VIS-IR study of brucite–clay–carbonate mixtures: Implications for Ceres surface composition

Angelis, Simone De; Manzari, Paola; Sanctis, M. C. De; Ammannito, E.; Iorio, Tatiana Di

doi:10.1016/j.icarus.2016.07.002

Cited by 12 publications

(4 citation statements)

References 30 publications

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“…The mismatch is possibly due to the specific NH 4 ‐saponite endmember's different broad spectral continuum shape 3–4 μm relative to Ceres (Figure 1), which introduces fit problems for that wavelength range. The brucite‐bearing assemblage (A5, Figure 2e) shows an unsatisfactory fit, as previously reported (De Angelis et al., 2016; De Sanctis et al, 2015, 2018).…”

Section: Results: Spectral Modeling Of Ceres' Surfacesupporting

confidence: 81%

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

et al. 2020

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The Visible-Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft revealed that aqueous secondary minerals-Mg-phyllosilicates, NH 4-bearing phases, and Mg/Ca carbonatesare ubiquitous on Ceres. Ceres' low reflectance requires dark phases, which were assumed to be amorphous carbon and/or magnetite (∼80 wt.%). In contrast, the Gamma Ray and Neutron Detector (GRaND) constrained the abundances of C (8-14 wt.%) and Fe (15-17 wt.%). Here, we reconcile the VIR-derived mineral composition with the GRaND-derived elemental composition. First, we model mineral abundances from VIR data, including either meteorite-derived insoluble organic matter (IOM), amorphous carbon, magnetite, or combination as the darkening agent and provide statistically rigorous error bars from a Bayesian algorithm combined with a radiative-transfer model. Elemental abundances of C and Fe are much higher than is suggested by the GRaND observations for all models satisfying VIR data. We then show that radiative transfer modeling predicts higher reflectance from a carbonaceous chondrite of known composition than its measured reflectance. Consequently, our second models use multiple carbonaceous chondrite endmembers, allowing for the possibility that their specific textures or minerals other than carbon or magnetite act as darkening agents, including sulfides and tochilinite. Unmixing models with carbonaceous chondrites eliminate the discrepancy in elemental abundances of C and Fe. Ceres' average reflectance spectrum and elemental abundances are best reproduced by carbonaceouschondrite-like materials (40-70 wt.%), IOM or amorphous carbon (10 wt.%), magnetite (3-8 wt.%), serpentine (10-25 wt.%), carbonates (4-12 wt.%), and NH 4-bearing phyllosilicates (1-11 wt.%). Plain Language Summary Ceres is a dwarf planet and the largest object in the main asteroid belt, consisting of ice and assemblages of hydrous minerals that incorporate water, ammonium, and carbon. An open question about Ceres is its surface composition and the nature of the materials that make its surface very dark. Whereas iron oxides and amorphous carbon have been suggested from the analyses of spectra at infrared wavelengths of light and mixture modeling using pure mineral or organic endmembers, elemental analysis independently found that C and Fe are not as abundant as posited by these analyses. Thus, another phase or set of phases must be responsible. The dark nature of Ceres is similar to the dark nature of carbonaceous chondrite meteorites, measured in laboratory. We find that the tiny nanometer-and micrometer-scale of darkening agents in these meteorites is not well-accounted for by existing physics-based mixture models of mineral and organic endmembers. Consequently, we use a spectral unmixing model that involves minerals, organics and carbonaceous chondrite meteorites to show that Ceres' surface contains multiple darkening agents of the style found in carbonaceous-chondrite meteorites and additional carbon, hydrous minerals, carbonates, and NH 4-bearing minerals.

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Section: Results: Spectral Modeling Of Ceres' Surfacesupporting

confidence: 81%

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

et al. 2020

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“…Part of this work has been done with brucite mixed with other components, as reported in De Angelis et al. (). The spectra of the mixture acquired with the VIR spare (De Angelis et al ) show bands due to the presence of brucite that are not seen in the Ceres spectrum.…”

Section: Observed Mineralogiesmentioning

confidence: 99%

Ceres's global and localized mineralogical composition determined by Dawn's Visible and Infrared Spectrometer (VIR)

Sanctis

Ammannito

Carrozzo

et al. 2018

Meteorit & Planetary Scien

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The Visible and Infrared Spectrometer (VIR) instrument on the Dawn mission observed Ceres's surface at different spatial resolutions, revealing a nearly uniform global distribution of surface mineralogy. Clearly, Ceres experienced extensive water-related processes and chemical differentiation. The surface is mainly composed of a dark component (carbon, magnetite?), Mg-phyllosilicates, ammoniated clays, carbonates, and salts. The observed species suggest endogenous, global-scale aqueous alteration. While mostly uniform at regional scale, Ceres's surface shows small localized areas with different species and/or variations in abundances. Few local exposures of water ice are seen, especially at higher latitudes. Sodium carbonates have been identified in several areas on the surface, notably in Occator bright faculae. Organic matter has also been discovered in several places, most conspicuously in a large area close to the Ernutet crater. The observed mineralogies, with the presence of ammoniated species and sodium salts, have a strong resemblance to materials found on other bodies of the outer solar system, such as Enceladus. This poses some questions about the original material from which Ceres accreted, suggesting a colder environment for such material with respect to Ceres's present position.

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“…6b) are dominated by the sharp and intense O-H stretching vibration in crystalline brucite at 3698 cm −1 . 54 Alongside, a smaller band located at ca. 1575 cm −1 is observed, which likely originates from bending vibrations of associated water molecules.…”

Section: Crystengcomm Papermentioning

confidence: 99%

New insights into the nucleation of magnesium hydroxide and the influence of poly(acrylic acid) during the early stages of Mg(OH)₂ crystallisation

et al. 2022

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VIS-IR study of brucite–clay–carbonate mixtures: Implications for Ceres surface composition

Cited by 12 publications

References 30 publications

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

Ceres's global and localized mineralogical composition determined by Dawn's Visible and Infrared Spectrometer (VIR)

New insights into the nucleation of magnesium hydroxide and the influence of poly(acrylic acid) during the early stages of Mg(OH)₂ crystallisation

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VIS-IR study of brucite–clay–carbonate mixtures: Implications for Ceres surface composition

Cited by 12 publications

References 30 publications

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible‐Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data

Ceres's global and localized mineralogical composition determined by Dawn's Visible and Infrared Spectrometer (VIR)

New insights into the nucleation of magnesium hydroxide and the influence of poly(acrylic acid) during the early stages of Mg(OH)2 crystallisation

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Product

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About

New insights into the nucleation of magnesium hydroxide and the influence of poly(acrylic acid) during the early stages of Mg(OH)₂ crystallisation