2,2,2,3,4,5,5,6- 1Swedish Institute of Space Physics, Kiruna, Sweden (stas@irf.se)
- 2Johns Hopkins University/Applied Physics Laboratory, Laurel, USA
- 3Southwest Research Institute, San Antonio, USA
- 4University of Bern, Bern, Switzerland
- 5Max Planck Institute for Solar System Research, Göttingen, Germany
- 6University of Oregon, Eugene, Oregon, USA
Comets are strong sources of energetic neutral atoms(ENAs)originating from solar wind charge exchange within their extended neutral gas environments. Moreover, acceleration processes in the vicinity of comets produce energetic particles with energies significantly higher than the solar wind, in the range of tens to hundreds of keV. Charge exchange of these particles generates high-energy ENAs that propagate like photons, unaffected by electromagnetic fields and only negligibly influenced by gravity. Observations of cometary high-energy ENAs reveal acceleration processes at the comet, characterize its neutral environment, and can effectively deliver direct samples of cometary material to the observation point. The JUICE spacecraft, carrying the high-energy ENA imager JENI (Jovian Energetic Neutrals and Ions), covering the energy range 1–110 keV (ENAs), attempted for the first time to detect ENAs from a comet in this energy range. The target was 3I/Atlas, an interstellar object, making this attempt particularly valuable. On 4 November, 3I/Atlas was at a minimum distance of 66 million km from the JUICE spacecraft. The comet was observed from 8 to 19 November, when the observation geometry became compatible with spacecraft constraints. During this period, the spacecraft–comet distance ranged from approximately 80 to 150 million km. For a reported outgassing rate of (1–2) × 1029 s-1, the expected ENA intensity is estimated to be 10-4 to 10-3 (eV cm² s sr)-1, which remains above the JENI detection limit of 10-5 (eV cm² s sr)-1 against the ultraviolet background. The 10-day observation period enabled extremely long integration times. The data from this period were downlinked in February and being analyzed. We report the results of these observations, which will either constitute the first direct detection of particles from an interstellar object or provide an upper limit for high-energy ENA intensity from a comet.
How to cite: Barabash, S., Clark, G., Brand, P., Kollmann, P., Mitchell, D., Regoli, L., Gkioulidou, M., Allegrini, F., Wurz, P., Krupp, N., Roussos, E., Turner, D., and Paty, C.: ESA’s JUICE: first-ever attempt to observe energetic neutral atoms from an interstellar object, the 3I/Atlas comet, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1226, https://doi.org/10.5194/epsc2026-1226, 2026.
