Impact cratering on porous targets in the strength regime

Abstract

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

Very weak carbonaceous asteroid simulants I: Mechanical properties and response to hypervelocity impacts

“…Our impact craters simulate the result from micrometeorite bombardment and the spall-to-pit diameter ratio (D2/D1) ranges between 2 and 4. The latter is slightly larger than the one for lunar microcraters that have spall-to-pit ratio around 3 and more precisely falling in the range 1.5-3, as it is reported by (Nakamura, 2017). The depth of our craters is large (see Tab. 3) and this can be explained by the large ratio of projectile-to-target density.…”

Impacts may provide heat for aqueous alteration and organic solid formation on asteroid parent bodies

“…Target samples. We used a porous gypsum block as a target simulating porous asteroids, since porous gypsum was previously used as an analog for small satellites and primitive porous planetesimals 12,[21][22][23] . The porous gypsum target was prepared as follows.…”

Crater shape as a possible record of the impact environment of metallic bodies: Effects of temperature, impact velocity and impactor density

“…We compared D and d quantitatively using π-group scaling (according to Equation 6 in cratering experiments on geologic materials were often compiled using the static strength such as tensile strength of the target (e.g., Housen and Holsapple, 2011;Suzuki et al, 2012;Nakamura, 2017). Figure 9 shows the temperature dependence of the tensile stress and the yield strength (Y)…”