Ryugu particles found outside the Hayabusa2 sample container

Introduction: Samples returned from C-type near-Earth asteroid (162173) Ryugu by the Hayabusa2 spacecraft are reported to be in close relation to CI chondrites [1-6]. They were collected at two different touchdown sites and separately stored in the sample catcher, which was transported into the sample container inside the reentry capsule to seal with a metal-to-metal sealing system [7-9]. The reentry capsule was transported from the capsule landing site (the Woomera Prohibited Area in South Australia) to the curation facility in JAXA, where the sample container was opened by the container opening devise. During this operation before installation of the sample container into the clean chamber [11], the sample container was cleaned to remove any particles present outside of the metal-to-metal sealing. In the cleaning operation, two millimeter-sized black particles (hereafter Q001 and Q002) were removed from the gap between the inner lid and the sample container (outside of the container sealing). In this study, we investigated mineralogical, petrographical, and chemical characteristics of Q001 and Q002 to relate them to Ryugu grains and/or potential contaminants [12].