HR: 16:15h
AN: P14A-02    [Abstracts]
TI: Aqueous Solution Chemistry on Mars
AU: * Quinn, R
EM: rquinn@mail.arc.nasa.gov
AF: SETI Institute, NASA Ames Research Center MS 239-4, Moffett Field, CA 94035, United States
AU: Hecht, M
EM: michael.h.hecht@jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Kounaves, S
EM: samuel.kounaves@tufts.edu
AF: Tufts University, Department of Chemistry, Medford, MA 02155, United States
AU: Young, S
EM: Suzanne.Young@tufts.edu
AF: Tufts University, Department of Chemistry, Medford, MA 02155, United States
AU: West, S
AF: Thermo Scientific, 81 Wyman Street, Waltham, MA 02454, United States
AU: Fisher, A
EM: anita.m.fisher@jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Grunthaner, P
EM: Paula.J.Grunthaner@jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: Currently en route to Mars, the Phoenix mission carries four wet chemistry cells designed to perform basic solution chemistry on martian soil. The measurement objectives are typical of those that would be performed on an unknown sample on Earth, including detection of common anions and cations, total conductivity, pH, redox potential, cyclic voltammetry (CV), etc. Both the challenge and the novelty arise from the necessity to perform these measurements with severely constrained resources in a harsh and (literally) alien environment. Sensors for all measurements are integrated into a common "beaker," with the ability to perform a two-point calibration of some sensors using a pair of low-concentration solutions. Sulfate measurement is performed with a crude titration. While most measurements use ion selective electrodes, halide interferences are resolved by independent chronopotentiometry (CP) measurements. No preconditioning of the soil-water mixture is possible, nor is any physical characterization of the introduced soil sample beyond coarse visual inspection. Among the idiosyncrasies of the measurement is the low external pressure, which requires that the analysis be performed close to the boiling point of water under an atmosphere consisting almost entirely of water vapor. Despite these liabilities, however, extensive laboratory characterization has validated the basic approach, and protocols for both CV and CP have been developed and tested. Enhancing the value of the measurement is the suite of coordinated observations, such as microscopy and evolved gas analysis, to be performed by other Phoenix instruments.
DE: 1060 Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
DE: 1094 Instruments and techniques
DE: 5410 Composition (1060, 3672)
DE: 5494 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting