Three-dimensional imaging of high-velocity-impact induced crack growth in carbonaceous meteorites
Three-dimensional imaging of high-velocity-impact induced crack growth in carbonaceous meteorites
复制标题
碳质陨石高速撞击诱发裂纹扩展的三维成像
DOI：
10.1016/j.icarus.2022.115371
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发表时间：
2023
期刊：
影响因子：
3.2
通讯作者：
Hasegawa S.
中科院分区：
文献类型：
--
作者：
Michikami T.;Tsuchiyama A.;Hagermann A.;Takeda A.;Shishido K.;Otsuka Y.;Sasaki O.;Nakamura M.;Okumura S.;Kano H.;Hasegawa S.
陨石的物质强度为小行星的构成和历史提供了有用的信息。然而，陨石的材料强度的独特测定是困难的，因为许多陨石表现出的强度范围很广。即使在单个样品中，复杂的纹理和矿物颗粒成分也使测量变得困难。Rekkami等人（2019年）研究了普通（L5）陨石中撞击引起的裂纹扩展，并指出裂纹扩展在很大程度上受到单个矿物颗粒（和/或球粒）强度的影响。在这项研究中，我们定性地研究了碳质陨石中矿物颗粒的强度。为此，我们使用X射线显微断层摄影术来研究如何影响陨石球粒在碳质陨石的影响引起的裂纹生长。将直径为1.0 mm的球形氧化铝射弹以2.0 km/s的标称撞击速度射入7个尺寸为1.1 - 2 cm的阿连德（CV）陨石靶样品的表面。此外，直径为0.8毫米的球形玻璃射弹以4.0公里/秒的标称撞击速度射入两个Murchison（CM）和两个Aguas Zarcas（CM）陨石靶样品的靶表面，靶样品的尺寸为102厘米。结果表明，CV陨石中的大多数裂纹倾向于沿着球粒的边界面生长，而CM样品中的大多数球粒相关裂纹的生长与球粒的边界面无关。这表明，裂纹的增长在很大程度上受到球粒强度的影响，如Rekkami等人（2019）所指出的。球粒的强度越弱，越有可能发生裂纹扩展，而不管球粒边界如何。我们发现CM陨石Murchison（可能还有Aguas Zarcas）中球粒的中稳态经历了水蚀变，球粒整体上变得结构脆弱。这表明，CM材料中的冲击引起的裂纹扩展不同于从以前的研究中推断的热疲劳引起的裂纹扩展。由于从小行星Bennu返回的样品材料被认为与CM陨石有关，我们建议观察Bennu样品中球粒的裂纹可能会告诉我们这些裂纹是由冲击引起的还是热疲劳引起的。
The material strength of meteorites provides useful information on the make-up and history of asteroids. However, the unique determination of the material strength of a meteorite is difficult because of the wide range of strengths many meteorites exhibit. Even within a single sample, complicated textures and mineral granular compositions make measurements difficult. Michikami et al. (2019) investigated the impact-induced crack growth in ordinary (L5) chondrites and indicated that crack growth is largely affected by the strength of individual mineral grains (and/or chondrules). In this study, we examine the strengths of mineral grains in carbonaceous meteorites qualitatively. To this end, we use X-ray microtomography to investigate how chondrules are affected by impact-induced crack growth in carbonaceous meteorites. Spherical alumina projectiles with a diameter of 1.0 mm were fired into the surfaces of seven Allende (CV) meteorite target samples with sizes of ∼1 to 2 cm at a nominal impact velocity of 2.0 km/s. In addition, spherical glass projectiles with a diameter 0.8 mm were fired into the target surfaces of two Murchison (CM) and two Aguas Zarcas (CM) meteorite target samples with sizes of ∼2 cm at a nominal impact velocity of 4.0 km/s. The results show that most cracks in CV chondrites tend to grow along the boundary surfaces of the chondrules, while most chondrule-related cracks in CM samples grow regardless of the boundary surfaces of the chondrules. This suggests that crack growth is largely affected by the chondrules' strength as indicated by Michikami et al. (2019). The weaker the strength of chondrules, the more likely crack growth tends to occur regardless of chondrule boundaries. We found that the mesostasis of chondrules in CM meteorite Murchison (and likely Aguas Zarcas) has experienced aqueous alteration and the chondrules have become structurally weak as a whole. This indicates that impact-induced crack propagation in CM chondrites differs from thermal-fatigue induced crack propagation inferred from previous studies. As the sample material to be returned from asteroid Bennu is considered to be related to CM chondrites, we propose that observation of the cracks in chondrules in Bennu samples might tell us whether those cracks are impact- or thermal-fatigue-induced.