regolithcovered

Regolith, from Latin for “fragment,” is a layer of loose, heterogeneous material that covers solid bedrock on many planetary bodies. When a surface is described as regolith-covered, bedrock is obscured by this unconsolidated layer, which can include dust, soil, broken rock, glassy shards, and volcanic ash. On Earth, regolith often includes soil and weathered rock, but on airless or air-processed bodies it is primarily produced by impact processes and space weathering.

Regolith forms through processes such as micrometeoroid bombardment, space weathering by solar wind and cosmic rays, thermal cycling that breaks rocks apart, and, where applicable, volcanic or tectonic activity. On the Moon, constant micrometeoroid impacts pulverize rock into fines and agglutinates, creating a thick, glassy surface layer. On Mars, wind-blown dust and deflated materials contribute to a regolith layer that covers bedrock; on asteroids regolith can be coarse or cohesive, depending on gravity and material properties.

Regolith is typically loose and heterogeneous, with a range of grain sizes and high porosity. Its thickness varies widely by location and history, from centimeters to tens of meters. Its physical properties, such as cohesion and bearing strength, differ markedly from bedrock, affecting lander or rover interactions, sampling strategies, and radar or seismic measurements used to probe subsurface structure.

Regolith-covered surfaces are central to planetary geology because they record impact histories and space weathering while presenting both challenges and opportunities for exploration. They influence landing safety, mobility, and excavation, and provide accessible material for scientific study and potential in-situ resource utilization. Examples include the lunar regolith studied by Apollo missions, Mars regolith examined by rovers and orbiters, and regolith on various asteroids explored by space missions.