Crater depth-to-diameter ratios on asteroid 162173 Ryugu
Crater depth-to-diameter ratios on asteroid 162173 Ryugu
复制标题
小行星 162173 Ryugu 上的陨石坑深度与直径之比
DOI：
10.1016/j.icarus.2020.114016
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发表时间：
2021
期刊：
影响因子：
3.2
通讯作者：
Kameda Shingo他
中科院分区：
文献类型：
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作者：
Noguchi Rina;Hirata Naoyuki;Hirata Naru;Shimaki Yuri;Nishikawa Naoki;Tanaka Sayuri;Sugiyama Takaaki;Morota Tomokatsu;Sugita Seiji;Cho Yuichiro;Honda Rie;Kameda Shingo他
近地小行星162173 Ryugu是隼鸟2号使命的目标，它被认为是一个旋转的顶部形状的碎石堆。陨石坑是Ryugu最突出的表面特征之一。它们的形状，特别是它们的深径比（d/D），可以为探测行星体的内部结构和表面过程提供重要的替代。在这里，我们报告的d/D的每一个撞击坑的Ryugu使用的形状模型来自立体照相测斜。我们发现，平均值，标准差，和观察到的范围d/D为整个陨石坑组分别为0.09，0.02，和0.03-0.15。除了可能的坑状陨石坑外，龙谷上的大型陨石坑（D> 50米）的最大d/D接近0.13，与岩石小行星上的新鲜简单陨石坑（如加斯普拉和伊达）相当。相反，小陨石坑（D< 50 m）的d/D随着陨石坑直径的增加而增加。这种现象意味着在龙谷上形成的一个较小的陨石坑是一个较浅的陨石坑。与丝川一样，龙谷的表面环境可能会抑制陨石坑变深。这尤其影响到较小的陨石坑，因为它们的正常小深度在Ryugu环境中减少，并且变得更浅。结果，小陨石坑迅速退化，超过了可以确定为候选陨石坑的程度。这可能是造成明显缺乏小陨石坑的原因。d/D与Hirata等人（2020）的火山口分类类型没有可靠的关系。对Ryugu陨石坑d/D的纬度和经度变化的研究表明，没有统计学上的显著趋势。
The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 mission, is noted to be a spinning top-shaped rubble-pile. Craters are among the most prominent surface features on Ryugu. Their shapes, particularly their depth-to-diameter ratio (d/D), can provide an important proxy for probing both the internal structure and surface processes of planetary bodies. Here, we report d/D of every impact crater on Ryugu using a shape model derived from stereo-photoclinometry. We found that the average, standard deviation, and observed range of d/D for the entire set of craters are 0.09, 0.02, and 0.03–0.15, respectively. Except for possible pit craters, the maximum d/D of large craters on Ryugu (D> 50 m) is close to 0.13, which is comparable with those of fresh simple craters on rocky asteroids, such as Gaspra and Ida. Conversely, the d/D of small craters (D< 50 m) increases with the crater diameter. This behavior implies that a smaller crater on Ryugu is formed as a shallower crater. As on Itokawa, the surface environment on Ryugu likely inhibits craters becoming deep. This especially affects smaller craters, as their normal small depth decreases in the Ryugu environment and they become still more shallow. As a result, small craters rapidly degrade beyond the point where they can be identified as candidate craters. This is likely responsible for the apparent lack of small craters. The d/D has no reliable relationship with the types of crater classification in Hirata et al. (2020). Examination of latitudinal and longitudinal variation in d/D of craters on Ryugu revealed no statistically significant trends.