A tale of 3 dwarf planets: Ices and organics on Sedna, Gonggong, and Quaoar from JWST spectroscopy

• DOI: 10.1016/j.icarus.2024.116017
• Publication Date: 2024-02-29T17:02:16Z
• Authors: 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-Vale...; J.I. Lunine; D.C. Hines
• Keywords: Pluto; Dwarf planet; Space weathering; Spectral resolution; Prism

The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than the methane-rich bodies of Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be spherical have possibly undergone interior melting differentiation. They also reside on very different orbits, making them an ideal suite for untangling effects size orbit present day surface composition. We observed with NIRSpec instrument James Webb Space Telescope (JWST). All three were low-resolution prism mode at wavelengths spanning 0.7 5.2 μm. was additionally 10× higher spectral resolution from 0.97 3.16 μm using medium-resolution gratings. Sedna's spectrum shows a number absorption features due ethane (C2H6), as well acetylene (C2H2), ethylene (C2H4), H2O, CO2. Gonggong's several, but fewer weaker, features, along stronger cleaner H2O CO2 complexed other molecules. Quaoar's even weaker deepest cleanest feature 3.2 HCN, ice. higher-resolution medium grating reveals several overtone combination bands methane (CH4). Spectra all objects show steep red slopes strong, broad absorptions between 2.7 3.6 indicative complex organic light hydrocarbons molecules interpreted products irradiation methane. infer that differences apparent abundances among these similarly-sized likely their distinctive which lead timescales retention charged particle environments. In cases, however, continued presence implies resupply surface. suggest internal geochemical evolution similar larger distinct KBOs. identification presented this paper is first step analysis, additional insight into relative mixing states materials surfaces will come future modeling data.