Dynamical environments of MU69: a state of chaotic clearing

The second (after Pluto) plausible target object for the New Horizons mission is 2014 MU69. It is a classical TNO, a primordial contact binary. Identifying any material in the vicinities of a target object is of an especial concern for planning cosmic fly-byes, as it is hazardous for a space probe. Luckily, no such material has been reported for MU69 up to now. The point of our report is that this lucky absence is just a dynamical consequence of the physical nature of MU69. Spinning gravitating dumbbells create zones of dynamical chaos around them, and this has a clearing effect: any material put in orbits around a rotating dumbbell (e.g., any material ejected from its surface) cannot be long-lived in such zones; it either escapes into space, or returns to the parent body's surface. As the orbiting matter is removed in this way, a spinning gravitating dumbbell clears its vicinities. We show that MU69 is able to create such a clearing, making itself a safe and hospitable target for a space mission. Therefore, the guest probe is expected to be safe on arrival.