Mini-tes Measurements of Santa Catarina-type, Stony-iron Meteorite Candidates by the Opportunity Rover

Introduction: After nearly 40 years of close-proximity reconnaissance, the precise role of water in the hydrogeologic and potential habitability history of Mars still remains one of the most enigmatic puzzles facing planetary science. Significant progress has been made, however, and general scientific opinion is now inclined to regard the earlier Noachian period of Mars’ history as possessing the greatest potential for having been truly ‘wet,’ with a progression toward dryer climates during much of the Hesparian and Amazonian periods. The effects of water during these more recent periods is likely to have been subtle, requiring a sensitive indicator of its interaction with the martian surface to recognize. Reduced meteoritic iron-nickel metal is likely the most sensitive material on the surface of Mars to aqueous alteration, oxidizing readily upon exposure to liquid water, and possibly even water vapor and ice. This sensitivity is wellknown on Earth where meteorite weathering presents a problem for curators to control, and researchers to compensate for in their analyses. Far from presenting a problem in the martian environment, however, this phenomenon can be applied to the assessment of more subtle aspects of martian climatic behavior where water may play a less major, but still significant, role. Thus a meteorite may, under the same set of conditions, provide evidence for water exposure where a martian basalt might not. At a time when phylosilicate occurrence is considered a site selection criterion for future ground missions because of its water implications, the occurrence of meteorites should be apportioned a similar weight in the “ground-truthing” of water exposure once successful landings are accomplished, particularly at midto highlattitudes. Background: Several meteorite candidates have been identified on Mars by the Mars Exploration Rover (MER) science teams at both rover locations [1]. The most recent of these, Santorini, is discussed elsewhere at this conference [2], with additional candidates discussed elsewhere still [3]. Four of the meteorite candidates have now been evaluated by the full suite of MER instruments (Alpha particle X-ray spectrometer (APXS), Mössbauer spectrometer (MB), and microscopic imager), including Barberton, Meridiani Planum, Santa Catarina (SC), and Santorini. Open questions remain for each of these relating to the degree of possible aqueous alteration they may have undergone to account for the presence of ferric iron oxides detected by Mössbauer spectroscopy [1,2]. That any such alteration might have occurred from water exposure in the near-equatorial latti tudes of Mars (where such alteration is not necessarily anticipated) is a question of no small significance to our paleoclimatic understanding of the region. As a remote sensing tool, the Mini-TES instrument has proven useful in identifying iron meteorite candidates at a distance on previous occasions at both MER sites [1]. SC was found among a large field of cobbles near the Cabo Anonimo promontory along the NNW rim of Victoria Crater during early reconnaissance of the Crater environs. Mini-TES measurements were collected for 11 cobbles in this area between sols 1046 and 1062 (including SC), and a 12 collected on sol 1190 during a second pass through the region en route to the Victoria Crater point of ingress (Figure 1). This abstract reports on Mini-TES results for these rocks.