ISOTOPE DISTRIBUTIONS AND ANOMALOUS MATERIALS IN RETURN SAMPLES FROM THE ASTEROID RYUGU. N. Sakamoto1, The Hayabusa2-initial-analysis chemistry team, The Hayabusa2-initial-analysis
core, 1Hokkaido University.
Introduction: The objective of the Hayabusa2 mission that sampled the C-type asteroid Ryugu in twotouchdown sites is to clarify the origin and evolution ofthe Solar System, especially the origin of organic matterand water [1], important constituents of Earth’s life. The
asteroid Ryugu is believed to contain abundant organicmatter formed in the early Solar System. Isotopic imaging allows us to observe distributions of organic matter,presolar grains, and minor elements. Here we report thepreliminary results on isotope imaging of the Ryugu
samples returned by the Hayabusa2 spacecraft.
Experimental: Polished sections from A0058C1001 and C0002-C1001, samples from 1st and 2nd
touchdown sites, respectively, were used. Their isotopic
distributions were collected using the Hokudai isotope
microscope system consisting of a stigmatic secondary
ion mass spectrometer (SIMS, Cameca ims-1270e7) anda stacked CMOS active pixel sensor (SCAPS) [2].
A 20 nA primary 16O− ion beam accelerated to 23
keV was focused onto the sample surface over 100×80µm2 through a square aperture. Secondary ion images of1 + 7 + 11 + 23
H , Li , B , Na+, 24Mg+, 27Al+, 28Si+, 39K+, 40Ca+,
and 56Fe+ were projected onto the SCAPS. Analyzed areas include 11 and 37 maps in A0058 and C0002, respectively, totaling ~384,000 µm2. Detailed analyticalconditions are described in [3].
Secondary ion images of 1H−, 12C−, 13C−, 12C14N−,12 15 − 16 − 17 − 18 − 19 − 28 − 31 − 32 −C N , O , O , O , F , Si , P , S , and 35Cl−
were collected using Cs+ ions at 2 nA and 15 keV impact
energy. Each map corresponds to a 50×50 µm area on
the sample surface. The exit slit was narrowed to avoid
interferences of 11B16O− on 12C15N− and 16OH− on 17O−.
Analyzed areas include 132 maps in C0002, ~330,000µm2 in total. Candidates of chemically and isotopicallyanomalous materials were analyzed repeatedly for confirmation. Most of the isotopically anomalous materials
were not completely sputtered away, allowing their identification by electron microscopy.
Results and Discussion: The images show abundant carbonaceous materials in matrices of the Ryugu
samples. These include globules and a large C- & N-rich
object (Fig. 1). We also observed isotopically anomalous carbonaceous materials, including 13C-rich SiC and15
N-rich grains (Fig. 2). Based on BSE images, three lithologies in the Ryugu samples can be tentatively identified: white, gray, and black. Light elements (C, N, F,Cl, and Na) are heterogeneously distributed among
these lithologies. We also identified several B-rich objects, and a Na-rich rim along the original surface ofA0058 sample (Fig. 3).

Fig. 1. Backscattered electron (BSE) image of C- and N-richmaterial in the C0002.

The chemical distributions and the presence of isotopically anomalous materials in the Ryugu samples indicate that the asteroid Ryugu was not chemically andisotopically homogenized; some primordial materials
survived during the extensive aqueous alteration it experienced. Carbon- and N-rich materials are important
ingredients of life and will be further studied in detail.
References: [1] S. Tachibana (2021) In Sample Return Missions (Ed. A. Longobardo), Elsevier, pp 147–
162. [2] H. Yurimoto et al. (2003) Appl. Surf. Sci. 203–204, 793–797. [3] S. Tagawa et al. (2021) Nat. Commun. 12, #2588.
The Hayabusa2-initial-analysis chemistry team:
T. Yokoyama, K. Nagashima, I. Nakai, E. D. Young, Y.
Abe, J. Aléon, C. M. O'D. Alexander, S. Amari, Y.
Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B-G. Choi, N. Dauphas, A. M. Davis, T. D. Rocco, W. Fujiya, R. Fukai, I. Gautam, M. K.
Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.
R. Huss, K. Ichida, T. Iizuka, T. R. Ireland, A. Ishikawa,
M. Ito, S. Itoh, N. Kawasaki, N. T. Kita, K. Kitajima, T.
Kleine, S. Komatani, A. N. Krot, M-C. Liu, Y. Masuda,
K. D. McKeegan, M. Morita, K. Motomura, F. Moynier,A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L.
Piani, L. Qin, S. S. Russell, N. Sakamoto, M.
Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada,T. Usui, S. Wada, M. Wadhwa, R. J. Walker, K. Yamashita, Q-Z. Yin, S. Yoneda, H. Yui, A-C. Zhang, H.
Yurimoto.

The Hayabusa2-initial-analysis core: S. Tachibana, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, H. Yurimoto, Y. Tsuda,
S. Watanabe.

Fig. 2. Isotopically anomalous objects in C0002. (a) 12C−, 13C−
and (b) BSE image of 13C-rich SiC grain (δ13C = +4,000‰),
about 150 nm in size. (c) 12C14N−, 12C15N− and (d) BSE imageof 15N-rich grain (δ15N = +700‰).
Fig. 3. (a) BSE, (b) 1H+, (c) 11B+ and (d) 23Na+ images obtainedin A0058.