  The dusty regolith covering the surfaces of asteroids and planetary
satellites differs in size, shape, and composition from terrestrial soil
particles and is subject to very different environmental conditions.
Experimental studies of the response of planetary regolith in the relevant
environmental conditions are thus necessary to facilitate future Solar System
exploration activities. We combined the results and provided new data analysis
elements for a series of impact experiments into simulated planetary regolith
in low-gravity conditions using two experimental setups: the Physics of
Regolith Impacts in Microgravity Experiment (PRIME) and the COLLisions Into
Dust Experiment (COLLIDE). Results of these experimental campaigns found that
there is a significant change in the regolith behavior with the gravity
environment. In a 10-2g environment (Lunar g levels), only embedding of the
impactor was observed and ejecta production was produced for most impacts at >
20 cm/s. Once at microgravity levels (<10-4g), the lowest impact energies also
produced impactor rebound. In these microgravity conditions, ejecta started to
be produced for impacts at > 10 cm/s. The measured ejecta speeds were lower
than the ones measured at reduced-gravity levels, but the ejected masses were
higher. The mean ejecta velocity shows a power-law dependence on the impact
energy with an index of ~0.7. When projectile rebound occurred, we observed
that its coefficients of restitution on the bed of regolith simulant decrease
by a factor of 10 with increasing impact speeds from ~5 cm/s up to 100 cm/s. We
could also observe an increased cohesion between the JSC-1 grains compared to
the quartz sand targets.
