Mathematics – Logic
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p24a..05z&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #P24A-05
Mathematics
Logic
5470 Surface Materials And Properties, 6225 Mars, 3672 Planetary Mineralogy And Petrology (5410), 1060 Planetary Geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
Scientific paper
The discovery of sulfate-rich layered deposits with hematite spherules at the landing site of the Opportunity rover is consistent with mineral deposition in an aqueous environment. We evaluated conditions responsible for the formation of the jarosite-gypsum-goethite assemblage in an ancient martian lake with speciation and reaction-path models that include concentrations and activities of solutes, and amounts of precipitated minerals. Variations in the ranges of water to rock (W/R) ratio, pH, K content, and oxygen fugacity were explored in models of aqueous reactions involving jarosite, jarosite-gypsum-goethite assemblages, pyrite, and compositions of martian meteorites. Our results show that formation of jarosite requires the pH to be about 1-3, depending on the W/R ratio. Lower W/R ratios make jarosite stable over a broader pH range. Goethite forms together with jarosite, except at very low pH, and the jarosite/goethite ratio decreases as the pH and the W/R ratio increase. Increases in the W/R ratio also lead to dissolution of gypsum, while raising the pH favors its precipitation. Formation of goethite from decomposing jarosite and dissolution of gypsum (suggested from microscopic images) is consistent with an increased W/R ratio at the end of the aqueous reactions. Dissolution of gypsum caused by a decrease in the pH should cause dissolution of goethite and precipitation of jarosite, and is less consistent with observations of hematite spherules. Neither volcanic emanations nor aqueous weathering of igneous rocks can account for low-pH conditions in a surface water reservoir several hundreds of km across. However, the jarosite-gypsum-goethite assemblage could have precipitated from acidic solutions formed through near-surface oxidation of pyrite-rich deposits. By analogy to Earth, such deposits may have formed through regional hydrothermal activity and/or biologic sulfate reduction in organic-rich sediments. Our hypothesis is that regional heating of the ice-bearing crust in the Meridiani Planum caused a release of subsurface waters, formation of pyrite-rich deposits, their oxidation by atmospheric oxygen, and precipitation of sulfates and goethite followed by dehydroxylation of goethite to hematite.
Shock Everett L.
Zolotov Mikhail Yu.
No associations
LandOfFree
Formation of Jarosite-bearing Deposits Through Aqueous Oxidation of Pyrite at the Meridiani Planum, Mars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Formation of Jarosite-bearing Deposits Through Aqueous Oxidation of Pyrite at the Meridiani Planum, Mars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Formation of Jarosite-bearing Deposits Through Aqueous Oxidation of Pyrite at the Meridiani Planum, Mars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1452907