This box includes two samples of regolith engineered to be chemically and physically identical to the surface dust of the two primary regions of the Moon. Lunar Mare Regolith Simulant is based on the darker regions of the moon, most of which are facing Earth. These areas are basins formed by lava flows after intense bombardment about 4 billion years ago. Lunar Highlands Regolith Simulant is based on the brighter and older regions of the moon. These areas include most of the moon's craters.