Characterization of Rock Types at Meridiani Planum, Mars Using Mer 13-filter Pancam Spectra

Introduction: The Mars Exploration Rover Opportunity has traversed more than 13 km across Meridiani Planum, finding evidence of ancient aqueous environments that, in the past, may have been suitable for life. Meridiani bedrock along the rover traverse is a mixture in composition and bulk mineralogy between a sulfate-rich sedimentary rock and hematite spherules (" blueberries ") [1]. On top of the bedrock, numerous loose rocks exist. These rocks consist of both local bedrock and " cobbles " of foreign origin. The cobbles provide a window into lithologic diversity and a chance to understand other types of martian rocks and meteorites. For example, several cobbles are interpreted as probable meteorites (e.g., Santa Catarina, Heat Shield, Barberton) [2]. Other rocks that have compositions different from the average bedrock (e.g., Jin, Bounce) may not be meteorites, but instead may be derived from locations deeper than the present surface and delivered to the current site as ejecta. Due to limitations dictated by mission operations, it is likely that not every interesting cobble was recognized or characterized. However, 13-filter (13F) Pan-cam images of specific targets and landscape scenes that contain cobbles were frequently collected. Therefore , we have been able to create a database of ar-chived 13F cobble spectra throughout the entire traverse and gather statistical information on the types of rocks that populate the Meridiani plains. In the summer of 2007, Opportunity experienced a global dust storm which coated the Mini-TES mirrors. Although work is ongoing to recover the Mini-TES capabilities, the team is now relying on Pancam as its primary remote sensing tool. Therefore, this study was also an attempt to establish a method to expand upon those of Mini-TES to remotely identify rocks of interest to make efficient use of the rover's current resources. Methodology: Pancam is a multiband, stereo-scopic, panoramic imager that covers the visible and near infrared wavelengths (432-1009 nm) [3]. In this study, we are interested in developing the ability to distinguish groups of cobbles and understand their location along Opportunity's traverse, including association with craters. It should be noted that for this study we did not use 13F spectra to determine mineralogy or composition of the cobbles, but instead used the spectra solely for grouping purposes. To create a database of cobble spectra, we extracted individual spectra from more than 200 rocks