JWST Spatial-Spectral Mapping of Green Comet C/2022 E3 (ZTF)

Abstract

We report a survey of molecular emission from cometary volatiles using the James Webb Space Telescope (JWST) toward Oort cloud comet C/2022 E3 (ZTF) carried out on UT 2023 February 28 and March 1 at a heliocentric distance (rH) of 1.33 au. These measurements of H2O, HCN, CH3OH, C2H6, CH4, CO, CO2, 13CO2, and OCS sampled post-perihelion molecular chemistry in C/2022 E3. A suite of near to mid-infrared OH (prompt emission) transitions were also detected. This work presents nucleus-centered spectra for all detected species, spatial-spectral maps of column density and rotational temperature as a function of distance from the nucleus for all except C2H6, HCN, and OH, and maps of co-measured continuum. The spatial distributions of both quantities were anisotropic for all mapped molecules; however, H2O showed distributions distinct from the remaining species. Coma-averaged values of the ortho-to-para ratio (OPR) for H2O and the 12CO2/13CO2 ratio derived from these maps were consistent with the statistical equilibrium value of 3 and the terrestrial value of 89, respectively. The modeled mass fraction of the sub-micron dust grains is dominated by amorphous carbon (56%) followed by amorphous Mg:Fe pyroxene (28%), crystalline olivine (10%), and amorphous Mg:Fe olivine (5%) with a crystalline mass fraction of 0.2385(0.0008). We compare the volatile and dust composition of C/2022 E3 (ZTF) against comets measured to date, including those surveyed by JWST.