In the run-up to the Apollo program, crushed terrestrial rocks were first used to simulate the anticipated soils that astronauts would encounter on the lunar surface.[2] In some cases the properties of these early simulants were substantially different from actual lunar soil, and the issues associated with the pervasive, fine-grained, sharp dust grains on the Moon came as a surprise.Returned Apollo and Luna samples were used as reference materials in order to target specific properties such as elemental chemistry or particle size distribution.Many of these simulants were criticized by prominent lunar scientist Larry Taylor for a lack of quality control and wasted money on features like nanophase iron that had no documented purpose.Multiple companies have tried to sell regolith simulants for profit, including Zybek Advanced Products, ORBITEC, and Deep Space Industries.