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The origins of perchlorate in the Martian soil

The origins of perchlorate in the Martian soil Perchlorate (ClO4−) has been detected on Mars, but its production and distribution are unclear. Mechanisms requiring atmospheric chlorine are insufficient for measured concentrations. We conducted studies under Mars conditions using halite (NaCl) alone, soil simulants consisting of silica (SiO2), Fe2O3, Al2O3, and TiO2. After 170 h irradiation, samples analyzed by ion chromatography (IC) showed ClO4− and ClO3− present in all samples. When SiO2 was added, yield increased from 2 to 42 nmol and 0.4 to 2.6 nmol, respectively. We attribute this to SiO2 and metal oxides acting as photocatalysts, generating O2− radicals from O2 which react with chloride. Results show ClO4− and ClO3− can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions, and explain high concentration of ClO4− and ClO4−/Cl− ratios detected by Phoenix. They provide evidence that its distribution on Mars is dictated by distribution of chlorine and provide insight into the oxidizing nature of the soil and its potential effects on organics. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geophysical Research Letters Wiley

The origins of perchlorate in the Martian soil

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References (50)

Publisher
Wiley
Copyright
©2015. American Geophysical Union. All Rights Reserved.
ISSN
0094-8276
eISSN
1944-8007
DOI
10.1002/2015GL064290
Publisher site
See Article on Publisher Site

Abstract

Perchlorate (ClO4−) has been detected on Mars, but its production and distribution are unclear. Mechanisms requiring atmospheric chlorine are insufficient for measured concentrations. We conducted studies under Mars conditions using halite (NaCl) alone, soil simulants consisting of silica (SiO2), Fe2O3, Al2O3, and TiO2. After 170 h irradiation, samples analyzed by ion chromatography (IC) showed ClO4− and ClO3− present in all samples. When SiO2 was added, yield increased from 2 to 42 nmol and 0.4 to 2.6 nmol, respectively. We attribute this to SiO2 and metal oxides acting as photocatalysts, generating O2− radicals from O2 which react with chloride. Results show ClO4− and ClO3− can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions, and explain high concentration of ClO4− and ClO4−/Cl− ratios detected by Phoenix. They provide evidence that its distribution on Mars is dictated by distribution of chlorine and provide insight into the oxidizing nature of the soil and its potential effects on organics.

Journal

Geophysical Research LettersWiley

Published: May 28, 2015

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