Phenomenology of soil erosion due to rocket exhaust on the Moon and the Mauna Kea lunar test site

The soil-blowing phenomena observed in the Apollo lunar missions have not previously been described in the literature in sufficient detail to elucidate the physical processes and to support the development of physics-based modeling of the plume effects. In part, this is because previous laboratory experiments have used overly simplistic model soils that fail to produce many of the phenomena seen in lunar landings, some of which therefore went unrecognized. Here, the Apollo descent videos, terrain photography, and ascent videos are interpreted with the assistance of field experiments using a more complex regolith. Rocket thruster firings were performed upon the tephra of a lunar test site on Mauna Kea in Hawaii. This tephra possesses embedded rocks, large fractions of gravel and dust, some cohesion, and natural geological lamination. This produced more realistic plume phenomenology. The relevant phenomena include the relationship of dust liberation with overall soil erosion rate, terrain bed forms created by the plume, dust tails associated with the exhumation and blowing of rocks, bed load transport, the removal of discrete layers of soil hypothesized to be the stratigraphic units corresponding to impact events, the total mass of ejected soil during a landing, and the brightening of the regolith around the landing site. This analysis provides insight into the erosion processes and nature of the regolith. This paper also synthesizes theory, experiment, simulation, and observational data to produce a clearer picture of the physical processes of lunar soil erosion.