Abstract

Aims: An asymmetric dust cloud was detected around the Moon by the Lunar Dust Experiment on board the Lunar Atmosphere and Dust Environment Explorer mission. We investigate the dynamics of the grains that escape the Moon and their configuration in the Earth-Moon system.

Methods: We use a plausible initial ejecta distribution and mass production rate for the ejected dust. Various forces, including the solar radiation pressure and the gravity of the Moon, Earth, and Sun, are considered in the dynamical model, and direct numerical integrations of trajectories of dust particles are performed. The final states, the average life spans, and the fraction of retrograde grains as functions of particle size are computed. The number density distribution in the Earth-Moon system is obtained through long-term simulations.

Results: The average life spans depend on the size of dust particles and show a rapid increase in the size range between 1 and 10 μm. About 3.6 × 10⁻³ kg s⁻¹ (~2%) particles ejected from the lunar surface escape the gravity of the Moon, and they form an asymmetric torus between the Earth and the Moon in the range [10 R_E, 50 R_E], which is offset toward the direction of the Sun. A considerable number of retrograde particles occur in the Earth-Moon system.