Hydrothermal Activities On C-complex Asteroids Induced By Radioactivity

By Keith Cowing
January 4, 2022
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Hydrothermal Activities On C-complex Asteroids Induced By Radioactivity
Chromium and Ti isotopic compositions of bulk meteorites.  54Cr and  50Ti denote parts per 10,000 deviations of 54Cr/52Cr and 50Ti/47Ti ratios, respectively, from terrestrial standard values. The  54Cr and  50Ti values of Jbilet Winselwan are identical to those of CM chondrites. Errors on the Jbilet Winselwan data are the 2 standard deviation of the replicated measurements (N = 5). Data of the other meteorites are from Burkhardt et al. (2019).

C-complex asteroids, rich in carbonaceous materials, are potential sources of Earth’s volatile inventories.

They are spectrally dark resembling primitive carbonaceous meteorites, and thus, C-complex asteroids are thought to be potential parent bodies of carbonaceous meteorites. However, the substantial number of C-complex asteroids exhibits surface spectra with weaker hydroxyl absorption than water-rich carbonaceous meteorites. Rather, they best correspond to meteorites showing evidence for dehydration, commonly attributed to impact heating.

Here, we report an old radiometric age of 4564.7 million years ago for Ca-carbonates from the Jbilet Winselwan meteorite analogous to dehydrated C-complex asteroids. The carbonates are enclosed by a high-temperature polymorph of Ca-sulfates, suggesting thermal metamorphism at >300°C subsequently after aqueous alteration. This old age indicates the early onset of aqueous alteration and subsequent thermal metamorphism driven by the decay of short-lived radionuclides rather than impact heating.

The breakup of original asteroids internally heated by radioactivity should result in asteroid families predominantly consisting of thermally metamorphosed materials. This explains the common occurrence of dehydrated C-complex asteroids.

Wataru Fujiya, Hisato Higashi, Yuki Hibiya, Shingo Sugawara, Akira Yamaguchi, Makoto Kimura, Ko Hashizume

Comments: 19 pages, 8 figures, 2 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2201.00996 [astro-ph.EP] (or arXiv:2201.00996v1 [astro-ph.EP] for this version)
Submission history
From: Wataru Fujiya
[v1] Tue, 4 Jan 2022 05:57:03 UTC (1,917 KB)

Astrobiology, Astrochemistry,

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