Near‐infrared spectroscopy of lacustrine sediments in the Great Salt Lake Desert: An analog study for Martian paleolake basins

Abstract

The identification and characterization of aqueous minerals within ancient lacustrine environments on Mars are a high priority for determining the past habitability of the red planet. Terrestrial analog studies are useful both for understanding the mineralogy of lacustrine sediments, how the mineralogy varies with location in a lacustrine environment, and for validating the use of certain techniques such as visible-near-infrared (VNIR) spectroscopy. In this study, sediments from the Pilot Valley paleolake basin of the Great Salt Lake desert were characterized using VNIR as an analog for Martian paleolake basins. The spectra and subsequent interpretations were then compared to mineralogical characterization by ground truth methods, including X-ray diffraction, automated scanning electron microscopy, and several geochemical analysis techniques. In general, there is good agreement between VNIR and ground truth methods on the major classes of minerals present in the lake sediments and VNIR spectra can also easily discriminate between clay-dominated and salt-dominated lacustrine terrains within the paleolake basin. However, detection of more detailed mineralogy is difficult with VNIR spectra alone as some minerals can dominate the spectra even at very low abundances. At this site, the VNIR spectra are dominated by absorption bands that are most consistent with gypsum and smectites, though the ground truth methods reveal more diverse mineral assemblages that include a variety of sulfates, primary and secondary phyllosilicates, carbonates, and chlorides. This study provides insight into the limitations regarding the use of VNIR in characterizing complex mineral assemblages inherent in lacustrine settings.

Constraints on the composition and particle size of chloride salt‐bearing deposits on Mars

“…Although halite is often found in association with other evaporite phases in lacustrine or playa depositional settings [e.g., Lynch et al , , and references therein], its presence as a major phase in these settings is consistent with the inferred abundances for the Martian deposits. Still, the apparent lack of additional evaporite phases, either due to geochemical fractionation or optical masking effects, must be addressed when comparing the Martian deposits to terrestrial lacustrine evaporative environments.…”

Field investigation of dried lakes in western United States as an analogue to desiccation fractures on Mars

“…However, a detailed characterization looks nearly impossible in the absence of other tools and experiments that would need to be carried out in situ. It should be noted that Lynch et al [] arrived to the same conclusions following their fieldwork in the Great Salt Lake Desert. Therefore, our conclusions, in this regard, are not new but are in support of theirs.…”

Remote sensing and in situ mineralogic survey of the Chilean salars: An analog to Mars evaporate deposits?

“…Sulfates were identified thanks to a drop in reflectance at 2.4 µm caused by vibrations of the SO 4 group (e.g., Gendrin et al, 2005;Cloutis et al, 2006;Bishop et al, 2009). Although a similar feature can also be attributed to chloride salts or chlorine oxyanion salts (e.g., Lynch et al, 2015) (Figure 5b, Clark et al, 1990Clark et al, , 2007Cloutis et al, 2006). Anhydrous chlorides and perchlorates (e.g., NaCl, MgCl 2 , NaClO 4 )…”

“…These minerals should have distinct VNIR properties, however, spectral libraries for sulfates are incomplete. Additionally, XRD analysis also distinguished between hydrated sulfates and hydrated Cl salts, which can have similar VNIR spectra, making detections sometimes problematic (e.g., Hanley et al, 2015;Lynch et al, 2015 Bibring et al, 2004;Murchie et al, 2007;Pieters et al, 2009) (Pilorget andBibring, 2013, De Angelis et al, 2014;Korablev et al, 2015Korablev et al, , 2016Maurice et al, 2015).…”