Improved gravitational grain size separation method

Salemi, Enzo; Tessari, Umberto; Colombani, Micol Mastrocicco Nicolò

doi:10.1016/j.clay.2010.03.014

Cited by 23 publications

(9 citation statements)

References 16 publications

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“…The sample was provided as a <45‐μm size fraction. We crushed and isolated the <10‐μm size fraction in ethanol using Stokes' settling method (Day, ; Gee & Bauder, ; Salemi et al, ). Details of the sample chemistry and mineralogy are provided in Thomson et al ().…”

Section: Samples and Methodsmentioning

confidence: 99%

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

et al. 2018

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The origins of the Martian moons Phobos and Deimos have been the subjects of considerable debate. Visible and near‐infrared spectra of these bodies are dark and nearly featureless, with red slopes of varying degrees. These spectra are generally consistent with those of carbonaceous asteroids, leading to the hypothesis that Phobos and Deimos are captured carbonaceous asteroids. The shapes and inclinations of the orbits of Phobos and Deimos present problems for the asteroid capture hypothesis. This had led researchers to suggest that Phobos and Deimos coaccreted with Mars or that they are the result of an impact with Mars or in the Mars vicinity. In this work, we reexamine Mars Global Surveyor Thermal Emission Spectrometer (MGS‐TES) data of Phobos and compare spectra of the Phobos surface to mid‐IR spectra of the ungrouped C2 meteorite Tagish Lake (a suggested analog for D‐class asteroids) and particulate basalt and phyllosilicate samples (mixed with carbon black to reduce their visible albedos) acquired in a simulated airless body environment. We find that Tagish Lake is a poor mid‐IR spectral analog to Phobos and that major spectral features in the Phobos spectrum are best matched by a silicate transparency feature similar to that found for finely particulate basalt. Other features in the spectrum are likely best explained by a phyllosilicate component. We suggest that these results indicate that at a portion of the Phobos surface regolith is derived from the Martian crust.

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Section: Samples and Methodsmentioning

confidence: 99%

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

et al. 2018

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“…The same enstatite sample that was used to retrieve the oriented optical constants was ground into finer particle sizes using a mortar and pestle and dry sieved to obtain particle size separates with median diameters of 32.1, 48.4, and 93.9 μm. Additionally, the finest particle size, with a median diameter of 3.3 μm, was separated using Stokes' settling method [ Salemi et al , ]. Particulate samples were washed to remove clinging fines, then actual particle size distributions were measured using a Malvern Mastersizer 2000 laser diffractometer available in the Department of Geosciences at Stony Brook University (Figure ).…”

Section: Methodsmentioning

confidence: 99%

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

2017

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Mid‐infrared spectroscopy is a useful tool for remotely sensing the composition of Earth and other planets. Quantitative mineralogical investigations are possible using remotely sensed data; however, the difficulty in modeling complex interactions of light with particles that are on the order of the wavelength limits the usefulness of the remote sensing data. As part of an effort to develop a more effective treatment of light scattering in planetary regolith, we explore the ability of T‐matrix and radiative transfer (RT) hybrid models to produce emissivity spectra that are consistent with laboratory measurements. Parameters obtained from T‐matrix calculations are used in three different RT models to construct emissivity spectra of enstatite particles of different sizes. Compared to the widely used Mie/RT hybrid models, the T‐matrix/RT hybrid models produce more consistent emissivity spectra for the finest particle size fraction (3.3 μm). Overall, T‐matrix hybrid models produce improved emissivity spectra, but larger particle sizes are still difficult to model. The improvement observed in T‐matrix/RT hybrid models is a result of the inclusion of multiple scattering in closely packed media, and it demonstrates the importance of the implementation of physically realistic factors in developing a more effective light scattering model for planetary regolith. Further development and implementation of this and similar hybrid models will result in an improvement in quantitative assessments of planetary particulate surfaces from mid‐infrared spectra.

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“…The flood basalt and halite samples were crushed with a steel mortar and pestle and dry sieved to produce a range of coarse size fractions. To produce a <10 µm size fraction, samples were separated in ethanol using Stokes' settling method [ Day , ; Gee and Bauder , ; Salemi et al , ]. Subsequent to settling, samples were dried at 80°C.…”

Section: Methodsmentioning

confidence: 99%

Constraints on the composition and particle size of chloride salt‐bearing deposits on Mars

et al. 2016

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Chloride salt‐bearing deposits on Mars were discovered using the Mars Odyssey Thermal Emission Imaging System (THEMIS) and have been characterized by both mid‐infrared (MIR) and visible‐to‐near‐infrared (VNIR) remote sensing instruments. The chloride salt‐bearing deposits exhibit a blue slope at MIR wavelengths and a featureless red slope at VNIR wavelengths. These deposits also lack strong 3 µm bands in VNIR spectra, indicating that they are desiccated compared to the surrounding regolith. The lack of VNIR spectral features suggests that an anhydrous chloride salt, the most likely of which is halite, is responsible for the observed spectral slope. In this work, we use laboratory spectra and a hybrid T‐matrix/Hapke light scattering model to constrain the particle sizes and salt abundances of the Martian chloride salt‐bearing deposits. Our work shows that the two broad spectral classes of these deposits observed by THEMIS can be explained by a difference in the particle size of the admixed silicate regolith. In all cases, chloride salt abundances of 10–25% are required to match the THEMIS data. The chloride salt abundances determined in this work suggest deposition in a lacustrine/playa setting or in association with late‐stage groundwater upwelling.

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Improved gravitational grain size separation method

Cited by 23 publications

References 16 publications

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

MGS‐TES Spectra Suggest a Basaltic Component in the Regolith of Phobos

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

Constraints on the composition and particle size of chloride salt‐bearing deposits on Mars

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