Laser Irradiation of Carbonaceous Chondrite Simulants: Space Weathering Implications for C-complex Asteroids

By Keith Cowing
Status Report
April 19, 2024
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Laser Irradiation of Carbonaceous Chondrite Simulants: Space Weathering Implications for C-complex Asteroids
Secondary electron (SE) SEM images of a CI (a and c) and CM (b and d) simulant pellet before and after irradiation. Panels a and b show images of the fresh material, while panels c and d are of representative laser-irradiated regions. The white scale bar at the lower left side of each panel corresponds to 2 𝜇𝑚 in length. — astro-ph.EP

Surfaces of carbonaceous asteroids (C-complex) have shown diverse contrasting spectral variations, which may be related to space weathering.

We performed laser irradiation experiments on CI and CM simulant material under vacuum to mimic the spectral alteration induced by micrometeorite impacts. We used in situ ultraviolet-visible and near-infrared reflectance spectroscopy to analyze spectral alterations in response to pulsed laser irradiation, as well as scanning electron microscopy and x-ray photoelectron spectroscopy to search for microstructural and compositional changes.

Laser irradiation causes an increase in spectral slope (reddening) and a decrease in the albedo (darkening), and these changes are stronger in the ultraviolet-visible region. These spectral changes are likely driven by the excess iron found in the altered surface region, although other factors, such as the observed structural changes, may also contribute.

Additionally, while the 0.27~μm band appears relatively stable under laser irradiation, a broad feature at 0.6~μm rapidly disappears with laser irradiation, suggesting that space weathering may inhibit the detection of any feature in this spectral region, including the 0.7~μm band, which has typically been used an indicator of hydration.

Comparing our laboratory results with optical spectrophotometry observations of C-complex asteroids, we find that the majority of objects are spectrally red and possess colors that are similar to our irradiated material rather than our fresh samples. Furthermore, we also find that younger''and older” C-complex families have similar colors, suggesting that the space weathering process is near-equal or faster than the time it takes to refresh the surfaces of these airless bodies.

Andy J. López-Oquendo, Mark J. Loeffler, David E. Trilling

Comments: 13 pages, 7 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2404.11814 [astro-ph.EP] (or arXiv:2404.11814v1 [astro-ph.EP] for this version)
Submission history
From: Andy López-Oquendo
[v1] Thu, 18 Apr 2024 00:25:54 UTC (10,822 KB)

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) 🖖🏻