Comets and Asteroids

Coma Volatile Composition And Thermal Physics In Comet C/2022 E3 (ZTF) Measured Near Closest Approach To Earth With NASA-IRTF

By Keith Cowing
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astro-ph.EP
February 11, 2026
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Coma Volatile Composition And Thermal Physics In Comet C/2022 E3 (ZTF) Measured Near Closest Approach To Earth With NASA-IRTF
Upper. Detections of H2O, HCN, C2H2, and OH∗ in E3 covering iSHELL echelle order 170–172. The uppermost trace is the observed cometary spectrum with the telluric transmittance model superimposed. Below are individual molecular fluorescence models color-coded by species. The bottom trace shows the residual (cometary spectrum minus all models) with the 1σ uncertainty envelope overlaid and shaded. Lower. Zoomed plots covering the gray shaded regions indicated in the upper panel. In this case, the uppermost trace is the telluric-subtracted comet spectrum, with individual fluorescence models plotted below. We searched for NH2, a potentially confounding species in this spectral region, but did not detect it. Our 3σ upper limit is NH2/H2O < 0.03%. -- astro-ph.EP

The 2023 perihelion passage of comet C/2022 E3 (ZTF) afforded an opportunity to measure the abundances and spatial distributions of coma volatiles in an Oort cloud comet at high spatial resolution near its close approach to Earth (Δmin∼0.28 au on UT February 1).

We conducted near-infrared spectroscopic observations of C/2022 E3 (ZTF) using iSHELL at the NASA Infrared Telescope Facility on UT 2023 February 9. Our measurements securely detected fluorescent emission from H2O, CO, OCS, CH3OH, CH4, C2H6, C2H2, and HCN.

For each instrumental setting we took exposures with the slit oriented parallel and also perpendicular to the projected Sun-comet vector, thereby enabling a test of the spatial distributions of these molecules. We report rotational temperatures, production rates, and abundance ratios (i.e., mixing ratios) for all sampled species.

Our measurements found that molecular abundances in C/2022 E3 were depleted compared to their average values in Oort cloud comets with the exception of OCS, which was consistent. The H2O production rate varied significantly and was likely tied to nucleus rotation effects.

Measurements at the two slit orientations showed distinct column density and rotational temperature profiles for H2O. Peak temperatures occurred off-nucleus and slower cooling was present in the anti-sunward hemisphere, consistent with the presence of icy grain sublimation in the coma.

Nathan X. Roth, Michael A. DiSanti, Boncho P. Bonev, Neil Dello Russo, Erika L. Gibb, Ronald J. Vervack Jr., Mohammad Saki, Adam J. McKay, Hideyo Kawakita, Stefanie N. Milam, Martin A. Cordiner, K. D. Foster

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2602.07188 [astro-ph.EP] (or arXiv:2602.07188v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2602.07188
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Submission history
From: Nathan Roth
[v1] Fri, 6 Feb 2026 20:43:52 UTC (2,660 KB)
https://arxiv.org/abs/2602.07188
Astrobiology,

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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