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Linking mineralogy and spectroscopy of highly aqueously altered CM and CI carbonaceous chondrites in preparation for primitive asteroid sample return
Author(s) -
Bates H. C.,
King A. J.,
Donaldson Hanna K. L.,
Bowles N. E.,
Russell S. S.
Publication year - 2020
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13411
Subject(s) - chondrite , asteroid , meteorite , carbonaceous chondrite , regolith , geology , mineralogy , aqueous solution , parent body , astrobiology , infrared spectroscopy , spectroscopy , analytical chemistry (journal) , chemistry , physics , astronomy , organic chemistry , chromatography
The highly hydrated, petrologic type 1 CM and CI carbonaceous chondrites likely derived from primitive, water‐rich asteroids, two of which are the targets for JAXA 's Hayabusa2 and NASA 's OSIRIS ‐ RE x missions. We have collected visible and near‐infrared ( VNIR ) and mid infrared ( MIR ) reflectance spectra from well‐characterized CM 1/2, CM 1, and CI 1 chondrites and identified trends related to their mineralogy and degree of secondary processing. The spectral slope between 0.65 and 1.05 μm decreases with increasing total phyllosilicate abundance and increasing magnetite abundance, both of which are associated with more extensive aqueous alteration. Furthermore, features at ~3 μm shift from centers near 2.80 μm in the intermediately altered CM 1/2 chondrites to near 2.73 μm in the highly altered CM 1 chondrites. The Christiansen features ( CF ) and the transparency features shift to shorter wavelengths as the phyllosilicate composition of the meteorites becomes more Mg‐rich, which occurs as aqueous alteration proceeds. Spectra also show a feature near 6 μm, which is related to the presence of phyllosilicates, but is not a reliable parameter for estimating the degree of aqueous alteration. The observed trends can be used to estimate the surface mineralogy and the degree of aqueous alteration in remote observations of asteroids. For example, (1) Ceres has a sharp feature near 2.72 μm, which is similar in both position and shape to the same feature in the spectra of the highly altered CM 1 MIL 05137, suggesting abundant Mg‐rich phyllosilicates on the surface. Notably, both OSIRIS ‐ RE x and Hayabusa2 have onboard instruments which cover the VNIR and MIR wavelength ranges, so the results presented here will help in corroborating initial results from Bennu and Ryugu.