3D Simulations of the Early Martian Hydrological Cycle Mediated by a
H2-CO2 Greenhouse
Abstract
For decades the scientific community has been trying to reconcile
abundant evidence for fluvial activity on Noachian and early Hesperian
Mars with the faint young Sun and reasonable constraints on ancient
atmospheric pressure and composition. Recently, the investigation of
H2-CO2 collision induced absorption has opened up a new avenue to warm
Noachian Mars. We use the ROCKE-3D global climate model to simulate
plausible states of the ancient Martian climate with this absorptive
warming and reasonable constraints on surface paleopressure. We find
that 1.5-2 bar CO2-dominated atmospheres with 3% H2 can produce global
mean surface temperatures above freezing, while also providing
sufficient warming to avoid surface atmospheric CO2 condensation at
0°-45° obliquity. Simulations conducted with both modern topography and
a paleotopography, before Tharsis formed, highlight the importance of
Tharsis as a cold trap for water on the planet. Additionally, we find
that low obliquity (modern and 0°) is more conducive to rainfall over
valley network locations than high (45°) obliquity.