In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

“…Previous studies of hypervelocity impacts on fluffy materials have shown that the resultant craters generally have bowlshaped bottoms (Housen & Holsapple 2003;Schultz et al 2007;Yasui et al 2012). This is one reason for believing that the circular depressions found on 67P and other comets with steep-walls and flat-bottoms are not of impact origin although we cannot rule out that some of the pits may have been related to impact events.…”

Impact experiments of exotic dust grain capture by highly porous primitive bodies

“…However, the increase in a is probably owing to the change in projectile mass and shape when projectile deformation starts at a dynamic pressure of 4-7 times the tensile strength of the projectiles as described in Section 3.1. Yasui et al (2012) also suggested that deformation and disruption of the original projectile may cause higher drag coefficient C d . It could also be due to an increase in target density in front of the projectile, which was observed as conical caps of less porous glass beads (described in the previous section).…”

“…However, it is not clear how far the understand ing thus gained can be extrapolated to dust penetration into small porous primitive bodies in a planetary system. Laboratory impact experiments of cratering and disruption processes of porous targets have been conducted and scaling laws have been studied (Love et al, 1993;Housen and Holsapple, 2003;Setoh et al, 2010;Yasui et al, 2012 ). In this study, we focus on the penetration process of projectiles into highly porous targets to gain a better understanding of the physical processes of dust penetration into small porous bodies.…”

“…We conducted impact-penetration experiments of millimeter-sized metal and rock projectiles into highly porous sintered targets, which consisted of pores that were much smaller than the projectiles themselv es. Yasui et al (2012) performed similar experiments of a gypsum target with bulk porosity of 50% using metal and nylon projectiles for observation of crater formatio n and projectile penetration. Targets in this study were much porous with bulk porosities up to 94%.…”

Experimental Simulations of Hypervelocity Impact Penetration of Asteroids Into the Terrestrial Ocean and Benthic Cratering

“…In previous hypervelocity impact experiments in which low‐density sintered glass beads were used as a target, the mass of the largest fragment of rock or metal projectiles decreased with increasing impact velocity at initial dynamic pressures exceeding 10–20 times the tensile strength of the projectile (Okamoto et al., 2013). The microparticulation of the projectile in the early stages of impact resulted in a decrease in penetration depth within low‐density porous targets (e.g., glass‐on‐aerogel impact; nylon‐on‐polystyrene impact; Al 2 O 3 ‐on‐aerogel impact; Al 2 O 3 ‐on‐polystyrene impact; SUS‐on‐gypsum impact; Burchell et al., 2001; Ishibashi et al., 1990; Kitazawa et al., 1999; Tsou, 1990; Yasui et al., 2012). As ordinary chondrite projectiles also deformed and fragmented during the traverse of the water column in the 5‐km/s impact (Figure 4 and Figures and ), the chondrite‐on‐H 2 O(l) impact at v i > 5 km/s should result in further fragmentation and an increase in the effective cross‐sectional area of the chondrite fragments.…”