Geomorphic and stratigraphic studies of Mars prove extensive liquid water flowed and pooled on the surface early in Mars’ history. Martian paleoclimate models, however, have difficulty simulating climate conditions warm enough to maintain liquid water on early Mars. Reconciling the geologic record and paleoclimatic simulations of Mars is critical to understanding Mars’ early history, atmospheric conditions, and paleoclimate. This study uses an adapted lake energy balance model to investigate the connections between Martian geology and climate. The Lake Modeling on Mars for Atmospheric Reconstructions and Simulations (LakeM2ARS) model is modified from an earth-based lake model to function in Martian conditions. We use LakeM2ARS to investigate conditions necessary to simulate a lake in Gale crater. Working at a localized scale, we combine climate input from the Mars Weather Research & Forecasting general circulation model with geologic constraints from Curiosity rover observations; in doing so, we identify potential climatic conditions required to maintain a seasonal liquid lake. We successfully model lakes in Gale crater while varying initial climate conditions, lake size, and water salinity. Our results show that ice-free conditions in a plausible Gale crater lake are best supported when the lake is small, ~10 m deep, and air temperatures reach or are just above freezing seasonally during a Martian year. Continued use and iteration of LakeM2ARS will strengthen connections between Mars’ paleoclimate and geology to inform climate models and enhance our understanding of conditions on early Mars.

Lacustrine, riverine, and spring carbonates are archives of terrestrial climate change and are extensively used to study paleoenvironments. Clumped isotope thermometry has been applied to freshwater carbonates to reconstruct temperatures, however, limited work has been done to evaluate comparative relationships between clumped isotopes and temperature in different types of modern freshwater carbonates. Therefore, in this study, we assemble an extensive calibration dataset with 135 samples of modern lacustrine, fluvial, and spring carbonates from 96 sites and constrain the relationship between independent observations of water temperature and the clumped isotopic composition of carbonates (denoted by Δ47). We restandardize and synthesize published data and report 159 new measurements of 25 samples. We derive a composite freshwater calibration and also evaluate differences in the Δ47-temperature dependence for different types of materials to examine whether material-specific calibrations may be justified. When material type is considered, there is a convergence of slopes between biological carbonates (freshwater gastropods and bivalves), micrite, biologically-mediated carbonates (microbialites and tufas), travertines, and other recently published syntheses, but statistically significant differences in intercepts between some materials, possibly due to seasonal biases, kinetic isotope effects, and/or varying degrees of biological influence. Δ47-based reconstructions of water δ18O generally yield values within 2‰ of measured water δ18O when using a material-specific calibration. We explore the implications of applying these new calibrations in reconstructing temperature in three case studies.