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

Meteorit & Planetary Scien

et al. 2013

Self Cite

Abstract-Some meteorites consist of a mix of components of various parent bodies that were presumably brought together by past collisions. Impact experiments have been performed to investigate the degree of target fragmentation during such collisions. However, much less attention has been paid to the fate of the impactors. Here, we report the results of our study of the empirical relationship between the degree of projectile fragmentation and the impact conditions. Millimeter-sized pyrophyllite and basalt projectiles were impacted onto regolithlike sand targets and an aluminum target at velocities of up to 960 m s À1 . Experiments using millimeter-sized pyrophyllite blocks as targets were also conducted to fill the gap between this study and the previous studies of centimeter-sized rock targets. The catastrophic disruption threshold for a projectile is defined as the energy density at which the mass of the largest fragment is the half of the original mass. The thresholds with the sand target were 4.5 AE 1.1 9 10 4 and 9.0 AE 1.9 9 10 4 J kg À1 , for pyrophyllite and basalt projectiles, respectively. These values are two orders of magnitude larger than the threshold for impacts between pyrophyllite projectiles onto aluminum targets, but are qualitatively consistent with the fact that the compressive and tensile strengths of basalt are larger than those of pyrophyllite. The threshold for pyrophyllite projectiles and the aluminum target agrees with the threshold for aluminum projectiles and pyrophyllite targets within the margin of error. Consistent with a previous result, the threshold depended on the size of the rocks with a power of approximately À0.4 (Housen and Holsapple 1999). Destruction of rock projectiles occurred when the peak pressure was about ten times the tensile strength of the rocks.

\frac{m_{L, p}}{M_{p}} = 10^{a} {(\frac{P_{i}}{Y_{t}})}^{- b},

where a = 2.16 ± 0.93 and 2.26 ± 0.53, b = −1.81 ± 0.65 and −2.37 ± 0.38, for WP and basalt projectiles versus sand, respectively.…”

Section: Discussionsupporting

confidence: 86%

Section: Discussionsupporting

confidence: 67%

Degree of impactor fragmentation under collision with a regolith surface—Laboratory impact experiments of rock projectiles

Nagaoka

Takasawa

Meteorit & Planetary Scien

et al. 2013

Self Cite

“…The compressive strength of HGB87 (1.7 ± 0.4 MPa) agreed to within 1  with a target prepared using the same peak temperature and duration in a previous study, which had a compressive strength of 1.4 ± 0.4 MPa (fluffy87 in Okamoto et al, 2013). The compressive strength of HGB94 (0.09 ± 0.03 MPa) was lower than one with the same porosity, which had a compressive strength of 0.47 ± 0.13 MPa (fluffy94 in Okamoto et al, 2013), because of the lower peak temperature used during the heating process in this study. The compressive strength decreased with the increase of mixing fraction of perlite grains, i.e., HGB87 > mix2:1 > mix1:1.…”

Section: Methodssupporting

confidence: 78%

“…The results revealed that the cavity below the impact point in a highly porous target becomes bulb-shaped when the projectile is broken (Okamoto et al, 2013;. Figure 5 presents an example of a cavity.…”

Section: Cavitymentioning

confidence: 99%

Collisional disruption of highly porous targets in the strength regime: Effects of mixture

Murakami

Planetary and Space Science

Yokoyama

et al. 2020

Self Cite

Highly porous small bodies are thought to have been ubiquitous in the early solar system. Therefore, it is essential to understand the collision process of highly porous objects when considering the collisional evolution of primitive small bodies in the solar system. To date, impact disruption experiments have been conducted using high-porosity targets made of ice, pumice, gypsum, and glass, and numerical simulations of impact fracture of porous bodies have also been conducted. However, a variety of internal structures of high-porosity bodies are possible. Therefore, laboratory experiments and numerical simulations in the wide parameter space are necessary.In this study, high-porosity targets of sintered hollow glass beads and targets made by mixing perlite with hollow beads were used in a collision disruption experiment to investigate the effects of the mixture on collisional destruction of high-porosity bodies.Among the targets prepared under the same sintering conditions, it was found that the targets with more impurities tend to have lower compressive strength and lower resistance against impact disruption. Further, destruction of the mixture targets required more impact energy density than would have been expected from compressive strength. It is likely that the perlite grains in the target matrix inhibit crack growth through the glass framework. The mass fraction of the largest fragment collapsed to a single function of a scaling parameter of energy density in the strength regime ( ) when assuming ratios of tensile strength to compressive strength based on a relationship obtained for ice-silicate mixtures. However, the dependence on is much larger than that shown for porous targets with different internal microstructures from the targets in this study. The depth of the deep cavity specific to the high-porosity target was well represented by a dimensionless parameter using the compressive strength of both the pure glass and mixture targets. The empirical relationship of cavity depth was shown to hold for various targets used in previous studies irrespective of the internal microstructure of the targets.

“…On the other hand, the cavity depth of porous targets including highly porous aerogels increases more rapidly with the density ratio (Love et al, 1993;Michikami et al, 2007). A semi-empirical expression for the penetration depth of an impactor for highly porous targets with a linear dependence on the density ratio has been proposed as follows (Okamoto et al, 2013):…”

Section: Depth Of Cratermentioning

confidence: 99%

Impact cratering on porous targets in the strength regime

Planetary and Space Science

2017

Self Cite

Cratering on small bodies is crucial for the collision cascade and also contributes to the ejection of dust particles into interplanetary space. A crater cavity forms against the mechanical strength of the surface, gravitational acceleration, or both. The formation of moderately sized craters that are sufficiently larger than the thickness of the regolith on small bodies, in which mechanical strength plays the dominant role rather than gravitational acceleration, is in the strength regime. The formation of microcraters on blocks on the surface is also within the strength regime. On the other hand, the formation of a crater of a size comparable to the thickness of the regolith is affected by both gravitational acceleration and cohesion between regolith particles.In this short review, we compile data from the literature pertaining to impact cratering experiments on porous targets, and summarize the ratio of spall diameter to pit diameter, the depth, diameter, and volume of the crater cavity, and the ratio of depth to diameter. Among targets with various porosities studied in the laboratory to date, based on conventional scaling laws (Holsapple and Schmidt, J. Geophys. Res., 87, 1849-1870