Extremely small traces of elemental boron were detected in Lunar regolith. Hawaiian volcanic ash has been used as Martian regolith simulant by researchers since 1998. Chlorine is very rare in lunar regolith. Martian soil is the fine regolith found on the surface of Mars. Over twenty different methods have been proposed for oxygen extraction from the lunar regolith. The composition of the lunar regolith can also be used to infer its source origin. The term "Martian soil" typically refers to the finer fraction of regolith. Regolith breccias with similar protoliths are also common. The density of lunar regolith is about 1.5 g/cm. The soil becomes very dense beneath the top layer of regolith. Soil consequently encompasses a variety of regolith components identified at landing sites. Badlands are partially characterized by their thin to nonexistent regolith layers. This stems in latitudinal and altitudinal climate gradients in regolith formation. The surface of Ceres is globally homogeneous, with an ice-free regolith in the equatorial regions. In addition to lacking significant regolith, they also lack much vegetation.