Wishstone to Watchtower: Amorphous alteration of plagioclase-rich rocks in Gusev crater, Mars

Steven Ruff, Victoria E. Hamilton

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Previous observations by the Spirit rover in Gusev crater revealed a suite of rocks dubbed Wishstone and Watchtower Class in which the parent lithology and daughter products of a distinctive style of aqueous alteration are evident. Results from Spirit's Miniature Thermal Emission Spectrometer (Mini-TES; ∼2000-340 cm-1) were compromised by dust contamination of one of the instrument's mirrors, for which a correction has since been developed. Now we have documented nearly 200 examples of rocks encompassing the span of alteration from Wishstone Class, which spectrally resemble minimally altered plagioclase-phyric basalt, to the most altered Watchtower Class. Among them is a rock dubbed Bruce that may be a previously unrecognized alteration spectral end-member. We employed factor analysis/target transformation and linear least-squares modeling to investigate the spectral characteristics and mineralogy of these rocks. Our results amplify those of a prior preliminary analysis showing that alteration produced a material resembling basaltic glass that masks the spectral features of plagioclase. The association of this amorphous silicate component with a ferric iron nanophase oxide phase identified via Spirit's Mössbauer spectrometer is now clearly shown by our data, further characterizing the distinctive mineralogic expression of the alteration. These components and the absence of any recognizable secondary silicates or opaline silica may be an expression of alteration in the extreme aridity and cold of the martian environment. Similar mineralogic characteristics of soil measured with the CheMin X-ray diffraction instrument on the Curiosity rover in Gale crater may be an indication that this alteration process is widespread on Mars.

Original languageEnglish (US)
Pages (from-to)235-251
Number of pages17
JournalAmerican Mineralogist
Volume102
Issue number2
DOIs
StatePublished - Feb 1 2017

Fingerprint

Mars craters
plagioclase
crater
Mars
Rocks
rocks
Silicates
rock
Spectrometers
spectrometer
silicate
Lithology
Mineralogy
craters
Factor analysis
aridity
silicates
factor analysis
iron oxide
Dust

Keywords

  • alteration
  • amorphous materials
  • Mars
  • plagioclase
  • spectroscopy
  • thermal infrared

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Wishstone to Watchtower : Amorphous alteration of plagioclase-rich rocks in Gusev crater, Mars. / Ruff, Steven; Hamilton, Victoria E.

In: American Mineralogist, Vol. 102, No. 2, 01.02.2017, p. 235-251.

Research output: Contribution to journalArticle

@article{041501eafedc4014af05f108a5f6360f,
title = "Wishstone to Watchtower: Amorphous alteration of plagioclase-rich rocks in Gusev crater, Mars",
abstract = "Previous observations by the Spirit rover in Gusev crater revealed a suite of rocks dubbed Wishstone and Watchtower Class in which the parent lithology and daughter products of a distinctive style of aqueous alteration are evident. Results from Spirit's Miniature Thermal Emission Spectrometer (Mini-TES; ∼2000-340 cm-1) were compromised by dust contamination of one of the instrument's mirrors, for which a correction has since been developed. Now we have documented nearly 200 examples of rocks encompassing the span of alteration from Wishstone Class, which spectrally resemble minimally altered plagioclase-phyric basalt, to the most altered Watchtower Class. Among them is a rock dubbed Bruce that may be a previously unrecognized alteration spectral end-member. We employed factor analysis/target transformation and linear least-squares modeling to investigate the spectral characteristics and mineralogy of these rocks. Our results amplify those of a prior preliminary analysis showing that alteration produced a material resembling basaltic glass that masks the spectral features of plagioclase. The association of this amorphous silicate component with a ferric iron nanophase oxide phase identified via Spirit's M{\"o}ssbauer spectrometer is now clearly shown by our data, further characterizing the distinctive mineralogic expression of the alteration. These components and the absence of any recognizable secondary silicates or opaline silica may be an expression of alteration in the extreme aridity and cold of the martian environment. Similar mineralogic characteristics of soil measured with the CheMin X-ray diffraction instrument on the Curiosity rover in Gale crater may be an indication that this alteration process is widespread on Mars.",
keywords = "alteration, amorphous materials, Mars, plagioclase, spectroscopy, thermal infrared",
author = "Steven Ruff and Hamilton, {Victoria E.}",
year = "2017",
month = "2",
day = "1",
doi = "10.2138/am-2017-5618",
language = "English (US)",
volume = "102",
pages = "235--251",
journal = "American Mineralogist",
issn = "0003-004X",
publisher = "Mineralogical Society of America",
number = "2",

}

TY - JOUR

T1 - Wishstone to Watchtower

T2 - Amorphous alteration of plagioclase-rich rocks in Gusev crater, Mars

AU - Ruff, Steven

AU - Hamilton, Victoria E.

PY - 2017/2/1

Y1 - 2017/2/1

N2 - Previous observations by the Spirit rover in Gusev crater revealed a suite of rocks dubbed Wishstone and Watchtower Class in which the parent lithology and daughter products of a distinctive style of aqueous alteration are evident. Results from Spirit's Miniature Thermal Emission Spectrometer (Mini-TES; ∼2000-340 cm-1) were compromised by dust contamination of one of the instrument's mirrors, for which a correction has since been developed. Now we have documented nearly 200 examples of rocks encompassing the span of alteration from Wishstone Class, which spectrally resemble minimally altered plagioclase-phyric basalt, to the most altered Watchtower Class. Among them is a rock dubbed Bruce that may be a previously unrecognized alteration spectral end-member. We employed factor analysis/target transformation and linear least-squares modeling to investigate the spectral characteristics and mineralogy of these rocks. Our results amplify those of a prior preliminary analysis showing that alteration produced a material resembling basaltic glass that masks the spectral features of plagioclase. The association of this amorphous silicate component with a ferric iron nanophase oxide phase identified via Spirit's Mössbauer spectrometer is now clearly shown by our data, further characterizing the distinctive mineralogic expression of the alteration. These components and the absence of any recognizable secondary silicates or opaline silica may be an expression of alteration in the extreme aridity and cold of the martian environment. Similar mineralogic characteristics of soil measured with the CheMin X-ray diffraction instrument on the Curiosity rover in Gale crater may be an indication that this alteration process is widespread on Mars.

AB - Previous observations by the Spirit rover in Gusev crater revealed a suite of rocks dubbed Wishstone and Watchtower Class in which the parent lithology and daughter products of a distinctive style of aqueous alteration are evident. Results from Spirit's Miniature Thermal Emission Spectrometer (Mini-TES; ∼2000-340 cm-1) were compromised by dust contamination of one of the instrument's mirrors, for which a correction has since been developed. Now we have documented nearly 200 examples of rocks encompassing the span of alteration from Wishstone Class, which spectrally resemble minimally altered plagioclase-phyric basalt, to the most altered Watchtower Class. Among them is a rock dubbed Bruce that may be a previously unrecognized alteration spectral end-member. We employed factor analysis/target transformation and linear least-squares modeling to investigate the spectral characteristics and mineralogy of these rocks. Our results amplify those of a prior preliminary analysis showing that alteration produced a material resembling basaltic glass that masks the spectral features of plagioclase. The association of this amorphous silicate component with a ferric iron nanophase oxide phase identified via Spirit's Mössbauer spectrometer is now clearly shown by our data, further characterizing the distinctive mineralogic expression of the alteration. These components and the absence of any recognizable secondary silicates or opaline silica may be an expression of alteration in the extreme aridity and cold of the martian environment. Similar mineralogic characteristics of soil measured with the CheMin X-ray diffraction instrument on the Curiosity rover in Gale crater may be an indication that this alteration process is widespread on Mars.

KW - alteration

KW - amorphous materials

KW - Mars

KW - plagioclase

KW - spectroscopy

KW - thermal infrared

UR - http://www.scopus.com/inward/record.url?scp=85012257849&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85012257849&partnerID=8YFLogxK

U2 - 10.2138/am-2017-5618

DO - 10.2138/am-2017-5618

M3 - Article

AN - SCOPUS:85012257849

VL - 102

SP - 235

EP - 251

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 2

ER -