Lifetime of micron-sized water-ice particles in the Solar System: Implications for interstellar Comet 3I/ATLAS

Abstract We investigate the lifetimes of spherical water-ice particles with radii r = 0.5, 1, and 2 μm. Their lifetimes τ exceeds the age of the Solar System if they are placed at heliocentric distances greater than 3.3–4.5 au. Particles having r = 0.5 μm last 1 y at rh ~ 2 au and 1 d at rh ~ 1.4 au. When their radii increase to r = 1 μm, τ ~ 1 y and 1 d are achieved at rh ~ 1.8 au and 1.3 au, respectively, and the lifetime of particles with r = 2 μm exceeds 1 d even at rh ~ 1 au. Water-ice particles with r ≤ 1 μm were previously detected in interstellar Comet 3I/ATLAS on its inbound path to the inner Solar System. While these particles cannot survive its perihelion passage, they returned to the coma in mid-November of 2025.