Lunar regolith is the unconsolidated material found on the surface of the Moon and in the Moon's tenuous atmosphere. Lunar soil 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.[1] Lunar soil differs substantially in properties from terrestrial soil. Lunar dust is even finer regolith than lunar soil, with grain sizes less than one millimeter.[2]