British Columbia’s Unassuming Planetary Laboratory: How a Handful of Frozen Saline Lakes Can Help Us Understand Brines Across the Solar System

Zoom Link for Colloquium 05/24/2022 3:00pm PST.

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Presented By Jacob Buffo


Introduction:  Mounting observational and theoretical evidence supports the ubiquity of brines across the solar system. This fact, combined with their indelible link to astrobiology and icy world geophysics, has led to the prioritization of improving our understanding of brine-rich systems (e.g., their dynamics, longevity, habitability, and observable signatures) in the lens of planetary exploration, planetary protection, resource identification, and the search for life beyond Earth.

A fundamental challenge in expanding our knowledge of solar system brines is the fact that all the proposed brine-bearing worlds (less Earth) reside beyond the frost line. As such, stable/metastable brines are buried beneath/within icy shells, caps, or regolith, complicating their direct measurement unless active plume or effusive processes are occurring, and placing any near surface brines in a perpetual battle against impending solidification. Until direct in situ missions (e.g., penetrators) become consistently tenable, we will continue to rely upon our ability to relate remote sensing measurements of icy world surfaces to their subterranean brine properties and processes.

Our current understanding of this quantitative relationship between ice and underlying ocean/brine properties is based on studies of terrestrial analog systems (e.g., sea ice, Antarctic dry valley lakes) and predictive multiphase reactive transport models. While well-constrained terrestrial analog systems provide an exceptional compositional endmember (i.e., NaCl dominated systems), they represent a small subset of potential planetary brine chemistries. Furthermore, the successful extension of terrestrial analog dynamics to the spatiotemporal scales and chemical diversity of planetary ices relies on the accuracy and applicability of these numerical models – itself a novel field – which in turn require analog benchmark data to validate.

Field Site/Work: The Cariboo Plateau of south-central British Columbia houses an array of compositionally diverse hypersaline lakes. Many of the chemistries represented in these systems are unique to the area (e.g., MgSO4 and NaCO3 dominated ice-brine systems) and may more closely represent the compositions of oceans and brines of icy worlds across the solar system than does our NaCl dominated ocean or the brines of other terrestrial analog ice-brine environments (e.g., Dry Valley lakes).

The lakes form perennial ice covers, offering a unique opportunity to investigate the thermal and physicochemical properties of ices derived from unique planetary relevant brines as well as the characteristics of their parent fluid, their formation history, and thus the quantitative relation between ice observational properties and their underlying parent brines.

I will present thermal, physical, and biogeochemical profiles of these unique ices and discuss their relevance to the identification and characterization of planetary brines.

2D Model of Planetary Ice-Brine Systems: To extend the knowledge garnered from these unique analog environments to planetary systems I have modified the two-dimensional multiphase reactive transport model SOFTBALL to accommodate diverse brine chemistries and planetary environmental conditions. The model tracks several habitability relevant parameters including water content and ice/brine compositions.

I will additionally present results benchmarking the numerical model against the physicochemical profiles of the hypersaline lakes, bolstering confidence in its application to a diverse array of planetary chemistries/environments, and discuss the significant implications the model’s use will have in our ability to forecast the dynamics, evolution, and properties of ice-brine systems throughout the solar system in the lens of planetary exploration and planetary protection.