Thermal alteration: A possible reason for the inconsistency between OMEGA/CRISM and TES detections of phyllosilicates on Mars?

Che, C.; Glotch, T. D.

doi:10.1002/2013gl058649

Cited by 11 publications

(4 citation statements)

References 31 publications

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“…This supports the hypothesis that phyllosilicates in Nili Fossae are old and might have been structurally disordered by impacts, rather than generated by them [e.g., Michalski et al, 2010]. More recently, Che and Glotch [2014] directly matched TES phyllosilicate spectra in the Nili Fossae region with the laboratory emissivity spectra of thermally altered nontronite heated to~400°C using a factor analysis and target transformation (FATT) algorithm [Thomas and Bandfield, 2013]. These results directly support our hypothesis that impact-induced structural disorder may contribute to the ambiguity of phyllosilicate detections by MIR spectroscopic techniques.…”

Section: Introductionsupporting

confidence: 75%

“…Indeed, it has been demonstrated by laboratory spectroscopy and modeling that preexisting phyllosilicates can survive postimpact exhumation temperatures [ Fairén et al , ], but not without minor thermal alteration, and near‐infrared (NIR) spectral features from Toro crater ejecta have been found to be consistent with thermally treated nontronite [ Gavin and Chevrier , ]. In addition, a unique spectral feature centered at 450 cm −1 in Mars Global Surveyor Thermal Emission Spectrometer (TES) data and associated with the detections by the Mars Express/Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) VNIR imaging spectrometer of nontronite‐rich deposits around Nili Fossae [ Michalski et al , ], has been shown to be consistent with nontronite after thermal alteration to 400°C [ Che and Glotch , ]. A detailed examination of the effects of shock metamorphism on clay mineral spectroscopy may thus provide valuable insights for the analysis and interpretation of Martian remote sensing data.…”

Section: Introductionmentioning

confidence: 99%

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Structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 GPa

Friedlander

Glotch

Bish

et al. 2015

J. Geophys. Res. Planets

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Many phyllosilicate deposits remotely detected on Mars occur within bombarded terrains. Shock metamorphism from meteor impacts alters mineral structures, producing changed mineral spectra. Thus, impacts have likely affected the spectra of remotely sensed Martian phyllosilicates. We present spectral analysis results for a natural nontronite sample before and after laboratory-generated impacts over five peak pressures between 10 and 40 GPa. We conducted a suite of spectroscopic analyses to characterize the sample's impact-induced structural and spectral changes. Nontronite becomes increasingly disordered with increasing peak impact pressure. Every infrared spectroscopic technique used showed evidence of structural changes at shock pressures above~25 GPa. Reflectance spectroscopy in the visible near-infrared region is primarily sensitive to the vibrations of metal-OH and interlayer H 2 O groups in the nontronite octahedral sheet. Midinfrared (MIR) spectroscopic techniques are sensitive to the vibrations of silicon and oxygen in the nontronite tetrahedral sheet. Because the tetrahedral and octahedral sheets of nontronite deform differently, impact-driven structural deformation may contribute to differences in phyllosilicate detection between remote sensing techniques sensitive to different parts of the nontronite structure. Observed spectroscopic changes also indicated that the sample's octahedral and tetrahedral sheets were structurally deformed but not completely dehydroxylated. This finding is an important distinction from previous studies of thermally altered phyllosilicates in which dehydroxylation follows dehydration in a stepwise progression preceding structural deformation. Impact alteration may thus complicate mineral-specific identifications based on the location of OH-group bands in remotely detected spectra. This is a key implication for Martian remote sensing arising from our results.

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Section: Introductionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 GPa

Friedlander

Glotch

Bish

et al. 2015

J. Geophys. Res. Planets

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“…To identify spectral end‐members, we also use factor analysis and target transformation (FATT) [ Malinowski , ], a statistical principal component‐based approach. This method has been primarily applied to mid‐IR remote sensing data sets [ Bandfield et al ., ; Glotch et al ., ; Glotch and Rogers , ] but has recently been successfully applied to VNIR remote sensing data sets from Mars and the Moon [ Thomas and Bandfield , ; Che and Glotch , ; Friedlander et al ., ]. Factor analysis can be applied to any data set with independently varying components that add linearly.…”

Section: Data Sets and Methodsmentioning

confidence: 99%

End‐member identification and spectral mixture analysis of CRISM hyperspectral data: A case study on southwest Melas Chasma, Mars

et al. 2016

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We present spectral unmixing results over the southwest Melas Chasma region, where a variety of hydrated minerals were identified. We use the Discrete Ordinate Radiative Transfer radiative transfer model to simultaneously model Mars atmospheric gases, aerosols, and surface scattering and retrieve the single‐scattering albedos (SSAs) modeled by the Hapke bidirectional scattering function from Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data. We employ a spectral unmixing algorithm to quantitatively analyze the mineral abundances by modeling the atmospherically corrected CRISM SSAs using a nonnegative least squares linear deconvolution algorithm. To build the spectral library used for spectral unmixing, we use the factor analysis and target transformation technique to recover spectral end‐members within the CRISM scenes. We investigate several distinct geologic units, including an interbedded polyhydrated and monohydrated sulfate unit (interbedded unit 1) and an interbedded phyllosilicate‐sulfate unit (interbedded unit 2). Our spectral unmixing results indicate that polyhydrated sulfates in the interbedded unit 1 have a much lower abundance (~10%) than that of the surrounding unit (~20%) and thus may have been partially dehydrated into kieserite to form the interbedded strata, supporting a two‐staged precipitation‐dehydration formation hypothesis. In the interbedded unit 2 phyllosilicates have an abundance of ~40% and are interbedded with ~20% sulfates. The results, in combination with thermodynamic calculations performed previously, suggest that the interbedded phyllosilicates and sulfates likely formed through coupled basalt weathering and evaporation. The methodology developed in this study provides a powerful tool to derive the mineral abundances, aiming to better constrain the formation processes of minerals and past aqueous environment on Mars.

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“…Spectra of submarine terrestrial clays were compared to available CRISM spectra of Martian clays; the results showed that the largest group of clays (smectitic samples with FeO/MgO ratios ≈10-30, supposedly between submarine and low-submarine environment) were found on the Noachian highlands of Mars (Michalski et al, 2015) where no ocean was ever reported or possibly be present. Even the presence of smectite is not unambiguously the proof of formation in ponding water (Ehlmann et al, 2013) and might be the result of thermal alteration by lava instead (Che & Glotch, 2014). Another possibility is that phyllosilicates were formed by >400 °C hot hydrothermal fluids under the surface (Ehlmann et al, 2011), where the lithostatic pressure of the rocks still allows the stability of liquid water, and then exposed as outcrops upon erosion or transport by subsequent lava flows (Leone, 2017).…”

Section: Mineralogical Argumentsmentioning

confidence: 99%

The Absence of an Ocean and the Fate of Water all Over the Martian History

Leone

2020

Earth and Space Science

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Existing data returned in >40 years of planetary missions to Mars provided a good basis to understand that an ocean never existed on the surface of the planet during its whole history. The presence of environmental indicators like unaltered jarosite and olivine deposited by the early volcanic activity can be seen as evidence that liquid water was never abundant nor widespread on the surface of Mars since the pre-Noachian or Noachian at least. There is a dramatic mismatch with the water equivalent volume of the outflow channels sources with the volume needed to form an ocean. The ubiquitous presence of large volcanoes, with their huge lava fields exactly where liquid water was claimed to be abundant during the Noachian age, makes now very clear that lava and not water was involved in the formation of the outflow channels and the fluvial networks. As a consequence, cheaper robotic exploration might be favored with respect to the ambitious human exploration program planned for Mars. Unless enough water supplies will be brought to the equatorial regions from the poles through long pipelines, or from nearby asteroids through cargo ships, it will be very difficult to exploit the rich equatorial resources brought up from the mantle by the massive volcanism that characterized the early history of the planet. Digging deeply the equatorial regions searching for water would be too expensive, of uncertain reward, and thus unpractical. et al., 1997), on the other side of Chryse Planitia far away from the landing site of

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Thermal alteration: A possible reason for the inconsistency between OMEGA/CRISM and TES detections of phyllosilicates on Mars?

Cited by 11 publications

References 31 publications

Structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 GPa

Structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 GPa

End‐member identification and spectral mixture analysis of CRISM hyperspectral data: A case study on southwest Melas Chasma, Mars

The Absence of an Ocean and the Fate of Water all Over the Martian History

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