Ryugu particles found outside the Hayabusa2 sample container
Ryugu particles found outside the Hayabusa2 sample container
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DOI：
10.2343/geochemj.gj22017
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发表时间：
2022-01-01
影响因子：
0.8
通讯作者：
Tachibana, Shogo
中科院分区：
文献类型：
--
作者：
Nakato, Aiko;Inada, Shiori;Tachibana, Shogo
隼鸟2号航天器探索了C型近地小行星（162173）Ryugu，并将在两次着陆操作中收集的小行星物质返回地球，作为碳质小行星的第一个样本。在洁净室系统中安全地打开了密封有类似于5g Ryugu样品的样品容器，没有严重暴露于地面大气。在样品容器的制备操作过程中，在样品容器的密封部分外部发现两个深色毫米至亚毫米尺寸的颗粒。因为它们看起来与样品容器内的Ryugu粒子相似，所以这些粒子被命名为Q粒子（Q来自可疑）。在这项研究中，我们调查了Q颗粒（Q001和Q002）的矿物学和岩相学，比较它们与潜在的污染物（再入舱的烧蚀材料和在胶囊着陆场的细沙颗粒），Ryugu样品，和CI陨石。Q颗粒与Ryugu样品和CI陨石非常相似，但没有CI陨石经历的陆地风化的证据。因此，我们得出结论，Q粒子来自Ryugu，并在样品容器中的样品收集器封闭操作之前从空间中的样品收集器（样品储存罐）中排出。最有可能的情况是，在回收样品收集反射器的过程中，Q粒子从样品收集器中逃逸，这是样品容器关闭的必要操作。
The Hayabusa2 spacecraft explored C-type near-Earth asteroid (162173) Ryugu and returned asteroidal materials, collected during two touchdown operations, to the Earth as the first sample from carbonaceous-type asteroid. The sample container, in which similar to 5 g of Ryugu sample was enclosed, was safely opened in the clean chamber system with no severe exposure to the terrestrial atmosphere. In the course of preparation operation of the sample container, two dark-colored millimeter- to sub-millimeter-sized particles were found outside the sealing part of the sample container. Because they look similar to the Ryugu particles inside the sample container, the particles were named as Q particles (Q from questionable). In this study, we investigated Q particles (Q001 and Q002) mineralogically and petrographically to compare them with potential contaminants (the ablator material of the reentry capsule and fine sand particles at the capsule landing site), Ryugu sample, and CI chondrites. The Q particles show close resemblance to Ryugu sample and CI chondrites, but have no evidence of terrestrial weathering that CI chondrites experienced. We therefore conclude that the Q particles are originated from Ryugu and were expelled from the sample catcher (sample storage canister) in space prior to the enclosure operation of the sample catcher in the sample container. The most likely scenario is that the Q particles escaped from the sample catcher during the retrieval of the sample collection reflector, which was the necessary operation for the sample container closing.