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Experimental Simulations of Hypervelocity Impact Penetration of Asteroids Into the Terrestrial Ocean and Benthic Cratering
Journal of Geophysical Research: Planets ( IF 4.8 ) Pub Date : 2020-11-04 , DOI: 10.1029/2019je006291
Manabu Nishizawa 1, 2 , Yohei Matsui 3, 4, 5 , Konomi Suda 1, 6 , Takuya Saito 1, 2 , Takazo Shibuya 1, 2, 3, 4 , Ken Takai 1, 2, 3, 4 , Sunao Hasegawa 7 , Hajime Yano 2, 7
Affiliation  

Seafloor cratering is an important process that records the impact history of the Earth, affects projectile survivability, and determines the mass of ejecta from benthic rock that is transported to the atmosphere. We report experimental hypervelocity impacts of chondrite and other projectiles (olivine, stainless‐steel, polycarbonate) on a water‐covered iron target to derive a scaling relationship for benthic cratering. In situ observations of 5‐km/s impacts quantify the deceleration of projectiles in the water column by shock‐induced deformation and fragmentation. The minimum water depths at which multiple craters appeared on the benthic target were two and four times the projectile diameter for chondrite and stainless steel, respectively. Based on the observed deceleration of projectiles in water, the cratering efficiency of a benthic target for a given impact velocity is predicted to follow an exponential decay law in terms of water depth normalized by projectile diameter (H/d), given by πv ∝ exp(−(H/d)/κ), when a projectile of original mass collides with the target. Comparing the volume of the largest crater in the experiments and that derived from the scaling relation, mass ratios of the largest projectile fragment to original projectile in the 5‐km/s impact were calculated to be 0.1–0.3 (H/d = 2–6) and 1.0 ± 0.3 (H/d = 5.5) for chondrite and stainless steel, respectively. Using the scaling relationship, the volume of the transient crater on oceanic crust by an asteroid impact is estimated to be smaller than previously predicted by hydrocode simulation when the asteroid fragmentation in the water column controls seafloor cratering.

中文翻译:

小行星撞击地球的超高速撞击和底栖火山口的实验模拟

海底陨石坑是一个重要的过程,它记录着地球的撞击历史,影响射弹的生存能力,并确定从底栖岩石中输送到大气中的喷射量。我们报告了球粒陨石和其他弹丸(橄榄石,不锈钢,聚碳酸酯)对水覆盖的铁靶的实验性超高速影响,以得出底栖火山口的比例关系。以5 km / s的冲击力进行的原位观测可以通过冲击引起的变形和破碎来量化水柱中弹丸的减速度。在底栖目标上出现多个陨石坑的最小水深分别是球粒陨石和不锈钢的弹丸直径的两倍和四倍。根据观察到的弹丸在水中的减速度,ħ / d),通过π给定v  αEXP( - (ħ / d)/ κ),当与目标原始质量的碰撞抛射。比较实验中最大的弹坑的体积和从比例关系得出的弹坑,在5 km / s的撞击中,最大弹丸碎片与原始弹丸的质量比经计算为0.1–0.3(H / d  = 2– 6)和1.0±0.3(H / d = 5.5)分别用于球粒陨石和不锈钢。使用比例关系,当水柱中的小行星破碎控制海底火山口时,小行星撞击在海洋地壳上的瞬变火山口的体积估计要比先前通过水力模拟模拟预测的体积小。
更新日期:2020-12-14
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