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Characterization of phyllosilicates observed in the central Mawrth Vallis region, Mars, their potential formational processes, and implications for past climate

McKeown, Nancy K. and Bishop, Janice L. and Dobrea, Eldar Z. Noe and Ehlmann, Bethany L. and Parente, Mario and Mustard, John F. and Murchie, Scott L. and Swayze, Gregg A. and Bibring, Jean-Pierre and Silver, Eli A. (2009) Characterization of phyllosilicates observed in the central Mawrth Vallis region, Mars, their potential formational processes, and implications for past climate. Journal of Geophysical Research E, 114 . Art. No. E00D10. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20121016-073623940

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Abstract

Mawrth Vallis contains one of the largest exposures of phyllosilicates on Mars. Nontronite, montmorillonite, kaolinite, and hydrated silica have been identified throughout the region using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). In addition, saponite has been identified in one observation within a crater. These individual minerals are identified and distinguished by features at 1.38–1.42, ∼1.91, and 2.17–2.41 μm. There are two main phyllosilicate units in the Mawrth Vallis region. The lowermost unit is nontronite bearing, unconformably overlain by an Al-phyllosilicate unit containing montmorillonite plus hydrated silica, with a thin layer of kaolinite plus hydrated silica at the top of the unit. These two units are draped by a spectrally unremarkable capping unit. Smectites generally form in neutral to alkaline environments, while kaolinite and hydrated silica typically form in slightly acidic conditions; thus, the observed phyllosilicates may reflect a change in aqueous chemistry. Spectra retrieved near the boundary between the nontronite and Al-phyllosilicate units exhibit a strong positive slope from 1 to 2 μm, likely from a ferrous component within the rock. This ferrous component indicates either rapid deposition in an oxidizing environment or reducing conditions. Formation of each of the phyllosilicate minerals identified requires liquid water, thus indicating a regional wet period in the Noachian when these units formed. The two main phyllosilicate units may be extensive layers of altered volcanic ash. Other potential formational processes include sediment deposition into a marine or lacustrine basin or pedogenesis.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2008JE003301DOIUNSPECIFIED
http://www.agu.org/pubs/crossref/2009/2008JE003301.shtmlPublisherUNSPECIFIED
Additional Information:© 2009 American Geophysical Union. Received 14 November 2008; accepted 22 July 2009; published 26 November 2009. Partial support to N.K.M. was provided by the Naval Post-graduate School Center for Remote Sensing, by the University Affiliated Research Center at UCSC, and by NASA’s Mars Fundamental Research program. Additional support was provided by NASA’s Mars Data Analysis program and the MRO/CRISM mission. Formal reviews by David Bish and Damien Loizeau greatly improved this paper. We would like to thank the MRO/CRISM Team for the collection and initial processing of the images and Frank Seelos, Olivier Barnouin-Jha, and team for creating the browse products available online at http://crism-map.jhuapl.edu/.
Funders:
Funding AgencyGrant Number
Naval Post-graduate School Center for Remote Sensing UNSPECIFIED
UCSC University Affiliated Research CenterUNSPECIFIED
NASA Mars Fundamental Research ProgramUNSPECIFIED
NASA Mars Data Analysis programUNSPECIFIED
MRO/CRISM missionUNSPECIFIED
Subject Keywords:Mawrth Vallis; phyllosilicates; CRISM
Record Number:CaltechAUTHORS:20121016-073623940
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121016-073623940
Official Citation: McKeown, N. K., J. L. Bishop, E. Z. Noe Dobrea, B. L. Ehlmann, M. Parente, J. F. Mustard, S. L. Murchie, G. A. Swayze, J.-P. Bibring, and E. A. Silver (2009), Characterization of phyllosilicates observed in the central Mawrth Vallis region, Mars, their potential formational processes, and implications for past climate, J. Geophys. Res., 114, E00D10, doi:10.1029/2008JE003301, [printed 115(E2), 2010].
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34907
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 Oct 2012 15:06
Last Modified:27 Dec 2012 02:52

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