Reflectance spectroscopy of insoluble organic matter (IOM) and carbonaceous meteorites

1Hannah H. Kaplan,2Ralph E. Milliken,3Conel M. O’D. Alexander,4Christopher D. K. Herd
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13264]
1Department of Space Studies, Southwest Research Institute, Boulder, Colorado, 80302 USA
2Department of Earth, Environmental, and Planetary Sciences, Brown University, , Providence, Rhode Island, 02912 USA
3Department of Terrestrial Magnetism, Carnegie Institution of Washington, , Washington, DC, 20015 USA
4Department of Earth and Atmospheric Sciences, University of Alberta, , Edmonton, AB T6G 2E3 Canada
Published by arrangement with John Wiley & Sons

Insoluble organic matter (IOM) is the major organic component of chondritic meteorites and may be akin to organic materials from comets and interplanetary dust particles (IDPs). Reflectance spectra of IOM in the range 0.35–25 μm are presented as a tool for interpreting organic chemistry from remote measurements of asteroids, comets, IDPs, and other planetary bodies. Absorptions in the IOM spectra were strongly related to elemental H/C (atom) ratio. The aliphatic 3.4 μm absorption in IOM spectra increased linearly in strength with increasing H/C for H/C > 0.4, but was absent at lower H/C values. When meteorite spectra from the Reflectance Experiment Laboratory (RELAB) spectral catalog (n = 85) were reanalyzed at 3.4 μm, this detection limit (H/C > 0.4) persisted. Aromatic absorption features seen in IOM spectra were not observed in the meteorite spectra due to overlapping absorptions. However, the 3.4 μm aliphatic absorption strength for the bulk meteorites was correlated with both H/C of the meteorite’s IOM and bulk C (wt%). Gaussian modeling of the 3 μm region provided an additional estimate of bulk C for the meteorites, along with bulk H (wt%), which is related to phyllosilicate abundance. These relationships lay the foundation for determining organic and phyllosilicate abundances from reflectance spectra. Both the full IOM spectra and the spectral parameters discussed here will aid in the interpretation of data from asteroid missions (e.g., OSIRIS‐REx, Hayabusa2), and may be able to place unknown spectral samples within the context of the meteorite collection.

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