A new climate model developed by a team at Rice University suggests that ancient lakes on Mars may have persisted for decades under thin, seasonal ice covers, rather than requiring a warm climate. This research offers a potential explanation for the geological evidence of past liquid water on Mars, addressing inconsistencies with previous climate models that struggled to account for long-term liquid water under the planet's early, cold, and thin atmosphere.
Background on Martian Water
Mars currently features a dry, frozen surface, yet geological evidence indicates a past with liquid water. NASA's Curiosity rover and other missions have identified numerous features, including lake basins, water-shaped channels, deposited sediments, and minerals formed in lakes. These observations, particularly from Gale Crater, suggest the presence of standing water over significant periods approximately 3.6 billion years ago. Earlier climate models faced challenges in explaining the long-term presence of liquid water under the early Martian atmosphere, which was characterized by a weak sun and a thin, carbon dioxide-rich composition, conditions typically associated with a frozen planet. Short-term warming events were deemed insufficient to account for the observed long-lived lake features.
The LakeM2ARS Model
The research team, led by Eleanor Moreland and including co-authors Professor Kirsten Siebach and Professor Sylvia Dee, adapted an Earth-based climate modeling tool, Proxy System Modeling, for Martian conditions. This reconfigured version, named Lake Modeling on Mars with Atmospheric Reconstructions and Simulations (LakeM2ARS), was developed over several years to align with the physics of Mars. It incorporated Mars' lower gravity, carbon dioxide-rich atmosphere, and significant seasonal variations. The team utilized mineral, rock layer, and chemical data from rovers as proxies for past climate indicators. The findings from this research were published in the journal Advancing Earth and Space Sciences.
Seasonal Ice Mechanism and Simulation Results
The LakeM2ARS model proposes that thin, seasonal ice, rather than permanent thick ice, could have protected the lakes from complete freezing. The mechanism suggests that ice would have formed during colder periods, minimizing heat loss and evaporation. This ice would then melt in warmer periods, allowing for solar warming of the water below. This cyclical process could have maintained lake stability for years or decades, permitting the water to remain liquid for extended durations.
The team conducted 64 simulations using data from Gale Crater, with each simulation covering 30 Martian years (approximately 56 Earth years). While some scenarios indicated lakes freezing solid, others demonstrated lakes maintaining liquid water with a predictable thin seasonal ice cover. The study indicates that this thin ice acted as an insulator, preventing rapid heat loss and substantial evaporation, which could explain the undisturbed nature of ancient lake beds.
Implications and Future Research
This proposed mechanism could account for the preservation of Martian lake beds, shorelines, and sediment layers, as thin, temporary ice would leave minimal geological evidence of glacial erosion. This contrasts with what might be expected from extensive, long-term ice sheets. The model suggests that liquid water could have persisted on early Mars without requiring warm, stable climates comparable to Earth's, only intermittent conditions that allowed surface water to endure longer than previously estimated.
The research team plans to apply the LakeM2ARS model to other Martian regions to assess the potential for similar lakes. They also intend to investigate the impact of atmospheric pressure and subsurface water on lake stability over time. Should similar patterns be observed across the planet, it would further support the hypothesis that even a cold early Mars could have sustained year-round liquid water, guiding future searches for signs of ancient habitability and revising current interpretations of Mars’ watery past.