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Magnetic changes accompanying the thermal decomposition of nontronite /in air/ and its relevance to Martian mineralogyIt is found that the thermal treatment of nontronite in air, for long periods at 700 C or short periods at 900 C, results in the destruction of the nontronite structure, a distinct reddening in color, and a large increase in magnetic susceptibility and saturation magnetization. Measurements and calculations of the magnetic properties suggest that the magnetism is due to the presence of ultrafine particles of alpha or gamma Fe2O3. The highly magnetic thermally treated nontronite is amorphous to X-rays consistent with an ultrafine grain size. Prolonged heating results in the growth of alpha Fe2O3, while reflectivity spectra of a sample heated for 1 hr at 900 C indicate the presence of an opaque, magnetite-like phase in addition to alpha Fe2O3. It is found that the thermally treated nontronite has chemical, color, and magnetic properties similar to those found by Viking on Mars. It is concluded that these results indicate an origin for the fine grained Martian surface material by repeated impacts into an Fe-rich smectite-charged regolith (Weldon et al., 1980).
Document ID
19830034362
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Moskowitz, B. M.
(Princeton Univ. NJ, United States)
Hargraves, R. B.
(Princeton University Princeton, NJ, United States)
Date Acquired
August 11, 2013
Publication Date
November 30, 1982
Subject Category
Lunar And Planetary Exploration
Accession Number
83A15580
Funding Number(s)
CONTRACT_GRANT: NSG-7602
Distribution Limits
Public
Copyright
Other

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