Astrogeology

Grain Size Effects on UV-MIR (0.2-14 micron) Spectra of Carbonaceous Chondrite Groups

By Keith Cowing
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astro-ph.EP
January 22, 2024
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Grain Size Effects on UV-MIR (0.2-14 micron) Spectra of Carbonaceous Chondrite Groups
Principal component values for all six meteorites studied at different grain sizes are shown with the “α-line” boundary from DeMeo et al. (2009) that separates the S- and C/X-complexes. Grain size variations can be seen by using the dotted line interconnecting PC values of measurements of the same meteorite at different grain sizes. Marker size increases with grain size which includes values of 45-90 µm, 90-150 µm, 150-300 µm, 300-500 µm, and 500-1,000 µm. The Lunar-style space weathering trend from Binzel et al. (2019) is shown with blue dots and a corresponding arrow showing the direction of increasing space weathering. The carbonaceous space weathering trend from Lantz et al. (2018) is shown with the brown arrow indicating that the measured weathering trend would move in either direction depending on the meteorite composition. It also shows that differentiating between space weathering and grain size effects would be challenging in PC space. — astro-ph.EP

Carbonaceous chondrites are among the most important meteorite types and have played a vital role in deciphering the origin and evolution of our solar system.

They have been linked to low-albedo C-type asteroids, but due to subdued absorption bands, definitive asteroid-meteorite linkages remain elusive. A majority of these existing linkages rely on fine-grained (typically < 45 micron) powders across a limited wavelength range in the visible to near-infrared (0.35-2.5 microns).

While this is useful in interpreting the fine-grained regolith of larger main-belt objects like Ceres, recent spacecraft missions to smaller near-Earth asteroids (NEAs), such as Bennu and Ryugu, have shown that their surfaces are dominated by larger grain size material. To better interpret the surfaces of these smaller, carbonaceous NEAs, we obtained laboratory reflectance spectra of seven carbonaceous chondrite meteorite groups (CI, CM, CO, CV, CR, CK, C2-ungrouped) over the ultraviolet to mid-infrared range (0.2-14 microns).

Each meteorite contained five grain size bins (45-1000 microns) to help constrain spectral grain size effects. We find a correlation between grain size and absolute reflectance, spectral slope, band depth, and the Christiansen feature band center. Principal component analysis of grain size variation illustrates a similar trend to lunar-style space weathering.

We also show that the Bus-DeMeo asteroid taxonomic classification of our samples is affected by grain size, specifically shifting CM2 Aguas Zarcas from a Ch-type to B-type with increasing grain size. This has implications for the parent body of the OSIRIS-REx target, Bennu. With Aguas Zarcas, we present results from Hapke modeling.

David C. Cantillo, Vishnu Reddy, Adam Battle, Benjamin N. L. Sharkey, Neil C. Pearson, Tanner Campbell, Akash Satpathy, Mario De Florio, Roberto Furfaro, Juan Sanchez

Comments: 40 pages, 15 figures, published in the Planetary Science Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2401.10377 [astro-ph.EP] (or arXiv:2401.10377v1 [astro-ph.EP] for this version)
Journal reference: Planet. Sci. J. 4 177 (2023)
Related DOI:
https://doi.org/10.3847/PSJ/acf298
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Submission history
From: David Cantillo
[v1] Thu, 18 Jan 2024 21:02:17 UTC (3,528 KB)
https://arxiv.org/abs/2401.10377

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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