MINERALOGIC MAPPING OF HUYGENS CRATER, MARS: A TRANSECT OF THE HIGHLANDS CRUST AND HELLAS BASIN RIM

Huygens crater is a well preserved peak ring structure on Mars centered at 13.5°S, 55.5°E in the Noachian highlands. With a diameter of ~450 km, it uplifted and exhumed Noachian crustal materials from depths greater than 30 km. We utilize multispectral and hyperspectral visible/near-infrared (0.36-3.9 micron) data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) to map the exposed mafic and alteration minerals present in and around the crater. Twelve Lambert albedo multispectral map tiles are used for regional analysis and unit delineation while prototype MTRDR hyperspectral images are analyzed for specific mineral phases at the outcrop scale. Four mineralogy-based units are defined: olivine type I (OT1)-, olivine type II (OT2)-, low calcium pyroxene (LCP)-, and phyllosilicate-bearing material. The OT1-bearing unit is associated with topographically lower, flat-lying plains, including the floor of Huygens and the infilled floors of smaller surrounding craters. OT2-bearing material appears to be associated with similar plains morphology in craters primarily in the southwest part of the study region. While both OT1 and OT2 exhibit spectral signatures of olivine and pyroxene, they differ in the relative contributions of each of these mineral types, with OT1 showing more of a “pure” olivine signature while OT2 has an enrichment of high-calcium pyroxene (HCP). Exposures of LCP, on the other hand, occur in distinct knob-forming outcrops concentrated in the southern portion of the map area, interior to the Hellas rim boundary, and perhaps representing uplifted Hellas impact material. Phyllosilicate-bearing materials are localized and have been exposed by impact cratering, with signatures observed on crater rims, walls, and in ejecta blankets. Phyllosilicates identified both inside and outside Huygens include Fg/Mg smectites and less commonly Al-bearing phyllosilicates; carbonates are also a possibility at some locations. By mapping the distribution of different mineral types exposed in and around Huygens, we offer unique insight into emplacement and alteration history of the highlands crust.