ALTERED BASALTS FROM HAWAII AS AN ANALOG FOR ALTERATION ON MARS

Characterization of aqueous alteration and related minerals on the surface of Mars has provided powerful pieces of evidence for determining both current and past surface and near-surface processes. Careful study of similar alteration within comparable background lithologies on Earth can provide useful data for reference when analyzing the more limited data available from Mars. The Humu‘ula Groundwater Research Project provides a rare opportunity to observe lower temperature, lower sulfidation type aqueous alteration assemblages within several thousand feet of continuous section of basaltic rock as a Mars crustal analog, without the complications usually observed by terrestrial surface weathering. As described in a companion abstract, several hundred VIS-SWIR bulk reflectance spectra were collected along core to broadly identify alteration zonation and unique assemblages. Using VIS-SWIR spectral data collected with the Ultra Compact Imaging Spectrometer (UCIS) instrument from Jet Propulsion Laboratory, combined with scanning electron microscopy, small cut-slabs taken from the core which were representative of different zones of alteration will be analyzed on approximately the same cut-face. From this process, bulk spectra taken on the slabs will be decomposed to 80 micrometer reflectance pixels by UCIS, and verified by backscatter composition mapping. This project will result in a highly-verified spectral library of bulk spectra representing many recently identified assemblages of interest for Mars study in regions like Nili Fossae. Initial bulk and UCIS spectral mapping and SEM imaging has noted magnesium and calcium rich phyllosilicates, multiple different zeolites, zones of smectite-illite alteration, and possible hydrated silica.

Through further study of the data, we hope to determine genetic sources of alteration throughout the column which can later be tied to stratigraphy and similar processes on Mars. On Mars, phyllosilicates in particular are of great interest though their provenance is not well known and can include formation in groundwater aquifers, in hydrothermal systems, or via interaction of ground water or ice with upwelling warm fluids from various possible sources. We hope data from this project will provide a framework for identifying genetic sources of alteration on Mars.