Initial Analysis of Volatile Components in the Hayabusa2 Samples
Ryuji Okazaki1, Bernard Marty2, Henner Busemann3, Yayoi N. Miura4, Keita Yamada5, Saburo Sakai6, Ko Hashizume7, Kenichi Bajo8, Shun Sekimoto9, Fumio Kitajima1, Kevin Righter10, Alex Meshik11, Jamie Gilmour12, Naoyoshi Iwata13, EvelynFüri2, Sarah Crowther12, Naoki Shirai14, Mitsuru Ebihara15, Yoshinori Takano6, Akizumi Ishida16, Reika Yokochi17, Olga
Pravdivseva11, Jisun Park18, 19, Toru Yada20, Kunihiko Nishiizumi21, Keisuke Nagao22, Jong Ik Lee22, Michael Broadley2,David Byrne2, My Riebe3, Patricia Clay12, Akihiro Kano4, Marc Caffee23, Shinsuke Kawagucci6, Yohei Matsui6, Ryu
Uemura24, Makoto Inagaki9, Daniela Krietsch3, Colin Maden3, Mizuki Yamamoto1, Hisayoshi Yurimoto8, Tomoki
Nakamura16, Takaaki Noguchi9, Hiroshi Naraoka1, Hikaru Yabuta25, Kanako Sakamoto20, Shogo Tachibana4, 20, Sei-ichiro
Watanabe24 and Yuichi Tsuda20
1

Kyushu Univ., 2CRPG, 3ETH, 4Univ. of Tokyo., 5Tokyo Inst. Tech., 6JAMSTEC, 7Ibaraki Univ., 8Hokkaido Univ., 9Kyoto U.,
10NASA JSC, 11Washington Univ., 12Univ. Manchester, 13Yamagata Univ., 14Tokyo Metro., 15Waseda Univ., 16Tohoku Univ.,
17Chicago Univ., 18Kingsborough Comm. Coll., ,19AMNH, 20JAXA, 21UC Berkeley, 22KOPRI, 23Purdue Univ., 24Nagoya Univ.,
25
Hiroshima Univ.

The major objectives of the Hayabusa2-initial-analysis volatile team are (1) to determine the pristine volatile components inthe parental materials of the returned Ryugu samples, and (2) to elucidate the origin and chronological history of the asteroidRyugu, as well as the evolution of the solar system through determination of volatile carrier phases and abundances of volatilecomponents (e.g., presolar grain abundances). Our analytical data will be linked with remote sensing (NIRS3, ONCs, TIR, andLIDAR) data and theoretical modeling [e.g., 1-5]. For example, the erosion rate and the degree of gardening of the surface layerof the asteroid Ryugu can be estimated based on trapped solar wind (SW) and cosmic ray produced (cosmogenic) nuclides,
which will be discussed in conjunction with the results based on the remote sensing data [3-5]. Taken together, these will provide
characteristics of the surface materials, such as the degree and duration of the alteration by SW/cosmic ray irradiation andmicrometeorite bombardments.
Our analytical plan for the Ryugu samples consists of three approaches (Fig. 1): One is analyses of native volatiles in theRyugu samples which have been treated WITHOUT air-exposure throughout the whole process, since the collection from theasteroid Ryugu to the gas extraction in the laboratories. The goal of this work is to quantify the indigenous compositions with asminimal terrestrial (atmospheric, biological, and unintentional man-made pollution) contamination as possible. We will obtain

Figure 1.

Analytical flow of the volatile team of the Hayabusa2 initial analysis.

the abundances and isotopic compositions of nitrogen, noble gases, and volatile elements (e.g., H and C in H2, CO, and CO2,methane, and ethane).
The second approach is analyses of the neutron-irradiated samples to determine the Ar-Ar and I-Xe ages and halogen
abundances by noble gas isotope measurements at U. Manchester and Kyushu U., and to obtain abundances of minor/traceelements (e.g., Co, Ni, and Ir) by neutron activation analysis (NAA) at KURNS. Prior to neutron-irradiation, nanoSIMS analysis
will be carried out at AORI on the same samples that are used for the Ar-Ar/I-Xe/halogen analysis at Kyushu U. to understandthe distribution and isotopic compositions of volatile elements (H, C, N, and O).
The third approach is measurements of cosmogenic long-lived nuclides and noble gas isotopes, which are performed fordifferent samples prepared under an atmospheric environment. The preliminary result of cosmogenic nuclides is reported by [6].
Most of Hayabusa2 samples allocated to the volatile team have been transported to Kyushu Univ. from JAXA, and locatedin a N2 glove box installed at Kyushu Univ., and pelletized without air-exposure in June 2021, except for two particles for thevolatile element analysis at TITECH/JAMSTEC and five samples for cosmogenic nuclides which were directly allocated toBerkeley U. from JAXA. Twenty four pellets have been prepared (Fig. 2), and sent back to JAXA to perform FTIR and FESEM
observations. After these observations, 16 out of 24 samples have been distributed to our team laboratories, ETH, U. Manchester,Washington U., CNRS-Nancy, Ibaraki U., TITECH/JAMSTEC, and Kyushu U. to measure native volatile compositions. Before
analysis, we measured the sample weight without air-exposure by using a small weighing container (Fig. 3). These careful
operations enable us to obtain the most intact, fresh volatile compositions of the asteroid Ryugu.

Figure 2. The Hayabusa2 samples pelletized onto a Cu disk without air-exposure (2a). TheCu disk is installed in a metal holder for NanoSIMS analysis and transportation. Enlarged
view of the sample is shown in Fig. 2b.
Figure 3. The small weighing
container developed for theHayabusa2 initial analysis.

The remainder of the samples, six pellets have been transported to Tohoku U. and coated with Os and Pt as an antistatictreatment. These samples have now been exposed to the atmosphere. After coating, the 6 samples were shipped to AORI andinvestigate with NanoSIMS in August 2021. The result of the nanoSIMS analysis will be reported by Drs. Hashizume andIshida somewhere else.
Following NanoSIMS analysis, the 6 pellet samples were transported to Kyushu U. for installation in diamond container
for the NAA. The neutron irradiation and NAA are scheduled to be completed in October. After the NAA, the 6 samples will
be analyzed for Ar-Ar age dating. For I-Xe dating and halogen analysis, two other pellet samples, different from the 6 samples
that have been analyzed for nanoSIMS and NAA, have been distributed to U. Manchester in July. Now all of these preparatory
steps are over and the Ryugu samples are ready for the experiments. We believe that all analyses will proceed successfully.
References[1] Sugita S. et al. 2019. Science 364, eaaw0422 1-11. [2] Kitazato K. et al. 2019. Science 364, 272-275. [3] Tatsumi E. et al.
2021. Nature Astronomy doi.org/10.1038/s41550-020-1179-z. [4] Morota T. et al. 2020. Science 368, 654–659. [5] Tachibana
S. et al. 2021. in review. [6] Nishiizumi K. et al. 2021. This issue.