COLUMBIA RIVER BASALT WEATHERING RIND VARIABILITY: IMPLICATIONS FOR REMOTE SENSING STUDIES AT MARS

Images acquired by the MastCam and MastCam-Z cameras on the Curiosity and Mars 2020 rovers will serve as the primary data to determine which materials to target for further investigation during mission operations. Because weathered rocks will be of considerable interest, understanding what weathering rind colors tell us about actual internal rock variability is crucial on Mars, where rovers need to both conserve time and resources while sampling the widest array of rocks. To address this matter, we investigated the rind surface and fresh interior of two Columbia River Basalt samples from the same flow that differ in weathering rind color and texture. We spectrally characterized the rind and interior using Visible-Near Infrared (VNIR) and Thermal Infrared (TIR) spectra. Using Scanning Electron Microscopy (SEM), Backscatter Electron Imaging (BSE), Energy Dispersion Spectroscopy (EDS), and X-ray diffraction (XRD), we characterized the morphological, elemental and mineralogical properties of each sample at the rind surface and the interior in order to determine what properties might contribute to spectral and textural differences between the weathered rocks. While XRD, EDS and spectral data revealed similar mineralogical weathering trends between each sample’s interior and rind, SEM data of the rinds display varying morphologies, suggesting the samples are at different successive stages in the weathering process. We conclude that the key differences in the weathering rinds are a result of different rates of weathering due to slight variations in weathering sub environments, and/or variations in time spent exposed to surface weathering conditions. Our results indicate that differences in weathered appearance do not necessarily result from different petrological properties, and that similar weathering trends could be observed despite differences in appearance among rocks we may sample on Mars.