Collisional history of asteroid Itokawa
Collisional history of asteroid Itokawa
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DOI：
10.1130/g39138.1
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发表时间：
2017-09-01
期刊：
影响因子：
5.8
通讯作者：
Yada, T.
中科院分区：
文献类型：
--
作者：
Jourdan, F.;Timms, N. E.;Yada, T.
返回进行研究的地外原地样本（例如，与陨石相反，陨石为样品及其分析提供了已知的地质背景。小行星25143 Itokawa是一颗碎石堆小行星，由一颗遭受灾难性破坏的单体母小行星碎片重新积聚而成，隼鸟号空间探测器（日本宇宙航空研究开发机构）从该小行星上回收了风化层尘埃颗粒。利用电子背散射衍射和40 Ar/39 Ar测年技术对两个尘埃颗粒进行了分析。其中一个颗粒的40 Ar/39 Ar坪年龄为2.3 +/- 0.1 Ga，显示出15-25 GPa的冲击压力。我们开发了一个新的温度-压力-孔隙度模型，结合扩散模型，表明只有当小行星在约1000 ℃时已经由多孔材料制成时，撞击过程中相对较低的压力和较高的温度才能协调一致。2.3因此，如果小行星丝川已经形成，从而提供了灾难性小行星分裂的最小年龄。第二个粒子没有变形的迹象，表明冲击压力为
In situ extraterrestrial samples returned for study (e.g., from the Moon) are crucial in understanding the origin and evolution of the Solar System as, contrary to meteorites, they provide a known geological context for the samples and their analyses. Asteroid 25143 Itokawa is a rubble-pile asteroid consisting of reaccumulated fragments from a catastrophically disrupted monolithic parent asteroid, and from which regolith dust particles have been recovered by the Hayabusa space probe (Japan Aerospace Exploration Agency). We analyzed two dust particles using electron backscatter diffraction and 40Ar/39Ar dating techniques. One of the grains, showing signs of 15-25 GPa impact shock pressure, yielded a 40Ar/39Ar plateau age of 2.3 +/- 0.1 Ga. We developed a novel temperature-pressure-porosity model, coupled with diffusion models to show that the relatively low pressure and high temperature i Lnvolved in the impact process can be reconciled only if the asteroid was already made of porous material at ca. 2.3 Ga and, thus, if asteroid Itokawa was already formed, thereby providing a minimum age for catastrophic asteroid breakup. A second particle shows no sign of deformation, indicating shock pressure of