Molecular Dynamics Simulations of Water Formation and Retention by Micrometeoroid Impact on Lunar Surface

Abstract Reactive molecular dynamics simulations are carried out to study water formation and retention during impacts by nanometer sized micrometeoroids on lunar surface at the atomic‐scale. Results show that water molecules are generated and lost simultaneously during an impact. For a hydroxylated surface under average solar wind condition, the water molecules produced by a nanometer sized cosmic dust with an impact velocity of 8 km/s to 20 km/s ranges from about 44% to 275% of that existed before impact. However, the increase in water content at the impact site is only from 5% to 73% due to ejections caused by impact. While micrometeoroid impact may generate a substantial amount of new water molecules, the amount of water lost to space also increases significantly at higher impact velocities. Hence, the increase in local lunar water content is strongly affected by the impact velocity.