Crater shape as a possible record of the impact environment of metallic bodies: Effects of temperature, impact velocity and impactor density. (arXiv:2103.03128v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ogawa_R/0/1/0/all/0/1">Ryo Ogawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nakamura_A/0/1/0/all/0/1">Akiko M. Nakamura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Suzuki_A/0/1/0/all/0/1">Ayako Suzuki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hasegawa_S/0/1/0/all/0/1">Sunao Hasegawa</a>
Metallic bodies that were the cores of differentiated bodies are sources of
iron meteorites and are considered to have formed early in the terrestrial
planet region before migrating to the main asteroid belt. Surface temperatures
and mutual collision velocities differ between the terrestrial planet region
and the main asteroid belt. To investigate the dependence of crater shape on
temperature, velocity and impactor density, we conducted impact experiments on
room- and low-temperature iron meteorite and iron alloy targets (carbon steel
SS400 and iron-nickel alloy) with velocities of 0.8-7 km/s. The projectiles
were rock cylinders and metal spheres and cylinders. Oblique impact experiments
were also conducted using stainless steel projectiles and SS400 steel targets
which produced more prominent radial patterns downrange at room temperature
than at low temperature. Crater diameters and depths were measured and compiled
using non-dimensional parameter sets based on the $pi$-group crater scaling
relations. Two-dimensional numerical simulations were conducted using iSALE-2D
code with the Johnson-Cook strength model. Both experimental and numerical
results showed that the crater depth and diameter decreased with decreasing
temperature, which strengthened the target, and with decreasing impact
velocity. The decreasing tendency was more prominent for depth than for
diameter, i.e., the depth/diameter ratio was smaller for the low temperature
and low velocity conditions. The depth/diameter ratios of craters formed by
rock projectiles were shallower than those of craters formed by metallic
projectiles. Our results imply that the frequency distribution of the
depth/diameter ratio for craters on the surface of metallic bodies may be used
as a probe of the past impact environment of metallic bodies.
Metallic bodies that were the cores of differentiated bodies are sources of
iron meteorites and are considered to have formed early in the terrestrial
planet region before migrating to the main asteroid belt. Surface temperatures
and mutual collision velocities differ between the terrestrial planet region
and the main asteroid belt. To investigate the dependence of crater shape on
temperature, velocity and impactor density, we conducted impact experiments on
room- and low-temperature iron meteorite and iron alloy targets (carbon steel
SS400 and iron-nickel alloy) with velocities of 0.8-7 km/s. The projectiles
were rock cylinders and metal spheres and cylinders. Oblique impact experiments
were also conducted using stainless steel projectiles and SS400 steel targets
which produced more prominent radial patterns downrange at room temperature
than at low temperature. Crater diameters and depths were measured and compiled
using non-dimensional parameter sets based on the $pi$-group crater scaling
relations. Two-dimensional numerical simulations were conducted using iSALE-2D
code with the Johnson-Cook strength model. Both experimental and numerical
results showed that the crater depth and diameter decreased with decreasing
temperature, which strengthened the target, and with decreasing impact
velocity. The decreasing tendency was more prominent for depth than for
diameter, i.e., the depth/diameter ratio was smaller for the low temperature
and low velocity conditions. The depth/diameter ratios of craters formed by
rock projectiles were shallower than those of craters formed by metallic
projectiles. Our results imply that the frequency distribution of the
depth/diameter ratio for craters on the surface of metallic bodies may be used
as a probe of the past impact environment of metallic bodies.
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