Astrochemistry

A Broad Set of Solar and Cosmochemical Data Indicates High C-N-O Abundances For Our Solar System

By Keith Cowing

Status Report

astro-ph.EP

September 16, 2024

Filed under asteroid, astro-ph.EP, astrochemistry, astrogeology, Bennu, chondrites, Comet, Comet 67P/Churyumov-Gerasimenko, KBO, meteorite, organic chemistry, Pluto-Charon system, Protoplanetary Disk, Rosetta, Ryugu

A Broad Set of Solar and Cosmochemical Data Indicates High C-N-O Abundances For Our Solar System — The predicted uncompressed density of the Pluto-Charon system (colored curves) as the fraction of the protosolar C inventory contained in refractory organics increases from 0% to 100%, assuming the canonical protosolar abundances in Lodders 2021 (L21, see Table 1). The horizontal black dashed line represents the average uncompressed density of the system ∼ 1800 kg m⁻³ (Barr & Schwamb 2016; McKinnon et al. 2017), taken to be the most representative value we have for the bulk composition of large KBOs. The gray area shows the 3σ uncertainty (± 20 kg m⁻³ , Brozovi´c et al. 2015, McKinnon et al. 2017, Nimmo et al. 2017). — astro-ph.EP

We examine the role of refractory organics as a major C carrier in the outer protosolar nebula and its implications for the compositions of large Kuiper belt objects (KBOs) and CI chondrites.

By utilizing Rosetta measurements of refractory organics in comet 67P/Churyumov-Gerasimenko, we show that they would make up a large fraction of the protosolar C inventory in the KBO-forming region based on the current widely adopted solar abundances.

However, this would free up too much O to form water ice, producing solid material that is not sufficiently rock-rich to explain the uncompressed density of the Pluto-Charon system and other large KBOs; the former has been argued as the most representative value we have for the bulk composition of large KBOs (Barr & Schawmb 2016, Bierson & Nimmo 2019).

This inconsistency further highlights the solar abundances problem – an ongoing challenge in reconciling spectroscopically determined heavy element abundances with helioseismology constraints. By employing a new dataset from solar CNO neutrinos and solar wind measurements of C, N, and O, we show that the uncompressed density of the Pluto-Charon system can be reproduced over a wide range of scenarios.

We show that a lack of sulfates in Ryugu and Bennu samples implies a lower amount of water ice initially accreted into CI chondrite parent bodies than previously thought. These data are found to be consistent with the solar C/O ratio implied by the new dataset. Our predictions can be tested by future neutrino, helioseismology, and cosmochemical measurements.

Ngoc Truong, Christopher R. Glein, Jonathan I. Lunine

Comments: 32 pages, 10 figures, 3 tables, accepted for publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2409.02103 [astro-ph.EP](or arXiv:2409.02103v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.02103
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Submission history
From: Ngoc Truong
[v1] Tue, 3 Sep 2024 17:57:18 UTC (1,131 KB)
https://arxiv.org/abs/2409.02103

Astrobiology, Astrochemistry,

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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