The C-type asteroid Ryugu:
A first detailed look by Phase2 Curation Kochi (Ph2K)
M. Ito1, N. Tomioka1, M. Uesugi2, A. Yamaguchi3, N. Imae3, N. Shirai4, T. Ohigashi5, M. Kimura3, M-C. Liu6,
R.C Greenwood7, K. Uesugi2, A. Nakato8, K. Yogata8, H. Yuzawa5, Y. Kodama9*, M. Yasutake2, R. Findlay7, I.A Franchi7,
J.A. Malley7, K. Hirahara10, A. Tsuchiyama11, A. Takeuchi2, I. Sakurai12, I. Okada12, Y. Karouji13, T. Yada8, M. Abe8,T. Usui8, S. Watanabe12, and Y. Tsuda8.
18

JAMSTEC Kochi, 2JASRI/SPring-8, 3NIPR, 4Tokyo Met. Univ., 5UVSOR/IMS, 6UCLA, 7Open Univ.,
JAXA/ISAS, 9MWJ, 10Osaka Univ., 11Ritsumeikan Univ., 12Nagoya Univ., 13JAXA/JSEC, *Toyo Corp.

The Hayabusa2 spacecraft successfully returned toFigure 1. Largest Ryugu sample (A0002) for the Phase 2 curation
Earth surface materials from the C-type asteroid 162173
Kochi. (a) optical and (b) 3D-reconstruct images
Ryugu on December 6th 2020. The sample capsule contained(a)(b)a large number of small grains (a few to several mm in size),
collected from touchdown sites 1 and 2 on Ryugu, with a total
mass of ~5.4 g [1, 2]. After initial characterization of thegrains by JAXA curation (e.g., size, weight, FTIR andMicrOMEGA spectroscopic survey), we received eight grains(four from Room A and four from Room C) on June 17, 2021
(Figure 1 and Table 1). Detailed study of the materials
returned from Ryugu will provide critical information about the origin and early evolution of the Solar System and in particular,
the nature of the asteroid-meteorite connection, water-rock interactions on asteroids, the evolution of organics on small bodies,
the diversity and history of asteroid families in the main belt.
On June 19, 2021, we started initial characterization studies of all our samples using synchrotron radiation-based CTand XRD at the SPring-8. An air-tight sealed carbon nano-tube sample holder was used for CT analysis. In order to avoid
degradation and contamination due to interaction with the terrestrial atmosphere (water vapor and oxygen gas) [3], all of thesample preparation (chipping by a chisel, cutting by a counter balanced diamond wire saw, and epoxy mount preparation) wasconducted in a glove box in an atmosphere of pure, dry N2 (Dew point: -80 to -60˚C, O2 ~50 to 100 ppm). Once we had acquired
high-resolution, detailed three-dimensional structural and crystallographic information (0.85 µm/pixel for CT) for each of oursamples, we were able to define a priority list for the next phase of the analytical campaign, which involved coordinated micro
and bulk analysis.
The micro-analysis plan proposed by Ph2K involves the use of a wide range of multi-beam instruments to acquiredetailed micro-textural and chemical information about the samples at a sub-micrometer scale. Ongoing studies have involved
the use of FIB, STXM-NEXAFS, NanoSIMS and TEM [4]. In parallel, we are conducting bulk analysis of the samples using
SEM-EDS, EPMA, Raman spectroscopy, XRD, large geometry type SIMS, high precision O isotopic analysis by laser
fluorination and INAA. We have used air-tight containers (a facility-to-facility transfer container, FFTC [4]) for sample
transportation to nation-wide institutes by hand carry. With the assistance UK embassy in Tokyo, a few representative grains
were delivered to the Open University without any potentially invasive inspection (i.e., X-ray).
In this talk, we will present the preliminary results of the Ph2K coordinated micro-analysis and systematic bulk chemical
analysis campaign, which is focused on providing a detailed understanding of these precious Ryugu returned samples.
References: [1] Morota T. et al. 2020. Science 368, 654–659. [2] Yada et al. 2021. Abstract#2008, 52nd LPSC. [3] Uesugi M.
et al. 2020. Rev. Sci. Instrum. 91, 035107. [4] Ito M. et al., 2020. Earth, Planets and Space 72, 133.
Table 1. The Ryugu samples for the Phase2 curation Kochi
Sample No.

mgµm

SPring-8

Microanalysis(STXM, NanoSIMS, TEM)

Bulk Analysis(SEM-EDS, EPMA, Raman)

A0002

19.3

4,092

HR-CT, XRD, XRD-CT

Y

A0029

9.1

3,069

HR-CT, XRD, XRD-CT

Y

Y

A0037

7.8

3,129

HR-CT, XRD, Phase-contrast CTY

Y

A0098

1.9

1,868

HR-CT

C0009

11.1

3,520

HR-CT, XRD, XRD-CT

C0014

6.8

3,527

HR-CT

C00681.68

1,980

HR-CT

C0087

2

3.242

HR-CT

High Precision
O isotopes

SIMS

Y

XRD

YY
YY

INAA

YYYY

YYY

Y

Y

YYYYY