CNHOS contents with their isotopic compositions and preliminary organic profiles
from the Hayabusa2 samples
Yoshinori Takano1, Hiroshi Naraoka2, Nanako O. Ogawa1, Yasuhiro Oba3, Toshiki Koga1, Toshihiro Yoshimura1,
Saburo Sakai1, Naohiko Ohkouchi1, Hisayoshi Yurimoto3, Tomoki Nakamura4, Takaaki Noguchi5,
Ryuji Okazaki2, Hikaru Yabuta6, Kanako Sakamoto7, Shogo Tachibana7,8, Sei-ichiro Watanabe9,
Yuichi Tsuda7 and the Hayabusa2-initial-analysis SOM team
1

JAMSTEC, 2 Kyushu Univ., 3 Hokkaido Univ., 4 Tohoku Univ., 5 Kyoto Univ.,
6Hiroshima Univ., 7 JAXA, 8 Univ. Tokyo, 9 Nagoya Univ.

The successful collection and recovery of the Ryugu sample [1,2] are leading us to a valuable opportunity for revealing theproperties of the carbonaceous asteroid in the Solar System history; -What is Ryugu? -What are the origins and characteristicsof light elements (C, N, H, O, and S)? -What do their isotopic compositions tell us? -How do they record the primordial chemical
evolution on the asteroid? -How did the interaction of water, organic matter, and minerals affect the evolution and diversity ofindigenous molecules? To answer those important issues by using state-of-the-art small-scale analysis, the SOM (SolubleOrganic Matter) team have been firstly focusing on (i) the initial bulk profiles, especially for the elemental abundance of carbon(C), nitrogen (N), hydrogen (H), oxygen (O), sulfur (S) with the isotopic compositions of δ13C, δ15N, δD, δ18O and δ34S,
respectively, and (ii) the molecular profiles to understand more deeply for nature of indigenous SOM [3-5]. For instance, if
endogenous water-mineral interactions occurred in the asteroid, some aqueous alteration signatures (e.g., process relevant
products including carbonates and other precipitates) should have been recorded to the pristine sample in the bulk and molecularlevels. Assuming the interactions above mentioned, we can trace the potential in-situ temperature of the alteration process byusing clumped isotope surveys of minerals [6]. To assess the objectives, we have been conducting rehearsal analyses foranalytical optimizations and sequential sample processes [3-5, e.g., Figure 1], with a scope of solid and soluble organic aspects[6-9]. In order to deal with samples of unknown identity, especially for bulk nitrogen scale, we validated the dynamic range ofδ15N profiles covered on the basis of pioneering works and compilations for the Inner and Outer Solar System [e.g., 10].

Figure 1 The high precision and high accuracy analytical optimization using reference standards of carbon (C), nitrogen (N),and sulfur (S) for covering wide range isotopic compositions: (a) δ13C, ‰ vs. VPDB; within 13C-enriched and 13C-depleted
profiles, (b) δ15N, ‰ vs. Air; within 15N-enriched and 15N-depleted profiles, (c) δ34S, ‰ vs. VCDT; within 34S-enriched and34
S-depleted profiles. The x-axis and y-axis stand for the nominal value (= expected) and the measured value (= observed),respectively. Prior to the Hayabusa2 samples, those analytical validations using the nano-EA/IRMS system [3,4,7] wereperformed during the rehearsal analyses (e.g., several carbonaceous chondrite of CM2 and C2-ungrouped: unpublished data)
at JAMSTEC. We have confirmed that there was no memory effect in the analytical lines due to sequential process. For
further of optimization ultra-small-scale sulfur (S) quantification with δ34S validation, please see the latest update [11].

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Figure 2 (a, b) Capturing the representative colors during the sequential solvent extraction and the wet chemical treatment
for the Hayabusa2 samples (Ryugu, sample ID: A106 & C107). After solid-liquid separation, the colored supernatant withyellowish and pinkish colors were observed in both A106 and C107, the photo taken in the cleanroom at Dept. Earth Planet
Sci., Kyushu Univ. Since dissolved inorganic elements and organic-inorganic complex molecules also have some kind ofchromaticity depending on the affinity of the solvent, we are in the process of conducting detailed verification. Please see
also the residue of insoluble organic matter (IOM, black color) on the bottom of the vial. The onsite RGB color scale is shown.

We observed some of the colored supernatant during the sequential solvent extraction processes of Ryugu sample (Figure2). These extraction samples have been safely distributed to the SOM team members and are being analyzed in detail at theirlaboratories [12]. The residue of IOM fraction has been also seamlessly transported to the other initial analysis team for furtherdescription [13]. Here, we note that the colors of the extract show the chemical responses of the extractable indigenous organic
molecules to the inherent affinity of the solvent from low to high polarity (i.e., dependent on hydrophilicity, hydrophobicity, andamphiphilicity with both properties). Also, the colored supernatant may indicate that there is a certain amount of components
with a significant absorption spectrum (e.g., chemically various carbon skeleton with N-, S-, O-hetero structures). Regarding themolecular-level analysis, we are currently in the process of combining the pieces of the raw data profiles [12], and we expect
synergistic discussions at this symposium in terms of native organic properties within the history of the Ryugu.

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[11] Ogawa N. O. et al., #PR0203, Geochem. Soc. Jpn. (2021).
[12] Naraoka H., Takano Y., Dworkin, J. P., this symposium. & the other reports from the Hayabusa2-initial-analysis SOM team.
[13] Initial reports from the Hayabusa2-chemistry, -stone, -sand, -volatile, -IOM team at this symposium.