Geologic Mapping of Gusev Crater Informed by Comparative Studies of Volcanic Embayment Relationships on Earth and Mars

Gusev crater is a 160 km diameter impact crater located near the southern highland-northern lowland dichotomy boundary on Mars. The geological history of Gusev crater is complex, with features formed by a host of processes (including impact, fluvial, volcanic, hydrothermal, aeolian and possibly lacustrine) and with a record of activity spanning much of Martian history. The geologic diversity of the Gusev crater region, seen initially from orbital data, was further revealed through in-situ exploration of the Columbia Hills and surrounding volcanic plains by the MER Spirit rover between 2004 and 2010. The proposed investigation is designed to advance knowledge of the evolution of Gusev crater, which remains a site of interest for future exploration, through detailed geomorphic and geologic mapping analyses informed by analogue studies of embayment relationships in volcanic settings on Earth.

In order to better understand its geologic history, we will produce a new 1:250,000-scale geologic map of Gusev crater [174-177°E, 13-16°S] to be published through the NASA/USGS Planetary Geologic Mapping Program. This mapping study will focus on the geologic evolution of the floor and rim of Gusev crater through geologic mapping and analysis of volcanic, tectonic, erosional, and depositional landforms. The previously published 1:500,000 scale U.S. Geological Survey Map I-2666 (Kuzmin et al., 2000) that includes Gusev crater was based only on Viking mission data. Digital geologic mapping and related analyses of the geomorphic, morphometric, and spatial characteristics of features will be done using Geographic Information System (GIS) software. We will also compile crater size-frequency distributions to investigate the relative and absolute ages for the geologic units and volcanic flows defined by mapping.

Landforms associated with embayment of the preexisting landscape by lava flows are prominent in Gusev crater and common in other craters, including the notable example of Jezero crater. The small-scale morphological and compositional signatures of lava embayment are little studied. In order to assist in the interpretations of geologic features in Gusev crater and specifically for derivation of the geologic history of its floor units, we will conduct detailed analyses of embayment and contact relationships in volcanic settings at a series of terrestrial analogue sites. Candidate sites include the Snake River Plain (Craters of the Moon National Monument, Idaho), El Malpais National Monument (New Mexico), and central California (Mojave Desert). These analogue studies are designed to calibrate interpretations of contact/embayment relationships as observed from orbit in Gusev crater and to examine scale dependencies through investigations of the small-scale morphologic, topographic, and compositional characteristics of contacts between volcanic flows and older bedrock outcrops, other volcanic deposits (e.g., cinder cones, pyroclastic deposits), and sediments. We expect that this work will have direct application to investigations of Jezero crater.