Lunar Dirt

Lunar dirt is the fine fraction of the regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial dirt. The physical properties of lunar dirt are primarily the result of mechanical disintegration of basaltic and anorthositic rock, caused by continual meteoric impacts and bombardment by solar and interstellar charged atomic particles over years. The process is largely one of mechanical weathering in which the particles are ground to finer and finer size over time. This situation contrasts fundamentally to terrestrial dirt formation, mediated by the presence of molecular oxygen, humidity, atmospheric wind, and a robust array of contributing biological processes. Lunar dirt typically refers to only the finer fraction of lunar regolith, which is composed of grains 1 cm in diameter or less, but is often used interchangeably. Lunar dust generally connotes even finer materials than lunar dirt.