Mechanism responsible for Bennu’s particle ejection

Determine the physical mechanism responsible for the episodic ejection of centimeter-sized particles from near-Earth asteroid (101955) Bennu, distinguishing among proposed processes such as thermal fracture, electrostatic launch, and micrometeoroid impacts.

Background

The OSIRIS-REx mission observed Bennu episodically ejecting centimeter-sized particles at speeds ranging from a few centimeters per second to approximately 3 m s−1. Because Bennu is a near-Earth asteroid with a warm surface environment that makes near-surface water-ice sublimation unlikely, several alternative mechanisms have been proposed, including thermal fracture, electrostatic particle launch, and micrometeoroid impacts.

The observations and modeling presented in the paper constrain Bennu’s mass-loss rate but do not identify the physical process that initiates particle ejection. Resolving this mechanism is important for understanding Bennu’s activity and the broader origins of active-asteroid behavior.