Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations

Abstract

[1] Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.

Estimating rock compressive strength from Rock Abrasion Tool (RAT) grinds

“…Rock and outcrop targets encountered by Spirit were classified according to their geochemical, spectral, and physical properties [ Ming et al ., ; Morris et al ., ; Squyres et al ., ; McCoy et al ., ; Crumpler et al ., ]. The largest division in inferred strength between rock types is between Adirondack‐class rocks (including Adirondack, Mazatzal, and Humphrey) and rock and outcrop materials found in the Columbia Hills, a distinction noted previously [e.g., Squyres et al ., ].…”

Mars

“…Orbital observations had earlier shown that the rim of Gusev was breached by an outflow channel, but Spirit observations indicated that any fluvial sediments within the crater have been buried by basaltic lavas and soil. Spirit's traverse into the Columbia Hills (Crumpler et al, 2011;Squyres et al, 2006a) and Inner Valley (Squyres et al, 2007) found aqueously altered rocks of uncertain origin, soils, and pyroclastic deposits. Spirit's traverse into the Columbia Hills (Crumpler et al, 2011;Squyres et al, 2006a) and Inner Valley (Squyres et al, 2007) found aqueously altered rocks of uncertain origin, soils, and pyroclastic deposits.…”

Alteration mineralogy of Home Plate and Columbia Hills—Formation conditions in context to impact, volcanism, and fluvial activity

“…We discuss sedimentation last, but sedimentation presumably began shortly after the formation of the impact crater (Cabrol ; Crumpler et al. ). Spirit found neither the nature nor ubiquity of sediments that were expected from the fact that Gusev crater is the catchment area for Ma'am Vallis (Kuzmin et al.…”