Prospects for the Crossing of Comet 3I/ATLAS’s Ion Tail

Abstract During 2025 October–November, interstellar comet 3I/ATLAS, will pass upstream of the Europa Clipper and Hera spacecraft. Here, we identify two potential opportunities for in situ observations of 3I’s ion tail by immersion, facilitated by the close alignment between the comet’s hyperbolic trajectory with the ecliptic plane. During the period 2025 October 30–November 6, it is predicted that Europa Clipper will potentially be immersed within the ion tail of 3I/ATLAS, providing the opportunity to detect the signatures of an interstellar comet’s ion tail. Characteristic changes to the solar wind are also expected to be observed; a magnetic draping structure associated with the comet may be identifiable. It is further predicted that spacecraft Hera will possibly be immersed within the ion tail of 3I/ATLAS during the period 2025 October 25–November 1.