“…Particle size plays an important role in controlling the spectral characteristics of powders (e.g., Salisbury and Eastes 1985, Crown and Pieters 1987, Salisbury and Wald 1992, Clark 1999 and in particular very fine particle sizes have unique spectral effects (Mustard andHays 1997, Cooper andMustard 1999). Therefore care was taken to match the physical properties of the martian surface materials, especially a particle size of less than 15 µm (Moore et al 1987, Erard et al 1994, Pollack et al 1995, Ferguson et al 1999, Tomasko et al 1999.…”