The oxidation-reduction potential of aqueous soil solutions at the Mars Phoenix landing site
Article first published online: 23 JUL 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 14, July 2011
How to Cite
2011), The oxidation-reduction potential of aqueous soil solutions at the Mars Phoenix landing site, Geophys. Res. Lett., 38, L14202, doi:10.1029/2011GL047671., , , and (
- Issue published online: 23 JUL 2011
- Article first published online: 23 JUL 2011
- Manuscript Accepted: 3 JUN 2011
- Manuscript Revised: 2 JUN 2011
- Manuscript Received: 4 APR 2011
- NASA Phoenix mission;
- oxidation-reduction potential;
 Results from the Mars Phoenix mission Wet Chemistry Laboratory (WCL) are used to determine the oxidation-reduction potential (Eh) of the Phoenix WCL Rosy Red sample soil solution. The measured Eh 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 Eh changes correspond to changes in solution H+ activity, which is controlled mainly by changes in headspace PCO2 and solution CO32−, HCO3−, and CO2 concentrations. If measured at a PCO2 of 8 mbar in water, rather than in WCL test solution, the Eh 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.