291-11 Interpreting Mg-carbonate signatures and geochemical properties in Martian analog lakes using VNIR/SWIR reflectance spectroscopy

Session: Mineralogy in the Solar System

Presenting Author:

Sydney Cloutier

Authors:

Cloutier, Sydney Marie¹, Horgan, Briony Heather Noelle², Bryant, Roger³, Raudsepp, Maija⁴, Wilson, Sasha⁵, Olson, Stephanie⁶

(1) Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA, (2) Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, , (3) Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA, (4) Department of Physical Science, MacEwan University, Edmonton, AB, Canada, (5) Department of Earth and Atmospheric Science, University of Alberta, Edmonton, AB, , (6) Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA,

Abstract:

On Mars, magnesium carbonates have been detected in numerous settings and provide key insights into potential habitable and past aqueous environments. However, Mg-carbonate spectral detection is limited by its co-occurrence with clays and sulfates. This phenomenon arises when diagnostic carbonate absorptions are obscured—a process known as spectral masking. Since visible/near-infrared to shortwave infrared (VNIR/SWIR; 0.35–2.5 µm) spectroscopy is the primary technique used to identify carbon-bearing deposits from orbit, understanding how mixed mineral assemblages influence spectral signatures is essential for reconstructing ancient Martian environments. We investigate whether VNIR/SWIR reflectance spectroscopy can distinguish magnesium carbonate-producing alkaline lakes with varying geochemical conditions and evaluate the extent to which sediment spectra preserve information regarding depositional context.

A total of 37 Earth analog sediment samples from the Cariboo Plateau, Canada and Lake Salda, Turkey were analyzed using VNIR/SWIR reflectance spectroscopy, spectral parameter calculations, quantitative X-ray diffraction (XRD), and comparisons with published geochemical datasets. Principal component analysis separated six statistically significant spectral clusters (silhouette score = 0.61; PERMANOVA pseudo-F = 31.26, p = 0.001) corresponding to discrete mineral assemblages and lake chemistries. The clusters differentiate spectrally weak, moderate, and strong Mg-clay assemblages, hydromagnesite-bearing sediments, and sulfate-dominated sediments, while preserving trends in lake geochemistry. Alkalinity (F = 30.15, p < 0.001, η² = 0.829) and sulfate concentration (F = 831.73, p < 0.001, η² = 0.993) emerged as the strongest controls on spectral properties and mineralogy.

Reflectance spectra preserve relevant geochemical information beyond mineral identification but also reveal notable limitations for carbonate detection in VNIR/SWIR. Mg-carbonate absorptions were heavily masked by Mg-clays and sulfates, even in sediments containing up to ~60 wt% carbonate, demonstrating that abundant carbonate does not automatically exhibit a diagnostic spectral signal. Despite this masking, spectral clustering remained consistent with mineralogical and geochemical data—indicating that physical conditions can encode within the overall spectral response. These findings suggest that weak or absent carbonate absorptions in Martian orbital datasets should not immediately be interpreted as evidence for carbonate-poor environments but may instead reflect mineral mixing. By quantitatively linking reflectance spectra with lake geochemistry and mineralogy, this work provides an improved framework for interpreting CRISM observations of carbonate-bearing terrains, including Jezero crater, and strengthens the use of terrestrial alkaline lakes as analogs for ancient habitable environments on Mars.

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