Climate Simulations of Early Mars With Estimated Precipitation, Runoff, and Erosion Rates

Abstract

The debate over the early Martian climate is among the most intriguing in planetary science. Although the geologic evidence generally supports a warmer and wetter climate, climate models have had difficulty simulating such a scenario, leading some to suggest that the observed fluvial geology (e.g., valley networks, modified landscapes) on the Martian surface could have formed in a cold climate instead. However, as we have originally predicted using a single‐column radiative‐convective climate model (Ramirez, Kopparapu, Zugger, et al., 2014, https://doi.org/10.1038/ngeo2000), warming from CO2‐H2 collision‐induced absorption on a volcanically active early Mars could have raised mean surface temperatures above the freezing point, with later calculations showing that this is achievable with hydrogen concentrations as low as ~1%. Nevertheless, these predictions should be tested against more complex models. Here we use an advanced energy balance model that includes a northern lowlands ocean to show that mean surface temperatures near or slightly above the freezing point of water were necessary to carve the valley networks. Our scenario is consistent with a relatively large ocean as has been suggested. Valley network distributions would have been global prior to subsequent removal processes. At lower mean surface temperatures and smaller ocean sizes, precipitation and surface erosion efficiency diminish. The warm period may have been approximately <107 years, perhaps suggesting that episodic warming mechanisms were not needed. Atmospheric collapse and permanently glaciated conditions occur once surface ice coverage exceeds a threshold depending on collision‐induced absorption assumptions. Our results support an early warm and semiarid climate consistent with many geologic observations.

Collision‐Induced Absorption of CH4‐CO2 and H2‐CO2 Complexes and Their Effect on the Ancient Martian Atmosphere

“…These results support a recent study by Ramirez et al. (2020), which showed that warming from CO 2 ‐H 2 CIA would likely be between the extremes of using N 2 ‐H 2 CIA and the CIA values from Wordsworth et al. (2017).…”

“…The temperatures are still higher than those derived in Ramirez et al (2014), using the weaker N 2 CIAs, which would require 3-4 bar total pressure to achieve the same temperatures. These results support a recent study by Ramirez et al (2020), which showed that warming from CO 2 -H 2 CIA would likely be between the extremes of using N 2 -H 2 CIA and the CIA values from Wordsworth et al (2017). Mean surface temperatures above 273 K can be reached with the new CIA if surface pressures exceed ∼3 bar for a 10% CH 4 atmosphere or with 5% hydrogen and less than 2 bar of surface pressure.…”

“…Additional studies (Kamada et al., 2020; Ramirez, 2017; Ramirez et al., 2020) used the cross sections from Wordsworth et al. (2017) in Martian climate models and found that the inclusion of CIA between CO 2 and H 2 does result in a warm and wet early Mars that agrees with the paleopressure and climate stability constraints with only 3% hydrogen concentration.…”

Mars: Life, Subglacial Oceans, Abiogenic Photosynthesis, Seasonal Increases and Replenishment of Atmospheric Oxygen

“…Many investigators believe that ancient Mars was wet and habitable (Ehlmann et al 2011;Fairén 2020;Squyres and Knoll 2006;McKay 2010;Vago and Westall 2017;Grotzinger et al 2014;Jaumann et al 2014), and that in addition to thousands of lakes, oceans of water were at least temporarily present (Duxbury 2000;Fawdon et al 2018;Parker 1986;Head et al 1999;Ivanov et al 2014;Dickeson and Davis 2020;Fairén et al 2003). However, if ancient Mars had a stable, long-duration Earth-like ocean is subject to considerable debate and no clear consensus has emerged, except in regard to the generally agreed belief that oceans of water may have flowed across the surface of the northern hemisphere (Ramirez et al 2020;Carr and Head 2019;Dickeson and Davis 2020) What became of the Martian lakes and its oceans of water is also subject to much debate; though one contributing possibility may be abiotic photosynthesis. If over the course of the last 4 billion years the production of atmospheric oxygen has been completely abiotic, then this would have resulted in the complete evaporation of a planet-wide ocean of water with an initial depth of 50 to 80 meters (Barth 1974;Zhang et al 2012).…”

Early Mars may have boasted a large ocean and cool climate

“…The "cold and frozen" camp credits melting ice with scooping out the valleys. Now, new research (1) suggests that a large ocean was indeed required to form the features across the planet's surface. But rather than warm and wet, the planet would have been cool and semi-arid.…”