Initial analysis of Hayabusa2 returned samples from asteroid (162173) Ryugu
Shogo Tachibana1,2, Hisayoshi Yurimoto3, Tomoki Nakamura4, Takaaki Noguchi5,6, Ryuji Okazaki6, Hikaru Yabuta7, Hiroshi
Naraoka6, Kanako Sakamoto2, Sei-ichiro Watanabe8, Yuichi Tsuda2, and the Hayabusa2 Initial Analysis team
1Univ. Tokyo, 2ISAS, JAXA, 3Hokkaido Univ, 4Tohoku Univ., 5Kyushu Univ., 6Kyoto Univ., 7Hiroshima Univ., 8Nagoya Univ.
The JAXA’s Hayabusa2 spacecraft explored C-type near-Earth asteroid (162173) Ryugu from June 2018 to November 2019,
during which two touchdown operations were made to collect surface and subsurface samples. The Hayabusa2 delivered its
reentry capsule on December 6, 2020 to Woomera, South Australia [1]. The sample container inside the reentry capsule wasopened in the clean chamber system dedicated to Ryugu samples at ISAS, JAXA. Dark particles were found in both chambers
A and C, which were used for the storage of the samples collected at the first and second touchdown, respectively. The total
amount of the samples exceeds 5 g, which is much larger than the minimum requirement of 0.1 g [2]. Many millimeter-sizedparticles were present with fine powdery materials, and centimeter-sized grains, close to the maximum obtainable size [3],were found in the chamber C. The color, morphology, and spectroscopic features of the grains indicates that they well
represent the surface materials of Ryugu.
The initial analysis of a fraction of returned samples, led by the Hayabusa2 project, has begun in June 2021 after the6-month sample description at the ISAS curation facility without exposure to the air. The initial analysis aims at maximizing
the scientific achievement of the project with answering important fundamental questions such as what materials Ryugu
consists of, how Ryugu evolved from its formation to the present, and how similar or different Ryugu samples are to theknown meteorites. The findings from Ryugu samples are expected to invoke cosmochemical discussion on the origin andevolution of the Solar System architecture such as the isotopic dichotomy in the early Solar System, the delivery of water andorganics to the inner Solar System, and the asteroid-comet continuum. The initial analysis also aims at providing the groundtruth for the remote sensing data obtained by the Hayabusa2 spacecraft.
The initial analysis team consists of six sub-teams for 1) chemistry (elements and isotopes) (Lead: Hisayoshi
Yurimoto, Hokkaido University), 2) petrology and mineralogy of coarse grains (mm-sized grains [stone]) (Lead: Tomoki
Nakamura, Tohoku University), 3) petrology and mineralogy of fine grains (<100 μm-sized grains [sand]) (Lead: Takaaki
Noguchi, Kyoto University/Kyushu University), 4) volatiles (Lead: Ryuji Okazaki, Kyushu University), 5) insoluble organicmatter (macromolecular organics) (Lead: Hikaru Yabuta, Hiroshima University), and 6) soluble organic matter (organicmolecules) (Lead: Hiroshi Naraoka, Kyushu University). The total number of teams members is nearly 300 from fourteencountries. The initial analysis will continue for 12 months. The data obtained during the initial analysis will be archived in theJAXA curatorial sample database to prove the potential of the samples to the community.
Three hundred milligrams of Ryugu samples (6 % of the total samples by mass) have been allocated from JAXA tothe initial analysis team; Twenty two grains, which were individually photographed, weighed, and spectroscopically examinedin the clean chamber system, and ten aggregate samples that mainly consist of particles smaller than 1 mm in diameter (Table1).
Table 1. Samples allocated to the Hayabusa2 initial analysis team.
Individual grains
Individual grains
Aggregates
Aggregates(Chamber A)(Chamber C)(Chamber A)(Chamber C)
A0026 3.9 mg
C0002 93.5 mg
A0104 0.3 mg
C0105 0.4 mg
A0040 3.0 mg
C0023 5.0 mg
A0105 4.0 mg
C0106 4.0 mg
A0055 5.9 mg
C0025 5.6 mg
A0106 38.4 mg
C0107 38.8 mg
A0058 3.3 mg
C0033 2.4 mg
A0107 31.0 mg
C0108 33.0 mg
A0063 3.8 mg
C0040 4.9 mg
A0108 3.5 mg
C0109 3.7 mg
A0064 6.7 mg
C0046 2.6 mg
A0067 3.6 mg
C0055 0.8 mg
A0080 1.4 mg
C0057 0.9 mg
A0086 0.9 mg
C0061 1.3 mg
A0089 1.0 mg
C0076 4.7 mg
A0094 1.8 mg
C0103 1.5 mg

The allocated samples have been individually investigated by each sub-team or by collaboration of multiple sub-teams. The
C0002 grain from the chamber C is the third largest particle (~9 x 5 x 4 mm) among all the returned particles (Table 1). Thisgrain has been analyzed by all six sub-teams.
In this presentation we discuss the goals and overall activities of the initial analysis of Ryugu samples. Preliminary
results of elemental and isotopic analyses, mineralogical and petrological observation, and analyses of volatiles and organic
components will be presented from each sub team at the meeting [e.g., 4–22].
References[1] Tachibana S. et al. (2021) 51st LPSC, Abstract #1289. [2] Tachibana S. et al. (2014) Geochem. J. 48, 571–587. [3] Sawada
H. et al. (2017) Space Sci. Rev. 208, 81–106. [4] The Hayabusa2-initial-analysis chemistry team et al. (2021) this meeting. [5]Nakamura T. et al. (2021) this meeting. [6] Noguchi T. et al. (2021) this meeting. [7] Okazaki R. et al. (2021) this meeting. [8]Yabuta H. et al. (2021) this meeting. [9] Naraoka H. et al. (2021) this meeting. [10] Tsuchiyama A. et al. (2021) this meeting.
[11] Dionnet Z. et al. (2021) this meeting. [12] Rubino S. et al. (2021) this meeting. [13] Viennet J.-C. et al. (2021) thismeeting. [14] Matsumoto T. et al. (2021) this meeting. [15] Nishiizumi K. et al. (2021) this meeting. [16] Kebukawa Y. et al.
(2021) this meeting. [17] Bonal L. et al. (2021) this meeting. [18] Stroud R. M. et al. (2021) this meeting. [19] Nittler L. R. etal. (2021) this meeting. [20] Takano Y. et al. (2021) this meeting. [21] Orthous-Daunay F.-R. et al. (2021) this meeting. [22]Schmitt-Kopplin P. et al. (2021) this meeting.