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The oxidation‐reduction potential of aqueous soil solutions at the Mars Phoenix landing site
Author(s) -
Quinn Richard C.,
Chittenden Julie D.,
Kounaves Samuel P.,
Hecht Michael H.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl047671
Subject(s) - aqueous solution , ferrous , phoenix , mars exploration program , soil water , martian soil , chemistry , redox , metal , environmental chemistry , inorganic chemistry , environmental science , astrobiology , soil science , martian , organic chemistry , martian surface , physics , metropolitan area , medicine , pathology
Results from the Mars Phoenix mission Wet Chemistry Laboratory (WCL) are used to determine the oxidation‐reduction potential (E h ) of the Phoenix WCL Rosy Red sample soil solution. The measured E h of the Rosy Red sample in the WCL aqueous test solution was 253 ± 6 mV at a pH of 7.7 ± 0.1. Measured solution E h changes correspond to changes in solution H + activity, which is controlled mainly by changes in headspace P CO2 and solution CO 3 2− , HCO 3 − , and CO 2 concentrations. If measured at a P CO2 of 8 mbar in water, rather than in WCL test solution, the E h of the Rosy Red soil solution would be ∼300 mV. The results of laboratory experiments using analog salt mixtures are compatible with the possible presence of low levels (ppm) of metal peroxides or other oxidants and indicate that levels of readily soluble ferrous iron in the soil are below 1 ppm.