Identification of phyllosilicates and hydrated sulfates in an unnamed crater and Lampland crater in Thaumasia highlands, Mars

The occurrence of hydrous and hydrated minerals on Mars is closely associated with impact craters. We identified suits of hydrated minerals from two craters in the Thaumasia highlands—Lampland crater (35.54°S 280.48°E) and an unnamed crater (31.5°S 288.0°E). Images acquired by the CTX is used to observe the morphology and NIR spectral data acquired by CRISM is used for mineral identification. Lampland craters has a 70 km diameter with an intact central peak and a partially degraded ejecta. The other unnamed crater has 40 km diameter and shows degraded ejecta and few scattered mounds in the central region that are possibly the remnants of a central peak. In the unnamed crater, absorption are found at 1.4 and 1.9 µm in the center and crater walls in CRISM multispectral data product, which are due to hydrated minerals. Absorption near 2.28-2.32 µm is also observed within the central mound of the unnamed crater, which can be ascribed to Fe/Mg smectites. In Lampland crater, signatures of phyllosilicates are observed at 1.4, 1.9 and 2.3 μm. Additional absorptions at 1.6, 2.1 and 2.4 μm indicate the presence of hydrated sulfates.

The minerals exposed in the central regions of the craters could be impact excavated. However, for the minerals present along the walls, an impact-excavation origin is unlikely, since these minerals are present in the lower walls. Possible origin for these minerals, occurring along the walls could possibly be from former paleolakes, as feeder channels are present around the periphery of the crater walls that could lead to the formation of such a lake. A second possibility could be the upwelling and evaporation of circulating groundwater that could precipitate the sulfates. Presence of sulfates within impact craters is previously reported in Columbus and Cross craters and few other smaller craters in the surrounding area and ascribed to upwelling groundwater. These paleolake site are significant for astrobiological exploration as these could potentially preserve biosignatures in the lake sediments.