Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor
Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor
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DOI：
10.1016/j.icarus.2021.114530
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发表时间：
2021-05-21
期刊：
影响因子：
3.2
通讯作者：
Iijima, Yu-ichi
中科院分区：
文献类型：
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作者：
Honda, Rie;Arakawa, Masahiko;Iijima, Yu-ichi
通过对比光学导航相机拍摄到的琉球表面撞击前后的图像，研究了由Hayabusa2‘S小型随身携带撞击器(SCI)在形成人工撞击坑的同时对琉球表面进行表面处理的过程。研究了重铺过程的三个不同方面：陨石坑边缘轮廓，巨石的运动和新巨石的出现，以及琉球表面在SCI陨石坑周围的运动矢量。平均陨石坑边缘高度h推导如下：h=h(R)exp[-(r/R-rim1)/lambda(Rim)]，其中R-rim是SCI陨石坑边缘半径8.8m，拟合参数h(R)为0.475 m，lambda(Rim)为0.245。SCI陨石坑的喷发盖层厚度比根据天然陨石坑观测和陨石坑形成理论估算的厚度都要薄。然而，通过考虑到体积中撞击后图像中出现的新巨石，喷出物毯子厚度的这种差异得到了解决。已发现巨石的运动按其机制可分为：陨石坑形成过程中挖掘流动产生的拖曳运动、后退抛射物产生的推动运动、冈本巨石轻微运动产生的拖曳运动和SCI撞击本身引起的地震震动引起的运动。地震震动导致巨石在距SCI陨石坑中心15米范围内的大部分地区距离原址3厘米以上，根据实验室实验，撞击产生的地震波的最大加速度是琉球表面重力的7倍(Matsue等人)。[2020年]Icarus，338,113520)，并且在距陨石坑中心15米到30米的区域内的大约10%的巨石中检测到移动了>；3厘米的巨石的地震震动的证据，根据先前的实验室实验推断该区域经历的加速度大于琉球表面的重力(Matsue et al.[2020年]伊卡洛斯，338,113520)。
The resurfacing process on Ryugu accompanying the artificial impact crater formation by Hayabusa2's Small Carry-on Impactor (SCI) was studied by comparing pre- and post-impact images of this region captured by an optical navigation camera. Three different aspects of the resurfacing process were examined: the crater rim profiles, the motion of boulders and the appearance of new boulders, and the motion vectors of Ryugu's surface around the SCI crater. The averaged crater rim height, h, was derived as follows: h = h(r) exp [-(r/R-rim 1)/lambda(rim)], where R-rim is the SCI crater rim radius of 8.8 m, the fitted parameter, h(r), is 0.475 m, and the lambda(rim) is 0.245. The ejecta blanket thickness of the SCI crater was thinner than that estimated from both the observation of natural craters and the crater formation theory. However, this discrepancy of the ejecta blanket thickness was resolved by taking into account the new boulders appearing in the post-impact images in the volume. The motion of the discovered boulders could be classified by its mechanisms as follows: a dragging motion created by excavation flow during the crater formation, a pushing motion created by falling-back ejecta, a dragging motion created by the slight motion of the Okamoto boulder, and a motion caused by seismic shaking induced by the SCI impact itself. The seismic shaking caused boulders to move farther than 3 cm from the original site in most of the region within 15 m distance from the SCI crater center, where the maximum acceleration of the impact induced seismic waves 7 times larger than the surface gravity of Ryugu based on the laboratory experiments (Matsue et al. [2020] Icarus, 338, 113520), and the evidence of the seismic shaking for boulders with a movement of >3 cm was detected in about 10% of the boulders in the region between 15 m and 30 m from the crater center, which region was inferred to experience acceleration larger than the Ryugu's surface gravity based on previous laboratory experiments (Matsue et al. [2020] Icarus, 338, 113520).