Mineralogic Mapping of Huygens Crater, Mars: a Transect of the Highlands Crust and Hellas Basin Rim

Eighth International Conference on Mars (2014) 1038.pdf

MINERALOGIC MAPPING OF HUYGENS CRATER, MARS: A TRANSECT OF THE HIGHLANDS CRUST AND HELLAS BASIN RIM. S. E. Ackiss, K. D. Seelos, and D. L. Buczkowski, Johns Hopkins Universi- ty Applied Physics Laboratory, Laurel, MD 20723 ([email protected]).

Introduction: Huygens crater is a well preserved bearing minerals, and hydrated minerals like sulfates peak ring structure on Mars centered at 13.5°S, 55.5°E and phyllosilicates. Twelve CRISM multispectral map in the Noachian highlands between Terras Tyrrhena tiles (~230 m/pix and corrected to Lambert Albedo) and Sabaea (Fig. 1). With a diameter of ~450 km, it were used to understand regional mineralogic trends uplifted and exhumed Noachian crustal materials from and define unit contacts. Summary parameters [9] depths greater than 30 km, likely including Hellas rim showing spectral absorptions associated with the mafic material. minerals olivine (OLINDEX), low-calcium pyroxene In neighboring terrains, numerous small outcrops of (LCP, LCPINDEX), and high-calcium pyroxene (HCP, aqueously altered minerals, such as phyllosilicates, HCPINDEX) were examined. Summary parameters have been identified [1-2] as well as frequent expanses that highlight the presence of hydrated minerals were of mafic-bearing plains [3-6]. By mapping the distribu- also utilized. Specifically, the D2300 parameter aided tion of these different mineral types in and around in the identification of Fe/Mg phyllosilicate-bearing Huygens, we offer unique insight into the emplacement materials while the BD1900 parameter showed the and alteration history of the highlands crust. presence of other hydrated minerals. Contacts were drawn where data is present and believable (spatially coherent, or inconsistent with noise) at 1:250K scale and in some cases inferred by morphology across gaps in CRISM coverage. Once units were identified, we used CRISM targeted hyperspectral data (~18 m/pix) to confirm the detections, understand specific mineralogy (e.g., type of phyllosilicate), and explore morpho- logic and stratigraphic relationships.

Fig. 1. Regional context showing Huygens crater; Solid white circle shows crater rim, white dashed circle shows peak ring, black line traces a graben system circumferential to Hellas basin [10]. Yellow box shows location of Fig. 3. Data sets and Methods: We utilize data from the Compact Reconnaissaince Imaging Spectrometer for Mars (CRISM) as well as multiple other global data sets. Basemap data include Thermal Emission Imag- ing System (THEMIS) daytime IR (100 m/pix) and nighttime IR (265 pix/deg or ~230 m/pix), as well as Fig. 2. Mineralogic map of Huygens crater. Red units denote Mars Orbiter Laser Altimeter (MOLA) topographic olivine-bearing material, blue units denote HCP-bearing data (128 pix/deg or ~460 m/pix). Each basemap was material, green units denote LCP-dominated material, and imported into ArcGIS 10.1 where the geodatabase and yellow units denote aquously altered material. mapping contacts were developed and stored. Mapping Results: Units and Distribution: Four The CRISM instrument [8] acquires visible and mineralogy-based units were defined for the Huygens near infrared (0.36-3.9 µm) data that record infor- study region: olivine-, HCP-, LCP-bearing, and aque- mation about primary mafic mineraology, ferric- ously altered material (Fig. 2). Eighth International Conference on Mars (2014) 1038.pdf

The olivine-bearing unit is associated with topo- graphically lower, flat-lying plains, including most of the floor of Huygens and the infilled floors of smaller surrounding craters. It is also observed on intercrater plains consistent with high thermal interia, olivine- bearing “bedrock” units described by [5]. Mapped occurrances of HCP-bearing material are associated and gradiational with similar plains morphology to that of the olivine-bearing unit. Outcrops are found in areas on the floor of Huygens as well as smaller craters throughout the study region. Exposures of LCP occur in distinct outcrops con- centrated in the southern portion of the map area, interior to the circumferential Hellas graben system. LCP is usually associated with a more erosionally-resistant, knob-forming material (Figure 3). Aqueously altered materials are localized with exposures typically associated with impact crater rims, walls, and ejecta blankets. They are identified both inside (on the floor of) and outside Huygens and include Fe/Mg smectites, Al-bearing phyllosilicates, and hydrated carbonates (see also [11]). Comparison to Existing Geologic Map: Olivine- and HCP-bearing units roughly correspond to Hesperi- an plain units of [7] (Hr and Hpl3). All of the other mineralogic units fall within areas mapped as Npld (Noachain dissected terrain). Summary: Huygens crater represents a unique transect of the Noachain crust and Hellas rim region. We have identified 4 major mineralogic units in and around Huygens: olivine- and HCP-bearing plains, LCP-bearing outcrops, and aqueously altered materials. Fig. 3. Subset of Huygens study region (see Fig. 1). (A) The superposition of olivine- and HCP-bearing units CRISM mafic parameter composite (R=OLINDEX, G= on Huygens and surrounding crater floors as well as LCPINDEX, B=HCPINDEX) over THEMIS daytime IR. (B) intercrater plains is consistent with later emplacement. Mapped mineralogic units (see Fig. 2) and targeted data In contrast, knob-forming LCP-bearing outcrops are footprints. Black arrow shows location of FRT00011D18, spatially limited interior to the circumferential graben which (C) shows the relationship between mafic-bearing system and may be evidence of widespread crustal up- units [same composite as (A)] and (D) highlights the pres- lift associated with Hellas formation [12]. Phyllosili- ence of Fe-bearing phyllosilicates (in red; R=D2300, cates and other hydrated alteration materials are scat- G=BD2210, B=BD1900_2). Both C and D are displayed tered throughout the study area within Noachain-aged over infrared albedo (IRA). terrains, exposed via subsequent impact events. No References: [1] Bibring, J.-P., et al. (2005) Sci., 307, pattern was observed between specific alteration min- 1576-1581. [2] Loizeau, D., et al. (2012) Icarus, 219, eralogy and outcrop location, consistent with previous 476-497 [3] Koeppen, W. C., et al. (2008) JGR, 113, research [e.g., 1-2]. E05001. [4] Mustard, J. F., et al. (2005) Sci., 307, 1594- Acknowledgements: This work was supported by 1597. [5] Rogers, D., et al. (2011) JGR, 116, E08005. [6] the NASA Mars Data Analysis Program (grant number Rogers, D. and Nazarian, A. H. (2014) JGR, 118, 1094- NNX10AO25G) and in part by an appointment to the 1113. [7] Greeley and Guest (1987) USGS Misc. Invest. Postgraduate Research Participation Program at Series, Map I-1802-B. [8] Murchie, S. L., et al. (2007) JHUAPL administered by the Oak Ridge Institute for JGR, 112, E05S03. [9] Pelkey, S. M. et al. (2007) JGR, Science and Education (ORISE) program. 112, E05S14. [10] Wichman and Schultz (1989) JGR, 94, 17333-17357. [11] Wray, J. J., et al. (2011) LPSC Ab- stract 2635. [12] Skok, J. R., et al. (2012) JGR,117, E00J18.