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Detection Of Propadiene (CH2CCH2), Propene (C3H6) And Non-detection Of Propane (C3H8) In Jupiter’s Northern Polar Stratosphere

By Keith Cowing
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astro-ph.EP
May 25, 2026
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Detection Of Propadiene (CH2CCH2), Propene (C3H6) And Non-detection Of Propane (C3H8) In Jupiter’s Northern Polar Stratosphere
A northern polar projection of Jupiter indicating the latitude and longitude ranges adopted for coaddition of individual spectra. The circumference latitude is 40◦ (planetocentric), enclosed concentric circles are spaced by 4◦ in latitude. The magenta line represents the statistical mean position of the auroral oval (Bonfond et al., 2017). Spatial bins in black represent regions that do not overlap in latitude with the auroral oval, blue and red spatial bins represents areas outside and inside the auroral oval, respectively. TEXES achieves diffraction-limited spatial resolutions of 0.7” to 1.4” over the wavelength range adopted in this study, which corresponds to a latitude-longitude footprint of 5-10◦ at 60◦N. — astro-ph.EP

We report the first detection of stratospheric propadiene (CH2CCH2) and propene (C3H6) at Jupiter’s mid-to-high northern latitudes using IRTF-TEXES measurements recorded on March 5-6, 2025.

Using radiative transfer software to quantitatively test for the presence of propadiene and propene, we report a >12-σ detection of propadiene and a >17-σ detection of propene inside Jupiter’s northern auroral region (henceforth ‘NAR’), where the species are most concentrated.

For example, at 62∘N inside Jupiter’s NAR, we derive a 1-mbar propadiene abundance of 2.0 ± 0.2 ppbv, which is 40 ± 3 higher than abundances predicted by the Moses & Poppe (2017) photochemical model (henceforth ‘MP17’), and significantly higher than the 1.2-ppbv upper limit abundance derived at 42∘N (the lowest latitude sampled by the observations).

Similarly, we derive a 1-mbar propene abundance of 8.1 ± 0.5 ppbv at 62∘N inside Jupiter’s NAR, which is 28 ± 2 higher than the MP17 predicted abundance and higher than the 6-ppbv 1-mbar upper limit abundance derived at 42∘N.

The fact that propadiene and propene are most enriched inside Jupiter’s NAR strongly suggests that perturbations to the chemistry by auroral-related heating and exogenous ions/electrons are responsible for their significant enrichment. Spectral features of propane (C3H8) were not detected at any of the locations sampled by the data: 3-σ upper limits of 10 ppbv were derived at the 10-mbar level at 62∘N inside Jupiter’s NAR.

The non-detection of propane could, in part, be explained by the vertical sensitivity of its spectral features to deeper pressures, where there is negligible auroral-related heating. The results of this work advocate for development of ion-neutral chemistry models of Jupiter’s polar stratosphere.

James A. Sinclair, Thomas K. Greathouse, Rohini S. Giles, Keeyoon Sung, Conor A. Nixon, Nicholas A. Lombardo, Vincent Hue, Julianne I. Moses, Leigh N. Fletcher, Patrick G. J. Irwin, Glenn S. Orton

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2605.19007 [astro-ph.EP] (or arXiv:2605.19007v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2605.19007
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Journal reference: Sinclair et al., 2026, Icarus 457, 117156
Related DOI:
https://doi.org/10.1016/j.icarus.2026.117156
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Submission history
From: James Sinclair
[v1] Mon, 18 May 2026 18:30:07 UTC (754 KB)
https://arxiv.org/abs/2605.19007

Astrobiology, astrochemistry,

Keith Cowing

Biologist, Explorers Club Fellow, ex-NASA Space Biologist and Payload integrator, Editor of NASAWatch.com and Astrobiology.com, Lapsed climber, Explorer, Synaesthete, Former Challenger Center board member 🖖🏻

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