SMART‐1 end of life shallow regolith impact simulations

Abstract

The SMART-1 end-of-life impact with the lunar surface was simulated with impacts in a two stage light-gas gun onto inclined basalt targets with a shallow surface layer of sand. This simulated the probable impact site, where a loose regolith will have overlaid a well consolidated basaltic layer of rock. The impact angles used were at 5°and 10°from the horizontal. The impact speed was~2 km s À1 and the projectiles were 2.03 mm diameter aluminum spheres. The sand depth was between approximately 0.8 and 1.8 times the projectile diameter, implying a loose lunar surface regolith of similar dimensions to the SMART-1 spacecraft. A crater in the basement rock itself was only observed in the impact at 10°incidence, and where the depth of loose surface material was less than the projectile diameter, in which case the basement rock also contained a small pit-like crater. In all cases, the projectile ricocheted away from the impact site at a shallow angle. This implies that at the SMART-1 impact site the crater will have a complicated structure, with exposed basement rock and some excavated rock displaced nearby, and the main spacecraft body itself will not be present at the main crater.

Hypervelocity impacts into ice‐topped layered targets: Investigating the effects of ice crust thickness and subsurface density on crater morphology

“…Thus, in general, flat bottom craters which appear to be shallower than expected show that the impact occurred in a layered material, with the upper layer having less strength than the lower layer. This is well observed for example on the Moon (see Wilcox et al [2005] or Bart [2014]) and reproduced in laboratory studies of impacts on sand over basalt (e.g., Burchell et al 2015). However, where the impact has occurred in a layered target, where it is the top layer that is the strongest and most cohesive, the influence of the subsurface on the overall crater shape needs to be inferred by considering the steepness of crater walls in cross-sectional profiles.…”

“… or Bart ) and reproduced in laboratory studies of impacts on sand over basalt (e.g., Burchell et al. ). However, where the impact has occurred in a layered target, where it is the top layer that is the strongest and most cohesive, the influence of the subsurface on the overall crater shape needs to be inferred by considering the steepness of crater walls in cross‐sectional profiles.…”

Impacts on the Moon: Analysis methods and size distribution of impactors

“…In 2019 the Small Carry-on Impactor (SCI) of JAXA's Hayabusa2 sample return mission hit the surface of its target near-Earth asteroid (162173) Ryugu (Arakawa et al, 2020), while a new large scale impact experiment is being prepared on Dimorphos, the satellite of near-Earth asteroid (65803) Didymos, by NASA's DART mission in 2022 (Cheng et al, 2016). In several cases laboratory impact studies have been done in order to accompany the aforementioned artificial experiments (see for example Schultz et al, 2005;Burchell et al, 2015).…”