Experimental Constraints on Trace Element Behavior during Martian Fe- Oxidation Processes at Meridiani Planum

Introduction: The APXS (Alpha-Particle X-Ray Spectrometer) onboard the Mars Exploration Rovers (MER) has returned element abundances of over 200 soil and rock samples at both the Opportunity and Spirit landing sites [1]. Besides major elements, a selection of trace element concentrations including Ni, Cr, and Zn are also available. These data demonstrate that the trace element abundances of Meridiani outcrop material are variable (Table 1) and their behavior is very poorly understood [2]. Accordingly, it is of interest to set up a series experiments to investigate controls and behaviors of these key trace elements during Martian surficial processes. Tosca et al.[3] have proposed a mechanism that diagenetic oxidation and maturation of initially formed Fe sulfate minerals (such as melanterite) may account for the presence of jarosite and hematite in Meridiani Planum outcrop. In this model, the trace element behavior during low pH aqueous-mediated diagenesis processes may be partially responsible for their distribution observed by MER in situ analyses. Therefore, in this study, a series of Fe-oxidation experiments with added Ni, Cr, and Zn were conducted to investigate their behavior during oxidation and reaction with precipitation products.