MMX samples curation in Europe
Enrica Bonato1, Jörn Helbert1, Ansgar Greshake2, Lutz Hecht2, Tomohiro Usui3
German Aerospace Centre (DLR), Institute for Planetary Research, Berlin, Germany
2
Museum für Naturkunde, Berlin, Germany
3
ISAS, JAXA, Japan1

In 2024 the Martian Moons eXploration (MMX) mission from JAXA will be launched to the Martian Moons Phobos and Deimos toinvestigate their nature and improve our understanding about their formation. In 2029 samples from Phobos will be returned back to Earth as
MMX is the latest JAXA’s sample return mission. Samples returned to Earth by the MMX mission will be retrieved by JAXA andtransferred to the JAXA ISAS Sample receiving laboratory for initial description, followed by initial proprietary analyses performed by the
MMX Science Sub-Teams (SSTs), which will include a number of ESA-appointed MMX participating scientists from ESA Member States.
The duration of these activities is determined by the MMX Sample Allocation Committee (SAC), and it is estimated to last approximately
one year. It is planned that JAXA will thereafter transfer an allocation of samples to ESA for use by scientists and laboratories in the ESA
Member States. Sample Curation Facilities (hereafter SCFs) at the German Aerospace Centre (DLR) and at the National Centre for SpaceStudies (CNES) will host and handle the MMX Samples provided to the ESA Science Program. After transfer to the SCFs the samples will
be catalogued (if not done by JAXA) in preparation for an ESA Announcements of Opportunity (AOs) to allocate the Samples to scientists
and laboratories in the ESA Member States.
In preparation to this major effort, we are working on the setup of an analytical and curation facility in Berlin, in cooperation between the
DLR and the Museum für Naturkunde (MfN). Within the analytical facility it will be possible to carry out the basic characterization of thesamples in controlled environmental conditions, for then being able to move on to more specialized facilities for more in depth examination.
The curatorial expertise is being developed on the existing expertise from the Meteorite Collection based at the MfN and in collaboration
with the JAXA curation facilities. Current curators, together with the younger generation are being trained and working on skillset exchange.

Can SIMS measurements constrain the D/H ratio of water on Ryugu?
Larry R. Nittler1,2, Jens Barosch,1 and Rhonda M. Stroud3,2
The Hayabusa2-initial-analysis Organic Macromolecule and Core Teams
1
Earth and Planets Laboratory, Carnegie Institution of Washington, USA.
2
School of Earth and Space Exploration, Arizona State University, USA
3
US Naval Research Laboratory, Washington DC, USA
We have previously reported the use of the Cameca NanoSIMS ion microprobe to characterize H, C, and N isotopes
on a sub-micrometer scale in particles returned by the Hayabusa2 spacecraft from C-asteroid Ryugu [1, 2]. These data
show that macromolecular organic-rich particles in Ryugu samples are remarkably isotopically heterogeneous on µm
scales with compositional distributions similar to those of carbonaceous chondrites (CCs), including CIs, the closest
meteorite analog to Ryugu [3]. Recently, Piani et al. [4] have used large-geometry SIMS (Cameca ims-1280) data toconclude that Ryugu water has δD/H = +74 ± 117 ‰. Since the NanoSIMS has much higher spatial resolution than
the ims-1280, we have re-examined our data to investigate whether they can provide additional information on
Ryugu’s water composition. Our results agree well with those of [4], but we argue below that it is not possible withcurrent ion probe data sets to infer the H2O D/H composition on Ryugu with any degree of confidence.
Prior work on CCs and Ryugu samples [4-6] has assumed that ~10-µm-scale SIMS H-isotope measurements
represent two-component mixtures between water of hydration (with C/H=0) and organic matter (with higher C/H),
based on observed correlations between measured C/H and D/H ratios. Extrapolation of fitted linear trends to the data
to C/H=0 then yields the inferred D/H of the intrinsic H2O. Shown as grey circles in Fig. 1d are the C/H ratios and δDvalues we have previously found in organic-rich particles, typically a few 100 nm in diameter, based on 20 fragments
of Ryugu particles A0108-13 (12 fragments) and C0109-2 (8 fragments) pressed into Au foils. The instrumental massfractionation and C/H calibration were corrected based on a terrestrial organic standard. The large scatter in these dataprecludes linear extrapolation. We thus chose to bin the imaging data by defining regions-of-interest (ROIs) in each
image whose C/H ratios spanned specific intervals (e.g., Figs. 1a-c). The C/H and D/H ratios are generally correlated
within an image (e.g., Fig. 1c) but the variable presence of anomalously D-rich or D-poor grains (hot/coldspots) often
leads to non-linear trends. Nevertheless, when the data are combined for all 20 particles, clear linear trends areobserved below C/H~1 for both the Chamber A and Chamber C grains (green and orange symbols in Fig. 1d-e).
Outliers are due to the presence of D hotspots or coldspots. The solid green and orange lines indicate linear fits to thedata below C/H=1 (excluding outliers). The fit lines intersect the Y-axis at δD=142 ‰ and 82 ‰, respectively, in
excellent agreement with the results of [4] (red error bar), acquired with a different instrument on different samples.
The linear trends seen in Fig. 1d,e support the idea that, when averaged over relatively large areas, the data represent
two-component mixing. At the high C/H end, the endmember is clearly the average of the ubiquitous C-rich particles
present throughout the Ryugu samples, i.e., the grey symbols in Fig. 1d. We note that insoluble organic matter (IOM)
extracted from CI chondrites [magenta star; 7] lies close to but slightly above the Ryugu trend lines. This supports
previous measurements indicating that Ryugu IOM has lower D/H than IOM from CIs [8] but could also reflect apossible mis-calibration of the C/H ratios from measured C/H secondary ion signals in the NanoSIMS. The
identification of the low C/H endmember is more ambiguous. Transmission electron microscopy and synchrotronbased transmission x-ray microscopy studies have shown that in Ryugu samples the phyllosilicates are intimately
mixed with a “diffuse” organic material [9-11]. This diffuse C (“dC”) is spectroscopically distinct from the larger
particulate organic grains, for example showing a CO3 feature (not associated with carbonate minerals) and often
showing a higher abundance of aliphatic compounds [11]. The intimate association of the dC with the clay minerals
means that even at the highest NanoSIMS spatial resolution, one cannot distinguish H coming from the dC and thatcoming from the water. Thus, the trend in fact represents 3-component mixing where the low C/H endmember is itself
a mixture of H2O and dC. Since the two forms of organics (dC and particles) are spectrally distinct, they also couldδD/H

have distinct C/H and D/H ratios on average. For example, the black lines on Fig 1e indicate mixing between waterwith δD= -200 or -500 ‰ (as inferred for CI chondrites by [12]) and supposed diffuse C components arbitrarily
assumed to have C/H~0.6 (based on assumed higher aliphatic content) and δD~2000 or 3000‰, respectively. Since
these lines intersect with the low-C/H end of the Ryugu trends, the data are fully consistent with Ryugu water having
a D/H much lower than inferred by [4], if the dC indeed has higher D/H and/or lower C/H on average than the larger
organic grains and the mixing ratio between dC and phyllosilicates is roughly constant on the scale of themeasurements. Without a way to independently determine the composition of the dC, we conclude that SIMS
measurements like those used here and by [4-6] cannot unambiguously resolve the D/H of water in Ryugu samples.
Moreover, dC has also been seen to be present in CI, CM, and CR chondrites [13], suggesting that previous SIMS
D/H measurements of these should be revisited. Finally, we note that under O- primary ion bombardment, thesecondary ion yield of H+ is higher from hydrated silicates than from organics [14]. High-resolution NanoSIMS
measurements of Ryugu
2000
a
b
c
samples with the Hyperion RF
1500
HC
plasma O source, compared
1000
with Cs-based measurementsof the same materials, may
500
allow for better discrimination
C/H
0-0.180.86-1.00
0.18-0.34 1.0-1.2
of the water endmember from
0.34-0.52 1.2-1.4
C/H
5 µm
0.52-0.7 1.4-1.6-500
0.7-0.86
0.0
0.5
1.0
1.5
2.0 the dC and provide a better
estimate of the D/H of Ryugu
4000de
C-rich Particles
water.
Binned C/H A
3000

δD/H (‰)

Binned C/H C
CI IOM

Diffuse
C?

2000
1000
0
0
0.0

0.5

1.0

1.5

C/H

2.0

2.5

-1000
3.0
0.0

0.2

0.4

0.6

0.8

C/H

1.0

1.2

1.4

Figure 1. a) Color-coded
NanoSIMS map of H and C in a
Ryugu particle b) ROIs definedby pixels within selected C/Hratio bins. c) δD versus C/H for
ROIs from panel b. d,e) δD versus
C/H for 20 analyzed Ryugu
fragments. Vertical red error bar
is y-intercept reported by [4].

References[1] Barosch J. et al. 2022. Abstract #2050. 53d LPSC. [2] Nittler L. R. et al. 2022. Goldschmidt Conference. [3]Yokoyama T et al. 2022. Science abn7850. [4] Piani L. et al. 2022. Abstract #6058. 85th MetSoc Meeting. [5] Piani
L. et al. 2021. Earth & Planetary Science Letters 567: 117008. [6] Piani L. et al. 2018. Nature Astronomy 2:317-323.
[7] Alexander C. M. O’D. et al. 2007. Geochimica et Cosmochimica Acta 71: 4380–4403. [8] Remusat L. et al. 2022.
Abstract #6197. 85th MetSoc Meeting. [9] Yabuta H. et al. 2022. Abstract #2241. 53d LPSC. [10] De Gregorio B.
T., et al. 2022. Abstract #1634. 53rd LPSC. [11] Stroud R. M., et al. 2022. Abstract #2052. 53d LPSC. [12] Alexander
C. M. O’D. et al. 2012. Science 337: 721–723. [13] Le Guillou C. et al. 2014. Geochimica et Cosmochimica Acta
131: 368–392. [14] Deloule E. and Robert F. 1995. Geochimica et Cosmochimica Acta 59: 4695–4706.
The Hayabusa2-initial-analysis Organic Macromolecule and Core Teams: H. Yabuta, G. D. Cody, C. Engrand,
Y. Kebukawa, B. De Gregorio, L. Bonal, L. Remusat, R. Stroud, E. Quirico, L. R. Nittler, M. Hashiguchi, M. Komatsu,
E. Dartois, J. Mathurin, J. Duprat, T. Okumura, Y. Takahashi, Y. Takeichi, D. Kilcoyne, S. Yamashita, A. Dazzi, A.
Deniset-Besseau, S. Sandford, Z. Martins, Y. Tamenori, T. Ohigashi, H. Suga, D. Wakabayashi, M. Verdier-Paoletti,
S. Mostefaoui, G. Montagnac, J. Barosch, K. Kamide, M. Shigenaka, L. Bejach, T. Noguchi, H. Yurimoto, T.
Nakamura, R. Okazaki, H. Naraoka, K. Sakamoto, S. Tachibana, S. Watanabe, and Y. Tsuda

Pentlandite: A Compositional Indicator of Oxygen Fugacity for Chondrites
D. L. Schrader1, T. J. Zega2, J. Davidson1, T. J. McCoy3, and K. J. Domanik2
Buseck Center for Meteorite Studies, School of Earth and Space Exploration, Arizona State University, AZ 85287, USA(devin.schrader@asu.edu), 2Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. 3Department ofMineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0119, USA.
1

Introduction: Fe-sulfides are ubiquitous in chondrites and are sensitive indicators of formation and alteration conditionsin the protoplanetary disk and small Solar System bodies [e.g., 1–14]. We previously constrained a minimum oxygen fugacity(fO2) needed to form pentlandite, (Fe,Ni)9S8, [6,7] and identified trends with pentlandite compositions between distinct
meteorite groups [6,7]. We also identified a relationship between the at.% Fe/S ratio of pyrrhotite group sulfides and the fO2 offormation, either in the protoplanetary disk or the parent body during aqueous or thermal alteration [13]. Since pentlandite
formed with pyrrhotite (they are typically intergrown in these chondrite groups [1–14]; Figure 1), fO2 may have also influenced
pentlandite compositions. Here we report the chemical compositions of pentlandite in chondrites that experienced a wide rangeof formation and parent body alteration conditions (including fO2 [13]). This compositional analysis enables investigation ofpotential trend(s) with the pyrrhotite at.% Fe/S ratio, and by extension fO2.
Samples and Analytical Procedures: We determined the
major and minor element compositions of pentlandite in each of thefollowing 54 chondrites: CI (Alais), a C1-ungrouped (Miller Range[MIL] 090292), C2-ungrouped (Tarda and Tagish Lake), CY(Belgica [B]-7904), CM1/2 (Allan Hills [ALH] 83100 and Kolang[two lithologies]), unheated CM2s (Aguas Zarcas [multiple
lithologies], Mighei, Queen Alexandra Range [QUE] 97990, Theil
Mountains [TIL] 91722, and D’Angelo Bluff [DNG] 06004), stage I
heated CM2 (Asuka [A]-881458), stage II heated CM2 (Yamato[Y]-793321), CM-like (Sutter’s Mill), CO3.00 (Dominion Range[DOM] 08006), CR1 (Grosvenor Mountains [GRO] 95577), CR-an(Al Rais), CR2 (Elephant Moraine [EET] 87770, EET 92048, EET
96259, Gao-Guenie (b), Graves Nunatak [GRA] 95229, LaPaz Ice
Figure 1. Backscattered electron image of a pyrrhotite
Field[LAP] 02342, LAP 04720, MIL 090657, Northwest Africa(Po) – pentlandite (Pn) intergrowth in Tarda (C2-ung).
Mag = magnetite.
[NWA] 801, Pecora Escarpment [PCA] 91082, QUE 99177, Shişr
033, and Y-793495), shock-heated CR2 (GRO 03116), CV3OxA(Allende), CV3OxB (Bali), and CV3Red (Vigarano), CK4 (ALH 85002 and Karoonda), CK5 (Larkman Nunatak [LAR] 06868),
CK6 (Lewis Cliff [LEW] 87009), L3.05 (EET 90161 and QUE 97008), LL3 (Semarkona and Vicência), LL4 (Hamlet andSoko-Banja), LL5 (Chelyabinsk and Siena), LL6 (Appley Bridge and Saint-Séverin), R3 (MET 01149), R3.6 (LAP 031275),
R5 (LAP 03639), and R6 (LAP 04840 and MIL 11207) chondrites. We acquired high-resolution backscatter electron images(e.g., Figure 1) and quantitative chemical compositions with the JEOL-8530F Hyperprobe electron microprobe analyzer(EPMA) at Arizona State University (ASU) and the Cameca SX-100 EPMA at the University of Arizona (UA) following [13].
Some pentlandite compositions were previously reported [6,7,10,11].
Results and Discussion: Our data show that there is a relationship between the at.% Fe/S ratio of pyrrhotite (data from[13]) and pentlandite compositions. Moreover, because the at.% Fe/S ratio of pyrrhotite is a proxy for fO2 [13], these results
indicate that there must also be a relationship between fO2 and pentlandite composition. This relationship holds whether
pentlandite formed: (1) during chondrule formation in the protoplanetary disk (i.e., during chondrule cooling, as previously
noted by [6,8,10,11] for CR2, CO3.00, and LL3.00 chondrites), (2) during thermal alteration on the parent asteroid underrelatively reducing (i.e., LL4–6 chondrites) or oxidizing (i.e., R4–6 and CK chondrites) conditions, or (3) during oxidizing
aqueous alteration (i.e., as in CI, CM1, C1-ung, and C2-ung chondrites). Therefore, in addition to the at.% Fe/S ratio of
pyrrhotite, the chemical compositions of pentlandite can also be used as a proxy for the fO2 of formation. This discovery has
implications for the interpretation of pentlandite compositions in meteorites and in asteroid returned samples from Ryugu andBennu.
References: [1] Zolensky M. E. et al. (2002) Meteorit. Planet. Sci. 37:737–761. [2] Bullock E. S. et al. (2005) Geochim.
Cosmochim. Acta 69:2687–2700. [3] Schrader D. L. et al. (2008) Geochim. Cosmochim. Acta 72:6124–6140. [4] Berger E. L.
et al. (2011) Geochim. Cosmochim. Acta 75:3501–3513. [5] Harries D. and Langenhorst F. (2013) Meteorit. Planet. Sci.

48:879–903. [6] Schrader D. L. et al. (2015) Meteorit. Planet. Sci. 50:15–50. [7] Schrader D. L. et al. (2016) Geochim.
Cosmochim. Acta 189:359–376. [8] Schrader D. L. et al. (2018) Earth Planet. Sci. Lett. 504:30–37. [9] Singerling S. A. andBrearley A. J. (2018) Meteorit. Planet. Sci. 53:2078–2106. [10] Davidson J. et al. (2019) Geochim. Cosmochim. Acta 265:259–
278. [11] Davidson J. et al. (2019) Geochim. Cosmochim. Acta 267:240–256. [12] Singerling S. A. and Brearley A. J. (2020)
Meteorit. Planet. Sci. 55:496–523. [13] Schrader D. L. et al. (2021) Geochim. Cosmochim. Acta 303:66–91. [14] Holt M. C.
and Herd C. D. K. (2022) Meteorit. Planet. Sci. 57:1267–1287.
Acknowledgements: We thank the Smithsonian Institution, NASA/NSF, the ASU Buseck Center for Meteorite Studies(BCMS), and the National Institute of Polar Research (NiPR) for the loan of the meteorites used in this study, and NASA grant
NNX17AE53G (DLS PI, TJZ Co-I) and the BCMS for funding this research. US Antarctic meteorite samples are recovered by
the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized andcurated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Officeat NASA Johnson Space Center.

1

H and 13C Solid state Nuclear Magnetic Resonance (NMR) spectroscopyof an HCl extracted Ryugu C0002 particle

G. D. Cody1, H. Yabuta2, and the Hayabusa2-initial-analysis IOM team1
2

Earth and Planets Laboratory, Carnegie Institute for Science, Washington, DC, USA
Hiroshima University, Hiroshima, Japan

Introduction: 1H and 13C solid state NMR studies of extraterrestrial organic solids (Insoluble Organic
Matter, IOM) in carbonaceous chondritic meteorites has the potential to reveal the extent of IOM’s
molecular evolution that occurred due to parent body processing (largely hydrothermal) in the interiorof the original planetesimal from which the meteorite was derived. For example 1H and 13C NMR
studies of IOM from CR, CI, CM, and an ungrouped C meteorites (Tagish Lake, TL) reveal that there
is a wide range of molecular evolution where the least evolved was the CR IOM and the degree ofmolecular evolution increased from CI to CM to TL (Cody and Alexander, 2005). Subsequent NMR
studies of discrete TL clasts with differing degrees of alteration revealed a high degree of molecular
evolution across them (Herd et al., 2011). In all previous studies, relatively large (10’s of mg) samplesof pure IOM were available (note for typical CC meteorites, recoverable IOM constitutes ~ 1 wt % of
the meteorite, 10 mg of IOM would require ~ 1gm of meteorite). For studies of Ryugu we were
provided with a single particle that had been treated with aqueous HCL (to remove any carbonate) from
C0002 that was ~ 1 mg where in principle 10 ng of IOM is expected. Notwithstanding the obvious
challenges we endeavored to see what could be seen.
Experimental: All NMR experiments were performed at the W. M. Keck Solid State NMR facility at
the Earth and Planets Laboratory at a static magnetic field of 7.05 Tesla. 1H NMR analysis was
performed using 2.5 mm rotor diameter Magic Angle Spinning (MAS) probe with the resonant
frequency of 1H being 300 MHz. The samples were spun at 22 KHz to reduce line broadening
associated with H dipolar coupling. In order to reduce 1H background signal arising from hydrogenoutside the rotor we applied the DEPTH pulse sequence. The rotors capable of spinning faster than 20
KHz use endcaps and drive tips made of an aromatic polymer, Torlon, that is inside the rotor and willcontribute some background 1H signal. This background signal is generally negligible with 10-20 mg
of pure organic matter. With the very small Ryugu sample it was expected and observed that theTorlon’s 1H back ground signal would be substantial. 13C solid state NMR was attempted using a 5 mmprobe (with MAS = 11.5 KHz) with Teflon (no H) inserts and a background suppression pulse scheme
before Variable Amplitude Cross Polarization to maximize signal. We were unable to obtain any 13C
signal which is not unexpected given how little organic carbon is in a 1 mg Ryugu sample. We arepleased to report that no sample was lost during transfer into and out of both rotors and the sample wasreturned to Japan intact and unperturbed by the analysis. Thus the sample handling protocols adopted
were sufficient.
Results: As expected the 1H NMR signal is dominated by 1H in the aromatic polymer, Torlon (Fig.1),
at 7.1 ppm. We do detect a 1H NMR signal at 1.3 ppm that arises from the Ryugu particle. In previous
1
H studies of pure IOM, aliphatic H appears at 1.3 ppm, so it may be that we are detecting Ryugu’s
aliphatic H. Note that IOM’s aromatic H peak lies exactly at 7.1 ppm so it coincides with the backgroundsignal. It is now known that Ryugu mineralogy contains considerable amounts of saponitic clays, withtwo 1H peaks at 4 and 0.35 ppm (Levin et al. 2004), thus the H from this clay is expected to be ~ 10 X
that in IOM. However we don’t see any H’s from saponitic clay (Fig. 1). The most likely explanationis that the iron content of clays in the Ryugu sample are high enough that paramagnetic Fe “spoils” thesignal from saponite H’s and as IOM largely exists in the matrix as discrete organic grains, IOM signal
persists. 1H NMR of natural montmorillonite exhibits no signal due to Fe cations in its structure (Levinet al. 2004).
It is tempting to subtract the background signal from the bkgd+Ryugu particle, when one does
this one finds that the line width of the Torlon is slightly greater than that of Torlon+Ryugu signal suchthat obvious spectra subtraction artifacts eventually arise and place a maximum constraint on how muchbackground subtraction can be performed, without this constraint one could range from majority
aromatic-H to nearly 100 % aliphatic-H, neither case having been observed in any previous studies oftype 1 and 2 chondritic IOM. Previous 1H NMR analyses of IOM (Cody and Alexander, 2005; Herd etal. 2011) have been shown that there is a strong linear correlation between the Fraction of either
aliphatic or aromatic H (FARO-H) with atomic H/C (*100) (see Fig.2) and with the fraction of aromatic
carbon (FARO-C). Thus, using the restriction of maximum background subtraction we can place aminimum constraint on FARO-H of 0.5 (there is no restriction on how large FARO-H could be beyond
assuming that there was no Torlon background). This places a maximum constraint of H/C*100 being
58 (there is no constraint on how low H/C*100 could be). Similarly, we can constrain a minimum as
to how low FARO-C could be at 0.64 (the only constraint as to how high it could be is controlled by the
1.3 ppm feature). These values would suggest that Ryugu’s IOM has slightly greater molecular
evolution than what has been observed in CM and CI derived IOM (Cody and Alexander 2005), butmuch less than observed for the most molecularly evolved Tagish Lake IOM (Fig. 2).

Figure 1: 1H solid state NMR spectrum of
1 mg Ryugu particle from Chamber C (black).
The background signal from Torlon is in Red

Figure 2: Background subtraction
reveals a minimum FARO-H and amaximum H/C. The red circles arevalues for IOM from the different Tagish
Lake clasts. The red lines highlight anequally possible Ryugu composition

This study demonstrates that it is possible to obtains 1H NMR spectra of Ryugu samples. In the
future, if it were possible to obtain 100 mg of Ryugu particles, 1 mg of pure IOM could be isolated.
This would increase the 1H signal by 100 X vastly reducing the background signal. We have obtained
fairly high quality 13C NMR spectra on mg quantities of IOM, so additional molecular information
would be obtained directly. Alternatively, if 20 mg of HCL extracted Ryugu particles were available(our 2.5 mm rotors can only handle 20 mg) these could be analyzed directly where the 1H signal wouldbe ~ 20 X that observed in Fig. 1. The advantage to this later approach would be that NMR is nondestructive and the sample would be available for other analyses by other researchers.
References:
Cody, G.D. and Alexander, C.M.O.D. (2005) NMR studies of chemical structural variation of insoluble organic
matter from different carbonaceous chondrite groups. Geochimica et Cosmochimica Acta 69, 1085-1097.
Herd, C.D.K., et al. (2011) Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake
meteorite. Science-SOM 332.
Levin et al. (2004) J. Applied Physics, 96, 5685

Oxygen isotope analyses of magnetite in Ryugu
Noriko T. Kita1, Kouki Kitajima1, Kazuhide Nagashima2, Noriyuki Kawasaki3, Naoya Sakamoto3, Hisayoshi Yurimoto3,
The Hayabusa2-initial-analysis chemistry team, The Hayabusa2-initial-analysis core.
1
Department of Geoscience, University of Wisconsin-Madison, USA
2
University of Hawaii, USA and 3Hokkaido University, Japan
Samples from the CI-like asteroid Ryugu consist mainly of minerals that were produced by aqueous alteration in its
parent asteroid, such as phyllosilicates, dolomite, magnetite, and pyrrhotite [1]. A secondary ion mass spectrometer (SIMS) has
been used to analyze in-situ oxygen 3-isotope ratios (δ17O and δ18O) of these alteration minerals in order to understand theaqueous activity that Ryugu parent body had experienced. Yokoyama et al. [1] reported δ17O, δ18O, and ∆17O (= δ17O –0.52×δ18O) of dolomite and magnetite in the polished section A0058-C1001 of Ryugu along with those in the Ivuna CI
chondrite. Nagashima et al. [2] reported δ17O, δ18O, and ∆17O of dolomite, calcite, and magnetite in the Ryugu polished section
C0002-C1001. In A0058-C1001, a pair of magnetite and dolomite grains were found within 100 µm of each other and withindistinguishable ∆17O values of ~ 0‰. By applying oxygen isotope thermometry between dolomite and magnetite, [1]estimated the temperature of co-precipitation of the Ryugu dolomite and magnetite, 37±10°C. Oxygen isotope analyses fromanother magnetite and dolomite pair in C0002-C1001 indicate a higher equilibrium temperature of 104±22˚C [2]. However,multiple analyses of magnetite grains in Ryugu and Ivuna show a significant range of δ18O and ∆17O [1-2], suggesting
magnetite might have recorded multiple stages of aqueous activity on the Ryugu and Ivuna parent asteroid(s).
SIMS oxygen isotope analyses of magnetite are known to produce analytical artifacts due to crystal orientation thatcan degrade the analytical reproducibility of δ18O (2-3‰ in 2SD [3]), though the effect is mass-dependent and would notaffect ∆17O. Huberty et al. [3] used lower primary ion acceleration voltage in the Cameca IMS 1280 (changed from 10 kV to 3kV) and improved the analytical reproducibility (0.7‰; 2SD), likely related to lower total impact energy and smaller incident
angle of primary ions to sample surface. Here, we report a new set of SIMS oxygen 3-isotope analyses of magnetite in the
Ryugu samples using the IMS 1280 at the University of Wisconsin-Madison under 3 kV primary acceleration voltage in orderto obtain higher accuracy in δ18O analyses.
We analyzed magnetite grains (typically ≤10 µm) from two polished sections of Ryugu, A0058-C1002 and C0002C1001. The primary Cs+ ion beam was accelerated by +3 kV at the Cs ion source and focused to sample surface (at –10 kV)
resulting in an impact energy of 13 keV. The primary beam was focused to 3 µm with 14 pA intensity and rastered over 2 µm
squares, which resulted in 3×4 µm SIMS pits after 10 min of analysis (Fig. 1). The 16O– intensity was typically 1.7×107 cps formagnetite. Other conditions were similar to those in [4]. The external reproducibility of δ18O from 30 randomly oriented
magnetite standard 5830 [3] was 1.0‰ (2SD), similar to both internal and external errors of a single grain (0.7-0.9‰). The
external reproducibility of δ17O and ∆17O were ~1.5‰. After the analyses, SIMS pits were examined using a Hitachi S-3400
scanning electron microscope (SEM).
Figure 1. Two types of SIMS pit textures formagnetite grains in Ryugu after SIMS
oxygen isotope analyses. Magnetite grains
showing smooth SIMS pit textures (A) often
show well-defined crystal faces, indicating
slow growth. Magnetite grains showing
porous SIMS pit textures (B) often show
fibrous textures, suggesting rapid growth.

SEM observations show that all SIMS spots were within magnetite grains analyzed and none of the analyses were
rejected. There are two types of pit textures, smooth and porous, which often correspond to magnetite with defined crystal
faces and fibrous grains, respectively (Fig. 1). Results of analyses are shown in Fig. 2. and compared to magnetite analyses
reported by [1] using 20 keV impact energy. Both datasets are very similar to each other, though new data show two groups ofmagnetite analyses according to the range of δ18O values, from –4‰ to –1‰ and from +3‰ to +7‰, which correspond tomagnetite grains with smooth and porous pit textures, respectively. The ∆17O values of the lower δ18O group vary from 0‰ to+2‰, while the higher δ18O group shows consistently higher ∆17O values (2-3‰). Some of the smooth magnetite analyses inA0058-C1002 are very similar to those equilibrated with dolomite in A0058-C1001 (δ18O ~ –3‰ and ∆17O ~ 0‰). Assumingthat 16O-poor H2O ice accreted to the Ryugu parent asteroid, melted, and interacted with relatively 16O-rich anhydrous silicates[2], these results suggest that porous (fibrous) magnetite with high ∆17O values formed during an early stage of aqueous
activity, while other magnetite without porosity mostly formed later stages and likely in oxygen isotope equilibrium with otherminerals. However, small variations in ∆17O values among magnetite with lower δ18O may suggest that fluid activity in the
Ryugu parent asteroid could have been localized and the oxygen isotope ratios of the fluid might have been variable.

Figure 2. SIMS oxygen 3-isotope analyses of minerals in Ryugu. (A, B) Analyses of magnetite and dolomite in A0058-C1001 and Ivuna CI
chondrite [1]. (C, D) Analyses of magnetite using 13 keV impact energy (This work). TF and CCAM are terrestrial mass fractionation andCarbonaceous chondrite anhydrous mineral lines [5], respectively.

References[1] Yokoyama T. et al. Science, 10.1126/science.abn7850 (2022). [2] Nagashima K. et al. this volume. [3] Huberty J. M. et al.
Chemical Geology, 276, 269–283 (2010). [4] Ushikubo T. et al. Geochim. Cosmochim. Acta 90, 242-264 (2012). [5] Clayton
R. N. et al. Earth Planet. Sci. Lett. 34, 209–224 (1977).
The Hayabusa2-initial-analysis chemistry team: T. Yokoyama, K. Nagashima, 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.
Di 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, Yuki Masuda, K.D. McKeegan, M. Morita, K. Motomura, F. Moynier, I. Nakai, 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, E.D. Young, 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.

Magnetite and non-magnetite framboids in Ryugu sample
Yuki Kimura1, Takeharu Kato2, Satoshi Anada2, Ryuji Yoshida2, Kazuo Yamamoto2, Toshiaki Tanigaki3, Tetsuya Akashi3,
Hiroto Kasai3, Tomoki Nakamura4, Toru Matsumoto5, Takaaki Noguchi5, Masahiko Sato6, Tomoyo Morita4, Mizuha Kikuiri4,
Kana Amano4, Eiichi Kagawa4, Hisayoshi Yurimoto7, Ryuji Okazaki8, Hikaru Yabuta9, Hiroshi Naraoka8, Kanako Sakamoto10,
Sei-ichiro Watanabe11, Yuichi Tsuda10, and Shogo Tachibana5,101
Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
2
Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, 456-8587, Japan
3
Research & Development Group, Hitachi, Ltd., Hatoyama, Saitama, 350-0395, Japan
4
Department of Earth Sciences, Tohoku University, Sendai 980-8578, Japan
5
Division of Earth and Planetary Sciences, Kyoto University; Kyoto 606-8502, Japan
6
Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan
7
Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
8
Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 819-0395, Japan
9
Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan10
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan
11
Department of Earth and Environmental Sciences, Nagoya University, Nagoya 464-8601, Japan

There are many magnetite (Fe3O4) particles found in chondrites together with clay minerals [1,2] suggesting thatthey were formed by aqueous alteration [3]. Magnetite can record magnetic field environment at the time of its
formation as natural remanent magnetization [4]. Therefore, it is important to know when and how magnetite particles
formed in order to estimate the magnetic field environment of the early solar system and to understand the physicalevolutionary processes that have a relationship with the magnetic filed. A large amount of magnetite is also found in
Ryugu samples [5] and it has been confirmend that submicron-scale magnetite is a main carrier of the natural remanent
magnetization [6]. We conducted electron holography to visualize the magnetic domain structure of the flamboidal
magnetite and found that the magnetite particles have a concentric circular magnetic field (vortex structure) and an
external leakage of the magnetic field that could be a carrier of remanent magnetization [5,6]. In addition to the typicalframboidal magnetite, here we report the discovery of a flamboidal magnetite-like mineral that does not exhibit amagnetic field in a sample.
Figure 1 shows a part of a typical flamboidal magnetite in an ultrathin section extracted from a Ryugu sample A0064FO007 using a cryo-focused ion beam (FIB; NB5000, Hitachi High-Tech) under -90oC at Japan Fine Ceramics Center (JFCC).
The bright-field transmission electron microscope (TEM) image shows at least eight magnetite particles of ~1 μm in diametersurrounded by phyllosilicates at the bottom part. The upper side of the image corresponds to the surface of the parent sample
before they were extracted. The strong contrast area marked with W on the upper side is tungsten that was deposited before
processing to prevent damage by FIB machining. Figures 1 i and ii show magnetic flux distribution images corresponding to
two boxes observed by electron holography using a specially designed TEM (HF-3300, Hitachi High-Tech) at JFCC. The
concentric stripes inside the particles represent the phase change due to magnetization, because the internal potential has been
subtracted by taking images from the back and front. Namely, magnetite particles have a vortex magnetic domain structure.
In addition, an external magnetic field can be seen on the outside of the particle. Magnetite particles are thought to haveformed by aqueous alteration between 3.1-6.8 million years after the formation of first mineral, calcium–aluminium-richinclusion, at the beginning of the Solar system [7]. The external magnetic field is a result of the magnetic field environmentthat existed when magnetite formed by aqueous alteration in the parent body of Ryugu [6].
Figure 2 shows a high-angle annular dark field scanning TEM (STEM-HAADF) image of an ultrathin section of a portionof a flamboid from a different fragment in the Ryugu sample A0064-FO007, which was broken into several pieces when fixed
to the indium plate for easier handling, extracted using the cryo-FIB. Similar to the Fig. 1, several spherical particles of ~1
μm can be seen. Corresponding magnetic flux distribution image has been shown in Fig. 2B. Unlike i and ii in Fig. 1, thecontrast within the particles is flat and there is no magnetic domain structure characteristic of magnetite. Elemental
composition analysis using an energy dispersive X-ray spectroscopy (EDS) confirms that the particles are iron oxide (Fig. 2C).
Although it looks like typical framboidal magnetitee, electron energy-loss spectroscopy analysis indicated that the bonding
states of oxygen and iron were clearly different from that of magnetite. The observed bonding state was consistent with

wüstite (Fe1-y O), which is antiferromagnetic and does not acquire remanent magnetization.. Although particles appeared tobe framboidal magnetite based on a micrograph, these particles were actually wüstite. We refer to this particle as framboidal
pseudo-magnetite.
The framboidal pseudo-magnetite is present on the top surface of the host sample, and the bottom is a matrix composed
mainly of phyllosilicates. TEM-EDS mapping showed iron-rich region that may be leached from the pseudo-magnetite into
the matrix. Magnetite with porous surface texture and metallic iron has been found in the analysis by Sand team [8].
Sample analysis in the first Hayabusa mission has reported the formation of iron particles on a silicate grain by space
weathering [9]. In case of our pseudo-magnetite, although the presence of metallic iron particulates was also confirmed, they
appear to be coarser than those found in previous studies and are We expect that framboidal pseudo-magnetite may also haveformed by space weathering of magnetite, but different mechanisms from other two samples. Similar pseudo-magnetite
particles have also been found in other FIB thin sections. We will discuss the formation process of framboidal pseudomagnetite at the symposium.

Figure 1.

TEM image of a thin section of a typical magnetic framboid extracted from the sample A0064-FO007 and its characteristic

magnetic structure observed by electron holography.

Figure 2.

Framboidal pseudo-magnetite.

prepared by FIB.

Arrows show the direction of the magnetic flux.

A. STEM-HAADF image of a thin section of a fragment from the sample A0064-FO007

B. Magnetic flux distribution image obtained from the reconstruction of remanent magnetic state of magnetites observed

by electron holography.

Uniform contrast indicate that the particles are not magnetic minerals.

C. Corresponding elemental mapping ofiron.

The authors acknowledge the Ministry of Education, Culture, Sports, Science and Technology (MEXT) (grants
JPMXS0450200421, JPMXS0450200521).
References[1] Brown, P. G. et al. 2000. Science 290:320. [2] Zolensky, M. E. et al. 2002. Meteoritics & Planetary Science 37:737. [3]Kerridge, J. F., Mackay, A. L. & Boynton, W. V. 1979. Science 205:395. [4] Dunlop, D. J., and Özdemir, Ö. 1997. Rock
Magnetism: Fundamentals and Frontiers, Cambridge University Press, 573 pp. [5] Nakamura, T. et al. 2022. Sciencedoi.10.1126/science.abn8671. [6] Sato, M. et al 2022. Journal of Geophysical Research under review. [7] Yokoyama T. et
al. 2022. Science doi.10.1126/science.abn7850. [8] Matsumoto, T. et al. 2022. LPSC 1693. [9] Noguchi, T. et al. 2011.
Science 333:1121.

Nitrization of magnetite on the surface of C-type asteroid Ryugu.
T. Matsumoto1,2, T. Noguchi2, A. Miyake2, Y. Igami2, M. Haruta3, Y. Seto4, M. Miyahara5, N. Tomioka6, D. Harries7,
the Min-Pet Fine sub-team and the Hayabusa 2 initial analysis core.
1
The Hakubi Center for Advanced Research, Kyoto University, 2Division of Earth and Planetary Sciences, Kyoto University,
3
Institute for Chemical Research, Kyoto University. 4Department of Geoscience, Osaka Metropolitan University, 5Graduate
School of Advanced Science and Engineering, Hiroshima University, 6Japan Agency for Marine-Earth Science andTechnology, 7Luxembourg Institute of Science and Technology, European Space Resources Innovation Centre.
(E-mail: matsumoto.toru.2z@kyoto-u.ac.jp)

Introductions: JAXA's Hayabusa2 spacecraft recovered samples from the C-type carbonaceous asteroid Ryugu [1]. The initial
analysis of the Ryugu samples showed that they correspond to CI carbonaceous chondrite meteorites [2, 3]. Because the Ryugu
samples were collected from the surface of Ryugu, they provide us with the first opportunity to understand phenomena
occurring at the surface of the carbonaceous asteroid. Materials on airless bodies are gradually modified by exposure to solar
wind and micrometeorite impacts. This process is called space weathering [4]. The evidence of space weathering has beenfound in Ryugu samples through the initial analysis. Dehydration of the phyllosilicate surface is the major modification by
space weathering on Ryugu [5]. In addition, loss of volatile elements including hydrogen, carbon, oxygen, and sulfur havebeen identified in space-weathered anhydrous minerals [6]. In this study, we focused on the surface modifications of Ryugu
samples related to nitrogen. It has been suggested that the nitrogen isotopes in Ryugu samples are affected by surface processes[7]. Thus far, there is no mineralogical observation related to the behavior of nitrogen on Ryugu’s surface. The goal of thisstudy is to understand how nitrogen is involved in the chemical evolution of regolith on Ryugu. Here, we describe nitrogenconcentration on the surfaces of space-weathered magnetites in Ryugu samples.
Methods: We investigated three fine Ryugu grains, A104-021012, A104-028098, and A104-026006. These three grains were
preserved in a glove-box filled with purified nitrogen gas. The grains are attached on gold plates using epoxy resin, and wereobserved by scanning electron microscopy (SEM) to analyze their surface morphologies. After the surface observation,
electron-transparent sections were extracted from the grain surface using a focused ion beam system. The extracted sections
were observed by scanning transmission electron microscopy (TEM/STEM). We applied 4D-STEM imaging (electron
diffraction mapping using nano-beam) to identify nanometer-sized inclusions.
Results: FIB sections from A104-021012 and A104-028098 include assemblages of framboidal magnetites with 0.5 to 1 µm in
diameter. An FIB section from A104-026006 contains a spherulitic magnetite with 10 µm in diameter. These magnetite grainsare embedded in the fine-grained matrix composed mainly of phyllosilicates. Their exposed surfaces show porous textures thatsuggest surface modifications. STEM-EDS analysis showed that magnetites in A104-0210012 have the uppermost layers
showing high Fe/O ratio. Electron diffraction patterns corresponding to body-centered cubic (bcc) iron were obtained from theiron-rich layer. Magnetite grains in A104-026006 and A104-028098 also have iron-rich layers at the surface. In addition, theiron-rich layers are also rich in sulfur and nitrogen (Fig.1). Electron diffraction patterns from the iron-rich layer in A104026006 indicate the appearance of bcc-iron metal and troilite. Additionally, we obtained electron diffraction patterns showing a
cubic crystal that has the lattice parameter corresponding to roaldite (Fe4N). Thin coatings of silicon and magnesium wereidentified on the modified magnetites in A104-021012, A104-028098, and A104-026006.
Discussion: The increase of Fe/O ratio and the formation of iron metals at the magnetite surface is likely due to selective lossof oxygen from magnetite caused by solar wind implantation and micrometeorite bombardments [6]. Because sulfur andnitrogen are not included in bulk magnetite, these elements would have been supplied to the exposed surfaces of magnetite.
Impact vapors produced from carbonaceous chondrite likely have high sulfur fugacity enough to form iron sulfides [8].
Therefore, the sulfur enrichment and troilite formation at the magnetite surface in Ryugu samples may have been caused bysulfization of iron metals, when the space-weathered magnetite is exposed to vapors formed by micro-impacts. Iron nitrides
have been identified in carbonaceous chondrites as the products formed by gas-metal interaction in the NH3-rich nebular gas[9], and in iron meteorites as metamorphic products under high pressure [10]. In contrast, iron nitrides we observed are likely
associated with space weathering of magnetite and may have been formed thorough surface processes on Ryugu. One possible
mechanism for the concentration of nitrogen is implantation of solar wind nitrogen as suggested in lunar regolith samples from
the Moon [11]. Another possible mechanism is the chemical reaction between space-weathered magnetites and nitrogencompounds included in impact vapors on Ryugu. Because iron metal is highly reactive with ammonia gas that leads to theformation of iron nitrides [12], nitrization of iron metals on space weathered magnetites may have occurred when the surfacesare exposed to ammonia-beaning gases. Ammonia may be included in impact vapors from CI chondrite materials [13]. In
addition. ammonia-rich vapors can be produced from nitrogen-rich organic materials, and/or ammonium compounds, such as
NH4+ salts and NH4+ phyllosilicates, that could be supplied to the Ryugu’s surface as interplanetary dust. Our observation willshed light on the migration of nitrogen and/or influx of nitrogen on the carbonaceous asteroid.

Figure 1. Elemental maps of magnetite surface (A104-026006) obtained by STEM-EDS analysis. Left, center, and right figures show the
distributions of nitrogen, sulfur, and iron, respectively. SW-rim indicates the space-weathered rim enriched in iron, sulfur, and nitrogen. Mgt
indicates magnetite.

References[1] Sugita S. et al. 2019. Science 364, 252.
[2] Yokoyama T. et al. 2022. Science eabn7850.
[3] Nakamura T. et al. 2022. Science eabn8671.
[4] Pieters C. and Noble S. K. 2016. J. Geophys. Res. Planet 121, 1865-1884.
[5] Noguchi T. et al. 2022. LPS LIII. Abstract #1747.
[6] Matsumoto T. et al. 2022. LPS LIII, Abstract #1693.
[7] Okazaki R. et al. 2022. LPS LIII, Abstract #. 1348
[8] Thompson M. S. et al. 2019. Icarus 319, 499-511.
[9] Harries D. et al. 2018. 81st Annual Meeting of The Meteoritical Society. Abstract #2067.
[10] Buchwald V. F. and Nielsen H. P. 1981. LPS XII. pp. 112-114.
[11] Hashizume K. et al. 2001. Science 290. 1142-1145.
[12] Mittemeijer, E. J. & Slycke, J. T. 1996. Surf. Eng. 12, 152–162[13] Kuwahara H. and Sugita. S. 2015. Icarus 257. 290-301.

Neutron Capture 36Cl in Ryugu Samples
Kunihiko Nishiizumi1, Marc W. Caffee2, Jozef Masarik3, Keisuke Nagao4, Ryuji Okazaki5, Hisayoshi Yurimoto6, Tomoki
Nakamura7 Takaaki Noguchi8, Hiroshi Naraoka5, Hikaru Yabuta9, Kanako Sakamoto10, Shogo Tachibana11, 12, Sei-ichiro
Watanabe10, 12, Yuichi Tsuda10
1Space Sci. Lab., Univ. of California, Berkeley, CA 94720-7450, USA., 2Dept. of Phys. & Astro., Purdue Univ., West Lafayette,
IN 47907-2036, USA., 3Comenius Univ., Batislava, Slovakia, 4KOPRI, Incheon 21990, Korea,5Kyushu Univ., Fukuoka 8190395, Japan, 6Hokkaido Univ., 7Tohoku Univ.,8Kyoto Univ.,9Hiroshima Univ., 10ISAS/JAXA, 11Univ. of Tokyo, 12Nagoya Univ.
Hayabusa2 arrived at the C-type asteroid 162173 Ryugu in Jun. 2018, and successfully collected surface samples from two
sampling sites, returning ~5.4 g of samples to Earth on Dec. 6, 2020. The surface samples stored in Chamber A were collectedby the 1st touchdown (TD) on Ryugu’s surface on Feb. 21, 2019. A crater (diameter of ~14 m) on Ryugu’s surface was madeusing a collision device - denoted “Small Carry-on Impactor (SCI)” - on Apr. 5, 2019 [1]. The samples in Chamber C werecollected proximal to this artificial crater and are possibly ejecta from the north side of the crater by the 2nd TD on Jul. 11, 2019[2].
Our studies are based on the measurement of those nuclides produced in asteroidal surface materials by cosmic rays - bothsolar (SCR) and galactic cosmic rays (GCR). Cosmic-ray-produced (cosmogenic) nuclides are used to determine the durationand nature of the exposure of materials to energetic particles. Our goals are to understand both the fundamental processes on
the asteroidal surface and the evolutionary history of its surface materials. With this information we hope to better understandasteroid-meteoroid evolutionary dynamics. For Hayabusa2 samples, there are several specific questions we aim to address: (1)are the Chamber C samples, collected during the 2nd TD ejecta deposits from the artificial crater, (2) if so, what is the original
depth of each recovered sample in the Ryugu regolith, and (3) what is the surface exposure time, mixing rate, and erosion/escaperate of Ryugu’s surface? To answer these questions, we were allocated and received 2 particles from Chamber A (A0105-19
and -20) and 6 particles from Chamber C (C0106-09, -10, -11, -12, C0002-V01, and -V02) for measurements of cosmogenic
radionuclides and noble gases. Each sample is several hundred µm in size.
As a part of initial analysis of Ryugu we have measured cosmogenic 10Be (t1/2 = 1.36 x 106 yr) [3], 26Al (7.05 x 105 yr) [4],and stable noble gases [5] in above samples. The Table 1 summarizes 26Al, 10Be, and cosmogenic 21Ne concentrations in eachsample. Based on those measurements, we found that sampling depth of A0105-19 was 10-15 g/cm2 and A0105-20 was ~5g/cm2. The exposure ages of both A0105 samples were 6.4-7.5 Myr. The chamber A samples were exposed to cosmic rays
at Ryugu’s near surface (~10 cm), as expected, and had similar exposure ages of ~7 Myr. On the other hand, the four C0106
particles were exposed at depth of ~50, 110, 130, and 145 g/cm2 respectively and had exposure ages of ~1.6, 3.2, 4.5, and 5.8
Myr respectively. Our results indicate that Chamber C samples are mixture of particles ejected from various depths on Ryugu
by the SCI impact. It is noteworthy that all four particles had different exposure ages on Ryugu. Exposure depths of eachsample are also shown in Table 1.
To further study of the exposure condition of Ryugu surface materials, we analyzed cosmogenic 36Cl (3.01 x 105 yr). Afterdissolution of each sample with a few drops of HF-HNO3 mixture, Cl was separated as AgCl prior to Be and Al separation [3,4]. After chemically purified AgCl, the concentration of 36Cl was measured by accelerator mass spectrometry (AMS) at Purdue
University [6], using a 36Cl AMS standard [7] for normalization. The concentrations of 36Cl (dpm/kg) in each Ryugu sample
are shown in Table 1 along with that of Nogoya CM2 chondrite for validation. The 36Cl concentrations in all Ryugu samples
are more than an order of magnitude higher than that of Nogoya. The dominant production pathway for 10Be and 26Al is byhigh-energy neutron spallation reactions. Although 36Cl can be produced by both thermal neutron capture reaction, 35Cl (n,g)
36Cl, and high-energy neutron spallation on K, Ca, and Fe, the thermal neutron production of 36Cl is dominant owing to the highH and Cl concentrations in Ryugu. Using the MCNP Code System [8], we calculated GCR production rate of 36Cl by spallation
reactions for a body having a 2π geometry with Ryugu’s chemical compositions [9]. The obtained production rates are 5.4 36Cl
atom/min/kg at surface to 3.3 at ~150 g/cm2. The thermal neutron production of 36Cl is calculated by subtracting spallation
contribution from measured value and normalized to Cl concentration in Ryugu and shown in Table 1 as 36Clth. We adopted a
Cl concentration of 780 ppm [9]. The measured 36Cl concentrations in Ryugu are extraordinarily high. Among carbonaceouschondrites, only the CI chondrite Orgueil is higher, having 160 ± 1 dpm/kg (unpublished), assuming exposure in a 4π geometry.
This corresponds to 220 ± 3 dpm 36Cl /g Cl assuming 700 ppm Cl in Orgueil.
Assuming a chemical compositions for each particle the same as the bulk analysis of Ryugu [9], the thermal neutron produced
36Cl in Ryugu is maximum at slightly below 100 g/cm2 or between depth of C0106-10 and -11.
The depth of maximum
production for the low-energy neutron capture reaction on Ryugu is shifted toward surface compared to that of the Moon (~150

g/cm2). This occurs because Ryugu contains high H (0.94 %) and C (4.6 %) [9] which are effective moderators of neutrons.
Since we don’t have exact Cl concentration in each particle, it is hard to compare observed 36Cl concentration to model
calculation such as MCNP code system at present. Although we are planning measurements of thermal neutron capture 41Ca
(t1/2 = 0.10 Myr) in Ryugu, it requires larger sample size than this work because low thermal neutron capture cross section on
40Ca compared to that of 35Cl (0.43 b vs. 43.6 b) and lower AMS sensitivity of 41Ca measurements.
Table 1. Cosmogenic nuclide 36Cl, 26Al, 10Be, and 21Ne concentrations in Ryugu samples and Nogoya CM2 chondrite.
36Clb
36Cl c26Ald
10Bee
21Ne fSampleMass
Deptha
th
c
2
-9
(µg)
(g/cm )
(dpm/kg)(dpm/g Cl)(dpm/kg)(dpm/kg)(10 cm3
STP/g)
A0105-19242.9
531.1±2.333±327.1±1.1
12.76±0.37
7.55A0105-20
206.1
10-15
28.9±1.930±233.3±1.8
12.75±0.29
7.75
C0106-09122.8
5072.0±6.286±823.3±1.4
7.10±0.30
1.79C0106-10154.3
110116.5±6.9
144±925.7±1.3
7.48±0.26
3.58
C0106-11189.8
13023.4±2.526±325.5±1.2
7.21±0.43
5.07
C0106-12959.8
14524.2±0.927±123.8±0.77.36±0.33
6.54
C0002-V0145.3
12530.1±4.334±6
24.9±1.98.29±0.95
C0002-V02
11.1
125
11±13
21.9±5.1
7.87±1.80
Nogoya CM2459.4
2.2±0.5
2.09±0.13
Nogoya CM2343.7
2.2±0.6
7.7±0.5
2.12±0.09
Nogoya CM2
204.9
0.6±1.0
9.1±0.6
2.00±0.13
aEstimated depth based on 10Be and 26Al [4]; bThis work; cAfter subtraction of spallation component (see text); d[4]; e[3]; f[5].
Acknowledgments: We thank Hayabusa2 project and initial analysis team, especially Hayabusa2 curation members. Z. Nett
and K. C. Welten helped a part of laboratory works. Nogoya was obtained from Field Museum of Natural History. This work
was supported by NASA’s LARS program.
References[1] Arakawa M. et al. 2020. Science 368, 67-71. [2] Tsuda Y. et al. 2020. Acta Astronautica 171, 42-54. [3] Nishiizumi K. et al.
2021. Hayabusa Symposium 2021 S3-1. [4] Nishiizumi K. et al. 2022. Lunar Planet. Sci. 53, #1777. [5] Nagao K. et al. 2022.
Meteor. Planet. Sci. 57, A337 #6320. [6] Sharma P. et al. 2000. Nucl. Instrum. Methods Phys. Res. B 172, 112-123. [7] Sharma
P. et al. 1990. Nucl. Instrum. Methods Phys. Res. B52, 410-415. [8] Masarik J. and Reedy R. C. 1994. Geochim. Cosmochim.
Acta 58, 5307-5317. [9] Yokoyama T. et al. 2022. Science 10.1126/science.abn7850.

Lithological variation of asteroid Ryugu samples returned by the Hayabusa2 spacecraft:
Assessment from the 18 particles distributed to the initial analysis “Stone” team
T. Mikouchi1, H. Yoshida1, T. Nakamura2, M. Matsumoto2, A. Tsuchiyama3,4, J. Matsuno3, K. Tsutsui2, M. E. Zolensky5,
D. Nakashima2, M. Masuda1, K. Hagiya6, M. Kikuiri2, T. Morita2, K. Amano2, E. Kagawa2, H. Yurimoto7, T. Noguchi8,
R. Okazaki9, H. Yabuta10, H. Naraoka9, K. Sakamoto11, S. Tachibaba1,11, S. Watanabe12 and Y. Tsuda11
1
University of Tokyo, Japan (mikouchi@um.u-tokyo.ac.jp), 2Tohoku University, Japan, 3Ritsumeikan University, Japan,
4
Guangzhou Inst. of Geochemistry, Chinese Academy of Sciences, China, 5NASA John Space Center, USA, 6University of Hyogo,
Japan, 7Hokkaido University, Japan, 8Kyoto University, Japan, 9Kyushu University, Japan, 10Hiroshima University, Japan,
11
ISAS/JAXA, Japan, 12Nagoya University, Japan
Introduction: JAXA’s Hayabusa2 spacecraft successfully returned ~5.4 g of C-type asteroid Ryugu materials on Dec. 2020
[e.g., 1] and the recovered samples were extensively analyzed by initial analysis teams and Phase2 curation teams. The reported
results show that Ryugu samples are similar to CI chondrites in chemistry and mineralogy, showing evidence for aqueous alterationin the parent body [e.g., 2,3]. As a “stone” team of the initial analysis, we received 18 coarse particles (>1 mm) of Ryugu samples
to characterize their mineralogy and petrology. We found that the samples were breccias of mm-to-sub mm size clasts. All of theclasts are mainly composed of Mg-Fe phyllosilicates, but the alteration degree appears slightly different from one clast to another[3]. Here we report a lithological variation of Ryugu samples to propose their reasonable lithological classification based upon different mineral assemblages and associated mineralogy, which will provide important information to elucidate the formation andevolution of the Ryugu parent body.
Samples and Methods: We analyzed 18 coarse particles that are 7 Chamber A particles (A0026, A0055, A0063, A0064,
A0067, A0094 and A0106) and 11 Chamber C particles (C0002, C0023, C0025, C0033, C0040, C0046, C0055, C0061, C0076,
C0103 and C0107), respectively. Chamber A particles are from the first touchdown site while Chamber C particles are from thesecond touchdown site where the SCI impact experiment was carried out to attempt to collect subsurface materials [4]. In total 52
polished sections were prepared from all particles. The JEOL JXA-8530F field emission electron microprobe (FE-EPMA) at Univ.
of Tokyo was employed for both WDS X-ray mapping and quantitative analyses of constituent minerals using well-characterized
natural and synthetic standards after observation using back-scattered electron (BSE) images. X-ray mapping was carried out witha 1-3 m interval to understand distribution of
constituent minerals.
Results: Most of the analyzed polishedsections show brecciated textures on a scaleof mm to m (Fig. 1). In spite of such brecciation, all clasts are mainly composed of MgFe phyllosilicates that are TEM-scale mixtures of serpentine and saponite [3]. Other
minor phases include carbonates (Cacarbonates, magnesite (“breunnerite”) anddolomite), magnetite, Fe,Ni sulfides (pyrrhotite and pentlandite), Ca phosphate, olivine,
pyroxene, Mg,Na phosphate, Mn-rich ilmenite, spinel, chromite, Fe,Ni phosphide andFe,Ni metal.
Among these accessory phases, carbonates exhibit the most remarkable mineralogy because they are present as different minFig. 1. Mg and Fe X-ray maps (above) and MgCaSi and FeNiS composite
eral species in each clast, which appears to be
RGB maps (below) of the A0055-01 polished section. In this section lithologies III, V and VI were found (noted in the Fe map (upper right)). Yelrelated to the degree of aqueous alteration [3].
low~green phases in the MgCaSi map are dolomites. The same analysis was
When Ca carbonates are present, olivine anddone for all other polished sections.
pyroxene are also associated, suggesting thatsuch clasts are less altered compared to the others. In fact, the modeling calculation of progressive aqueous alteration of chondritic
anhydrous minerals predicts that only Ca carbonates form when the water to rock ratio is low [3], resulting in less aqueous alteration. Such modeling is in accordance with the Ryugu sample observation that
olivine and pyroxene are absent in clasts when Ca carbonates are absent andonly dolomite and/or magnesite are present. This observation indicates that
olivine and pyroxene are unaltered phases that survived aqueous alteration in
the parent body. The more water-rich alteration condition forms dolomite
and subsequently magnesite [3]. Rimming of magnesite on dolomite is observed, further supporting this proposal (Fig. 2). Similarly, Mg,Na phosphate
is absent when Ca carbonates are absent. The presence of Fe,Ni phosphideand Fe,Ni metal is associated with the presence of olivine and pyroxene. In
clasts with these phases, Ca phosphate is rare, suggesting that Ca phosphate
formed by aqueous alteration of Fe,Ni phosphide and Ca-bearing phases. As
noted in [3], there is the rare presence of olivine-rich clasts that appears to be
Fig. 2. BSE image of carbonates in A0067-02.
Magnesite surrounds the dolomite core, sugthe least altered clasts in Ryugu samples. In these clasts, dolomite and maggesting formation of magnesite after dolomite.
nesite are rare and GEMS-like material is present [3].
Discussion and Conclusion: In summarizing the above observations, we
tried to classify lithological variations of our coarse Ryugu particles based upon mineral assemblages and associated mineralogy,
mostly using X-ray mapping results of FE-EPMA. The key mineral phases for this classification are olivine and carbonates. The
presence/absence of olivine can broadly divide the clasts into two lithologies: olivine-bearing and olivine-free lithologies, corresponding to less altered and altered lithologies, respectively. Because olivine-bearing lithologies are rarer, olivine-free lithologies
are major lithologies of Ryugu samples [3]. We assigned rare olivine-rich clasts as “lithology I” and the other olivine-bearing clasts
as “lithology II”. For olivine-free lithologies, the carbonate mineralogy can further divide them into four: dolomite-bearing (“lithology III”), dolomite+magnesite-bearing (“lithology IV” (Fig. 2)), carbonate aggregates (“lithology V”) and carbonate-poor (“lithology VI”). We assigned lithology V clasts when carbonates show aggregate textures that are larger than 100 m in size. Because
we frequently found carbonate-poor clasts, we assigned lithology VI when carbonates are only ~<1 vol.% in abundance and smallin size (~<10 m). Except for these six types of different lithologies, there are exceptional lithologies such as coarse isolated mineral grains. The lithologies I to IV appear related to the degree of aqueous alteration by this order since the calculation of progressive aqueous alteration by increasing water to rock ratios predicts different carbonate species (Ca carbonate → dolomite → magnesite) matching with the observed carbonate mineralogy in these lithologies [3]. The lithologies V and VI would have been formed
at somewhat different conditions other than lithologies III and IV, respectively. We checked the phyllosilicate compositions ofdifferent lithologies and found that phyllosilicates in olivine-bearing lithologies (I and II) were more Fe and Na-rich compared tothose in olivine-free lithologies (III-VI). There are no clear compositional differences among phyllosilicates in lithologies III-VI,
except that phyllosilicates in lithology VI are slightly poorer in Fe and Na compared to those in lithologies III-V.
Thus, we propose that the lithology of Ryugu samples can be divided into 7 types (lithology I, II, III, IV, V, VI and others)
based upon mineralogy of constituent minerals in different clasts due to the brecciated nature of Ryugu samples. When we looked
at 18 coarse Ryugu particles that we analyzed, we found that olivine and pyroxene are absent in our Chamber A particles, namely
Chamber A particles include only lithologies III, IV, V, VI and others. In contrast, most of Chamber C particles contain olivine andpyroxene, which is lithology II in many cases. The largest section in our sample (C0002 plate 5) contains rare type lithology I
clasts although they are small (~100 m). Therefore, we clearly see that there is a mineralogical difference between Chamber A
and C particles. This observation may suggest heterogeneous distributions of materials with different degrees of aqueous alteration
at the two different sampling sites. However, we cannot rule out the possibility of sampling bias because the samples analyzed aresmall. Also, it is unclear whether such lithological differences are related to the subsurface sampling at the second touchdown siteby artificial crater formation.
References: [1] Yada T. et al. (2021) Nat. Astron. 6:214. [2] Yokoyama T. et al. (2022) Science 10.1126/science.abn7850. [3]Nakamura T. et al. (2022) Science 10.1126/science.abn8671. [4] Kadono T. et al. (2020) Astrophys. Jour. Lett., 899, L22.

Non-destructive analysis of C-type asteroid Ryugu using negative Muon:
Determination of bulk chemistry of Ryugu samples*K. Terada1, T. Nakamura2, K. Ninomiya1, T. Osawa3, T. Takahashi4, Y. Miyake5, S. Takeshita5, I. Umegaki5, I. Chiu1, M.
K. Kubo6, A. Taniguchi7, T. Wada2, S. Watanabe8, H. Yurimoto9, T. Noguchi7, R. Okazaki10, H. Yabuta11, H. Naraoka10 ,K. Sakamoto8, S. Tachibana4, S. Watanabe12, Y. Tsuda8 and J-PARC Muon Team13
1Osaka University, 2Tohoku University, 3Japan Atomic Energy Agency, 4The University of Tokyo, 5High Energy Accelerator
Research Organization, 6International Christian University, 7Kyoto University, 8Japan Aerospace Exploration Agency,
9Hokkaido University, 10Kyushu University, 11Hiroshima University, 12Nagoya University and 13Japan Proton Accelerator
Research Complex

We have been developing a non-destructive Muonic X-ray analysis for extraterrestrial materials [1, 2, 3, Figure-1(a)]. Sincemuon has a mass about 200 times greater than that of an electron, negative muon behaves as a heavy electron in the sample. In
the classical Bohr model, orbital radii of negative leptons (electron and/or muon) around an atomic nucleus are inversely
proportional to the lepton mass, and therefore a muon trapped by an atom has an orbit closer to the atomic nucleus than electrons
due to its ~200 times heavier mass (Figure-1(b)). As a result, muon-induced characteristic X-rays have about 200 times higher
energies than those associated with the orbital transition of electrons. For instance, electron-induced Kα–X-ray of C has anenergy of 0.3 keV, whereas muonic Kα–X-ray of C has an energy of 75 keV, which is large enough to penetrate a rock sample
of about 1 cm in size without significant self-absorption. Another advantage is that the position at which the characteristic Xrays are generated (i.e. the depth of penetration from the sample surface) can be controlled by controlling the momentum of theincident muons, making it possible to non-destructively analyse the chemical composition inside a material from light elements
to heavy elements.

Figure 1. (a) Muon beam line at J-PARC,(b) Schematic view of muon-induced characteristic X-ray.

Ten coarse Ryugu samples (A0026, A0064, A0067, A0094, C0002, C0025, C0033, C0061, C0076, and C0103), which wereallocated to the initial analysis STONE team, have been investigated at J-PARC MUSE (Japan Proton Accelerator ResearchComplex, MUon Science Establishment) [4]. Because of the muon beam size (more than 3 cm in diameter), we obtained a bulk
elemental abundance of total 122.86 mg (17.72 mg from chamber-A and 105.14 mg from chamber-C). For comparison, pelletsof the meteorites Murray (CM2; 306.5 mg) and Orgueil (CI; 195 mg) were also measured. In order to avoid the contaminationfrom atmosphere (N and O), during the analysis, samples were set in the chamber which was filled with helium [3]. Figure-3
shows the muonic X-ray spectra from Ryugu and Orgueil. Significant Muonic X-rays of C, N, O, Na, Mg, Si, S and Fe weredetected from Ryugu and Orgueil. Signals of Cu and Be, originated from the inside shield of vacuum chamber, the sample holder
and the detector windows, were also detected.

Figure 2. Muonic X-ray spectra of Ryugu and Orgueil (CI)We calculated elemental mass ratios X/Si (X=C, N, O, Na, Mg, S, and Fe) of Ryugu samples from relative intensity ratios ofmuonic X-rays using Murray with known X/Si ratios. The obtained mass ratios of C, N, O, Na, Mg, S and Fe relative to Si are
0.338±0.008, 0.019±0.009, 3.152±0.099, 0.039±0.006, 0.890±0.021, 0.510±0.019, and 1.620±0.040, respectively. Theseelemental ratios are in a good agreement with the reported values for CI chondrites [5] and the conventional solar abundance [6],except for the 25% lower O/Si for Ryugu relative to CI(Figure-3). This means that Ryugu is depleted in oxygen by
11.3 % by mass compared to CI, assuming similar Si
concentration for Ryugu to CI chondrites. The Ryugu samples
were prepared and analyzed in low oxygen conditions (<0.1%) and at low dew points (< -50°C), thus the very low
oxygen concentration is indigenous feature. This result is
consistent with [7], which was obtained from a chamber-A
grain (~1 mg). Lesser water content in Ryugu samples relative
to CI chondrites [7] is likely the main factor for the low oxygen
concentration.
Thus, we have succeeded in a non-destructive Muonic Xray analysis for Ryugu sample, including light elements such
C, N and O. This innovative technique will also be powerfulfor sample returns from the C-type asteroid Bennu and/orfrom the Martian satellite Phobos, which are expected to beenriched in organic matter.

References[1] K. Terada et al. (2014) Sci. Rep. 4, 5072
[2] K. Terada et al. (2017) Sci. Rep. 7, 15478[3] T. Osaka et al. (2022) Analytical Chemistry submitted[4] T. Nakamura et al. (2022) Science 10.1126/science.abn8671.
[5] K. Lodders (2021 )Space Science Reviews 217, 44[6] M. Asplund, A. M. Amarsi, N. Grevesse (2021) Astronomy & Astrophysics 653, A141.
[7] T. Yokoyama et al. (2022) Science 10.1126/science.abn7850.

Chondrule-like objects and CAIs in asteroid Ryugu: Earlier generations of chondrules
D. Nakashima1, T. Nakamura1, M. Zhang2, N. T. Kita2, T. Mikouchi3, H. Yoshida3, Y. Enokido1, T. Morita1, M. Kikuiri1, K.
Amano1, E. Kagawa1, T. Yada4, M. Nishimura4, A. Nakato4, A. Miyazaki4, K. Yogata4, M. Abe4, T. Okada4, T. Usui4, M. Yoshikawa4, T. Saiki4, S. Tanaka4, S. Nakazawa4, F. Terui5, H. Yurimoto6, T. Noguchi7, H. Yabuta8, H. Naraoka9, R. Okazaki9, K. Sakamoto4, S. Watanabe10, S. Tachibana3, and Y. Tsuda4
1
Tohoku University, Japan (dnaka@tohoku.ac.jp), 2University of Wisconsin-Madison, USA, 3University of Tokyo, Japan,
4
ISAS/JAXA, Japan, 5Kanagawa Institute of Technology, Japan, 6Hokkaido University, Japan, 7Kyoto University, Japan,
8
Hiroshima University, Japan, 9Kyushu University, Japan, 10Nagoya University, Japan.
Introduction: The Hayabusa2 spacecraft returned samples from C-type asteroid Ryugu [1]. The “stone” team, one of the six
initial analysis teams, received 16 stone samples from the ISAS curation facility and conducted analyses for elucidation of early
evolution of asteroid Ryugu [2]. The Ryugu samples mineralogically and chemically resemble CI chondrites [2-5]. It was suggested that the Ryugu original parent body formed beyond the H2O and CO2 snow lines (> 3 – 4 au) in the solar nebula at 1.8 – 2.9 Myr
after CAI formation [2]. Here we report oxygen isotope analyses (~ 1 µm spots; IMS-1280 at UW-Madison) of chondrule-like objects and CAIs observed in the Ryugu samples [2] and discuss the significance of the presence of chondrule-like objects and CAIs
in asteroid Ryugu and their origins.
Results: Small chondrule-like objects and CAIs (< 30 µm; Fig. 1) occur with isolated olivine, pyroxene, and spinel in lessaltered clasts in the polished section C0002-P5 and in polished sections of C0040-02 and C0076-10. The three chondrule-like objects have rounded-to-spherical shapes and consist of olivine with Mg# of ~ 99, FeNi metal, sulfide, and Al-Ti-free diopside but
free from glass or glass-altered phase. Two of the three chondrule-like objects contain low-iron, manganese-enriched (LIME) olivine [6], and one of them shows sub-µm-sized 120° triple junctions, which is evidence of annealing [7]. The two CAIs consist ofspinel and hibonite along with tiny perovskite inclusions. The oxygen isotope ratios show a bimodal distribution at peaks of ~ –43‰ and ~ 0‰ in 18O along the CCAM and the PCM lines [8,9] (Fig. 2). Oxygen isotope ratios of the individual objects are indistinguishable within the uncertainty. Two out of the three chondrule-like objects are 16O-rich with 17O of ~ –23‰ (C0002-P5C2-Chd and C0040-02-Chd), while the other is 16O-poor with 17O of ~ –3‰ (C0002-P5-C1-Chd). The two CAIs are 16O-rich with
17O of ~ –23‰ (C0040-02-CAI and C0076-10-CAI).
Discussion: Mg# of ~ 99 and the 17O value of ~ –3‰ for C0002-P5-C1-Chd are characteristic for type I chondrules in carbonaceous chondrites [10]. The two 16O-rich chondrule-like objects with Mg-rich olivine share characteristics with AOAs [11] andare likely to have been originally AOAs (or fragments) and melted (and annealed) by a heating event in the 16O-rich environment
possibly near the Sun. The three chondrule-like objects, which are dominated by Mg-rich olivine and free from glass, resemble
what has been proposed as earlier generations of chondrules [12]. If the three objects are earlier generations of chondrules, the two
distinct oxygen isotope ratios of 16O-rich and -poor are evidence for the argument that 16O-rich and -poor isotope reservoirs existed
in the early stage of the chondrule formation [10].
Spinel-rich CAIs accompanied by altered phases like the two Ryugu CAIs are observed in CM chondrites [e.g., 13]. However,
the two Ryugu CAIs are smaller than the CM-CAIs and as small as CAI-like Wild2 particles [14]. Spinel in the CM-CAIs contain
Cr2O3 mostly less than 0.6 wt% [13], while that in cometary CAIs contains more Cr2O3 than 1.7 wt% [15]. The relatively highCr2O3 contents are explained by addition of Cr from Cr-bearing gas or dust during the remelting events at few Myr after CAI formation [15,16]. Spinel in the two Ryugu CAIs contain Cr2O3 less than 0.2 wt%. It is possible that the two Ryugu CAIs escapedfrom remelting events that supplied Cr. If this is the case, the two Ryugu CAIs are possibly as old as the CM-CAIs.
The Ryugu original parent body formed at > 3 – 4 au from the Sun [2], while CAIs formed near the Sun [11]. Radial transportof the CAIs and the two 16O-rich chondrule-like objects to the region where the Ryugu original parent body formed is required.
Likewise, it has been suggested from the observations of chondrule-like and CAI-like Wild2 particles that chondrules and CAIs
were transported from the inner regions to the Kuiper belt in the solar nebula [14,17]. Given the smaller sizes of the cometarychondrules and CAIs than those in chondrites, radial transport favoring smaller objects to farther locations may have occurred in
the solar nebula; e.g., a combination of advection and turbulent diffusion [18]. If this is the case, the occurrence of chondrule-likeobjects, CAIs, isolated anhydrous grains that are likely to be fragments of chondrules and CAIs, and AOA-like porous olivine[2,19,20], which are as small as the Wild2 particles, suggests that the Ryugu parent body formed at farther location than any otherchondrite parent bodies and acquired these anhydrous objects transported from the inner regions of the solar nebula.
Chondrules in different chondrite groups have distinct chemical, isotopic, and physical properties, suggesting chondrule formation in local disk regions and subsequent accretion to their respective parent bodies without significant inward/outward migration [10]. The rarity of chondrules (and chondrule-like objects) in the Ryugu samples suggests the Ryugu parent body formation ina region scarce in chondrules. Instead, small chondrules and fragments may have been transported with CAIs from the inner regions of the solar nebula. Since the formation age of the Ryugu parent body is as early as those of major types of carbonaceouschondrite chondrules [2,21], chondrules typically observed in chondrites (~ 1 mm) should have presented in the inner regions of
the solar nebula when forming the Ryugu parent body. Considering radial outward transport favoring smaller objects, small fragments of relatively large chondrules may have also been provided and observed as isolated anhydrous grains in the Ryugu samples.
CAIs in the Ryugu samples are much less abundant (~ 20 ppm) than those in the Wild2 particles (~ 0.5%; [15]), suggesting destruction of the CAIs and chondrules in the Ryugu parent body during the extensive aqueous alteration. The observed chondrulelike objects and CAIs may have survived along with isolated anhydrous grains in less-altered regions in the Ryugu parent body.
References: [1] Yada T. et al. (2021) Nat. Astron. 6:214. [2] Nakamura T. et al. (2022) Science 10.1126/science.abn8671. [3]
Ito M. et al. (2022) Nat. Astron. 10.1038/s41550-022-01745-5. [4] Nakamura E. et al. (2022) Proc. Jpn. Acad. Ser. B 98:227. [5]Yokoyama T. et al. (2022) Science 10.1126/science.abn7850. [6] Klöck W. et al. (1989) Nature 339:126. [7] Han J. & Brearley A.J.
(2015) M&PS 50:904. [8] Clayton R.N. et al. (1977) EPSL 34:209. [9] Ushikubo T. et al. (2012) GCA 90:242. [10] Tenner T.J. etal. (2018) in Chondrules: Records of Protoplanetary Disk Processes 196. [11] Krot A.N. (2019) M&PS 54:1647. [12] Libourel G.
& Krot A.N. (2007) EPSL 254:1. [13] Rubin A.E. (2007) M&PS 42:1711. [14] Zolensky M.E. et al. (2006) Science 314:1735. [15]Joswiak D.J. et al. (2017) M&PS 52:1612. [16] Matzel J.E.P. et al. (2010) Science 332:1528. [17] Nakamura T. et al. (2008) Science 321:1664. [18] Hughes A.L.H. & Armitage P.J. (2010) ApJ 719:1633. [19] Liu M.-C. et al. (2022) Nat. Astron.
10.1038/s41550-022-01762-4. [20] Kawasaki N. et al. (2022) Sci. Adv. Submitted. [21] Fukuda K. et al. (2022) GCA 322:194.

Fig. 2: Oxygen three-isotope ratios of three chondrule-like objects
and two CAIs in the Ryugu samples. TF, PCM, and CCAM represent
the Terrestrial Fractionation line, the Primitive Chondrule Mineralline, and the Carbonaceous Chondrite Anhydrous Mineral line.
Fig. 1: BSE images of three chondrule-like objects and two CAIs in
the Ryugu samples analyzed for oxygen isotopes. SIMS analysis
spots are shown by the vertex of an open triangle. The rectangle areadrown by the dashed line in panel c corresponds to the region extracted by the FIB sectioning. Abbreviations: Ol, olivine; Mt, Fe-Ni metal;
Sul, Fe-sulfide; Ox, oxide; Diop, diopside; Sp, spinel; Hib, hibonite;
Pv, perovskite; Phyl, phyllosilicates.

GEMS-like material from asteroid Ryugu regolith
Hope A. Ishii1, John P. Bradley1, Elena Dobrică1, Kenta Ohtaki1, Takaaki Noguchi2,3, Toru Matsumoto4, the Min-Pet Fine Subteam and the Hayabusa2 initial analysis core1
Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
2
Division of Earth & Planetary Science, Kyoto University, Kyoto, Japan3
Department of Geology and Mineralogy, Kyushu University, Kyoto, Japan
4
Hakubi Center for Advanced Research, Kyoto University, Kyoto, Japan
Introduction: Because GEMS, glass with embedded metal (kamacite) and sulfides (pyrrhotite) are found in primitive
cometary particles and likely accreted at extremely low temperatures, their presence is often taken as an indicator of cosmic
primitivity and lack of alteration in meteoritic parent bodies [1]. GEMS are found in anhydrous, carbon-rich interplanetary dust
particles (IDPs) and have also been confirmed in Antarctic micrometeorites (MMs) [2]. GEMS-like materials, having similar
texture and morphology (glass with embedded opaques) have been reported in several chondrites, e.g. [3,4]. Close study insome chondrites shows key differences to GEMS in cometary-type particles, for example, in size range, glassy matrix
composition and mineralogy of opaques [5,6]. JAXA’s Hayabusa2 mission returned regolith from near-Earth Cb-type asteroid
162173 Ryugu, and GEMS-like material has recently been reported in Ryugu regolith grains within less-altered lithologies [7].
Samples and Methods: Two Ryugu grains with high porosity, A0104-029025 and C0105-039023, were identified late in theinitial analysis period and analyzed to determine if they contain GEMS. Initial characterization was performed by scanningelectron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on a JEOL JSM-7001F FE_SEM at Kyoto U. a
ThermoFisher Scios FIB-SEM at Kyushu U., and a ThermoFisher Helios Nanolab 660 FIB-SEM at U. Hawaii. SEM-EDS
characterization shows that grain A0104-029025 is ~50 µm in length and has a silica-rich matrix holding remnant olivine up to~5 µm across, pyrrhotite, pentlandite, magnetite, Mg-rich Cr-spinel, calcite, and a Fe-Ni-P-bearing phase. Grain C0105039023 is ~75 µm in length and its silica-rich matrix contains smaller remnant olivine and pyroxene grains, pyrrhotite,
pentlandite, magnetite, Cr-spinel, dolomite, calcite, phosphates, and a submicron-sized fragment of the Ta projectile. Using
Focused Ion Beam (FIB) methods, regions of both samples were extracted as blocks (e.g., Fig. 1), embedded in epoxy, andultramicrotomed to produce electron-transparent sections for analysis by scanning transmission electron microscopy (STEM).
STEM analyses were performed using a ThermoFisher TitanX 60-300 with 4-quadrant windowless EDS detector at the
Molecular Foundry, Lawrence Berkeley National Laboratory.
Figure 1. Preparation of FIB-extracted block from grain
C0105-039023. Clockwise from top left: SE image ofgrain; view with sample tilted and protective Pt layer
deposited; FIB milling to free block from grain; and final
block mounted on a Cu TEM half-grid, ready forembedding and ultramicrotomy [after 8].

Results: Observed at modest TEM magnifications,
C0105-039023 and A0104-029025 both containregions of abundant fine-grained layer silicate with
Fe-rich inclusions that has a GEMS-like appearance.
Anhydrous silicates were not observed in either of
the FIB-sections analyzed, although they wereobserved by SEM. C0105-039023 is dominated bycompact, well-ordered layer silicates and with
abundant pentlandite and pyrrhotite, minor Fe-oxides, and Mg,Ca-rich carbonates. High porosity in this grain is due to many
cracks in the interior. Some GEMS-like objects with rounded shapes were identified in C0105-039023. Closer investigations
revealed that, unlike in GEMS in cometary-type interplanetary dust particles and Antarctic micrometeorites, ultra-fine-grained
inclusions are absent; no kamacite was detected; both pyrrhotite and pentlandite are present; and the “matrix” is layer silicate.
We found that even in regions of the samples where imaging contrast appears uniform and suggestive of amorphous structure,poorly ordered fine fibers of layer silicate, a few basal spacings thick, are observed at high magnifications. Figure 2 shows afew GEMS-like objects in C0105-039023. Compositions of these GEMS-like objects are approximately chondritic in major
elements, like GEMS and other primitive objects. Higher carbon content in one GEMS-like object, relative to the surrounding
matrix, is somewhat suggestive of bona fide GEMS that might have altered in place. The presence of co-located Na and Cl,
presumably salt, in the same field of view as the GEMS-like objects underscores the significant role of aqueous processing inthese grains.

p

p

2

–
Figure 2. GEMS-like objects in Ryugu grain C0105-039023. Left: HAADF STEM image showing 3 GEMS-like objects located in upper
right, lower right and lower left quadrants of image. Middle: EDS map of Mg (blue), Fe (green), C (red), S (yellow), Ni (magenta) of same
region. One GEMS-like object is outlined in yellow and shown at higher magnification in an overlaid EDS map of Fe (red), S (blue) and Ni(green) showing presence of both pentlandite and pyrrhotite. The top right GEMS-like object has higher carbon content than surrounding
layer silicate matrix. Right: HAAF STEM image overlaid by Cl (blue) and Na (red) EDS maps showing presence of NaCl (bottom, middle),
indicative of aqueous processing.

A0104-029025 has two texturally distinct regions, one with high porosity and the other with lower porosity. The more porous
region consists of poorly ordered, hydrated silicate and fine-grained pyrrhotite. Pentlandite was not observed in the highporosity region. The less porous region contains finer-grained pyrrhotite, pentlandite, and a platy S-rich phase thought to be
proto-tochilinite. These mineralogical differences are evident in EDS maps over the boundary. No metal was observed in eitherof these two grains.
Discussion and Conclusions: Based on our observations, GEMS-like objects in porous Ryugu grains are not GEMS, asdefined according to their characteristics in cometary-type IDPs and MMs. We observed one GEMS-like object with higher
carbon content than its surroundings, suggestive of possible alteration in place of GEMS; however, the majority of GEMS-likeobjects contain pentlandite and pyrrhotite, no kamacite (metal) and have matrices that consist of poorly ordered hydrated
silicate. Instead, we conclude that the GEMS-like objects in the porous Ryugu grains we studied are sulfide clusters that codeposited with hydrated silicate. This interpretation of a likely role of aqueous processing is supported by the presence of NaClnear the GEMS-like objects in C0105-039023. For A0104-029025, we hypothesize that the observed boundary between highand lower porosities represents a leach front. The lower porosity region shows evidence of more extensive aqueous alterationin the form of pentlandite, reduced pyrrhotite grain size, and the platy sulfide that may result from oxidation of pyrrhotite. The
observation of anhydrous silicates by FE-SEM demonstrates that aqueous alteration in incomplete, and larger anhydrous
silicates in A0104-029025 support less heavy modification of that grain relative to C0105-039023. High porosity in bothgrains may reflect a sufficiently low degree of compaction and remnant porosity to allow aqueous alteration products to formin void spaces.
References[1] Ishii H.A. et al. (2018) Proc. National Academy Sci. 115:6608-6613. [2] Noguchi T. et al. (2015) Earth Planet. Sci. Lett.
410:1-11. [3] Leroux H. et al (2015) Geochimica et Cosmochimica Acta 170:247-265. [4] Nittler L. R. et al. (2019) Nature
Astronomy 3:659-666. [5] Ohtaki K. et al. (2021) Geochimica et Cosmochimica Acta 310:320-345. [6] Villalon K. R. et al.
(2021) ibid, 346-362. [7] oral presentation, Nakamura T. et al. (2022) LPS LIII, Abstract #1753. [8] Ohtaki K. et al. (2020)
Microscopy & Microanalysis 26:120-125.

Zinc, copper and calcium isotopic composition of Ryugu’s samples
Frédéric Moynier1, Marine Paquet1, Wei Dai1, Tetsuya Yokoyama2, Yan Hu1, The Hayabusa2-initialanalysis chemistry team, The Hayabusa2-initial-analysis core.
1
Université Paris Cité, Institut de physique du globe de Paris, CNRS; 75005 Paris, France
2

Department of Earth and Planetary Sciences, Tokyo Institute of Technology; Tokyo 152-8551, Japan.

In December 2020, the JAXA Hayabusa2 spacecraft returned to Earth with the first samples collected from a Cb-type
asteroid, (162173) Ryugu [1,2]. Initial analyses showed that Ryugu’s composition is close to that of the CI (Ivunalike) carbonaceous chondrite group [3,4], the chemically most primitive meteorites characterized by near-solar
abundances for most elements. Some isotopic signatures (Ti, Cr) of Ryugu overlap, however, with other carbonaceouschondrite (CC) groups. Zinc (Zn) and copper (Cu) are moderately volatile elements (MVE) that display variable
isotopic compositions across the different chondrite groups and could be used to further test the Ryugu/CI connection.
Furthermore, one notable chemical difference between Ryugu and CI chondrites is an apparent excess of over 50%
Ca in the former that may be related to a heterogeneous distribution of carbonates (dolomite and calcite) [3,5]. Given
that calcium in carbonates can be isotopically fractionated during aqueous alteration and carbonate precipitation,
leading to more than 1‰ variations in the 44Ca/40Ca ratio in terrestrial carbonates, it could be a useful tool forinvestigating the origin of the Ca excesses in the Ryugu samples compared to CI. In addition, Ca exhibits large isotopic
variations among bulk carbonaceous chondrites (CC), with the 44Ca/40Ca ratio range also spanning a range of 1 ‰,and therefore, Ca stable isotopes could be used to further test the Ryugu/CI connection.
Here we will present the first stable isotopic composition of Zn, Cu, [6] and Ca [7] from two Ryugu sampling sites.
We show that Ryugu and CI chondrites have identical Zn and Cu isotopic compositions, demonstrating their common
genetic heritage and ruling out any affinity with other groups of CC. Since Ryugu’s pristine samples match the solar
elemental composition for many elements, their Zn and Cu isotopic compositions likely represent the best estimatesof the proto-solar composition. Earth’s mass-independent Zn isotopic composition is intermediate between Ryugu/CC
and non-carbonaceous chondrites, suggesting a contribution of Ryugu-like material to Earth’s budgets of Zn and otherMVE. We also show that both Ryugu samples have similar Ca isotopic composition that falls within the range definedby CIs, notwithstanding their higher Ca contents. This similarity likely indicates that the Ca isotopic composition and
the Ca budget of CIs and Ryugu samples are dominated by carbonates and consistent with a major event involving
precipitation of carbonates in the Ryugu samples that has been dated by 53Mn-53Cr chronology to have occurred ~5Ma
after Solar System formation.

The Hayabusa2-initial-analysis chemistry team: 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. Di 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, Yuki Masuda, K.D. McKeegan, M. Morita, K. Motomura,
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.

References[1] Tachibana, S. et al. Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to
Earth. Science 375, 1011-1016, doi:10.1126/science.abj8624 (2022). [2] Yada, T. et al. Preliminary analysis of the
Hayabusa2 samples returned from C-type asteroid Ryugu. Nature Astronomy 6, 214-220, doi:10.1038/s41550-021-

01550-6 (2022). [3] Yokoyama, T. et al. The first returned samples from a C-type asteroid show kinship to thechemically most primitive meteorites. Science 10.1126/science.abn7850 (2022). [4] Nakamura, E., K., K., Tanaka,
R., Kunihiro, T. & Kitagawa, H. On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical
perspective. Proc. Jpn. Acad., Ser. B 6, 227-282 (2022). [5] Nakamura, T. et al. Science (accepted).[6] Paquet et al.
Copper and Zinc Isotopic Fingerprints of the Contribution of Ryugu-like Material to Earth’s Volatile Inventory.
Nature Astronomy (in revision). [7] Moynier et al. The Solar System calcium isotopic composition inferred from
Ryugu samples. Geochemical Perspective Letters (accepted).

Molybdenum and Osmium isotopic compositions of Ryugu sample
Nao Nakanishi1,2, Akira Ishikawa2, Tetsuya Yokoyama2, and Richard J. Walker1,
The Hayabusa2-initial-analysis chemistry team, The Hayabusa2-initial-analysis core.
1
Dept. of Geology, University of Maryland,USA
2
Dept. of Earth & Planetary Sciences, Tokyo Institute of Technology, JapanThe Hayabusa2 mission conducted two sampling sequences on the Cb-type asteroid Ryugu and brought 5.4 g of theasteroidal materials back to Earth. The initial analyses found that Ryugu samples are dominated by minerals that experienced
extensive aqueous alteration in the parent body and are related to CI (Ivuna-like) carbonaceous chondrites [1]. To further
investigate the origin of the materials that accreted to form Ryugu and chemical processes that affected these materials after
accretion we examined the isotopic compositions of the siderophile elements Os and Mo. Eleven 187Os/188Os ratios wereobtained from bulk Ryugu samples (A0106-A0107, and C0108 from both sampling locations) using N-TIMS (Triton Plus) at
Tokyo Tech. A composite sample of four bulk Ryugu samples that were combined (A0106-A0107, A0106, C0108, and C0107
from both sampling locations) was dedicated for the determination of the Mo isotopic composition of the composite using MCICP-MS (Neptune Plus) at UMd.
The bulk Ryugu samples have uniform 187Os/188Os ratios, averaging
0.1264 ± 0.0005 (2SD, n = 11) (Fig. 1), which is consistent with the187
Os/188Os ratio of bulk CI chondrites (0.1265 ± 0.0001, 2SD; [2]). Thisobservation supports the main conclusion of previous studies that Ryugu ismainly composed of materials related to CI chondrites [3]. The uniform
187
Os/188Os ratio implies homogeneous distribution of elemental Re/Os
ratios of the Ryugu materials. This is likely to reflect the redistribution of
Re and Os by aqueous alteration that occurred on the Ryugu parent body.
Given the sample size for one analysis (0.4–1.1 mg), the Re/Os
homogenization would be achieved even on a small scale.
The composite bulk Ryugu sample analyzed for Mo is characterized bypositive εiMo values (εiMo = [(iMo/96Mo)sample/(iMo/96Mo)standard − 1] ×104)
for 92Mo, 94Mo, 95Mo, and 97Mo, consistent with a deficit of s-process Mo
Figure 1. Os isotopic composition of Ryugu
isotopes (Fig. 2). Previous studies have shown that Mo isotopic data formaterials and chondrites. Reference data are from[2]. The error bars reflect the range of isotopic
carbonaceous (CC) and non-carbonaceous (NC) meteorites define twocompositions measured for each category (Ryugu:
95
94
separate linear trends on the ε Mo–ε Mo diagram (e.g., [4]). The Ryugu
2SD; Chondrites: 1SD).
sample plots on the CC line (Fig. 3), which is consistent with theobservation that Ryugu samples are also characterized by CC-type ε50Ti–
ε54Cr isotopic systematics [3]. The ε94Mo and ε95Mo values for thecomposite Ryugu sample are larger than those of any known bulk carbonaceous chondrites including CIs (Fig. 3).
There are at least three possible explanations for the large s-process deficits in the Ryugu sample. First, the measured Mo
isotopic composition might accurately reflect the composition of the bulk asteroid. In this case, it would suggest that Ryugu
formed from a nebular region with a Mo isotopic composition that differed from that of the limited number of CI chondrites
analyzed for Mo to date. This would be in conflict with the evidence from the lithophile Ti and Cr isotopic compositions.
Second, Mo isotopes might have been heterogeneously distributed on the asteroid Ryugu. In this case, the Mo isotopic
composition obtained from the ~70 mg of Ryugu material analyzed may not represent the bulk composition of the asteroid, andmay instead reflect the redistribution and concentration of strongly s-process depleted Mo by aqueous processes. Third isincomplete dissolution of presolar SiC grains during the acid digestion steps, given that SiC grains are resistant to dissolution
by the acid digestion techniques applied for this measurement. SiC is characterized by s-process-enriched compositions [e.g.,5]. A leachate study on Orgueil found that incomplete digestion creates anomalies in Mo isotopic composition [6]. Thus, the sprocess deficit may reflect an absence of the SiC component contribution to the bulk composition.

Figure 2. Mo isotopic composition of Ryugu andAllende analyzed in this study. The reference bulk
meteorite data are from [6-8]

Figure 3. ε95Mo-ε94Mo diagram of Ryugu material
and bulk Allende. The reference bulk meteorite data arefrom [8].

References[1] Yada T. et al. 2022. Nature Astronomy 6:214. [2] Walker R. J. et al. 2002. GCA 66:4187. [3] Yokoyama T. et al. 2022
Science abn7850. [4] Kleine, T. et al. 2020. Space Sci. Rev. 216:1. [5] Stephan T. et al. 2019. ApJ 877:101. [6] Dauphas N. et
al. 2002 ApJ 569:139. [7] Burkhardt C. et al. 2011. EPSL 312:390. [8] Yokoyama, T. et al. 2019. ApJ 883:62.
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. Di 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, Yuki 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.

Ryugu’s volatiles investigated using stepped combustion and EGA methods
A.B. Verchovsky1, F. A. J. Abernethy1, M. Anand1, I. A. Franchi1, M. M. Grady1, R. C. Greenwood1 and M. Suttle1, M. Ito2,
N. Tomioka2, M. Uesugi3, A. Yamaguchi4, M. Kimura4, N. Imae4, N. Shirai5, T. Ohigashi6,7, M-C. Liu8, M. Abe9, T. Usui9.
1
The Open University, Milton Keynes, MK7 6AA, UK. 2KOCHI JAMSTEC, 3JASRI/SPring-8, 4NIPR, 5 Kanagawa Univ.,
6
UVSOR IMS, 7PF/KEK 8LLNL, 9ISAS/JAXA, the Ph2K team, the MicrOmega team.

o

Carbon yeild , ng/ C

QMS signal, cps

Samples of the asteroid Ryugu collected by the Hayabusa 2 mission [e.g., 1-4] provide an excellent opportunity to undertakea comparative study for volatiles (e.g., H, C. N, S) measured in meteorites of similar type. This allows for a better understandingof the evolution of the meteoritic material during their transition through the atmosphere and residence on the surface of the
Earth. In this study, we present the abundances and isotopic compositions of C, N and some noble gases in a Hayabusa 2 sample
A0219 (as collaborative research under the Phase2 Kochi curation activity) and three CI meteorites (Orgueil, Ivuna and Alais).
These measurements were performed using stepped combustion QEGA (Quantitative Evolved Gas Analysis) methods. It is
important to note that utmost care has been taken to avoid any exposure of Hayabusa 2 material to the terrestrial atmosphere,
from the time of the recovery of the sample capsule in Australia to sample allocation and preparation (in gloves box filled withpure N2) and loading (with portable gate valve) for analysis by the Finesse instrument [5, 6] at the Open University. The sample
aliquots used for the stepped combustion and QEGA were 2 and 0.5 mg respectively.
1. Hydrogen. Release of H2 from A0219 during EGA occurs over a broad temperature range (400-1000 oC) with the major
peak at 730 oC, similar to what is observed for the three CIs and seems to be associated with decomposition/oxidation of theorganic macromolecular material. The total concentration (0.3 wt.%) of the molecular hydrogen in A0219 is also similar to thatfound in other CIs.
2. Water. In contrast to all other CIs analysed, the release of H2O in A0219
6
1.2 10ohas a single peak with maximum at ~550 C: for Orgueil, Ivuna and Alais, theA0219
6Orgueil
1.0 10Ivuna
H2O release is bimodal with an additional (apart from that at 530-570 oC) peak
Alais
o
o
5
at low (~250 C) temperature (Fig.1). The peak at 530-570 C is thought to be
8.0 10associated with structural transformation of phyllosilicates at which their5
6.0 10hydroxyl groups are released in the form of water. The low temperature peaks in
5
CIs can be related to the adsorbed and/or hydroxide decomposition water release,
4.0 10associated with terrestrial weathering. In another study, the Hyabusa 2 sample
5
2.0 10analysed by TG-MS [7] showed a small peak of water at 100 oC, which was taken
0.0
as evidence of heating on the surface of the asteroid to be limited to below 100
0 100 200 300 400 500 600 700 800 900 1000oo
C. However, the results here (Fig. 1) show no measurable water release below
Temperature, C
Figure 1. Release pattern of H2O.
~300 oC; the quadrupole MS signal at these temperatures is at the backgroundlevel (<100) cps. As saponite can readily resorb water from atmosphere, it ispossible that the release at 100 oC reported by Yokoyama et al. [6] is terrestrial contamination, and that the samples have beenheated on the Ryugu’s surface to temperatures of up to 300 oC. The total water content determined in A0219 (7.6±1.5 wt. %) issimilar to that published for other Hayabusa 2 samples [6].
3. Carbon. Stepped combustion results clearly indicate that most of
600
80
A0219
carbon in Hayabusa 2 (as in other CIs [8]) is associated with the
500
60
macromolecular organic material and carbonates (Fig. 2). CO2 from the latteris released at ~600 oC, characterised by a relatively high 13C values (up to400
4080‰) and present in CIs in variable amounts. In that sense, A0219 is not300
different from other CIs, though its carbonate concentration is relatively high.
20
The petrographic studies of the Hayabusa 2 samples [6, 8] confirm the200
presence of Ca, Ma and Fe carbonates. Clearly, A0219 contains very little, if
0100
any, presolar SiC, signature of which (~1200 ‰ in its pure form) is often seenin CIs as enhanced 13C (up to few hundred per mile) at 1100-1300o C. EGA
0-20
200 400 600 800 1000 1200 1400
data show that carbon is released as both CO2 at relatively low T and CO atoTemperture, C
higher T. Apart from decomposition of carbonates, these gases appear to be
Figure 2. Release of C and 13C variationsa result of oxidation of organic material in chemical reaction of the latter withduring stepped combustion.
the oxygen-bearing minerals. The total range of the carbon release is similar
to that observed for molecular hydrogen confirming that all the species are associated with the macromolecular organics. The
13

 C, ‰

o

Nitrogen yeild , ng/ C

total concentration of carbon determined by stepped combustion and QEGA are 6.3 and 4.6 wt. %, respectively that are within
the range observed for CIs.
4. Nitrogen. During stepped combustion, nitrogen release is correlated with
30
100
that of carbon indicating that it is one of the major constituents (along with C andA0219
H) of the macromolecular material. This is observed for the Hayabusa 2 and all CI
25
80
samples. The variations in 15N in the temperature steps are also similar to those20
seen in other CIs (Fig. 3). In particular a characteristic feature of the variations
60
15(along with the presence of the relatively isotopically heavy organic component)
40
is the excursion of the 15N to the isotopically light values at ~400 oC that could
10
be explained by contribution from presolar nanodiamonds, pure separates of which
20
5have 15N ~-350 ‰. However, the calculated concentration of the nanodiamonds
00
in the Hayabusa 2 sample using two-component mixing model with the
200 400 600 800 1000 1200 1400
oTemperture, C
isotopically heavy N shown by the dashed line (Fig. 3) and 15N = -350 ‰Figure 3. Release of N and 15N variations
assuming 1 % of the N in the nanodiamonds is significantly higher (by a factor of
during stepped combustion.
2-3) than in fact observed in the most primitive meteorites. The same is true for15 N, ‰

Orgueil and Tagish Lake [8]. Therefore, there must be another more significant
source of the isotopically light N component (possibly phase Q) with isotopic composition of N as light as the solar values (15N~-400 ‰), and which is oxidised in the same temperature range as nanodiamonds [5]. Nitrogen could not be identified by EGA
because of the dominant presence of CO at m/z=28.
5. Sulphur. Compared to all Cis, A0219 contains almost no sulphur. It is released at 300 oC and its estimated concentrationis ~1.2 ppm, while CIs contain a few wt. % of sulphur. It is a surprising result and the reason for such a low concentration is notcompletely clear but may reflect sample heterogeneity. Further analyses need to confirm it. Only a part of sulphur in CIs is
associated with terrestrial contamination. It follows from multicomponent sources of its release observed over a wide temperature
range including elemental, organic, sulphite and sulphide sulphur as well as from its isotopic composition [10]. Investigation ofother Hayabusa 2 samples by TG-MS [7] also indicated that the SO2 signal is very low though petrographic data showed thepresence of different sulphide minerals [7, 8]. On the other hand, in some works [11] it was suggested that most of sulphur inthe meteorites is due to terrestrial contamination. Therefore, the low S concentration in the Hayabusa 2 samples is arguably as aresult of the absence of any terrestrial contamination.
6. Noble gases. The 4He, 20Ne and 36Ar relative abundances in A0219 correspond to a mixture of solar and planetary (Q)components. The isotopic composition of Ne shows a very small contribution of the cosmogenic component: most of theexperimental points plots on the solar Ne fractionation line which is also a mixture of the solar and Q Ne, so that a contributionof the latter cannot be excluded. The data for other Hayabusa 2 grains [9] show Ne isotopic composition both without and withsome contribution of the cosmogenic component. The A0219 material and other Hayabusa 2 grains with very little cosmogenic
Ne contribution appear to have been exposed to solar wind radiation for a relatively short time being buried at a depth wheregalactic cosmic rays cannot penetrate for a longer time.
Conclusions. The EGA indicates that the A019 sample does not contain a low-temperature water release suggesting that its
presence in all other CIs is due to terrestrial contamination. The very low sulphur content in the sample may also be an indicationthat sulphur in other CIs is also mostly due to terrestrial contamination. The A0219 Hayabusa 2 sample shows many features in
C, N and noble gases abundance and isotopic compositions similar to those observed in CI chondrites. Carbonates concentrationin A0219 is relatively high compared to other CIs. Hayabusa 2 definitely belong to the CI meteorite clan.
References[1] Ito M. at al., 2022. Nat Astron (2022). https://doi.org/10.1038/s41550-022-01745-5. [2] Liu, MC., et al., 2022. Nat
Astron (2022). https://doi.org/10.1038/s41550-022-01762-4. [3] Greenwood R. C. et al., 2022. Nat Astron. 2022 (Accepted).
[4] Nakamura T. et al., 2022. Science 10.1126/science.abn8671. [5] Verchovsky A. B., 2017. Geochemistry International 55:
957. [6] Verchovsky et al. 2020. Planetary and Space Science 181, 104830. [7] Yokoyama T. et al., 2022. Science 7850. [8]Grady M. M. et al., 2002. Meteoritics & Planetary Science 37: 713. [9] Nakamura E. et al., 2022. Proc. Jpn. Acad. Ser. B 98:
227. [10] Airieaus S. A. et al., 2005. Geochim. at Cosmochim. Acta 69: 4166. [11] Velbel M. A. and Palmer E. E., 2011. Claysand Clay Minerals 59: 416.

Defect microstructure of pyrrhotite in regolith material returned from C-type asteroid 162173
Ryugu – evidence for shock metamorphism
Falko Langenhorst1, Dennis Harries2, Takaaki Noguchi3, Toru Matsumoto3,4, Akira Miyake3, Yohei Igami3, the Min-Pet“Sand” Team, and the Hayabusa2 Initial Analysis Core.
1
Institute of Geoscience, Friedrich Schiller University Jena; Carl-Zeiss-Promenade 10, D-07745 Jena, Germany;
2
Luxembourg Institute of Science and Technology, European Space Resources Innovation Centre; Belvaux, Luxembourg;
3
Division of Earth and Planetary Sciences, Kyoto University; Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;
4
The Hakubi Center for Advanced Research, Kyoto University; Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Introduction. The Hayabusa2 mission successfully returned regolith materials from two sampling sites of the C-type NearEarth Object (NEO) 162173 Ryugu [1]. Mineralogical characterization of samples revealed that aqueous alteration was anomnipresent process, which resulted mainly in the formation of phyllosilicates, carbonates, phosphates, and other phases
forming under hydrous conditions [2]. Since Ryugu is an airless body whose surface is directly exposed to interplanetary
space, it was also expected that regolith samples contain traces of space weathering (effects due to solar wind particle andmicrometeoroid bombardments). Effects of solar wind bombardment were discovered in several samples [3,4], while traces ofshock metamorphism are scarce [5], which is unusual considering the rubble pile nature of asteroid Ryugu.
Samples and methods. Ryugu samples from the two sampling sites were collected in separate chambers A and C of thesample catcher [2]. Within the activities of the Min-Pet “Sand” team, we have examined three samples from chamber A(A0058-T4, AP002-g03, AP007-g06), which probed the uppermost surface material of Ryugu. The three samples were firstinvestigated by field emission scanning electron microscope (FE-SEM: JSM-7001F at Kyoto University). We then extracted
electron-transparent sections of regions of interest on the Ryugu grains, using a focused ion beam (FIB) system (Helios
NanoLab G3 CX at Kyoto University). The FIB sections were finally observed using analytical transmission electron
microscopy (TEM, Tecnai G2 FEG at Univ. of Jena). Bright-field and dark-field TEM imaging techniques combined withselected area electron diffraction (SAED) were employed to characterize the defect microstructures.
Results. Among all the mineral grains in the three FIB sections, only a relatively large (9 x 4 µm dimensions) pyrrhotite grainfrom sample AP007-g06 turned out to exhibit a rich defect microstructure. This grain is only partially surrounded byphyllosilicates, where it displays well-developed faces parallel to (001), (010), and (011). At the free surface, the grain is
however irregularly shaped and pitted. Our previous investigation revealed a systematic variation in the superstructure typetowards the free surface with N values ranging from 4.0 (4C-pyrrhotite, x ≈ 0.125) in the grain interior to 5.9 (close to 6Cpyrrhotite, x=0.083) at the surface [4].
Additionally, we observe a high density of dislocations in various geometric configurations pervading the entire grain.
Straight, up to 1 µm long dislocations with dislocation lines parallel to [001] are most abundant (density up to 2 x 1013 m-2),
while dislocations reorganized in sub-grain boundaries and dislocation loops occur subordinately. The straight elongateddislocations are apparently glissile with 1/3[110](001) acting as slip system. Bright-field TEM images and SAED patterns
indicate also the presence of multiple microtwins on the (001) plane throughout the entire grain. Sub-grain boundaries anddislocation loops occur in the vicinity of internal voids that might have been once filled with fluid.
Discussion. This overall rich defect microstructure of pyrrhotite implies that the grain was affected by various processes. The
variation in the superstructure type below the irregular pitted surface was attributed to incipient space weathering, causing aloss of sulfur on the free surface and an inward diffusion of Fe into the grain interior [4]. Internal voids and dislocation loops
are, however, likely defects produced during aqueous alteration. The activation of a large number of perfect dislocations andmicrotwins on the basal plane are a typical response of monosulfides to dynamic loading [7]. Although no crater is observedon the surface, we interpret these defects as clue to shock metamorphism affecting the entire grain.
References[1] Watanabe S. et al. 2019. Science 364, 268-272. [2] Nakamura T. et al. 2022. Science 377,
https://doi.org/10.1126/science.abn8671. [3] Noguchi T. et al. 2022. Abstract #1747, 53rd LPSC, [4] Harries et al. 2022.
Meteoritics & Planetary Science 57: 6073. [5] Kikuiri M. et al. 2022. Meteoritics & Planetary Science 57: 6199. [6] Yada T. et
al. 2021. Abstract #2008, 52nd LPSC. [7] Langenhorst F. et al. 2014, Earth, Planets and Space 66: 118.

Chemical heterogeneity of insoluble organic matter in Ryugu grains
E. Quirico1, L. Bonal1 , Y. Kebukawa2, K. Amano3, H. Yabuta4, E. Dartois5, C. Engrand6, J. Mathurin7, J. Duprat8,
H. Yurimoto9, T. Nakamura3, T. Noguchi6, R. Okazaki10, H. Naraoka10, K. Sakamoto11, S. Tachibana12, S. Watanabe13, Y.
Tsuda3 and the Hayabusa2-initial-analysis IOM team1
Université Grenoble Alpes, CNRS, Institut de Planétologie et Astrophysique de Grenoble (IPAG), UMR 5274, Grenoble F38041, France. 2Yokohama National Univ., Yokohama 240-8501, Japan. 3Department of Earth Sciences. Tohoku University,
Senda 980-8578, Japan. 4Hiroshima University (Japan), 5ISMO, Université Paris-Saclay (France). 6IJCLab Université ParisSaclay/IN2P3 (France). 7Institut de Chimie Physique, Université Paris-Saclay (France). 8Museum National d’Histoire Naturelle,
Paris (France). 9Hokkaido University (Japan), 10Kyushu University (Japan), 11JAXA Sagamihara (Japan), 12Univ. of Tokyo(Japan), 13Nagoya University (Japan).
Introduction: The Hayabusa2 mission has returned to Earth 5.42 g of samples collected at the surface of asteroid Ryugu(Yada et al., 2022). Two touchdowns were operated: the first on February 21 2019 to collect material from the top surface, andthe second on July 11 2019, ~20 m north from the artificial crater generated by the impact experiment a few months ago, forprobing ejecta coming from deeper in the subsurface (Tsuda et al., 2020). The bulk and multi-instrumental mineralogical andisotopic characterization of Ryugu samples show that they are related to CI chondrites, but experienced a lower stage ofhydrothermalism resulting in a more reduced mineralogy (e.g. Nakamura et al., 2022). Insoluble organic matter (hereafter IOM)
has been extracted from Ryugu’s samples, and infrared spectroscopic analyses have revealed differences with respect to IOMs
extracted from historical falls as Alais, Ivuna and Orgueil (Yabuta et al., 2022; Kebukawa et al., 2022). Here, we investigate thechemical heterogeneity of IOM in a series of Ryugu grains selected from the A and C chambers, corresponding to the first andsecond touchdowns, respectively. Small grains (100-500 µm) were processed with an HF/HCl extraction protocol andcharacterized by micro-FTIR. Some of these grains were also analyzed by Raman micro-spectroscopy (Bonal et al. 2022).
Experimental: IOM samples were extracted with the HF/HCl protocol (Durand and Nicaise 1980), adapted to microsized grains. Infrared transmission spectra were collected with a Bruker HYPERION 3000 micro-FTIR, equipped with a MCTdetector. The spot size at the sample was ~50 µm x 50 µm and the spectral resolution was 4 cm-1. Measurements were run withan environmental cell maintained under secondary vacuum (~ 10-6 mbar) and the sample was heated at 80°C to remove adsorbed
terrestrial water.
Results and discussion: The samples are presented in Tab. 1 and some infrared spectra in Fig. 1. The spectra collectedfrom the series of samples show significant chemical variations, which can have different origins : (1) Terrestrial weathering
versus sample freshness; (2) Analytical artefacts; (3) Accretion of distinct organic precursors and (4) Post-accretional processes.
Ryugu samples are extremely fresh and have experienced little interactions with the terrestrial atmosphere. In contrast, thehistorical falls Alais, Orgueil and Ivuna fell in 1804, 1864 and 1938, respectively, and storage conditions in old times were not
optimized. However, systematic measurements on finds and falls covering a long period of time, including recent falls (e.g.
Tagish Lake, Mukundupura), do not support an IOM evolution controlled by terrestrial weathering (Alexander et al. 2007; Codyet al. 2005; Kebukawa et al., 2011; Orthous-Daunay et al., 2013; Quirico et al. 2018). The HF/HCl digestion protocol could be
subjected to analytical artifacts, such as oxidation and contamination (e.g. viton particles from the wires). However, we crosschecked the extraction quality by extracting IOM from well known chondrites (e.g. Orgueil), and in some cases in parallel with
two reactors filled from the same solvents and reagents. In the past, comparison with IOM samples obtained independently with
the CsF-technique developed at Carnegie Institute showed little difference with HF/HCl IOMs (Cody and Alexander 2005;
Quirico et al., 2018). Artifact measurements are known to arise with infrared micro-FTIR because IOM samples contain insoluble
minerals with varying sizes that generate scattering, which can blur the absorption signal. We have suspicions for C109-12, as
the baseline correction was uncertain in the region 1700-1600 cm-1. The accretion of different organic precursors is difficult toaddress here as no insights into petrography was available for our samples, and we cannot infer the presence of xenolithic clasts.
Last, post-accretional processes are a potential source of heterogeneity, as observed in recent falls like Tagish Lake and Sutter’sMills (e.g. Herd et a., 2011; Quirico et al., 2018). Mineralogy, bulk and isotopic compositions of Ryugu samples are consistent
with a CI chondrite, more reduced than the least altered CI Alais, and which experienced a hydrothermal event of lower intensity.
Therefore, we do not expect a significant impact of fluid circulation, regarding the similarities of IOM composition across CM
and CI chondrites when covering a broad range of petrologic subtypes. Last, a possible source of heterogeneity is short-duration
thermal metamorphism, rated as stages from I to IV (Nakamura, 2005). According to systematics on a broad array of C1 and C2
chondrites, ICH2/ICH3 appears as a suitable tracer of this process, while the aliphatic and carbonyl abundances are less accurate.
In this respect, C0109-12, A0108-6, A0108-10 and A0106-23,24,25 appear inconsistent with the CI chondrites Alais, Ivuna andOrgueil. C0109-12 displays a high ICH2/ICH3, a low intensity aliphatic band and a low intensity carbonyl band (Fig. 2). However,short-duration metamorphism is not confirmed by Raman spectroscopy and the baseline correction of the spectra of this sample
are questionable. A0108-6 and A0108-10 display a high ICH2/ICH3, but they were very thin and translucent samples, optically very
different than other IOMs. In addition, they display a strong OH band, which does not appear in other IOMs as well. Regarding
A0106-23,24,25, it looks similar to IOM from heated stage II C1 and C2 chondrites, but once again Raman spectroscopy does
not report short-duration heating for A0108-10, A0106-23,24,25. Accordingly, the spectral heterogeneity cannot be firmly
interpreted as the result of short duration heating. Last, the sample C0109-9 seems to depart from other samples in terms ofRaman characteristics. However, its infrared spectrum is similar to that of unheated C2s, and the Raman data likely suffer froma statistical bias.
Conclusion: Our data reveal chemical heterogeneity across the IOM samples extracted from a series of Ryugu grains
and aggregates. No clear differences are observed between the two chambers A and C. 6 samples are consistent with the IOMsof the three historical CI falls Alais, Ivuna and Orgueil, and strengthens the link with this chondrite class. 4 samples show
substantial differences, which cannot be firmly interpreted as the evidence of short duration heating.

References
Alexander C.M.O.’D et al. Geochimica Cosmochimica Acta, 7 4380-4403, 2007.
Bonal B. et al., 53rd Lunar and Planetary Science Conference, held 7-11 March, 2022 at The Woodlands, Texas. LPI
Contribution No. 2678, 2022, id.1331
Cody G. and C.M.O.’D Alexander. Geochimica Cosmochimica Acta, 69, 1085, 2005.
Kebukawa Y. et al. Geochimica Cosmochimica Acta, 75, 3530-3541, 2005.
Kebukawa Y. et al. 53rd Lunar and Planetary Science Conference, held 7-11 March, 2022 at The Woodlands, Texas. LPI
Contribution No. 2678, 2022, id.1271
Nakamura T. et al., 10.1126/science.abn8671, 2022.
Orthous-Daunay F.-R. et al. Icarus, 223, 534-543, 2013.
Quirico et al. Geochimica Cosmochimica Acta, 241, 17-37, 2018.
Tsuda, Y. et al. Hayabusa2 mission status: Landing, roving and cratering on asteroid Ryugu. Acta Astronautica 171, 42–54, 2020
Yabuta et al. 53rd Lunar and Planetary Science Conference, held 7-11 March, 2022 at The Woodlands, Texas. LPI Contribution
No. 2678, 2022, id.2241
Yada T. et al. Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu. Nat Astron 6, 214–220.

Properties of the asteroid Bennu’s surface based on contact measurements and their implications
D.J. Scheeres1, G. Brown1, R.-L. Ballouz2, E.B. Bierhaus3, E.R. Jawin4, P. Sánchez1, and K.J. Walsh5
1University of Colorado, Boulder, CO, USA
2Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
3Lockheed Martin Space, Littleton, CO, USA
4National Air and Space Museum, Smithsonian Institution, Washington, DC, USA
5Southwest Research Institute, Boulder, CO, USA
When the OSIRIS-REx S/C touched the surface of Bennu to carry out its sampling operations, it opened a new view into themechanical properties of rubble pile asteroids. The OREX S/C was able to take measurements of its deceleration as it
penetrated the surface, in advance of initiating its sampling process. Based on these measurements, optical observations ofsurface deformations during its penetration, and detailed granular mechanics modeling of the interaction, it was determinedthat the surface regolith covering was highly porous and had a very low level of cohesion [1]. Figure 1 (from [1]) shows themain data used in determining the Bennu surface mechanical properties. Figure 2 shows granular mechanics simulations in a
micro-gravity environment. The simulations capture the total spacecraft mass properties, the constant force spring in thesampling arm, and the geometry of the sampling head. The simulations show that for sufficiently low cohesion, the spacecraft
head penetrates the regolith and displaces it, without activating the constant force spring. This is the scenario that was seen in
the actual sampling event. Simulating regolith with stronger cohesive strength forces the spacecraft to stop and rebound,engaging the constant force spring.
Based on these measurements and modeling the surface packing fraction was determined to be as low as 0.25, half the inferredbulk packing fraction of the asteroid, and the cohesive strength on the order of 1 Pa or less. These properties imply that thesurface regolith may be significantly weaker than the sub-surface, potentially due to the lack of fines, which have the net effectof strengthening a rubble pile structure [2]. This is also consistent with other observations of the Bennu surface geology [3]and crater profiles [4].
The implications of these regolith properties can be explored relative to the larger-scale mass distributions detected on Bennu,
which found that the equatorial bulge region had a lower overall density than other regions of the asteroid [5]. Migration ofregolith into Bennu’s equatorial region brings this material within the rotational Roche lobe of the body where it isenergetically trapped, allowing for accumulation [5]. This process should have been accelerating over time, as the YORP effectcauses Bennu to spin more rapidly [6], moving the Roche lobe down to lower latitudes. Current predictions are that the surfaceof Bennu should start to lose regolith directly in about 400 Ky, assuming the YORP effect stays constant. In this talk, we willconsider the mechanics of this overall cycle of behavior, and note what likely outcomes should be found. These can then beinterpreted in light of the asteroid Ryugu, which has also been hypothesized to have undergone a period of past rapid spin [7].
References[1] K.J. Walsh, et al. Near-zero cohesion and loose packing of Bennu’s near subsurface revealed by
spacecraft contact, Sci. Adv., 8 (27), eabm6229. • DOI: 10.1126/sciadv.abm6229[2] P. Sánchez and D.J. Scheeres. 2014. “The Strength of Regolith and Rubble Pile Asteroids,” Meteoritics and Planetary
Science 49(5): 788-811[3] E. R. Jawin, et al. 2020. Global Patterns of Recent Mass Movement on Asteroid (101955) Bennu, JGR Planets
10.1029/2020JE006475[4] E.B. Bierhaus, et al. Crater population on asteroid (101955) Bennu indicates impact armouring and a young surface, Nature
Geoscience 15, pages 440–446 (2022)[5] D.J. Scheeres, et al. Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu, Science Advances 6,
eabc3350 (2020)[6] C. Hergenrother, et al. (2019). The Operational Environment and Rotational Acceleration of Asteroid (101955) Bennu fromOSIRIS-REx Observations, Nature Communications 10: 1291
[7] M. Hirabayashi, et al. (2019). The western bulge of 162173 Ryugu formed as a result of a rotationally driven deformation
process, ApJ Letters 874(1): L10

Figure 1: From Reference [1], these figures show the acceleration and surface imaging data used to constrain the mechanicalproperties of the regolith surface.

Weak
Cohesiont=0s

t = 2.7 s

t = 7.0 s

Stronger
Cohesion

Figure 2: Granular mechanics simulations of the OSIRIS-REx TAGSAM sampling in a micro-gravity environment. Weakly
cohesive regolith (top) allow the sampler head to penetrate and push the regolith. Stronger cohesion will stop the spacecraft
and cause a small rebound. The actual sampling event mimics the weakly cohesive case.

Formation of Moons and Equatorial Ridge around Top-shaped Asteroids after Surface Landslide:
Applications to asteroids Ryugu, Bennu, Didymos, and more
Ryuki Hyodo1 and Keisuke Sugiura2
1
ISAS/JAXA
2
ELSI
Top-shaped asteroids have been observed among near-Earth asteroids. About half of them are reported to have moons (on theorder of ∼1 wt.% of the top-shaped primary) and many of them have an equatorial ridge. A recent study has shown that theenigmatic top-shaped figure of asteroids (e.g., Ryugu, Bennu, and Didymos) could result from an axisymmetric landslide of
the primary during a fast spin-up near the breakup rotation period. Such a landslide would inevitably form a particulate disk
around an asteroid with a short timescale (∼3 hr). However, the long-term full dynamical evolution is not investigated. Here,
we perform a continuous simulation (∼700 hr) that investigates the sequence of events from the surface landslide that forms a
top-shaped asteroid and a particulate disk to disk evolution. We show that the disk quickly spreads and produces moons(within ∼300 hr). The mass of the formed moon is consistent with what is observed around the top-shaped asteroids. We also
demonstrate that an equatorial ridge is naturally formed because a fraction of the disk particles re-accretes selectively onto theequatorial region of the primary. We envision that Ryugu and Bennu could once have an ancient moon that was later lost due
to a successive moon’s orbital evolution. Alternatively, at a top-shaped asteroid that has a moon, such as Didymos, nosignificant orbital evolution of the moon has occurred that would result in its loss. Our study would also be qualitatively
applicable to any rubble-pile asteroids near the breakup rotation period.
The above abstract is obtained from Hyodo R. and Sugiura, K. (2022). "Formation of moons and equatorial ridge around topshaped asteroids after surface landslide". ApJL, 937, L36. https://doi.org/10.3847/2041-8213/ac922d

Schematic summary of our paper (a figure from Hyodo & Sugiura 2022, ApJL). Panel (a): a rubble-pile asteroid
spins up due to, for example, the YORP effect, small impacts, a close encounter with a planet, or re-accumulation after acatastrophic impact. Panel (b): a surface landslide occurs when a critical spin state is realized and a top-shaped figure isformed (Sugiura et al. 2021). Panel (c): a particulate disk spreads due to inelastic collisions and gravitational interactions
among particles. Panel (d): a moon is gravitationally accreted outside the Roche limit of the central top-shaped body, andan axisymmetric equatorial ridge is formed due to the re-accretion of disk particles. Panels (e) and (f): the formed moonis lost or remains, depending on the long-term orbital evolution between the moon and the primary.

Yarkovsky-Driven Orbital Migration of Asteroid Ryugu:
Implications for its Collisional History and Source Family
Masanori Kanamaru1, Seiji Sugita1 and Tomokatsu Morota1
1
The University of Tokyo

With the ongoing analysis of samples brought back from the asteroid Ryugu, there is a growing need to understand theirgeological/dynamical context. It is essential to identify the asteroid family from which the asteroid Ryugu originated and toclarify the orbital evolution path from the main belt to the near-Earth region.
In this study, we estimate the time scale of Ryugu's orbital evolution in the inner main belt based on a thermophysical simulation.
We simulated the temperature distribution on the surface of Ryugu over an orbit cycle using the current orbit, spin, andthermophysical properties (Watanabe et al. 2019; Okada et al. 2020), and calculated secular change in semi-major axis thatinduced by anisotropic thermal radiation, i.e., the Yarkovsky effect. A Yarkovsky drift rate was obtained by scaling that for thenear-Earth orbit to the inner main belt. The thermophysical simulation was performed by a dynamical simulator for asteroids,
Astrohsaper (Kanamaru et al. 2021).
As a result, it was estimated that Ryugu will take approximately 700 million years to migrate through the inner main belt from
2.1 to 2.5 au. The right panel of Figure 1 shows the time scales for Ryugu to reach the 𝜈! resonance by Yarkovsky as a functionof initial orbital elements. 𝜈! is the secular resonance with Saturn and one of the most powerful resonances as an escape hatch
to provide near-Earth asteroids.
In this region, there are two asteroid families that are possible candidates for the origin of Ryugu: Eulalia and New Polana as
shown in the left panel of Figure 1. The formation ages of these families are estimated as ~830 million years and ~1.4 billion
years, respectively (Bottke et al. 2015). The Yarkovsky time scale estimated in this study is comparable with the formation ageof Eulalia family, while it is shorter than that of New Polana family. If Ryugu originated from Eulalia family, Ryugu was formedat the same time with the family formation and was transported to the 𝜈! resonance. On the other hand, if Ryugu originatedfrom New Polana, a parent body of Ryugu was formed during the family formation. It is likely that Ryugu is a rubble pile of thesecond- or later generation that experienced multiple times of catastrophic disruption. Because the Yarkovsky drift is lesseffective for a massive body, Ryugu would have spent several hundred million years as the larger parent body.
In the future, we will attempt to shed light on the evolutionary history of Ryugu by comparing the results of analysis of returned
samples.

Figure 1. Potential source family of asteroid Ryugu and time scales to reach 𝜈! resonance.

References
Bottke, William F., David Vokrouhlický, Kevin J. Walsh, Marco Delbo, Patrick Michel, Dante S. Lauretta, Humberto
Campins, Harold C. Connolly, Daniel J. Scheeres, and Steven R. Chelsey. 2015. “In Search of the Source of Asteroid(101955) Bennu: Applications of the Stochastic YORP Model.” Icarus 247 (February): 191–217.
Kanamaru, Masanori, Sho Sasaki, Tomokatsu Morota, Yuichiro Cho, Eri Tatsumi, Masatoshi Hirabayashi, Naru Hirata, et al.
2021. “YORP Effect on Asteroid 162173 Ryugu: Implications for the Dynamical History.” Journal of GeophysicalResearch. Planets 126 (12). https://doi.org/10.1029/2021je006863.
Okada, Tatsuaki, Tetsuya Fukuhara, Satoshi Tanaka, Makoto Taguchi, Takehiko Arai, Hiroki Senshu, Naoya Sakatani, et al.
2020. “Highly Porous Nature of a Primitive Asteroid Revealed by Thermal Imaging.” Nature 579 (7800): 518–22.
Watanabe, S., M. Hirabayashi, N. Hirata, Na Hirata, R. Noguchi, Y. Shimaki, H. Ikeda, et al. 2019. “Hayabusa2 Arrives at the
Carbonaceous Asteroid 162173 Ryugu-A Spinning Top-Shaped Rubble Pile.”
https://doi.org/10.1126/science.aav8032.

The ESA Hera mission: detailed investigation of the NASA DART impact outcome andcharacterization of the binary asteroid Didymos
Patrick Michel1, for the Hera Science Team
1
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange Laboratory, Nice, France
The Hera mission is in development in the Space Safety Program of the European Space Agency (ESA) for launch in October
2024 [1]. It will perform a rendezvous with the binary asteroid (65803) Didymos in early 2027 and over 6 months, it will
investigate it as well as the outcome of the successful impact of the NASA DART probe on the small moon called Dimorphosof the Didymos system.
DART was launched on 24 November 2021 at 06:21 UTC and successfully performed an impact at about 6.1 km/s on the 160
meter-size Dimorphos on 26 September 2022 at 23:14 UTC. Two weeks before impact, it deployed the Italian LICIACube thatprovided images of the few minutes following the impact. A campaign of observations from Earth and space allowed obtaining
distant images of the event and is aimed at measuring the change of the orbital period of Dimorphos around Didymos resulting
from the impact.
The great success of the DART impact will be left with many questions. In particular, we need to know the outcome of the
impact on Dimorphos’ surface, e.g., whether it produced a crater and its size and/or whether it led to a global reshaping ofDimorphos. We also need an accurate measurement of the mass of Dimorphos, which will allow quantifying the momentum
enhancement factor, which is a crucial parameter to validate the kinetic impactor technique. We also need to determine indetail the physical, thermal and compositional properties of the asteroid, including for the first time internal properties, whichhave a great influence on the impact outcome. These are the objectives of the Hera mission, which will allow, with theknowledge provided by DART, having a fully documented deflection test and impact experiment to check our numericalimpact models, to be able to extrapolate this deflection test to other scenarios and to improve our understanding of the complex
geological properties and response of small asteroids.
To accomplish these objectives, with its mother spacecraft, which includes a JAXA contribution with the Thermal Infrared
Imager, and its two cubesats, Hera will perform the first rendez-vous with a binary asteroid, arriving at Didymos about 4 years
after DART. Hera will not only contribute greatly to the planetary defense effort by documenting entirely the DART impact,
so that numerical impact models can be validated at the real asteroid scale and so that this knowledge can be extrapolated toother scenarios. It will also contribute greatly to our understanding of asteroid processes in the very low gravity regime of avery small asteroid (Dimorphos) as well as to our knowledge of binary asteroids and asteroid geophysics. The mission
development is ongoing nominally and the various working groups of the Hera Science Team are working intensively tosupport this development and be best prepared to the surprises that Hera will offer during its visit to Didymos in 2027.
References[1] Michel P. et al. 2022. Planetary Science Journal 3:160.
Acknowledgments
We acknowledge funding support from the European Union’s Horizon 2020 research and innovation program under grant
agreement No. 870377 (project NEO-MAPP), the CNRS through the MITI interdisciplinary programs, CNES and ESA.

The ANIME mission and beyond: SmallSat exploration of near-Earth asteroids
Davide Perna11INAF – Rome Observatory (INAF-OAR)

Interest in near-Earth asteroids (NEAs) has rapidly grown in recent decades. The motivation is threefold: first, their proximity
allows us to discover and investigate small bodies down to the metre-size, thus enhancing our understanding of themechanisms underlying planetary formation; second, such information is also critical to mitigate their threat of collision with
the Earth; third, their near-future exploitation can exponentially expand the natural resources available to humankind.
Ground-based observations of thousands of NEAs have revealed the striking diversity existing within this populationin terms of physical properties. So far, only a handful of NEAs have been visited by space missions: each of them provided
unexpected discoveries and huge steps forward in our understanding of planetary sciences. Deep-space SmallSats represent a
new frontier for the solar system exploration. After the success of the NASA/JPL MarCO mission in 2018 and of the ASI
LICIACube mission which testified the impact of the NASA DART spacecraft onto asteroid Dimorphos in September 2022,
several further deep-space SmallSat missions will take place in the next few years, e.g. in the framework of ESA HERA andNASA Artemis projects.
The “Asteroid Nodal Intersection Multiple Encounters” (ANIME) mission has been proposed by an Italian consortium
led by INAF – Rome Observatory, and selected in 2021 by the Italian Space Agency (ASI) in the framework of a call for
future CubeSat missions. ANIME aims to explore three near-Earth asteroids, selected by virtue of their peculiar and yet
unexplored size and physical regimes, as well as their relevance in terms of planetary protection. The rationale behind the
ANIME target selection and interplanetary trajectory design lies in encountering asteroids that have a nodal passage in theproximity of the Earth, considering their relative positions and velocities (Fig. 1). With a launch envisaged in the 2026-2028
timeframe, the 20-kg, 12U CubeSat ANIME will flyby two Potentially Hazardous Asteroids, and then rendezvous withasteroid 2000 SG344. The study of such 40-m-sized object will allow constraining the latest theories about planetary systemformation scenarios, addressing questions about the monolithic vs. cohesive vs. rubble pile aggregation structure of small
asteroids. Moreover, 2000 SG344 presents a very high impact risk, with multiple potential collision solutions with our planet
during the course of the next century. It is also considered an excellent target for future human exploration thanks to its
accessibility.
Multiple similar/identical SmallSats (to maximize mission return while minimizing costs and risks) could be launchedprofiting of the same or separate mission opportunities, and then reach their respective targets using electric propulsion andoptimized interplanetary trajectories. Each SmallSat would flyby and/or rendezvous multiple NEAs, with encounters at thenodal points, to explore the diversity of such population. E.g., assuming an ANIME-like platform and mission durations
capped at 3 years, many mission scenarios with similar performances can be identified with total ΔV < 3 km/s. This outlines
the strong implementation flexibility of such mission concept, as the definitive choice of target NEAs can be easily updated
even at relatively late project phases, also considering the current exponential growth of NEA discoveries. This provides ahuge flexibility in terms of mission scenarios, which can be adapted to varying constraints. The strategic relevance of ANIME
and further SmallSat missions to NEAs also lies in the step forwards that will be taken in validating critical small spacecraft
technologies for deep space exploration.

Figure 1.

Reference ANIME trajectory for a launch in late 2026. Alternative flyby targets can be identified for different launch windows.