Comets and Asteroids

A Tale Of 3 Dwarf Planets: Ices And Organics On Sedna, Gonggong, And Quaoar From JWST Spectroscopy

By Keith Cowing
Status Report
October 1, 2023
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A Tale Of 3 Dwarf Planets: Ices And Organics On Sedna, Gonggong, And Quaoar From JWST Spectroscopy
IFU images from one of the two PRISM grating observations of Sedna, Gonggong, and Quaoar, collapsed along the entire wavelength axis. For Sedna and Gonggong, the 7×7 pixel yellow box 6 denotes the spectral extraction region, while the 21×21 pixel red box marks the inner boundary of the background region. Quaoar lies in a dense field of background stars, and all pixels outside of the 5×5 pixel yellow extraction box were masked, except for the two designated background regions, marked in red, which are free from visible astronomical sources. — astro-ph.EP

We observed Sedna, Gonggong, and Quaoar with the NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm.

Quaoar was also observed at 10x higher spectral resolution from 0.97 to 3.16 μm using medium-resolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane (C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.

Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a feature at 3.2 μm possibly due to HCN, and CO2 ice.

The higher-resolution medium grating spectrum of Quaoar reveals several overtone and combination bands of ethane and methane (CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions between 2.7 and 3.6 μm indicative of complex organic molecules.

The suite of light hydrocarbons and complex organic molecules are interpreted as the products of irradiation of methane. The differences in apparent abundances of irradiation products are likely due to their distinctive orbits, which lead to different timescales of methane retention and to different charged particle irradiation environments.

In all cases, however, the continued presence of light hydrocarbons implies a resupply of methane to the surface. We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs.

JWST NIRSpec spectra of Sedna, Gonggong, and Quaoar. All spectra are normalized to the mean between 1.8 and 1.9 μm. The three dwarf planets share many spectral similarities, but they also differ in several interesting and important ways. The higher spectral resolution medium grating spectrum (shown in gray) of Quaoar resolves features not detected in the prism spectrum, but otherwise agrees very well with the prism spectrum. Details of features detected in the medium grating spectrum are shown in Fig. 6. Section 4 in the text describes the interpretations labeled for the different features. — astro-ph.EP

J.P. Emery, I. Wong, R. Brunetto, J.C. Cook, N. Pinilla-Alonso, J.A. Stansberry, B.J. Holler, W.M. Grundy, S. Protopapa, A.C. Souza-Feliciano, E. Fernández-Valenzuela, J.I. Lunine, D.C. Hines

Comments: 32 pages, 9 figures, 5 tables, submitted to Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2309.15230 [astro-ph.EP] (or arXiv:2309.15230v1 [astro-ph.EP] for this version)
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Submission history
From: Joshau Emery
[v1] Tue, 26 Sep 2023 19:46:40 UTC (1,956 KB)
Astrobiology, Astrochemistry

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) 🖖🏻