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Rates of oxidative weathering on the surface of MarsA model of acid weathering is proposed for the iron-rich basalts on Mars. Aqueous oxidation of iron sulfides released SO4(2-) and H(+) ions that initiated the dissolution of basaltic ferromagnesian silicates and released Fe(2+) ions. The Fe(2+) ions eventually underwent ferrolysis reactions and produced insoluble hydrous ferric oxide phases. Measurements of the time-dependence of acid weathering reactions show that pyrrhotite is rapidly converted to pyrite plus dissolved ferrous iron, the rate of pyrite formation decreasing with rising pH and lower temperatures. On Mars, oxidation rates of dissolved Fe(2+) ions in equatorial melt-waters in contact with the atmosphere are estimated to lie in the range 0.3-3.0 ppb Fe/yr over the pH range 2 to 6. Oxidation of Fe(2+) ions is estimated to be extremely slow in brine eutectic solutions that might be present on Mars and to be negligible in the frozen regolith.
Document ID
19930046762
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Burns, Roger G.
(NASA Headquarters Washington, DC United States)
Fisher, Duncan S.
(MIT Cambridge, MA, United States)
Date Acquired
August 16, 2013
Publication Date
February 25, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: E2
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
93A30759
Funding Number(s)
CONTRACT_GRANT: NAGW-2037
CONTRACT_GRANT: NSF EAR-91-17857
Distribution Limits
Public
Copyright
Other

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