A coupled atmosphere-hydrosphere global climate model of early Mars: Reproduction of a 'cool and wet' scenario for the formation of water channels
Abstract
Martian water channels are considered evidence of a climate warm enough to allow the existence of long-term fluvial systems on early Mars during the Noachian and Hesperian boundary (3.85-3.6 Ga). Quantitative inferences of water channel formation from climate models are crucial to develop an accurate understanding of the early Martian environment. We present the results of a 3-dimensional Paleo Martian Global Climate Model (PMGCM) assuming the CO2/H2O atmosphere under the 'Faint Young Sun' (solar luminosity of 75% of the current value), with surface pressures between 0.5 and 2 bars. The PMGCM also has a hydrologic cycle module, which includes ocean thermodynamics, water vapor advection/convection/condensation/precipitation processes, and surface fluvial activities (e.g. fluvial and sediment transport). The simulation with a surface pressure exceeding 1.5 bars indicated that as per the PMGCM, the early Martian surface environment would have been 'cool' (between 'warm' and 'cold'); namely, the mean surface temperatures were high enough (> 273 K) during spring to autumn, to allow seasonal melting of snow-ice deposits, and low enough (< 273 K) during winter to produce considerable snow precipitation and accumulation. The PMGCM also indicated a 'wet' surface environment characterized by precipitation and seasonal melting of snow/ice (neither 'dry' nor 'permanent frozen' states), and enough fluvial sediment transport in the southern low-mid latitudes to reproduce Martian valley networks within a relatively short time (less than 10 million years). We suggest that a moderate climate, that is, 'cool and wet' conditions lying between 'warm and wet' and 'cold and frozen,' is preferable to explain the fluvial activity on early Mars, which does not need to consider non-climatic mechanisms such as warming by meteorite impacts.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1883K