Hera, Europa Clipper to Cross 3I/ATLAS Tail Oct–Nov

3I/ATLAS, discovered July 1, 2025, is the third confirmed interstellar object and is projected to reach perihelion in late October 2025 at roughly 1.4 AU from the Sun while remaining no closer than about 1.8 AU to Earth. Observations show it is active with an icy nucleus and bright coma; early size estimates put it on the order of tens of kilometers, though some analyses have produced anomalous mass/gravity estimates that remain debated. The comet's tail has grown rapidly and shown unusual behavior, including reports of a reversal from an anti-tail to a conventional tail and strong emissions of water and hydroxyl ions. ESA’s Hera and NASA’s Europa Clipper are predicted to pass through the object's ion tail between October 25 and November 6, 2025, offering a rare chance to directly sample interstellar material and study mass-loss and plasma interactions. Models such as "Tailcatcher" and variable solar-wind conditions make the exact encounter geometry and prospects for in-tail charged-particle measurements uncertain, and the discovery has also prompted some fringe conspiratorial commentary.