Material Trends from Remote Sensing Analysis of Paleolake Basins

Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6325.pdf

MATERIAL TRENDS FROM REMOTE SENSING ANALYSIS OF PALEOLAKE BASINS. J. Buz1, C. S. Edwards1, 1Northern Arizona University, Department of Astronomy and Planetary Sciences, Flagstaff, AZ 86001 ([email protected])

Introduction: Past, current, and future Mars rover missions have targeted basins with putative paleolakes [1–4]. Basins are geologically important because of their nature as sinks for fluids and sediments over areas much larger than themselves (e.g., [5]). Furthermore, and as a direct result of this catchment, basins often show remarkable mineralogical and sedimentological diversity [e.g., 1,6–9]. The materials they accumulate provide a record of previous environmental conditions as they are deposited in sedimentary layers. However, the ability of basins to collect a useful record of deposition unfortunately also leads to the accu- mulation of post-lacustrine materials fully or partially obscuring the lacustrine deposits. Remote sensing is re- lied upon for site selection and mission planning because it enables rough characterization of mineralogy and surface properties in the vicinity of a landed mission. The signal recorded through remote sensing in- struments, particularly in the Vis-NIR, combines both the material/layer of interest (in this case paleolacustrine deposits) and other confounding sources (e.g., atmos- phere, dust, regolith). In this work we will characterize the fundamental properties of paleolacustrine basins, specifically trends in grain size distributions and mineralogy across a basin. We will then evaluate how these properties may be mis- construed in remote sensing analysis through comparison of our remote sensing interpretations with in situ and laboratory measurements of the basin surface and materials at depth (i.e., below any potential post-lacustrine material). The results will be applied to remote sensing analysis of paleolacustrine sites on Mars with implications for future missions and past basin analysis. Methods: Paleolake basins of comparable size and with available Vis-NIR and IR data have been selected on Mars (Fig. 1) and Earth. On Mars, THEMIS and CRISM are used for remote sensing analysis in the IR and Vis-NIR respectively. The former dataset allows

for thermal inertia/grain size quantification while the Figure 1: Mars paleolacustrine sites selected for detailed latter for mineralogy. Analogous IR (MASTER, study. Images are calculated thermal inertia overlaid on ASTER) and Vis-NIR (AVIRIS, Hyperion) datasets are THEMIS daytime IR mosaics [12] A) Jezero B) available for Earth. Eberswalde C) Ismenius Lacus D) Kashira E) Rahe F) We calculate thermal inertia on Mars using the KRC Unnamed at 256.7° E, -39.2° N G) Unnamed at 129.3° thermal model [10] with the following inputs: E, -9.6° N H) Unnamed 125° E, -13.5° N MOLA/HRSC blend topography, slope and azimuth, TES lambert albedo, modeled atmospheric opacity for For mineral identification and chemistry on Mars we observation latitude and year, material properties of bas- use volcano-scan atmospherically corrected and photo- alt, and 12.5 µm surface temperature. Apparent thermal metrically corrected CRISM images [13]. We first iden- inertia is calculated on terrestrial remote sensing data tify minerals using summary parameters for common following [11]. Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6325.pdf

Mars materials [14,15] and follow-up with custom sum- Current/Future Work: A trial site, Stonewall mary parameters and detailed spectroscopic analysis. A Playa, will be visited. In situ and laboratory measure- similar pipeline exists for terrestrial data [16]. ments will be presented. Spectral analysis of CRISM Terrestrial sites will be visited and cores of ~60 cm data is ongoing. Further analysis of each hyperspectral will be collected across the same transects used for re- image will include mineral endmember determination mote sensing analysis. The depth of the cores is based and abundance estimates. We will employ the tech- off of previous literature on the thickness of regolith and niques in [26] to calculate degree of crystallinity or sil- desert pavement in the Great Basin (the region contain- ica content in the THEMIS data [27]. Mineral types, ing all of the terrestrial paleolacustrine sites of interest) their abundances throughout the basin, the crystallinity [17,18]. The cores will be subdivided into sub-samples and grain sizes will all help comparison between Mar- from various depths. Mineral abundances and grain size tian and terrestrial sites and aid in determining the rea- distributions will be quantified through laboratory anal- sons for material segregation. ysis (e.g., sieving, EMPA, XRD) to determine trends We will validate our results and interpretations of across the basin and with depth. the Martian remote sensing data by using data collected Preliminary Results: Thermal inertial for our Mar- by MER and MSL rovers. We will predict mineral tian sites is shown in Figure 1. In general, thermal iner- abundances and grain size distributions at Jezero and tia appears to increase with proximity to basin center. ground-truth with the Mars 2020 rover payload. This phenomenon is particularly pronounced at Isme- References: [1] Grotzinger J. P. et al. 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