The March issue of Discover isn't yet available on its website, but a report tells me that it has an article that "inspects the challenges of moon exploration and settlement posed by regolith, the abrasive dust covering most of the surface from a depth of 7 to perhaps more than 100 feet."

OED says it is erroneous from the Greek word for rug/blanket, plus the suffix lith. Apparently coined, 1897 G. P. MERRILL Treat. Rocks v. 299.