints on Early Mars Climate (2018, background): “But maximum CO2 + H2O(v) warming is too cold for H2O(l) rivers (Forget et al. 2013, Wordsworth et al. 2013, Turbet & Tran 2017).”
The habitability of Proxima Centauri b II. Possible climates and Observability (2016, background): “Low irradiated planets as Early Mars (Forget et al. 2013; Wordsworth et al. 2013, 2015; Turbet et al. 2016b), Archean Earth (Charnay et al. 2013), Snowball Earth-like planets (Turbet et al. 2016a) or exoplanets like Gliese 581d (Wordsworth et al. 2011); 2.”