Meteoroid Impacts as a Source of Bennu's Particle Ejection Events.

Area of Science:

• Planetary Science
• Asteroid Dynamics
• Space Weathering

Background:

• Asteroid Bennu exhibits unexplained particle ejection events.
• These events occurred near perihelion between December 2018 and February 2019.
• Ejected particles were <10 cm and formed temporary orbits around Bennu.

Purpose of the Study:

• Investigate if meteoroid impacts could explain Bennu's particle ejection events.
• Utilize NASA's Meteoroid Engineering Model 3.0 for impact simulations.
• Compare impact characteristics with observed ejection event timing and particle sizes.

Main Methods:

• Simulated meteoroid impacts on Bennu using NASA's Meteoroid Engineering Model 3.0.
• Analyzed projectile sources (comets) and orbital evolution (Poynting-Robertson drag).
• Applied crater scaling laws to estimate impact energy and resulting particle characteristics.

Main Results:

• Simulations indicate 7,000-J impacts occur biweekly near perihelion, favoring late afternoon.
• Impact energies can explain the size and mass of ejected particles if Bennu's surface is weakly cohesive.
• The timing of simulated impacts aligns with observed ejection events.

Conclusions:

• Meteoroid impacts are a plausible cause for Bennu's particle ejection events.
• This impact mechanism may be similar to that forming the Moon's asymmetric debris cloud.
• The frequency of ejection events is predicted to decrease as Bennu moves away from the Sun.