Size of particles ejected from an artificial impact crater on asteroid 162173 Ryugu
Size of particles ejected from an artificial impact crater on asteroid 162173 Ryugu
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小行星 162173 Ryugu 上的人工撞击坑喷出的颗粒大小
DOI：
10.1051/0004-6361/202039777
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发表时间：
2021
影响因子：
6.5
通讯作者：
Yano H.
中科院分区：
文献类型：
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作者：
Wada K.;Ishibashi K.;Kimura H.;Arakawa M.;Sawada H.;Ogawa K.;Shirai K.;Honda R.;Iijima Y.;Kadono T.;Sakatani N.;Mimasu Y.;Toda T.;Shimaki Y.;Nakazawa S.;Hayakawa H.;Saiki T.;Takagi Y.;Imamura H.;Okamoto C.;Hayakawa M.;Hirata N.;Yano H.
2019 年 4 月 5 日，由隼鸟 2 号小型随身撞击器加速的射弹在近地小行星 162173 Ryugu 的表面成功产生了最终表观直径为 14.5 ± 0.8 m 的人工撞击坑。在撞击坑时，可展开相机 3 拍摄了喷射物幕的清晰延时图像，喷射物幕是喷射粒子的集合，形成幕状结构。来自火山口。通过关注喷射物幕的光学深度并将其与理论模型进行比较，我们推断出喷射物颗粒的尺寸。因此，喷射物颗粒的典型尺寸估计为几厘米到分米，尽管它稍微取决于假设的尺寸分布。由于喷射物颗粒预计来自约 1 m 的深度，因此我们的结果表明，与我们观察到的许多米大小巨石的最上层相比，龙宫的地下层由相对较小的颗粒组成。我们的结果还表明，地下层中存在小于 1 毫米的颗粒缺陷。这些发现将对揭示龙宫和其他太阳系小天体的形成和表面演化过程发挥关键作用。
A projectile accelerated by the Hayabusa2 Small Carry-on Impactor successfully produced an artificial impact crater with a final apparent diameter of 14.5 ± 0.8 m on the surface of the near-Earth asteroid 162173 Ryugu on April 5, 2019. At the time of cratering, Deployable Camera 3 took clear time-lapse images of the ejecta curtain, an assemblage of ejected particles forming a curtain-like structure emerging from the crater. Focusing on the optical depth of the ejecta curtain and comparing it with a theoretical model, we infer the size of the ejecta particles. As a result, the typical size of the ejecta particles is estimated to be several centimeters to decimeters, although it slightly depends on the assumed size distribution. Since the ejecta particles are expected to come from a depth down to ~1 m, our result suggests that the subsurface layer of Ryugu is composed of relatively small particles compared to the uppermost layer on which we observe many meter-sized boulders. Our result also suggests a deficit of particles of less than ~1 mm in the subsurface layer. These findings will play a key role in revealing the formation and surface evolution process of Ryugu and other small Solar System bodies.