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Emissivity and reflectance spectra at different temperatures of hydrated and anhydrous sulphates: A contribution to investigate the composition and dynamic of icy planetary bodies

Comodi, P. and Fastelli, M. and Maturilli, Alessandro and Balic-Zunic, T. and Zucchini, A. (2021) Emissivity and reflectance spectra at different temperatures of hydrated and anhydrous sulphates: A contribution to investigate the composition and dynamic of icy planetary bodies. Icarus: International Journal of Solar System Studies, 355, p. 114132. Elsevier. doi: 10.1016/j.icarus.2020.114132. ISSN 0019-1035.

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S0019103520304747

Abstract

Accurate analyses of existing spacecraft data and telescopic observations are of fundamental importance to describe in detail the surface composition of icy planetary bodies, such as the icy galilean moons. However, the spectral library data to compare the remote data with planetary observations are usually restricted to small spectral ranges and collected only at room temperature. In this study, selected hydrated Mg-sulphates were studied. Emissivity and reflectance spectra were collected in the 3-20 μm and 0.25-16 μm range, respectively, with emissivity collected in the temperature range 300-673 K, and reflectance from 300 to 193 K. All samples were recovered after the heating and cooling cycles and were characterized by means X-ray powder diffraction. Rietveld refinements of the collected data were performed to evaluate the mineralogical composition of the samples before and after the thermal treatment. Both reflectance and emissivity measurements gave us information about the vibrational modes and overtones of SO4 and H2O. Moreover, the careful analysis of the collected data allowed us to study the influence of the cation substitution in the sulphate's crystal structures on the wavelength position of the SO4 vibrational modes. In particular, in simple salts [kieserite MgSO4·(H2O); hexahydrite MgSO4·6(H2O); gypsum CaSO4·2(H2O); thenardite Na2SO4; arcanite K2SO4; anhydrite CaSO4; barite BaSO4], the increase of the cation's radius gives a shift of the ν3 overtone towards higher wavenumbers, varying in the range 1880-2300 cm-1. On the other hand, it was observed that, in hydrated sulphates, that the increase of the strength of the hydrogen bond gives a shift of the ν3(SO4) overtones towards lower wavenumbers. At high temperature, the depth of several absorption bands in the emissivity spectra increases; however, when total or partial de-hydration occurs, a discontinuity in the deepening is observed due to the endothermic character of the dehydration phenomena. Among the investigated samples, several hydrated and anhydrous sulphates undergo de-hydration and/or phase transition at specific temperature conditions. This leads to the stabilization of new crystal structures with higher density compared to the low temperature hydrated ones. The likely occurrence of minerals dehydration will strongly affect the availability of free water in planetary depths and, as a consequence, the thickness of the icy crust. Likewise, the density changes between the different polymorphs will affect the buoyancy. This means that the structural behavior of the "non-icy" components of the icy crust have a significant impact on the structure and dynamics of the planetary bodies and have to be considered in planetological models.

Item URL in elib:https://elib.dlr.de/142393/
Document Type:Article
Title:Emissivity and reflectance spectra at different temperatures of hydrated and anhydrous sulphates: A contribution to investigate the composition and dynamic of icy planetary bodies
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Comodi, P.Department of Physics and Geology, Perugia University, ItalyUNSPECIFIED
Fastelli, M.Department of Physics and Geology, Perugia University, ItalyUNSPECIFIED
Maturilli, AlessandroAlessandro.Maturilli (at) dlr.dehttps://orcid.org/0000-0003-4613-9799
Balic-Zunic, T.Department of Geosciences and Natural Resource Management, University of Copenhagen, DenmarkUNSPECIFIED
Zucchini, A.Department of Physics and Geology, Perugia University, ItalyUNSPECIFIED
Date:February 2021
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:355
DOI :10.1016/j.icarus.2020.114132
Page Range:p. 114132
Publisher:Elsevier
ISSN:0019-1035
Status:Published
Keywords:Spectroscopy, Emissivity, Reflectance
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project BepiColombo - MERTIS and BELA
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Laboratories
Deposited By: Maturilli, Dr. Alessandro
Deposited On:31 May 2021 16:19
Last Modified:31 May 2021 16:19

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