Pigmenting agents in martian soils: Inferences from spectral, Mössbauer, and magnetic properties of nanophase and other iron oxides in Hawaiian palagonitic soil PN-9

Richard V. Morris, D. C. Golden, James F. Bell, Howard V. Lauer, John B. Adams

Research output: Contribution to journalArticle

96 Scopus citations

Abstract

We have examined a Hawaiian palagonitic tephra sample (PN-9) that has spectroscopic similarities to Martian bright regions using a number of analytical techniques, including Mössbauer and reflectance spectroscopy, X-ray diffraction, instrumental neutron activation analysis, electron probe microanalysis, transmission electron microscopy, and dithionite-citrate-bicarbonate extraction. Chemically, PN-9 has a Hawaiitic composition with alkali (and presumably silica) loss resulting from leaching by meteoric water during palagonitization; no Ce anomaly is present in the REE pattern. Mineralogically, our results show that nanophase ferric oxide (np-Ox) particles (either nanophase hematite (np-Hm) or a mixture of ferrihydrite and np-Hm) are responsible for the distinctive ferric doublet and visible-wavelength ferric absorption edge observed in Mössbauer and reflectivity spectra, respectively, for this and other spectrally similar palagonitic samples. The np-Ox particles appear to be imbedded in a hydrated aluminosilicate matrix material; no evidence was found for phyllosilicates. Other iron-bearing phases observed are titanomagnetite, which accounts for the magnetic nature of the sample; olivine; pyroxene; and glass. By analogy, np-Ox is likely the primary pigmenting agent of the bright soils and dust of Mars.

Original languageEnglish (US)
Pages (from-to)4597-4609
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume57
Issue number19
DOIs
StatePublished - Oct 1993
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology

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