（25143）Itokawa空间风化时间尺度的估算：对它的再生过程的启示
Estimation of space weathering timescale on (25143) Itokawa: Implications on its rejuvenation process
摘要：
上下文近地S-型小行星的空间风化时间尺度已经通过几种方法进行了研究（即，实验、样本分析和理论方法），但存在数量级差异。目的。利用Hayabusa-AMICA影像研究了近地S型小行星丝川的空间风化时间尺度，并进一步研究了小行星的演化过程。方法.我们专注于通过与行星际尘埃颗粒（IDP）的碰撞产生的巨石表面上的明亮斑点。我们比较了明亮的斑点大小分布与IDP通量模型，以确定空间风化时间尺度。结果结果发现，丝川巨砾表面的空间风化时间尺度为10 $^3$ a（在10 $^2$ -10 $^4$ a的范围内），这与太阳风轻离子的空间风化时间尺度一致。结论.根据这一结果，我们得出结论，丝川的表面在10 $^3$年的时间里已经风化了，但部分表面是通过最近的撞击引发的地震震动暴露出来的，该撞击造成了鸭井陨石坑。
英文摘要：
Context. The space weathering timescale of near-Earth S-type asteroids has been investigated by several approaches (i.e., experiments, sample analyses, and theoretical approaches), yet there are orders of magnitude differences. Aims. We aim to examine the space weathering timescale on a near-Earth S-type asteroid, Itokawa using Hayabusa-AMICA images and further investigate the evolutional process of the asteroid. Methods. We focused on bright mottles on the boulder surfaces generated via impacts with interplanetary dust particles (IDPs). We compared the bright mottle size distribution with an IDP flux model to determine the space weathering timescale. Results. As a result, we found that the space weathering timescale on Itokawa's boulder surfaces is 10$^3$ years (in the range of 10$^2$-10$^4$ years), which is consistent with the timescale of space weathering by light ions from the solar wind. Conclusions. From this result, we conclude that Itokawa's surface has been weathered shortly in 10$^3$ years but portions of the surface are exposed via seismic shaking triggered by a recent impact that created the Kamoi crater.
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