A plume of water vapour and icy particles originates near the south pole of Saturn's moon Enceladus, but the grains are moving more slowly than the vapour, which has been difficult to understand. It is shown that repeated wall collisions of grains, with re-acceleration by the gas, induce an effective friction, offering a natural explanation for the reduced grain velocity. Particle speed and size distributions that reproduce the observed and inferred properties of the dust plume are derived.
- Jürgen Schmidt
- Nikolai Brilliantov
- Sascha Kempf