NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The nanosphere iron mineral(s) in Mars soilA series of surface-modified clays containing nanophase (np) iron/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these 'Mars-soil analogs' were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxyl mineral such as 'green rust', or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable meaghemite (gamma-Fe203) by mild heat treatment and then to nanophase hematite (aplha-Fe203) by extensive heat treatment. Their chemical reactivity offers a plausible mechanism for the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxide and silicate phase surfaces. The mode of formation of these (nanophase) iron oxides on Mars is still unknown.
Document ID
19950044453
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Banin, A.
(The Hebrew Univ. Rehovot, Israel)
Ben-Shlomo, T.
(The Hebrew Univ. Rehovot, Israel)
Margulies, L.
(The Hebrew Univ. Rehovot, Israel)
Blake, D. F.
(NASA Ames Research Center Moffet Field, CA, United States)
Mancinelli, R. L.
(NASA Ames Research Center Moffet Field, CA, United States)
Gehring, A. U.
(Univ. of California, Berkeley, CA United States)
Date Acquired
August 16, 2013
Publication Date
November 25, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: E11
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
95A76052
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available