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What is controlling the reflectance spectra (0.35–150 µm) of hydrated (and dehydrated) carbonaceous chondrites?

Beck, Pierre and Maturilli, Alessandro and Garenne, A. and Vernazza, P. and Helbert, Jörn and Quirico, E. and Schmitt, B. (2018) What is controlling the reflectance spectra (0.35–150 µm) of hydrated (and dehydrated) carbonaceous chondrites? Icarus: International Journal of Solar System Studies, 313, pp. 124-138. Elsevier. DOI: 10.1016/j.icarus.2018.05.010 ISSN 0019-1035

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Official URL: http://dx.doi.org/10.1016/j.icarus.2018.05.010

Abstract

In order to determine the controls on the reflectance spectra of hydrated carbonaceous chondrites, reflectance spectra were measured for a series of samples with well-determined mineralogy, water-content, and thermal history. This includes 5 CR chondrites, 11 CM chondrites, and 7 thermally metamorphosed CM chondrites. These samples were characterized over the 0.35-150 μm range by reflectance spectroscopy in order to cover the full spectral range accessible from ground based observation, and that will be determined in the near-future by the Hayabusa-2 and Osiris-REx missions. While spectra show absorption features shortward of 35 μm, no strong absorption bands were identified in this suite of samples longward of 35 μm. This work shows that the 0.7-μm band observed in hydrated carbonaceous chondrites is correlated with the total water content as well as with the band depth at 2.7 μm, confirming the suggestion that they are related to Mg-rich, Fe-bearing phyllosilicates. A feature at 2.3 μm, diagnostic of such phyllosilicates was found for all samples with a detectable 0.7-μm band, also indicative of Mg-rich phyllosilicates. A strong variability is found in the shape of the 3-μm band among CM chondrites, and between CM, CR and thermally metamorphosed CM chondrites. Heavily altered CM chondrites show a single strong band around 2.72 μm while more thermally metamorphosed CM samples show an absorption band at higher wavelength. The CR chondrite GRO 95577 has a 3-μm feature very similar to those of extensively altered CM chondrites while other CR chondrite rather shows goethite-like signatures (possibly due to terrestrial weathering of metals). Thermally metamorphosed CM chondrites all have 3-μm features, which are not purely due to terrestrial adsorbed water. The band shape ranges from heavily altered CM-like to goethite-like. The overall reflectance was found to be significantly higher for CR chondrites than for CM chondrites. This is also true for the hydrated CR chondrite GRO 95577 whose reflectance spectrum is almost identical to spectra obtained for CM chondrites except that it is brighter by about 40% in the visible. Another possibility to distinguish hydrated CM from hydrated CR chondrites is to use the combination of band depths at 0.7 and 2.3 μm. When comparing the spectra obtained with Cg and Cgh spectral end member, it is found that the band depth determined for hydrated chondrites (0.7 and 2.3 μm) are always higher than calculated for these spectral endmembers. If one considers only asteroids with unambiguous hydration detection, band depth at 0.7 μm is of similar value to those measured for hydrated carbonaceous chondrites.

Item URL in elib:https://elib.dlr.de/121581/
Document Type:Article
Title:What is controlling the reflectance spectra (0.35–150 µm) of hydrated (and dehydrated) carbonaceous chondrites?
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Beck, PierreIAPG, FranceUNSPECIFIED
Maturilli, AlessandroAlessandro.Maturilli (at) dlr.deUNSPECIFIED
Garenne, A.IAPG, FranceUNSPECIFIED
Vernazza, P.LAM, Marseille, FranceUNSPECIFIED
Helbert, JörnJoern.Helbert (at) dlr.dehttps://orcid.org/0000-0001-5346-9505
Quirico, E.Grenoble Planetology LaboratoryUNSPECIFIED
Schmitt, B.Grenoble Planetology LaboratoryUNSPECIFIED
Date:October 2018
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:313
DOI :10.1016/j.icarus.2018.05.010
Page Range:pp. 124-138
Publisher:Elsevier
ISSN:0019-1035
Status:Published
Keywords:Meteorites; Asteroid; C-type; Aqueous alteration; Infrared spectroscopy
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):Project MASCOT Science and operation
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Leitungsbereich PF
Deposited By: Helbert, Dr.rer.nat. Jörn
Deposited On:10 Sep 2018 16:19
Last Modified:01 Dec 2018 19:53

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