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Effect of Solution pH and Chloride Concentration on Akaganeite Precipitation: Implications for Akaganeite Formation on MarsAkaganeite (Beta-FeOOH, chloride-containing Fe(III) (hydr)oxide) has been recently discovered on the surface of Mars by the Mars Science Laboratory Curiosity rover in Yellowknife Bay, Gale Crater, Mars [1] and from orbit by the Mars Reconnaissance Orbiter in Robert Sharp crater and Antoniadi basin [2]. However, the mechanism and aqueous environmental conditions of akaganeite formation (e.g., pH and chloride concentration) remain unknown. We have investigated formation of akaganeite through Fe(III) hydrolysis at variable initial pH and chloride concentrations. The formed Fe(III) precipitates were characterized by instruments similar to instruments on Mars robotic spacecraft. Syntheses were performed through hydrolysis of Fe(III) perchlorate with addition of Na cloride (Fe/Cl ratio between 0.5 and 5) and at initial pH of 1.5, 2, 4, 6 and 8 at 90degC. X-ray diffraction analysis revealed formation of akaganeite alone or in mixture with goethite, hematite and ferrihydrite at all initial pHs and Fe/Cl ratio between 0.5 and 2 while akaganeite precipitated only at pH 1.5 and Fe/Cl greater than2. Chloride content of akaganeite was affected by initial pH and decreased from 20-60 mg/g at pH 1.5 to less than 0.1 mg/g at pH 8. The synthesized akaganeite samples were also characterized by Mössbauer and infrared spectroscopy and volatiles were analysed by thermal and evolved gas analysis. The obtained characterization data will be compared to published data from rover and orbital missions [1-3] to determine martian akaganeite composition, crystallinity and formation conditions.
Document ID
20170004609
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Peretyazhko, T. A.
(Jacobs Technology, Inc. Houston, TX, United States)
Rampe, E. B.
(NASA Johnson Space Center Houston, TX, United States)
Clark, J. V.
(Jacobs Technology, Inc. Houston, TX, United States)
Archer, P. D., Jr.
(Jacobs Technology, Inc. Houston, TX, United States)
Morris, R. V.
(NASA Johnson Space Center Houston, TX, United States)
Ming, D. V.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
May 15, 2017
Publication Date
August 13, 2017
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-CN-39195
Meeting Information
Meeting: Goldschmidt 2017
Location: Paris
Country: France
Start Date: August 13, 2017
End Date: August 18, 2017
Sponsors: Geochemical Society, European Association of Geochemistry
Distribution Limits
Public
Copyright
Public Use Permitted.
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