Distribution of dust ejected from the lunar surface into the Earth-Moon system

TL;DR

This study models the dynamics of lunar dust particles ejected into the Earth-Moon system, revealing their distribution, lifespan, and the formation of an asymmetric dust torus influenced by various gravitational and radiation forces.

Contribution

The paper introduces a detailed numerical simulation of dust particle trajectories considering multiple forces, providing new insights into dust distribution and behavior in the Earth-Moon system.

Findings

Dust particles between 1 and 10 micrometers have lifespan dependent on size.

Approximately 2% of ejected lunar dust escapes and forms an asymmetric torus.

A significant number of retrograde dust particles are present in the system.

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 $1\, \mathrm{\mu m}$ and $10\, \mathrm{\mu m}$. About ${3.6\times10^{-3}\,\mathrm{kg/s}}$ ($\sim2\%$) 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 $[10\,R_\mathrm{E},50\,R_\mathrm{E}]$, which is offset toward the direction of the Sun. A considerable number of retrograde particles occur in the Earth-Moon system.