Paleomagnetic Evidence for Formation of Ryugu in the Distal Solar System
Elias N. Mansbach1, Eduardo A. Lima1, Michael Sowell2, Joseph L. Kirschvink2, Jodie B. Ream1, Roger R. Fu3, Saverio
Cambioni1, Xue-ning Bai4, Benjamin P. Weiss1
1

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology; Cambridge, MA,USA.
2

Division of Geological and Planetary Sciences, California Institute of Technology; Pasadena, CA, USA
3

Department of Earth and Planetary Sciences, Harvard University; Cambridge, MA, USA

4

Institute for Advanced Study and Department of Astronomy, Tsinghua University; Beijing, China

Paleomagnetic studies of meteorites have demonstrated that the solar nebula generated a magnetic field that likely played an
important role in accretion during the early solar system [1]. The nebular field reached intensities of 54 ± 21 µT at heliocentric
distances of 1-3 AU [2] and 101 ± 48 µT at 3-7 AU [3], and likely decayed by ~3-4 million years (Ma) after the formation of
calcium aluminum-rich inclusions (CAIs) [4-7]. However, with the possible exception of Tagish Lake and Wisconsin Range(WIS) 91600, these studies have been restricted to meteorites that formed at distances <7 AU [8, 9]. Tagish Lake is of particularinterest as its arrival to Earth from the asteroid belt implies that its parent body had been inwardly scattered, perhaps due to theformation and migration of the giant planets [9, 10].
The returned samples from asteroid (162173) Ryugu
by the Hayabusa2 mission currently provide the best
opportunity to study the nebular field in the distal solar system
as the parent body may have experienced aqueous alteration at
distances up to ~20 AU [11]. These particles are also highquality targets for paleomagnetic investigations as they are: 1)
in pristine condition since careful sample handling limits thepossibility of magnetic and terrestrial contamination, which
can lead to the creation of ferromagnetic minerals that mask
the primary record of the particles, and 2) contain single-vortex
framboidal magnetite which can retain magnetic records over
the age of the solar system [12]. If the magnetite shows
evidence of magnetization produced by an ancient field, thesource of the field could have been the nebular field or a
dynamo on the parent body. The latter case is of particularinterest since this would imply that the parent body was
Figure 1: Orthographic projection of endpoints of NRM vectors on
partially differentiated with a carbonaceous chondritic crust
the northeast (N-E) and up-east (Z-E) planes during alternating fielddemagnetization of particle A0397. The LC component is shown in[13]. Our current understanding of the lifetime of the nebula
red, the MC component in blue, and the HC range in black. No
suggests that if the natural remanent magnetization (NRM)
components are observed >24 mT.
was acquired < 4 Ma, the source of the field was the nebula
while a younger age would be indicative of a parent body dynamo. Initial Mn-Cr dating on carbonates that are thought to haveformed at the same time as the magnetite yielded an age of 3.1 – 6.8 Ma after the formation of CAIs [14], but more recent datingon carbonates using the same dating system and improved calibrations suggests alteration occurred < 1.8 Ma after CAI formation[15].
An initial paleomagnetic study of two Ryugu particles concluded that the particles formed in a > ~40 - 400 µT nebular
field [14, 16]. However, this magnetization may be post-sampling contamination because: 1) magnetite can have coercivities up
to 300 mT, but the NRMs of previously studied samples were unblocked to only 30 mT; 2) the previously studied samples had
been analyzed with an electron microprobe which may have imparted a weak isothermal remanent magnetization (IRM); and 3)
initial analysis of MasMag magnetometer data suggested that a boulder on Ryugu did not possess a measurable magnetization(< 3 × 10-6Am2 kg-1 at the m-scale) [17], yet the moment per unit mass of the reported samples is well above this limit (2.14 ×
10-5 Am2 kg-1).

To address the origin and nature of NRM in Ryugu, we
conducted an additional paleomagnetic analysis on threepreviously unstudied Ryugu particles: A0397, C0085b, andC0006. These samples have not been previously studied using a
microprobe or instrument with a strong magnet prior to our
paleomagnetic analysis.
Alternating field (AF) demagnetization of the NRM in
A0397 to 400 mT in steps of 0.5-1 mT revealed two non-origin
trending components (Fig. 1), a low coercivity (LC) component
that unblocked between 0 and 10.5 mT and a medium coercivity(MCs) component that unblocked between 11 and 23.5 mT.
Above >24 mT is a high coercivity (HC) range in which no
Figure 2: Predicted midplane nebular field assuming accretion
NRM components are observed. AF demagnetization of C0085b
around a solar mass star and that the nebular field and disk rotation
to 400 mT revealed three NRM components: an LC component
are aligned. Accretion rates are given at the right-hand side foreach curve. Colored lines represent constraints on heliocentricthat unblocked between 0 and 12.5 mT, and two MC
distance at which aqueous alteration occurred based on uppercomponents that unblocked between 13 and 19 mT and 19.5 andpaleointensity limits from particles C0085b and A0397.
23.5 mT, respectively. The second MC component was origintrending. As before, above >24 mT is a HC range containing no stable NRM. AF demagnetization of C0006 to 80 mT conductedin 5-10 mT steps revealed a non-origin trending LC component that unblocked between 0 and 20 mT with no apparent
components in the HC range above 20 mT.
Paleointensities estimated via the anhysteretic remanent magnetization (100 µT bias field and 260 mT AC field) method
for the LC components are 125.8 ± 28.9 (95% confidence interval, as for all below), 694.6 ± 145.5 and 44.8 ± 69.5 µT for A0397,
C0085b, and C006 respectively. The MC paleointensity for A0397 is 45.6 ± 31.6 µT, while the two MC paleointensities for
C0085b are 36.0 ± 44.4 and 62.3 ± 134.7. Importantly, the HC paleointensities are all also consistent with null paleofields: 26.4
± 30.6 µT for C0085b, 7.4 ± 9.2 µT for A0397, and 8.8 ± 16.4 µT for C0006. This indicates that there are magnetic recorders
with coercivities >24 mT in the particles that are capable of recording an ancient field but instead formed in the presence of anull or weak field.
Experiments conducted to determine the susceptibility of A0397 to viscous (VRM) remagnetization from prolonged
exposure to an Earth-strength field indicate that the total moment gained over 4.5 years (initial sampling to NRM
demagnetization) could account for 98% of the combined LC and MC components. We therefore suggest that the source of the
LC and MC components in our samples are overprints, most likely a VRM from sitting in Earth’s field and the field producedby spacecraft engines (10s of µT [16]) since sampling. The non-origin trending nature of the two A0397 components further
indicate that they are not primary. We suggest that the previously reported strong paleointensities are due to a weak IRM fromthe electron microprobe as ratio of NRM to saturating IRM is >10% and the components are not origin trending as well.
Our results have profound implications for the history of the Ryugu parent body. Taking the alteration age to be < 1.8
Ma after CAI-formation, our most stringent upper paleointensity limit of 7.4 µT indicates that alteration occurred at heliocentric
distances >15 AU for typical accretion rates during the main lifetime of the nebula of 10-8 M☉ yr-1 (and >5 AU for the lower
range of accretion rates during the main lifetime of the nebula) (Fig. 2). Given Ryugu’s current location (~1 AU), the parent
body may have been scattered inward prior to catastrophic disruption, but after experiencing aqueous alteration, due to influence
from the giant planets in a similar manner to that proposed for the parent body of Tagish Lake. Our results therefore provide
further evidence that the formation and migration of the giant planets led to a major reconstructing of the organization of thesolar system.
References[1] B. P. Weiss, X. Bai, R. R. Fu. 2021. Science Advances. 7. [2] R. R. Fu et al. 2014. Science. 346. [3] C. S. Borlina et al.
2021. Science Advances. 7. [4] R. R. Fu et al. 2020. Journal of Geophysical Research: Planets. 125. [5] J. Gattacceca, B. P.
Weiss, M. Gounelle. 2016. Earth and Planetary Science Letters. 455. [6] B. P. Weiss et al. 2008. Science. 322. [7] B. P. Weisset al. 2017. Earth and Planetary Science Letters. 468. [8] J. F. J. Bryson et al. 2020. The Astrophysical Journal. 896. [9] J. F. J.
Bryson et al. 2020. The Astrophysical Journal. 892. [10] S. N. Raymond, A. Izidoro. 2017. Sci Adv. 3. [11] T. Hopp et al.
2022. Science Advances. 8. [12] Y. Kimura et al. 2023. Sci Rep. 13. [13] B. P. Weiss et al. 2010. Space Science Reviews. 152.
[14] T. Nakamura et al. 2023. Science. 379. [15] K. A. McCain et al. 2023. Nature Astronomy. 7. [16] M. Sato et al. 2022.
Journal of Geophysical Research: Planets. 127. [17] D. Hercik et al. 2020. Journal of Geophysical Research: Planets. 125.

Experimental Constraints on the Concentration of Dirac Magnetic Monopoles in Primordial
Material returned from Asteroid Ryugu by JAXA’s Hayabusa2 Mission
Joseph L. Kirschvink1,2, Michael Sowell1, Chisato Anai2, Atsuko Kobayashi1,2, Yuhji Yamamoto2, Elias Mansbach3, Eduardo
Lima3, Masahiko Sato4, Chie Kato5, Hirosi Ooguri1,6, Tadayuki Takahashi6, Thomas Edward Melia6, Alexander Kusenko6,7,Volodymyr Takhistov6,8, Tomohiro Usui9
1
California Institute of Technology, Pasadena CA, USA2
Kochi Marine Core Research Institute, Kochi University, Japan
3
Massachusetts Institute of Technology; Cambridge, MA, USA
4
University of Tokyo, Tokyo, Japan; 5Kyushu University, Fukuoka, Japan
6
Kavli Institute of Physics and Mathematics of the Universe, University of Tokyo, Tokyo, Japan
7
University of California at Los Angeles, Los Angeles, CA, USA
8High Energy Accelerator Research Organization (KEK), Tsukuba, Japan
9
JAXA, Kanagawa, JapanIn 1931, Dirac postulated the existence of elementary particles with quantized magnetic charge as an explanation for theobserved quantization of electric charge. If found, Dirac magnetic monopoles (DMMs) would require a re-evaluation ofelectromagnetism and all related theories. However, DMMs have not yet been empirically discovered. Their predicted
magnetic charge, multiples of 2Φ0 (where Φ0 is the magnetic flux quantum: ~2.07 fWb), would be detected easily withmodern superconducting quantum interference device (SQUID) magnetometers. If cosmic DMMs were trapped on
ferromagnetic grains in pre-solar materials, then a promising place to search for them would be in material sampled fromprimitive small bodies, preferably returned by spacecraft on low-acceleration trajectories, since intense accelerations
experienced by meteorites could strip them of DMMs as they enter Earth’s atmosphere. By passing material through a 2G
SQUID rock magnetometer, a theoretical DMM trapped within ferromagnetic grains would return a change in measured
magnetic flux (ΔΦ) by multiples of 4Φ0, or ~8.23 fWb. We performed this experiment on three Hayabusa-2 samples returned
from the asteroid Ryugu: samples collected from the sites TD1 (A0397) and TD2 (C0006 and C0085), with a combined massof 18.7 mg. We measured ΔΦ as -0.3 ± 0.2 fWb for A0397, 0.3 ± 0.5 fWb for C0006, and 0.4 ± 1.1 fWb for C0085. Although
our numbers were not significantly different from zero and are well below the expected magnetic charge for DMMs, we only
sampled 18.7 mg of the ~5g of primitive asteroidal material returned from Ryugu, which is in turn an infinitesimal fraction of
the solar system. Due to their importance for all of science, we argue that all primitive materials returned from space missions
should be screened routinely for DMMs as part of their initial characterization in the sample receiving laboratories.

Summarized results of 22 pass-through experiments conducted on returned Ryugu samples A0397, C0006, and C0085. Here,ΔΦ is expressed as a percentage of 4Φ0 – the minimum quantized change in flux expected by a Dirac magnetic monopole.
Since ΔΦ of all samples is much lower than 4Φ0, we have not yet detected a magnetic monopole.

Electron holography observation of presudo-magnetites and metallic iron nanoparticles in space
weathered Ryugu sample
Yuki Kimura1, Takeharu Kato2, Satoshi Anada2, Ryuji Yoshida2, Kazuo Yamamoto2, Toshiaki Tanigaki3, Tetsuya Akashi3,
Hiroto Kasai3, Kosuke Kurosawa4, Tomoki Nakamura5, Takaaki Noguchi6, Masahiko Sato7, Toru Matsumoto6, Tomoyo
Morita5, Mizuha Kikuiri5, Kana Amano5, Eiichi Kagawa5, Toru Yada8, Masahiro Nishimura8, Aiko Nakato9, Akiko Miyazaki8,
Kasumi Yogata8, Masanao Abe8, Tatsuaki Okada8, Tomohiro Usui8, Makoto Yoshikawa8, Takanao Saiki8, Satoshi Tanaka8,
Fuyuto Terui10, Satoru Nakazawa8, Hisayoshi Yurimoto11, Ryuji Okazaki12, Hikaru Yabuta13, Hiroshi Naraoka12, Kanako
Sakamoto8, Sei-ichiro Watanabe14, Yuichi Tsuda8, and Shogo Tachibana6,81
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.
4Planetary Exploration Research Center, Chiba Institute of Technology, Narashino 275-0016, Japan.
5
Department of Earth Sciences, Tohoku University, Sendai 980-8578, Japan.
6
Division of Earth and Planetary Sciences, Kyoto University; Kyoto 606-8502, Japan.
7
Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan.
8Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan.
9
National Institute of Polar Research, Tashikawa 190-8518, Japan.
10
Kanagawa Institute of Technology, Atsugi 243-0292, Japan.
11
Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan.
12Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 819-0395, Japan.
13
Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
14
Department of Earth and Environmental Sciences, Nagoya University, Nagoya 464-8601, Japan.
The traces resulting from space weathering could provide a detailed understanding of interplanetary processes. However,most meteorites are composed of materials produced in the interior of the asteroid and have not undergone space weathering
on its surface. Analysis of samples gently collected from the surface of extraterrestrial bodies by spacecraft is therefore
useful for studying the details of space weathering [1,2].
Here, we focused on the space weathering of magnetite in samples brought back from the C-type asteroid Ryugu by the
Hayabusa2 spacecraft. Magnetite is an important mineral to record the nebular magnetic field, but studies on its space
weathering are limited. Magnetite is universally found in carbonaceous meteorites as a major product of aqueous alterationof asteroids during the early stages of solar system formation. In particular, since most of the samples recovered by the
Hayabusa2 spacecraft were collected from the surface of the asteroid, it is important to understand the degree of space
weathering influence on magnetite in order to interpret the origin of remanent magnetization. We have previously studied themagnetic domain structure of framboidal magnetite in recovered samples using electron holography [3,4]. In this study, we
report on our newly discovered flamboids, which does not show a typical magnetic domain structure of magnetite.
From an area with relatively abundant Fe and containing many spherical particles similar to framboidal magnetite wasselected from the surface of particle A0064-FO007 and an ultrathin section was prepared by focused ion beam (FIB)
machining without applying magnetic field greater than that of the Earth. The ultrathin section contained about a dozen
framboidal magnetite particles with sizes ranging from 500-900 nm (Fig. 1A). The magnetic domain structures of theseparticles were observed by electron holography (HF-3300EH; Hitachi High-Tech Corp., Tokyo), and it was found that themagnetic domains of each particle had a concentric magnetic structure typical of submicrometer-sized magnetite particles (Fig.
1B) [5-8].
Ultrathin sections taken from neighboring locations of the same particles also contained flamboidal particles of 400-800
nm in diameter, similar to Fig. 1A (Fig. 1C). The scanning transmission electron microscopy–energy-dispersive X-ray
spectrometry analysis of this particle confirmed that it was iron oxide, consistent with magnetite, but electron holography
showed no magnetic domain structure. This suggests that the particle is a nonmagnetic mineral and not magnetite. We
analyzed the bonding state of iron and oxygen using electron energy loss spectroscopy and found that this nonmagnetic particle
exhibited characteristics of both magnetite and wüstite in terms of the bonding state of iron and oxygen. We named suchparticles that exhibit both features of magnetite and wüstite, and do not show a magnetic domain structure "pseudo-magnetite".
Around the pseudo-magnetite particles, there was a decrease in signal intensity of various light elements in the region of
about 2 μm below the surface. In addition, the elemental mapping of iron shows many small iron particles that may have

been released or diffused from the pseudo-magnetite (Fig. 1E). More than 100 metallic iron particles of 30-400 nm were
easily counted in an alteration region 2 µm deep, 10 µm long, and 0.1 µm thick from the surface. Assuming that thisreduction is due to a micrometeoroid impact and that a 10-μm diameter region is altered to a depth of 2 μm in a single impact,
the total number of iron particles produced would be ~104, which could acquire remanent magnetization during an event
involving the formation of iron nanoparticles by a micrometeoroid impact. Therefore, the iron particle precipitation
associated with a micrometeoroid impact could play an important role as the remanence acquisition event.
Micrometeoroid impacts are thought to have occurred frequently within protoplanetary disks. However, the traces left
behind by these impacts are found only on the topmost surfaces of asteroids, so previous studies using meteorites have had
limited opportunities to study these traces. Even if a meteorite fell to Earth leaving behind pseudo-magnetite and ironparticles, these particles would be oxidized by weathering on the ground afterward. In addition to the samples obtained by
the Hayabusa2 spacecraft, the samples brought back from the asteroid Bennu by OSIRIS-REx will also have a chance to beanalyzed. In this process, it is necessary to avoid changes in remanent magnetization due to oxidation of pseudo-magnetiteand metallic iron nanoparticles. Although pseudomagnetite may represent only a small percentage of total magnetite, itspresence should be considered when analyzing extraterrestrial samples recovered from an asteroid surface. In ourpresentation, the event and timing of the micrometeorite impact and other suspect magnetite particles will be discussed.

Figure 1. Framboids with and without magnetic domain structures characteristic to magnetite. A and B. Bright field
TEM and the corresponding magnetic-flux-distribution images, respectively, of framboidal magnetite particles in a thin section
prepared from the A0064–FO007 sample of asteroid Ryugu. C. Bright field TEM image of pseudo-magnetite particles in a thinsection prepared from neighboring region of A. D. Magnetic-flux-distribution image, corresponding to the box d in C,
observed by electron holography. E. Elemental mapping of iron corresponding to the box e in C.
The authors thank the Ministry of Education, Culture, Sports, Science and Technology (MEXT) (grants
JPMXS0450200421, JPMXS0450200521) for financial support and JEOL for providing access to the tabletop SEM (JCM7000, NeoScope). We thank the developers of iSALE, including G. Collins, K. Wünnemann, B. Ivanov, J. Melosh, and D.
Elbeshausen. We also thank Tom Davison for the development of pySALEPlot.
References[1] Noguchi T. et al. 2011. Science 333:1121. [2] Noguchi T. et al. 2023. Nat. Astron. 7:170. [3] Nakamura T. et al. 2022.
Science 379: eabn8671. [4] Kimura Y. et al. 2023 Scientific Reports 13:14096. [5] Kimura Y. et al. 2013. Nat. Commun.
4:2649. [6] Almeida T. P. et al. 2014. Nat. Commun. 5:5154. [7] Almeida T. P. et al. Geophys. Res. Lett. 41:7041. [8]Kimura Y., Yamamoto K. & Wakita S. 2021. Astrophys. J. Lett. 917:L5.

Characterization Of Early Solar System Aqueous Fluids In Ryugu Samples
Michael Zolensky1, Robert Bodnar2, Andrei Dolocan3, JangMi Han4, Romy Hanna3, Iona Gearba3, Queenie Chan5,
Trevor Ireland6, Megumi Matsumoto7, Akira Tsuchiyama8.
1NASA JSC, Houston, TX 77058, USA (michael.e.zolensky@nasa.gov); 2Virginia Tech, Blacksburg VA 24060,
USA;3Univ. of Texas, Austin TX 78712, USA; 4University of Houston, Houston TX 77204, USA; 5Royal Holloway
University, Egham Hill, Egham TW20 0EX, UK; 6University of Queensland, St Lucia 4072, Queensland, Australia;
7
Tohoku University, Aoba-ku, Sendai, Miyagi, Japan; 8Ritsumeikan Univ., Kusatsu, Shiga, 525-8577, Japan
Introduction: The most direct and convincing evidence for the presence of water and organic molecules on
protoplanetary bodies is provided by fluid inclusions trapped in secondary minerals. Our previous research has
demonstrated that early solar system fluids have survived as fluid inclusions in a few astromaterials that escaped
significant shock, terrestrial alteration, and invasive sample handling [1-3]. We hypothesize that the bulk molecularand isotopic composition of individual fluid inclusions can be measured to provide ground truth for exploring andthermochemical modeling of the compositional and isotopic evolution of fluids in protoplanetary bodies including
asteroids, comets and icy moons.
This presentation is an update on our efforts to make measurements of elemental, molecular and isotopic
compositions of individual aqueous fluid inclusions in Ryugu samples.
Facilities: For the following XRCT and TOF-SIMS analysis, samples were prepared using the FEI Quanta 3D 600
Dual-beam Focused Ion Beam in the ARES -NASA-JSC Electron Beam Instrument Facility. For the X-ray Computed
Tomography (XRCT) scans we used the Zeiss 620 XRM instrument at the University of Texas High-Resolution Xray Computed Tomography Facility. For the Time of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS)
measurements we used the University of Texas Materials Institute’s TOF-SIMS 5 and TOF-SIMS 6 instruments (IONTOF GmbH) equipped with a pulsed Bi+ analysis ion beam (30 keV ion energy) and a O2+ sputtering ion beam (1 kV
ion energy). The TOF-SIMS instruments are capable of cooling the samples to -160 and -180C, respectively, andwithout this capability our measurements would be impossible.
Aqueous Fluids: Studies of aqueous alteration in primitive meteorites, based solely on secondary mineral
associations, have hinted that this process did not occur under a single set of conditions [4]. The temperatures ofalteration that have been suggested are highly variable, from below 0 to ~250°C. The fluid compositions must have
likewise varied, though this critical aspect is very poorly understood. Our previous molecular, O and H isotopic
measurements of fluids in halite in the Monahans and Zag meteorites [2,5] have shown considerable variation in fluid
composition even within individual crystals. For example, we suspect that early solar system aqueous fluids could
alternate between being S-rich and S-poor, based on the alternating pyrrhotite-magnetite alteration assemblage
observed in the Tagish Lake and Sutter’s Mill chondrites [6]. We know from our previous studies of aqueous fluidinclusions in extraterrestrial halite and calcite in the Sutter’s Mill C2 chondrite that the mineralizing fluids also
contained a significant concentration of mineralizing cations such as Fe, Mg, Ca, and volatiles such as CO 2 and Sbearing compounds in variable abundances (though the abundances are not yet determined) [2,7]. We observed CN-,a molecular fragment of a larger nitrogenous compound, in the aqueous fluid inclusions in a Ryugu pyrrhotite crystal[1-3]. Nakamura et al. [3] reported that the earliest formed phyllosilicates in Ryugu were rich in Na, indicating
significant compositional changes in the mineralizing fluid.
Ryugu Fluid Inclusion Measurements: Our recent successful, coordinated, XRCT and TOF-SIMS analyses ofindividual fluid inclusions in a Ryugu pyrrhotite crystal demonstrated that they consist of water, CO2, sulfur species,
and organic material, with H-, C-, O-, S- and OH- as the main fragments detected at these locations [1,3]. In addition,
various amounts of F-, Cl- and Ni- were found, together with Na+, Mg+, Al+, Cr+, K+ and Ca+. Larger organic fragments
such as C2-, C2H-, C3-, CO- and CN- were also detected, indicating the presence in these inclusions of more complex
organic molecules containing H, C, N and O. We can expect to see these and additional molecular fragments in other
Ryugu fluid inclusions. TOF-SIMS breaks apart molecules - it does not make new ones. Therefore, all these identified
species are fragments of once larger molecules which we can identify to some degree.
Measurement of the stable isotopic compositions of aqueous fluid inclusions in Ryugu samples will enable a
comparison with our measurements of a few fluid inclusions in carbonaceous chondrites (e.g. [7]), and fluids
calculated to have reacted with other primitive samples (CI chondrites, OCs, HEDs, ureilites) which have δD ranging
from ~0-3000‰. Actual direct measurements of preserved trapped fluids would thus inform us about fluid changes
during aqueous alteration in a large suite of primitive bodies. Russell et al. [8] has suggested that CI materials form

two groups with distinct water/rock ratios, temperature ranges, and hydrogen isotope compositions. Are these truly
distinct groups or do these just represent endmembers of a poorly sampled complete range (as also suggested byRussell et al., [8])? Our planned analyses of individual fluid inclusion oxygen and hydrogen isotope compositions in
Ryugu samples will settle this issue as we will either observe narrow compositions or a compositional continuum.
Polished Ryugu sample C00025 contains large sulfides, magnesite, magnetite and dolomite crystals (Fig 1). We
have already FIBed several foils from this sample and subjected one of the FIB foils to TOF-SIMS measurements.
We detected no filled fluid inclusions, however we were limited to analyzing inclusions larger than about 3 μm using
the M5 TOF-SIMS instrument, and it appears the inclusions were far smaller (Fig.1). We plan to repeat themeasurements of this sample using the newly-installed M6 TOF-SIMS, which has greatly expanded capabilities. We
made XRCT scans of two additional Ryugu grains (A0175 and C0043) (Fig 2). From these preliminary measurements
we know that A0175 contains numerous pyrrhotite, carbonate, and, probably, apatite crystals with fluid inclusion
candidates measuring at least 3-5 µm in diameter, which will permit our planned TOF-SIMS measurements.
The TOF-SIMS analytical data are counts under the peaks for each species. An example of the data is shown in
Figure 3, which shows counts for OH- (indicative of H2O) and C- (here indicative of CO2). This sample was a synthetic
fluid inclusion standard (quartz) prepared by Bob Bodnar where the inclusions contained a 1:1 mixture of H 2O and
CO2. As you can see from the included table, despite the fact that the sensitivity of the technique for CO 2 was much
lower than for H2O, 4/5 of the inclusions showed consistent counts for these species, meaning that with continued
calibration we can produce quantitative composition measurements for some species. We note that the signals for CO2
we observed in the Ryugu pyrrhotite crystal were more pronounced than those we obtained using the 50:50 standard,suggesting a very high abundance of CO2 in the Ryugu mineralizing fluid. In fact, solid CO2 sublimed rapidly in a
vacuum at our measurement temperature, making quantification very difficult.
In the coming year we will begin isotopic measurements of standards in synthetic fluid inclusions and Ryugu
pyrrhotites and carbonates we have already identified, as well as increasing our stock of pre-analyzed Ryugu crystals.
Fig. 1. Magnesite in Ryugu sample C00025 (left) BSE image ofMagnesite showing FIB pits. (right) SEI image FIB A foil
showing submicron-sized fluid inclusion candidates circled.
Acknowledgements: We thank JAXA for Ryugu samples, andthe NASA Hayabusa2 Participating Scientist Program.
References: [1] Zolensky et al. (2022) 85th Meeting of The
Meteoritical Society. Abstract 6011; [2] Bodnar et al. (2019) 50th
LPSC Abstracts; [3] Nakamura et al. (2022) Science 377,
10.1126/science.abn8671; [4] Brearley (2005) In Meteorites andthe Early Solar System II. D. S. Lauretta and H. Y. McSween Jr.,
Eds.; [5] Yurimoto et al. (2014) Geochemical Journal 48, 1-12;[6] Zolensky et al. (2014) MAPS 49, 1997-2016; [7] Tsuchiyama
et al. (2021) Science Advances 7, eabg9707; [8] Russell et al.
(2022) MAPS 57, 277–301.
(Left) Fig. 2. XRCT “slices” of
Ryugu sample A0175. Fluid
inclusion candidates are arrowed.
(a-e) Pyrrhotite crystals. (f-g)
Probable carbonates. (h) Possible
apatite crystal.
(Right) Fig. 3. Results of TOFSIMS measurements of synthetic
fluid inclusion standard (quartz),with inclusions that contain a 1:1
mixture of H2O and CO2. Inclusions are numbered to match thetable (e.g. ROl1=1). Counts = cts.

Three-dimensional description and characterization of lithologies in Ryugu sampleLéna Jossé1 , Zélia Dionnet1 , Alice Aléon-Toppani1 , Rosario Brunetto1 , Andrew King2 , Emmanuel Gardés3 , Eva Heripré4 ,Donia Baklouti1 , Zahia Djouadi1 , Cateline Lantz1 and Kentaro Hatakeda5
1
CNRS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, Orsay, France
2
SOLEIL Synchrotron, Gif-sur-Yvette, France
3
Laboratoire Magmas et Volcans, Clermont-Ferrand, France
4
Procédés et Ingénierie en Mécanique et Matériaux, Paris, France
5
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA), Japan

Ryugu is a rubble-pile asteroid. Similarly to CI chondrites, the samples returned by Hayabusa2 mission showed the presenceof adjoining fragments of different lithologies [1, 2]. These fragments are different in mineralogy, petrology, physical structure(size, porosity) and testify the heterogeneity of Ryugu’s asteroid, its complex geological history and evolution [3]. So far, several
lithologies have been observed and described partly in polished sections [1, 2, 3]. In this work we used micro-computed tomography (µ-XCT) to observe, analyze and investigate lithologies in 3D. We analyzed their properties (internal structure, shape, size,
composition, porosity) and their assemblages with each other in a Ryugu millimeter-sized sample with the objective to better
understand Ryugu’s heterogeneity and its complexity in term of formation and evolution.
We studied the 3D lithologies of the mm-sized (1.45×2.85×2.1 mm) sample A0159 from Chamber A. Data were obtainedat PSYCHÉ beam-line of Synchrotron SOLEIL (France) using a monochromatic X-ray beam operating at 25 keV. Our analysis
was conducted on 3D reconstructed images (CT-images, or “slices”) with a voxel volume of 1.295 µm3 and based on the linear
attenuation coefficient (LAC). As a first method of data processing, we used pixel segmentation, which classifies each voxel
into 5 major domains by its LAC value. The domains are, sorted by increasing LAC, 1-porosity, voids, fractures, 2-matrix,
3-carbonates, 4-sulfides and oxides. Some LAC values were difficult to associate with a specific domain so we classified themas 5-uncharacterized. This method allows us to obtain the proportion of each component within each slice and then in the entire
sampl5, but also the 3D reconstruction of each component.
Contrary to the first method, the local histogram segmentation considers areas of 49×49 voxels. For each area, the calculated
histogram of the proportion of pixels for a given LAC value gives access to i) the number of pixels for each of the 5 previously
cited domain and ii) the LAC histogram data distribution. Then, each area was locally described in regard to composition andphysical properties giving rise to lithologies. This method allowed us to obtain a 3D reconstruction of each lithology in thesample. Tomviz software was used for 3D representation and visualization.
Our preliminary results from the pixel segmentation
method showed that, on average, A0159 is made of 42.0±7.0 %of matrix component, 1.2±0.5 % of sulfides and oxides,
4.7±2.8 % of porosity, voids and/or fractures and 27.5±4.7 %of uncharacterized material (undefined components, or technique artifacts). Finally, carbonate components represents
24.1±2.5 % of the sample, a much higher value than previous studies [4]. The 3D reconstruction of carbonates shows
a mm-sized vein going through A0159 (fig. 1), indicating important fluid circulation. The vein is about 1100×900×100 µm
and it is the largest vein observed so far in a Ryugu sample.
Its presence explains the high proportion of carbonate materialin A0159. We detected two highly fractured plans along bothsides of the vein. The vein ends up with coarse and elongatedto rounded carbonate grains with inter-grains voids. In otherstudies, a complex and elongated structure of size >100 µm
was observed in sample C0041 and found to have a wide rangeof (Mg-Fe)-carbonate composition between siderite–magnesite(or breunnerite) [5, 6]. In sample C0009, [3] found elongatedCa-carbonates forming a chain that they proposed to be a potential remnant of a vein. The detection of a mm-sized vein in

A0159 suggests that Ryugu’s parent-body has probably undergone notable water flow through, at least, a mm-sized fracture
and that carbonate precipitated as a vein.

Figure 1: 3D reconstruction of the Ryugu sample A0159 (in grey)
combined with the distribution of carbonates (in yellow).

The preliminary results of the second method allowed us to detect several different lithologies. A study is ongoing todetermine the exact number of lithologies. These lithologies are mostly composed of matrix with various size and proportionof carbonates, sulfides, oxides, and porosity. One peculiar lithology is made of a compact matrix component, few carbonates,
uncharacterized material, sulfides and oxides. This lithology could match the ”massive domain” seen by [1] in A0035 or the”fine-grained dark lithology” in C0009 by [3]. The compact lithology is surrounded by long (up to 800 µm) and large fractures(up to 20 µm) and, similarly to [1], some fractures also cross the lithology. Another lithology is rich in rounded and elongatedgrains of carbonates about 50 µm in size and is located at the end of the vein. This lithology has many small fractures (up to
100 µm long and 10 µm large) which seem to be preferably located around the grains such as in A0037 [3]. However, crossing
and surrounding fractures are not present in each lithology. The second method is still ongoing and it is not clear yet whether
the carbonate vein crosses a single lithology. However, our preliminary results confirm that Ryugu is a breccia with adjoining
fragments of various size (from 100 to 500 µm), composition and physical properties. The analysis of the fractures (distribution,
size and shape) strongly indicates a heterogeneity in the mechanical properties of lithologies. All these observations testify thecomplexity of Ryugu and/or parent-body formation and evolution and its geological past.

References[1] E. Nakamura, K. Kobayashi, R. Tanaka, T. Kunihiro, H. Kitagawa, C. Potiszil, T. Ota, C. Sakaguchi, M. Yamanaka, D. M.
Ratnayake, et al., “On the origin and evolution of the asteroid ryugu: A comprehensive geochemical perspective,” Proceedings of the Japan Academy, Series B, vol. 98, no. 6, pp. 227–282, 2022.
[2] T. Nakamura, M. Matsumoto, K. Amano, Y. Enokido, M. Zolensky, T. Mikouchi, H. Genda, S. Tanaka, M. Zolotov,
K. Kurosawa, et al., “Formation and evolution of carbonaceous asteroid ryugu: Direct evidence from returned samples,”Science, p. eabn8671, 2022.
[3] A. Yamaguchi, N. Tomioka, M. Ito, N. Shirai, M. Kimura, R. C. Greenwood, M.-C. Liu, K. A. McCain, N. Matsuda,
M. Uesugi, et al., “Insight into multi-step geological evolution of c-type asteroids from ryugu particles,” Nature Astronomy, vol. 7, no. 4, pp. 398–405, 2023.
[4] C. Pilorget, T. Okada, V. Hamm, R. Brunetto, T. Yada, D. Loizeau, L. Riu, T. Usui, A. Moussi-Soffys, K. Hatakeda, et al.,“First compositional analysis of ryugu samples by the micromega hyperspectral microscope,” Nature Astronomy, vol. 6,
no. 2, pp. 221–225, 2022.
[5] D. Loizeau, C. Pilorget, L. Riu, R. Brunetto, J.-P. Bibring, A. Nakato, A. Aléon-Toppani, K. Hatakeda, K. Yogata, J. Carter,
et al., “Constraints on solar system early evolution by micromega analysis of ryugu carbonates,” Nature Astronomy, pp. 1–
7, 2023.
[6] A. Nakato, T. Yada, M. Nishimura, K. Yogata, A. Miyazaki, K. Nagashima, K. Hatakeda, K. Kumagai, Y. Hitomi, H. Soejima, et al., “Variations of the surface characteristics of ryugu returned samples,” Earth, Planets and Space, vol. 75, no. 1,
p. 45, 2023.

Size distribution and elemental compositions of anhydrous minerals in the Ryugu samples C0224 andC0260: Implications for radial transport mechanism and source regions of anhydrous minerals
D. Nakashima1, M. Matsumoto1, H. Yoshida2, T. Mikouchi2, T. Nakamura1
1
Tohoku University, Japan (dnaka@tohoku.ac.jp), 2University of Tokyo, Japan.
Introduction: Samples returned from C-type asteroid Ryugu by the Hayabusa2 spacecraft are mineralogically and chemicallysimilar to CI chondrites [1-4]. It was suggested from the initial analysis of the Ryugu samples that the Ryugu original parent bodyformed beyond the H2O and CO2 snow lines (> 3 – 4 au) in the solar nebula at 1.8 – 2.9 Myr after CAI formation [1]. Nakashima etal. [5] reported elemental compositions and oxygen isotope ratios of chondrule-like objects and Ca-Al-rich inclusions (CAIs) in the
Ryugu samples. The objects (< 30 µm) are as small as those from comet Wild2, suggesting radial transport favoring smaller objects
from the inner solar nebula (solar neighborhood and chondrule formation regions) to the formation location of the Ryugu original
parent body, which is farther from the Sun and scarce in chondrules [5]. Besides chondrule-like objects and CAIs, anhydrous minerals such as olivine, pyroxene, spinel, and hibonite occur in the Ryugu samples and are much more abundant [1]. In the present
study, we measured size distribution of anhydrous minerals in the newly allocated Ryugu samples (C0224 and C0260) using FESEM and FE-EPMA to test the hypothesis of radial transport favoring smaller objects [5] and elemental compositions to elucidate
the source regions of individual anhydrous minerals.
Results: Synchrotron radiation X-ray computed tomography at SPring-8 showed that C0224 has a homogeneous lithology except for the presence of large carbonate crystals of few hundred µm in size and C0260 contains clasts with different lithologies.
Three hundred ten anhydrous minerals including chondrule-like objects were found in eight polished sections from C0260 (C026001, 02, and 03) and C0224 (C0224-01, 02, 03, 04, and 05), and most of them were from C0260. Polished sections of C0224 wererepolished multiple times but only 6 grains were observed. Most anhydrous minerals occur along with calcite, Ca phosphate, andNa-Mg phosphate in FeO-rich phyllosilicate regions, which is characteristic for lithology II clasts (less-altered clasts; [6]). Anhydrous minerals have angular shapes, so that diameters are calculated from surface areas of anhydrous minerals using ImageJ assuming they have spherical shapes. The largest one is 24 µm and smallest one is 0.5 µm. As shown in Fig. 1a, the peak of size distribution of anhydrous minerals including chondrule-like objects occurs at 2 – 3 µm. It should be noted that we counted anhydrous
minerals detected by FE-SEM mapping, and therefore there is counting loss of tiny minerals (<< 1 µm). Olivine is most abundantfollowed by spinel, pyroxene, and hibonite. Mg#’s of olivine are from 89.5 to 99.4, which is consistent with the initial analysis [1].
Low-iron manganese-enriched (LIME) olivine with MnO/FeO ratio (wt%) exceeding 1 [7] is observed. Pyroxene and hibonite
grains are too small to obtain precise compositions. Spinel contains variable amounts of Cr2O3 (0.21 – 4.0 wt%).
Six chondrule-like objects are observed (Fig. 1b). They have rounded shapes and mainly consist of FeO-poor olivine with Mg#from 92.0 to 99.2 along with diopside, rounded (oxidized) Fe-Ni metal, and altered phase. The chondrule-like objects are similar to
those found in the initial analysis [1,5].
Discussion: Most anhydrous minerals occur in less-altered clasts in the Ryugu samples [1, this study]. The clasts have protected anhydrous minerals from aqueous alteration and brecciation for ~ 4.6 Gyr, so that sizes of the anhydrous minerals reflect thoseduring accretion onto the Ryugu original parent body. Our new data (Fig. 1a) show that anhydrous minerals in the Ryugu samples(< 24 µm) are smaller than chondrules in chondrites (~ 500 µm; [8]) and isolated olivine in chondrites (> 20 µm; [9]), suggestingradial transport favoring smaller objects to the formation location of the Ryugu original parent body. There are two possible mechanisms for radial transport: a combination of advection and turbulent diffusion [10] and photophoresis [11]. Both mechanisms cantransport grains smaller than 30 µm. While the Ryugu original parent body formed at ~ 2 Myr after the CAI formation [1], photophoresis transports 10 µm grains beyond 10 au later than ~ 5 Myr after the CAI formation [11]. Considering the time window, acombination of advection and turbulent diffusion that transports ≤ 20 µm grains beyond 25 au within 1 Myr [10] would be more
likely for Ryugu. It will be more plausible by size distributions of anhydrous minerals in other Ryugu samples and CI chondrites.
Olivine in type I chondrules is more enriched in Cr2O3 and CaO than olivine in amoeboid olivine aggregates (AOAs) (Fig. 2a)[5]. 16O-rich chondrule-like objects, CAIs, and 16O-rich olivine in the Ryugu samples are distributed in the AOA area, while 16Opoor chondrule-like object and 16O-poor olivine are distributed in the type I chondrule area. The difference in the elemental compositions of olivine with different origins is explained by AOA olivine condensation from a residual gas depleted in the refractoryelements followed by isolation from the gas before condensation of Cr [5]. Olivine depleted in Cr2O3 and CaO may have formed

near the Sun, and olivine relatively enriched in the two elements may have formed in the chondrule formation regions. Thus, it ispossible to deduce the source regions of isolated olivine and chondrule-like objects based on the Cr2O3 and CaO concentrations.
Many of isolated olivine grains and olivine in chondrule-like objects in C0260 and C0224 distribute in the AOA area (Fig. 2b),which is consistent with the FE-EPMA analysis of olivine in CI chondrites [12]. The AOA-like olivine may have formed near theSun. It is considered from the high abundance of AOA-like olivine in the Ryugu samples and frequent occurrence of 16O-rich olivine in Wild2 particles [13] that olivine formed near the Sun were transported to the outer regions of the early solar nebula andsurvived due to lack of chondrule forming event that erases 16O-rich signature and original elemental compositions. On the contrary, isolated olivine in chondrites distributes in the type I chondrule area (Fig. 2c), and 16O-rich olivine is rare in chondrites [14]. It
is considered that 16O-rich olivine passed the chondrule formation regions and/or melted during chondrule forming events.
Nakashima et al. [5] reported that spinel in the Ryugu CAIs contain small amounts of Cr 2O3 with < 0.2 wt% and suggested that
the CAIs escaped from remelting event and may be as old as the oldest CAIs. Isolated spinel in C0260 show variable Cr 2O3 concentrations up to 4.0 wt%. Therefore, spinel that acquired Cr by remelting events are also present in the Ryugu samples. Considering the time window of accretion (within ~ 2 Myr after CAI formation; [1]), remelting events may have occurred during that period.
References: [1] Nakamura T. et al. (2022) Science 10.1126/science.abn8671. [2] Ito M. et al. (2022) Nat. Astron.
10.1038/s41550-022-01745-5. [3] Nakamura E. et al. (2022) Proc. Jpn. Acad. Ser. B 98:227. [4] Yokoyama T. et al. (2022) Science 10.1126/science.abn7850. [5] Nakashima D. et al. (2023) Nat. Commun. 14:532. [6] Mikouchi T. et al. (2022) LPSC LIII,#1935. [7] Klöck W. et al. (1989) Nature 339:126. [8] Friedrich J. M. et al. (2015) Chem. Erde 75:419. [9] Jacquet E. et al. (2021)
M&PS 56:13. [10] Hughes A.L.H. & Armitage P.J. (2010) ApJ 719:1633. [11] Moudens A. et al. (2011) A&A 531:A106. [12]Mikouchi T. et al. (2023) 86th Annual Meeting of The Meteoritical Society, #6178. [13] Nakashima D. et al. (2012) EPSL 357358:355. [14] Tenner T.J. et al. (2018) in Chondrules: Records of Protoplanetary Disk Processes 196. [15] Kurat G. et al. (1989)
Meteoritics 24:35. [16] Jones R. H. et al. (2000) M&PS 35:849. [17] Ushikubo T. et al. (2012) GCA 90:242. [18] Yamanobe M. etal. (2018) Polar Sci. 15:29. [19] Chaumard N. et al. (2021) GCA 299:199. [20] Jacquet E. et al. (2021) M&PS 56:13. [21] Ushikubo T. & Kimura M. (2021) GCA 293:328. [22] Weisberg M. K. et al. (2021) GCA 300:279.
1.2

80

0.6

● C0002-P5-C1-Chd
1■ C0002-P5-C2-Chd▲ C0040-02-Chd〇 Type I chondrules
0.8〇 AOAs◎ 16O-rich chondrule (a006)● 16O-rich olivine (Lit.)○ 16O-poor olivine (Lit.) 0.6

0.4

0.4

0.2

0.2

1

(a)

(b) C0260-02-Chd2
0.8

Ol

Cr2O3 (wt%)

Number

60

40

1.2

(a) Fig. 4 in [5]1.200 (c)0.2
0.4olivine
0.6in chondrites
0.81
Isolated(b) Isolated olivine & olivine inchondrule-like objects in C0224 &C0260
Isolated olivine■ C0260-01-Chd1◆ C0260-01-Chd2▲ C0260-02-Chd1▼ C0260-02-Chd2
C0260-03-Chd1
C0260-03-Chd2

0
1.2
0

0.2

0.4

0.6

0.8

1

1.2

1
0.8
0.6

Diop

20

1um

0.4
0.2

0
0

0
0

5

10

15

20

25

30

Diameter (µm)
Fig. 1: Size distribution of anhydrous minerals including chondrulelike objects in C0224 and C0260 (a) and backscattered electron imageof the chondrule-like object C0260-02-Chd2 (b). Ol, olivine; Diop,
diopside.

0.2

0.4

0.6

0.8

1

1.2

CaO (wt%)
Fig. 2: Comparison of concentrations between Cr2O3 and CaO inolivine in chondrule-like objects, type I chondrules, AOAs, 16O-richand -poor chondrules (a), isolated olivine and olivine in chondrulelike objects in C0224 and C0260 (b), and isolated olivine in chondrites (c). The panel a is from Nakashima et al. [5]. Olivine data inthe panel c are from [15-22].

Microstructural and microchemical characteristics of dolomite in Ryugu regolith particles
Falko Langenhorst1,2, Kilian Pollok1, Tomoki Nakamura3, Tomoyo Morita3, Kana Amano3, Daisuke Nakashima3
and the Hayabusa2 initial analysis core team1
Institute of Geoscience, Friedrich Schiller University Jena, Germany
2
Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Manoa, USA
3
Tohoku University, Sendai, Japan.
Introduction. Previous studies of Ryugu material have reported that the regolith particles record extensive aqueous alteration
as the result of water activity in the original parent body [1,2]. The aqueous alteration finally resulted in the almost complete
overprint of the primary mineralogical composition and the precipitation of secondary minerals, i.e. phyllosilicates, carbonates,
phosphates, sulfides, and oxides. The isotopic 18O/16O and 13C/12C signatures of carbonates were recently studied in great detailto obtain information on the conditions of aqueous alteration [3]. Here, we focus on the characterization of the defectmicrostructures and nanoscale element distributions in dolomite of Ryugu samples to obtain further insights into the formation
history and mechanisms of carbonates.
Samples and methods. In the context of the Hayabusa2 initial analysis phase, we have mainly studied polished sections
prepared from larger particles recovered in the C chamber, i.e. C0033-01 and C0033-04, and C0055-01 [detailed in 1]. Elevenslices of carbonate-bearing regions were cut from the thin sections by focused ion beam (FIB) preparation on a scanningelectron microscope (SEM). Subsequent analytical transmission electron microscopy (TEM) were performed according to theprocedure described by [4].
Results and discussion. TEM observations reveal numerous curled dislocations as the most dominant lattice defect in almost
all dolomite grains. This shape of dislocation lines indicate that dislocations are not in glide configuration and thus may havebeen incorporated during imperfect growth from the aqueous fluid. In the vicinity of fractures, sample C0055-01 contains alsostraight glissile dislocations, which were previously assigned to mild shock [5]. Deformation twins, which are generally
regarded as typical for shock-metamorphosed carbonates, are however absent in C0055-01. An explanation for their absence
could be that deformation twinning in dolomite requires enhanced temperatures [6], which do not prevail during low shock
metamorphism [6].
Mapping of elemental distributions in scanning mode using energy-dispersive X-ray emission spectroscopy show complex andvariable zoning of dolomite grains. Many grains show sharp, non-concentric, up to 1 µm thin rims with a significant
enrichment in manganese (up to 8 wt% MnO). This observation points, at least, to a second precipitation event, when the fluid
became apparently enriched in manganese. A preferential mobilization of manganese might be explained by a (localized)change in the reduction potential. In addition, manganese-enriched dolomites with continuously decreasing manganeseconcentration from core to rim exist and monitor a gradual change in the fluid chemistry controlled by carbonate growth.
Most interesting is the observation of nanoscale modulations in the rims of dolomite. Such microstructures have also been
observed in sedimentary calcian dolomites and are interpreted as growth microstructures [7]. The modulations appear as
almost parallel lamellae with regular alternating light and dark contrast, resembling microstructures known for spinodal
decomposition. A periodical variation of the fluid composition at the mineral-solution interface during progressing growth is a
plausible explanation for this microchemical peculiarity [8].
Acknowledgements. We thank JAXA for providing access to the Ryugu particles. FIB-TEM facilities at FSU Jena were
funded by the Gottfried-Wilhelm-Leibniz award to FL (LA 830/14-1).
References[1] Nakamura T. et al. 2023 Science 379:eabn8671. [2] Nakamura E. et al. 2022 Proc. Jpn. Acad. Ser. B:227-282. [3] Fujiya W.
et al. 2023 Nature Geoscience 16:675-682. [4] Langenhorst F., et al. 2014 Earth Planets and Space 66:118. [5] Kikuiri M. et al.
2022 85th Annual Meeting of The Meteoritical Society:No. 2695. [6] Barber D.J. and Wenk H.R. 1979 Physics Chemistry
Minerals 5:141-165. [7] Reeder R.J. 1992 In: P. Buseck (editor), Reviews in Mineralogy 27:381-424. [8] Ruiz-Agudo E. andPutnis C.V. 2012 Mineralogical Magazine 76:227-253.

Investigating the ammonium-bearing phase in Ryugu samples
M. Ferrari1, L. Folco2, S. De Angelis1, M. Masotta2, A. Raponi1, M.C. De Sanctis1, E. Mugnaioli2,
R. Borriello2, M. Ciarniello1, E. Ammannito3, E. La Francesca1, L. Rossi1, M. Pedone3.
1
INAF-IAPS, Via del Fosso del Cavaliere 100, 00133, Rome, Italy (marco.ferrari@inaf.it); 2Dep. Earth Science, University of
Pisa, Via Santa Maria, 53, 56126, Pisa, Italy; 3ASI, Via del Politecnico, 00133, Rome, Italy.
Introduction
The JAXA/Hayabusa2 mission collected 5.4 g of samples from two different sites (i.e., A and C) on the surface of the C-type
asteroid (162173) Ryugu [1; 2]. This asteroid is characterized by a low albedo and by the presence of hydrous andcarbonaceous materials [3]. The Ryugu surface spectra collected by the Hayabusa2/NIRS 3 spectrometer reveal a narrowabsorption feature at 2.72 μm [4] resembling that observed on the surface of Ceres by the Dawn/VIR spectrometer [5; 6].
Laboratory analysis of returned grains confirmed that Ryugu samples contain hydrated silicates, sulfides, oxides, carbonates,and organics and have spectroscopic similarities to CI chondrites [7]. MicrOmega hyperspectral microscope observation [8]revealed the presence of a band at 3.06 μm, indicating the possible presence of NH-bearing phases in most of the returned
grains [9]. This ammonium-related absorption feature was confirmed by FTIR measurements [10]. The 3.06 μm band was also
observed in the spectra of Ceres by telescopic observations [11] and by the Dawn/VIR spectrometer that accurately
characterized its distribution on the dwarf planet's surface [12]. Current interpretations of Ceres spectra suggest that the most
likely mineralogical phases hosting ammonium are phyllosilicates [13; 14], but the presence of ammonium salts has also beeninferred in specific areas of the Cerean surface [15; 16]. Hydrated silicates represent the main reservoir of water in Ryugu
samples, and their presence is indicative of extensive aqueous alteration in the parent body, likely the alteration path that
occurred on Ceres. Even if phyllosilicates are the most likely carriers, the specific ammonium-bearing phase determining the3.06 μm band on Ryugu samples and the surface of Ceres is not fully constrained, nor are the processes that led to ammonium
enrichment on these C-type bodies.
Sample selection
Our selection criterion of the samples among those available in the first allocation (2022A) was the presence of the absorption
band at 3.06 µm as observed in the spectroscopic data obtained from the preliminary screening by FTIR and MicrOmega. We
have considered: 1. Similarities of the 3.06 µm absorption between Ryugu samples and Ceres spectra, in terms of wavelength
range and band center position; 2. The presence of surface features or morphological structures suggests some mineralogicaldiversity.
Through the first allocation, we obtained two samples: A0198 and C0091. The preliminary FTIR data provided by JAXA
collected on particle C0091 show the presence of a remarkable absorption close to 3.06 μm. On the contrary, the spectroscopic
data collected on particle A0198 show a shallow absorption ascribed to the presence of ammonium and several surface featuresthat comply with our scientific requirements. Moreover, the two assigned samples were collected at different sites which willallow us to make further considerations.
Objectives and research plan
With this work, we aim to contribute to the definition of the physical and mineralogical characteristics of the Ryugu asteroid tounderstand the initial stages of formation and evolution of C-type bodies; particular attention will be given to the identificationof the ammonium-bearing phase(s) and its/their interplay with hydrated silicates. In addition, we aim to define Ryugu's path ofalteration and its similarities with Ceres.
The following laboratory analyses will be used to characterize the samples:•VIS-IR imaging spectroscopy (0.4-5 μm) will be carried out with the SPectral IMager (SPIM) facility [17] on whole samples.
Data will allow a first characterization of the mineralogic composition of their external surface, including an assessment of thepresence of water, organic matter, and ammonium in addition to the minerals. Furthermore, by using the SPIM facility (i.e., theDawn/VIR replica), we can perform a compelling comparison between the data collected on the samples with those provided
by the Dawn/VIR spectrometer on Ceres;•X-ray microscopy (XRM). This non-destructive technique has been used to obtain a high-resolution (submicron scale) 3D
tomography of the samples, revealing their internal structure (including pore structure and fracturing), as well as themorphology and composition of the individual grains contained in them; XRM data will also enable the location of regions ofinterest (ROIs) within the samples to be analyzed by transmission electron microscopy (TEM);

•Raman µ-spectroscopy, to obtain compositional maps of the surface of the samples at the micro-metric scale;•Focused ion beam-field emission gun-scanning electron microscopy (FIB-FEG-SEM) will be used to identify the mainmineralogical phases and to extract the electron-transparent lamellae for TEM analyses;•Transmission Electron Microscopy (TEM), electron diffraction, and energy-dispersive X-ray spectroscopy (EDS) will be used
to identify cryptocrystalline mineral phases and crystal defects through high-resolution techniques.
Results
The VIS-NIR spectra obtained with the SPIM facility on the surface of the two particles show the almost ubiquitous presenceof a deep V-band centered at lengths slightly above 2.7 μm, and absorptions near 3.4 μm and in the range 3.7-3.9 μm, however,limited at specific points on the surface returning an inhomogeneous surface composition at the scale of ~40 µm (SPIM pixelsize). These absorption features can be related to the presence of phyllosilicates and carbonates, respectively.
In addition, at some specific points, the band at 3.06 μm is found indicating the presence of ammonium-bearing compounds.
The Raman spectra acquired on the two particles are characterized by a high fluorescence background and by the presence of
the Raman D and G-bands related to the presence of poorly ordered carbonaceous matter. The spectral parameters derived
from the mathematical fitting of the acquired spectra as band positions, and band intensity ratio do not differ significantly
between the two particles. Raman analysis identifies dolomite as the most common carbonate on both particles.
The interpretation of spectral data acquired by both particles is currently in progress. However, at the moment there do notappear to be notable differences in spectral terms (VIS-NIR and Raman) between the two particles coming from the twodifferent sampling sites.
The two samples (A0198 and C0091) are characterized by a generally similar composition in terms of phase abundance andcomposition. Energy Dispersive X-ray spectroscopic (EDX) data obtained using the FE-SEM confirmed the presence of
hydrated silicates, sulfides (Ni-rich and Fe-rich), carbonates, fosfates, and oxides (mainly magnetite). Sulfides form
dominantly euhedral grains (up to 5 µm in size), whereas oxides form submicrometric framboid, platy, or columnar structures.
The internal distribution of silicates, sulfides, and oxide in the interior of the two samples, as revealed by XRM data, is rather
homogeneous. Notably, sample C0091 displays a slightly smaller grain size and a slightly higher porosity compared to particle
A0198.
Conclusions
The notable similarities of the spectra of some Ryugu samples with Ceres' average spectrum [18] sparked scientific curiosity.
To date, interpretation of remotely sensed data coupled with spectroscopic investigation of analogs has not enabled a fullunderstanding of the mechanisms of ammonium enrichment and the nature of the mineral assemblage hosting ammonium on
the surface of C-type objects. Furthermore, studies on meteorites have not provided morphological and compositional
information on the mineral phases that preceded the alteration of their progenitor body.
Therefore, we consider that spectroscopic measurements and nanoscale mineralogical investigations that we are conducting on
the samples returned from Ryugu represent a unique opportunity to definitively establish the link, if any, between ammonium
and the mineralogy of this type of object.
References[1]Yada, T. et al. (2021) Nat. Astron.; [2] Watanabe, S. et al. (2019) Science; [3] Kitazato, K. et al. (2019) Science; [4]Kitazato, K. et al. (2021) Nat. Astron.; [5] De Sanctis, M.C. et al. (2011) Space Sci. Rev.; [6] De Sanctis, M.C. et al. (2015)
Nature; [7] Tachibana, S. et al. (2022) 53rd LPSC, #1265; [8] Bi-bring, J.-P. et al. (2017) Astrobiology; [9] Pilorget, C. et al.
(2022) Nat. Astron.; [10] Kebukawa, Y. et al. (2022) 53rd LPSC, #1271; [11] King, T.V. et al. (1992) Science; [12]Ammannito, E. et al. (2016) Science; [13] Ferrari, M. et al. (2019) Icarus; [14] De Angelis, S. et al. (2021) J. Geophys. Res.
Planets; [15] De Sanctis, M.C. et al. (2016) Nature; [16] Raponi, A. et al. (2019) Icarus. [17] Coradini, A. et al. (2011) EPSCDPS Joint meeting, #1043. [18] Raponi, A. et al. (2021) Life.

Speciation of various elements using scanning transmission/fluorescnece X-ray microscopy(STXM/SFXM) and bulk XANES analysis related to aqueous environment
in the Ryugu parent body
Takahiro Kawai1, Keisuke Fukushi2, Hiroki Suga3, Masayuki Uesugi3, Shohei Yamashita4, Ryoichi Nakada5, Mizuho Koike6,
Hideto Yoshida1, Masaki Ohura7, Megumi Matsumoto8, Tomoki Nakamura8, Yasuhito Sekine,9 and Yoshio Takahashi1*(*Presenting author)
1
Department of Earth and Planetary Science, Graduate School of Sceince, The University of Tokyo, 2Institute of Nature andEnvironmental Technology, Kanazawa University, 3Japan Synchrotron Radiation Research Institute (JASRI), 4photon Factory,
Institute of Materials Structure Science, High-Energy Accelerator Research Organization (PF, IMSS, KEK), 5Kochi Institutefor Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 6Department of Earth andPlanetary Systems Science, Hiroshima University, 7RIKEN SPring-8 Center, 8Dept. of Earth Sciences, Tohoku University,
9
Earth-Life Science Institute, Tokyo Institute of Technology
The parent body of the C-type asteroid Ryuguu is thought to have been rich in volatile elements and abundant in liquidwater, making it an important research target for the origin of water and organic matter on Earth. The water caused various
alteration in the surrounding minerals, resulting in layered silicates such as smectite (saponite) and serpentinite being the main
constituent minerals of the Ryugu (Nakamura et al., 2023). In this process, the organic matter of the Ryuguu parent body also
underwent chemical reactions and a wide variety of organic matter was synthesised (Naraoka et al., 2023). It is particularly
important to obtain information on the water environment during the aqueous alteration, as the products of chemical reactionsof organic matter in water depend on the pH and redox potential (Eh) of the water. In this study, speciation of various elements
including iron (Fe), magnesium (Mg), calcium (Ca), and carbon (C) was investigated using scanning transmission X-ray
microscopy (STXM) and bulk X-ray absorption near-edge structure (XANES) analysis in the soft X-ray region related to theaqueous environment in the Ryugu parent body. For the elements with conentrations below the detection limit of STXM,
scanning fluorescnece X-ray microscopy (SFXM), newly developed in SPring-8 and Photon Factory was applied such as
nitrogen (N) and sodium (Na). The speication of these elements in saponite is particularly important, since the Fe oxidaiton
state and chemical composition within the interlayer of the saponite can indciate Eh-pH condition of the Ryugu water.
The Fe(II)/Fe(III) ratio in the octahedral structure of saponite was conducted by STXM. Based on our laboratory
experiments, dithionite reduction of natural Fe-bering saponite corresponding to Eh range from -0.47 to -0.66 (V) at pH = 7
shows the Fe(II)/Fetotal ratio around 0.55. The incomplete reduction by dithionite reveals that Fe(II)-bering saponite is a strong
reductant. Assuming that the relationship between the Fe(II)/Fetotal ratio and Eh of nontronite in Gorski et al. (2013) is similar
to that of saponite, the Fe(II) /Fetotal ratio greater than 0.68 measured by STXM indicates that the Eh was less than -0.45 (V).
On the other hand, because saponite has a negative charge in its layered structure, cations from the aqueous phase areadsorbed between the saponite layers during aqueous alteration. In this case, as shown by Fukushi et al. (2019), which cations
are retained in the interlayer depends on the concentration of various cations in the coexisting aqueous phase and theselectivity coefficient K. Therefore, the cation composition in the water layer at the time of aqueous alteration can be estimatedfrom the interlayer cation ratio determined by various analytical methods. In this processes, speciation of Na, K, and Ca wereconduted to obtain their fractions retained in the interlayer. The comparison of the Al content in saponite enables us to estimate
the Mg content in the interlayer. Contents of these cations with assumptions of dissolved silica etc. were used to construct an
Eh-pH diagram of Mg. We have estimated pH range that can explain the presence of both saponite and dolomite, which arewidely distributed in the altered crust in the Ryugu particles. The pH range estimated by the method was pH from 7.8 to 10.
Although the range is somewhat wide, the range is consistent with the results suggested in Nakamura et al. (2022).
The cmbination of Eh around -0.45 (V) and the alkaline pH range estimated above showed that the water was highly
reducing, which reveals that H2 and CH4 were present in the Ryugu water if we assume the equilibrium condition. Such analkaline condition is suitable for the polymerisation of amino acids (Kitadai and Maruyama, 2018).
References: Fukushi K. et al. (2019) Semiarid climate and hyposaline lake on early Mars inferred from reconstructed waterchemistry at Gale. Nat. Commun. 10, 1–11.; Gorski C. A. et al. (2013) Redox properties of structural Fe in clay minerals: 3.
Relationships between smectite redox and structural properties. Environ. Sci. Technol. 47, 13477–13485.; Kitadai N. andMaruyama S. (2018) Origins of building blocks of life: A review. Geosci. Front. 9, 1117–1153.; Nakamura T. et al. (2023)
Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples. Science 379, eabn8671.;
Naraoka H. et al. (2023) Soluble organic molecules in samples of the carbonaceous asteroid (162173) Ryugu. Science 379,
eabn9033.

Investigating the organic compounds in the asteroid Ryugu
Imene Kerraouch1*, Rhonda Stroud1, Larry Nittler2, Cassandra Kraver2, Jens Barosch3,4 and Jianhua Wang3
Buseck Center for Meteorite Studies (BCMS), Arizona State University, USA; 2School of Earth and Space Exploration(SESE), Arizona State University, USA; 3 Earth and Planets Laboratory, Carnegie Institution for Science, USA; 4 Department ofGeoscience, University of Wisconsin-Madison, USA. *ikerraou@asu.edu
1

Organic compounds in meteorites provide insights into the carbon chemistry present in the interstellar medium and solar nebulaand on their alteration on the parent bodies. Further, delivery of these organic compounds could have contributed to Earth’s
habitability and life. However, studying these compounds in meteorites is complicated by their exposure to terrestrial organic
contamination after entering the Earth's atmosphere. As such, one of the goals of the Hayabusa2 sample return mission (asteroid(162173) Ryugu) is to understand the nature, origin, and evolution of organic compounds in the early solar system but fromsamples free of terrestrial organic contamination. Here, we examine further samples from asteroid Ryugu that were collectedduring the first touchdown (Chamber A, samples A0079 and A0169; allocated in first Ryugu AO). The goals of our research are
to understand diversity, origin, and formation mechanisms of the macromolecular material that dominates Ryugu organics, aswell as the secondary processes involved in their modification, such as heating and aqueous alteration.
Fragments of the two Ryugu samples up to a few 10s of microns in size were pressed
into Au foils for H, C, and N isotope analysis with the Carnegie NanoSIMS 50L ion
microprobe. We used a ~0.4 pA, ~100-nm Cs+ primary beam and acquired data for C
and N isotopes, including 12C2, 12C13C, 12C14N, and 12C15N, as well as 16O, 32S, andsecondary electrons. The prepared samples were then analyzed for 1H, D, and 12C andsecondary electrons with a slightly more intense primary beam. C-rich regions ofinterest (ROIs) were defined in the C-N images and subsequently located and analyzed
in the H-D images.
We have analyzed a total area of ~9,000 m2 across the two samples. Data reduction isin progress. The majority of C-rich ROIs appear rounded in the ion images and range
from ~100 to 900 nm with some to up to a few µm (e.g., Fig.1). Consistent with previous
measurements [2-6], our data shows that the organic material is on average enriched in
D and 15N with most ROIs having compositions consistent within error with averagevalues of D of a few 100 ‰ and 15N~ +50‰. However, one lath-like rectangulargrain was identified in a particle within A0079 (Fig. 1), similar in shape to a grainpreviously reported in Chamber C [5; Fig.3], but larger. This 4.5 × 1 μm grain has anextreme isotopic composition: δD ≈10,000 ‰ and δ15N ≈ +800‰. In order to clarify
the nature and origin of this unusual grain and other select C-rich ROIs, we are currently
extracting focused ion beam (FIB) lift-out sections of D and 15N hotspots. The FIB
sections will be studied with transmission electron microscopy, scanning transmission
electron microscopy, energy dispersive spectroscopy and electron energy loss
spectroscopy at Arizona State University. Results from these investigations will bepresented at the symposium.

Figure 1. (a) Secondary electron (SE)image of a Ryugu particle fromchamber A (A0079) pressed into gold
foil. (b) D and 15N-enriched lath-like(whisker) detected in same particle.

References: [1] Huss G. R. and Draine B. T. 2006. Highlights of Astronomy 2: 353–356. [2] Busemann H. et al. 2006. Science
312, 727–730. [3] Nittler L. R. et al. 2019. Nat. Astron. 3, 659–666. [4] Nittler L. R. et al. 2018). GCA 226, 107–131. [5] Barosch
J. et al. 2022. Abstract#2050. 53rd LPSC; [6] Yabuta, H. et al. 2023. Science 379, eabn9057.

Constraining Ryugu’s earliest fluid composition by the analyses of phosphates
Nicolas David Greber1,2, Johanna Marin-Carbonne3, Anne-Sophie Bouvier3, James Greenwood4, Thomas Bovay3, Martin
Robyr3, Cristina Martin Olmos3
1
Muséum d’histoire naturelle de Genève, Route de Malagnou 1, CH-1208 Genève, Switzerland
2
Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland
3
Institute of Earth Sciences, University of Lausanne, CH1015 Lausanne, Switzerland
4
Department of Earth & Environmental Sciences, Wesleyan University, 265 Church Street, Middletown, Connecticut 06459,
USA
Volatile elements and compounds like F, Cl, S, H2O and CO2, indisputably exert a strong influence on the nature and evolutionof (exo)planets, of which water is arguably the most prominent for the habitability of the Earth. Most volatiles were likely
brought to Earth by carbonaceous chondrite-like material, including asteroids, making the undisturbed material of Ryugu key
samples to improve our understanding of the distribution of water in our solar system and the origin of water on Earth.
The water concentration in CI chondrites is distinct from that of Ryugu (13 to 20 wt% compared to 6.8 wt%, respectively;[1,2]), which might be explained (i) by loss of water from Ryugu during the disruption of the parent body, (ii) impact heating,(iii) that CI chondrites derive from parent asteroids with higher water content than Ryugu, or (iv) that CI chondrites got
contaminated by water during their residence time on Earth [2-4]. Importantly, the apatite grains found in Ryugu likely
originate from the aqueous alteration of Ryugu that predates the events that might have lead to the loss of some of Ryugu’s
water inventory (see points i and ii, [5,6]). Thus, measuring the chemical and isotopic compositions (e.g. H, O, etc) of these
apatites will likely help to better constrain the initial composition of Ryugus water, prior to its disruption, which is the aim ofdifferent research projects currently ongoing.
We will present the developed method on how we measured the H-isotopic composition of the apatites in Ryugu and discuss
this preliminary results in the context of the initial dD value of Ryugu’s water.

References[1] Palme, H., and J. Zipfel. 2022. Meteoritics & Planetary Science 57.2:317-333.
[2] Yokoyama, et al. 2022. Science 379.6634:eabn7850.
[3] Ito, et al. 2022. Nature Astronomy 6.10:1163-1171.
[4] Kurosawa, et al. 2021. Communications Earth & Environment 2.1:146.
[5] Nakamura, et al. 2022. Proc. Jpn. Acad. Ser. B 98
[6] Sugita, et al. 2019. Science 364.6437:eaaw0422.

Interpreting the thermal alteration history from organic matter in Ryugu samples
Queenie Hoi Shan Chan1*, Tomoki Nakamura2, Michael Zolensky3, Jangmi Han4, Mizuha Kikuiri2, Kana Amano2, Ashley
King5, Charlotte Bays1,5, Peter Krizan1, Natasha Almeida5, Megumi Matsumoto2, Akira Tsuchiyama6,7,8, Akira Miyake9, Junya
Matsuno9, Luis Carlos Colocho Hurtarte10, Rosario Brunetto11, Mark Burchell12, Vassilia Spathis12, Ming Chang Liu13 andJunko Isa14, and the Hayabusa2 initial analysis Core team.
1

Centre for Dynamic Earth and the Solar System (CeDESS), Department of Earth Sciences, Royal Holloway University of
London, Egham TW20 0EX, UK. 2Department of Earth Sciences, Tohoku University, Tohoku University, Sendai 980-8578,
Japan. 3NASA Johnson Space Center; Houston TX 77058, USA. 4Department of Earth and Atmospheric Sciences, University of
Houston, Houston TX 77204, USA. 5Planetary Materials Group, Natural History Museum, London SW7 5BD, UK. 6Research
Organization of Science and Technology, Ritsumeikan University, Kusatsu 525-8577, Japan. 7Chinese Academy of Sciences(CAS) Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics andMaterials, Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China. 8CAS Center for Excellence in Deep Earth
Science, Guangzhou 510640, China. 9Division of Earth and Planetary Sciences, Kyoto University, Kyoto 606-8502, Japan.
10
Diamond Light Source, Didcot OX11 0DE, UK. 11Institut d’Astrophysique Spatiale (IAS), Université Paris-Saclay, Orsay
91405, France. 12Centre for Astrophysics and Planetary Science, School of Physics and Astronomy, University of Kent,
Canterbury CT2 7NZ, UK. 13Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, USA.
14
Earth-Life Science Institute, Tokyo 152-8550, Japan.
Introduction: The Hayabusa2 mission visited the near-Earth Cb-type asteroid (162173) Ryugu and has returned to Earthwith the surface material of Ryugu. Ryugu is an airless rubble pile asteroid exposed to space weathering [1]. Near infrared
remote observations recorded an absorption feature at 2.72 μm indicating the presence of OH–bearing hydrous components.
However, the 2.72 μm feature is weak, suggesting that Ryugu was once organic- and water-rich and subsequently dehydrated
by a brief period of surficial heating. This feature has also been observed in “thermally metamorphosed carbonaceouschondrites”, “CI-/CM-like”, or “CY” chondrites [2, 3]. Initial examination of the returned samples did not identify any
significant heating at >150 °C [4, 5]; however, amino acid analyses suggested similarities to thermally-altered meteorites on
the grounds of the predominant straight-chain n-ω-amino acid abundances [6]. It remains unclear as to what caused thenonconformal interpretations of the thermal alteration history of Ryugu.
Here we investigate the alteration history of Ryugu by comparing the organic composition of fresh Ryugu samples to thatof naturally and experimentally heated chondritic meteorites. This study describes a coordinated effort in analysing organic
matter in Ryugu samples using micro–x-ray computed tomography (μ-CT), micro-Raman spectroscopy, focused ion beam
(FIB), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), micro-X-ray diffraction (μXRD), scanning transmission X-ray microscopy (STXM), X-ray absorption near edge structure (XANES), and synchrotron
radiation-based X-ray computed tomography (SR-CT).
Samples and Analytical Techniques: We studied Ryugu samples allocated during the Hayabusa2 preliminary
examination (A0063-FC016, A0063-FC017, A0064-FO012, A0067-FC008, C0002-FC014, C0002-FC015, C0025-FC003,
C0033-FC003, C0046-FO003) and AO1 (A0009 and C0011), plus raw fragments of naturally long-term (CIs: Orgueil, Ivuna;
CMs: Murchison, Murray; CV: Allende; CRs: Grosvenor Mountains 95577; OCs: Yamato (Y)-74191, Queen Alexandra
Range 93010) and short-term heated meteorites (Belgica-7904, Jbilet Winselwan, Y-793321, Y-86720, Y-982086) [7, 8]. We
also analysed samples of Murchison, Murray and Orgueil experimentally heated to 300, 400, 500, 600, 700 and 900 °C for 1,
10, 50, 100, 500 and 1000 hours. Raman analyses were conducted using a Jobin-Yvon Horiba LabRAM HR Raman
microprobe with a 514 nm laser for which the power was maintained at <100 μW at the sample surface. The mineralogy of the
raw Ryugu samples was characterised using low-voltage SEM-EDS (FEI Quanta 650) and μ-XRD. We identified regions ofinterest (ROIs) within A0009 and C0011 by conducting μ-CT analysis using a cabinet-based industrial Zeiss Xradia Versa 520
CT system. Targeted ROIs were picked using sterile tools, pressed into indium, and prepared into electron-transparent sections(~100 nm thick) mounted on TEM Cu grids using a FEI Quanta 3D 600 dual beam FIB-SEM, which were studied by STXMXANES to determine the organic composition. Euhedral sulphide crystals were lifted and mounted on W-needles by the FIBSEM, and potential fluid inclusions within them were then located by SR-CT conducted at SPring-8 BL47XU at the X-ray
energy of 7 keV.
Results and Discussion: Increased heating of carbonaceous materials results in a transition from amorphous to graphitic
carbon, and such ordering is traceable using Raman spectroscopy as a cosmothermometer [9]. Raman spectroscopic analysis of

the Ryugu samples indicates significant heterogeneity (Figure 1), evident by Raman spectral features that are comparable tothe organic matter in both relatively unheated primitive chondrites and those that experienced short duration heating like Y793321, a Stage II heated chondrite [10].
The Raman spectral features of the organic matter inmost of the Ryugu samples are similar to those observed
from CIs, consistent with previous studies [11]. However,
localised areas within several Ryugu samples show awider G band, comparable to organic matter processed byshort duration heating. The Raman features of the organic
matter in broad areas within A0009, A0064 and C0011
clearly deviate from that observed from the other Ryugu
samples and Orgueil, with significantly lower D band
positions and D band widths that are comparable to
Figure 1. Comparison of the Raman D and G band parameters of Ryugu
chondritic organics that had been heated at elevated samples (yellow symbols), and naturally short-term heated samples
temperatures [9], and larger G band widths that are not (black symbols; Stage II CCs peak heating temperature ~250–500°C;
observed in naturally metamorphosed chondritic Stage IV CCs >750°C). Γ=Full width half maximum; ω = Peak location.
meteorites (Figure 1). These trends are similar to thoseexhibited by astromaterials heated by short-term heating, like interplanetary dust particles [12] and some meteorites [13]. The
Raman spectra of A0009, A0064 and C0011 are similar to those of Orgueil experimentally heated to 300 °C for 500 h.
Analysis of A0064 by SEM-EDS and μ-XRD shows
the presence of hydrated phyllosilicates, suggesting that theparticle did not experience significant heating above ~300–
400 °C. Moreover, the SR-CT data validated the μ-CT scans,and indicate that C0011 contains a sulphide grain hosting an
inclusion with X-ray attenuation that is clearly distinct fromair (Figure 2). Previous studies have revealed H2O and CO2
within such inclusions [14], suggesting that they have notbeen metamorphosed after aqueous alteration. Analysing Figure 2. SR-CT images of a sulphide grain picked from C0011.
these more “evolved” particles with STXM-XANES helped
us understand the organic structure corresponding to the Raman features. C-XANES spectra of A0009 and C0011 indicate thepresence of aromatic or olefinic groups (C=C) at ~285 eV and carboxylic groups (COOH) at ~288.5 eV within the matrix
associated with carbonate grains (CO3 absorption at 290.3 eV). While thermally stable oxygenated functional groups wereobserved in short term (impact induced) heated meteorites [15], the association of the organic matter with carbonates iscomparable to the carboxylic-rich diffuse organic matter in CM and CI chondrites [16]. Based on our coordinated investigation,
we have drawn two possible scenarios that can explain our observations: (1) some carbonaceous matter in Ryugu had
experienced post aqueous alteration short duration heating (impact induced and/or solar irradiation), resulting in the presenceof thermally stable oxygenated moieties like furan and phenol that were formed via dehydration and cyclisation ofpolyalcohols. These “evolved” materials were subsequently disrupted and redistributed by impacts, thermal fatigue, and/or
mass wasting processes [17], intermixed with fresh, undisturbed and pristine Ryugu materials. Alternatively, (2) the formationof the macromolecular organic matter occurred at the final stages of aqueous alteration in low-temperature, highly oxidizing
fluids, e.g., fluid with OH radicals contributing through H2O2 dissociation [18], co-precipitating carboxylic enrichedcomponents in the immediate vicinity of carbonate.
Acknowledgements: We are extremely grateful to the Astromaterials Science Research Group (ASRG) of ISAS/JAXA
for providing the Ryugu samples.
Reference: [1] Noguchi, T., et al. Science, 2011. 333: p. 1121-1125. [2] Kitazato, K., et al. Science, 2019. 364: p. 272275. [3] Vilas, F. The Astronomical Journal, 2008. 135: p. 1101. [4] Naraoka, H., et al. Science, 2023. 379(6634): p. eabn9033.
[5] Yabuta, H., et al. Science, 2023. 379(6634): p. eabn9057. [6] Parker, E.T., et al. GCA, 2023. 347: p. 42-57. [7] Tonui, E., etal. GCA, 2014. 126: p. 284-306. [8] Nakamura, T. JMPS, 2005. 100: p. 260-272. [9] Busemann, H., M.O.D. Alexander, and
L.R. Nittler. MAPS, 2007. 42: p. 1387-1416. [10] Nakamura, T. Earth and Planetary Science Letters, 2006. 242(1): p. 26-38.
[11] Yokoyama, T., et al. Science, 2022. 379(6634): p. eabn7850. [12] Chan, Q.H.S., et al. MAPS, 2020. 55(6): p. 1320-1348.
[13] Quirico, E., et al. GCA, 2014. 136: p. 80-99. [14] Zolensky, M., et al., Hayabusa Symposium. 2023. [15] Yabuta, H., et al.
MAPS, 2010. 45: p. 1446-1460. [16] Le Guillou, C., et al. GCA, 2014. 131: p. 368-392. [17] Morota, T., et al. Science, 2020.
368(6491): p. 654-659. [18] Cody, G.D. and C.M.O.D. Alexander. GCA, 2005. 69: p. 1085-1097.

First direct detection of large aromatic molecules on asteroid (162173) Ryugu sample C0083 andA00145: an interstellar heritage
Hassan Sabbah1, Ghylaine Quitté1, Karine Demyk and Christine Joblin11IRAP, Université Toulouse III – Paul Sabatier, CNRS, CNES, 31028 Toulouse Cedex 4, France
Although meteorite analysis has revealed various types of pre-solar grains, the presence of large polycyclic aromatichydrocarbons (PAHs) of interstellar origin has not been firmly established. Here we present a search for these compounds in
the C0083 and A00145 grains from the Ryugu asteroid. The experiment takes advantages of the ultra-sensitivity of the
AROMA (Astrochemistry Research of Organics with Molecular Analyzer) setup to target these species.
The AROMA setup was developed specifically for studying the carbonaceous molecular composition of meteorites and cosmic
dust analogues [1]. It consists of a laser desorption ionization (LDI) source combined with a segmented linear quadrupole ion
trap (LQIT), all connected to an orthogonal time-of-flight mass spectrometer (oTOF). The ion source is at a low pressure of 106
mbar and can be operated using a two-step laser desorption ionization scheme. This L2MS analysis provides ultra-sensitivity
for PAHs and fullerenes as demonstrated in our earlier study [2]. This laser technique also requires little or no sample
preparation and uses very little material.
Subsamples of the two Ryugu grains have been isolated and used either as bulk or crushed in the form of powder to improvesensitivity. The data obtained are compared to previous AROMA analyses of carbonaceous chondrites (CCs) such as
Murchison and Orgueil. This reveals a number of peculiarities in the distribution of PAHs in Ryugu grains. In particular wereport the presence of PAHs containing as much as 50 carbon atoms, which can be considered as interstellar candidates.
Moreover, we have identified aromatic compounds that incorporate nitrogen (N) and oxygen (O) heteroatoms, with carbon
atoms extending up to 48. These findings impact our view on the complexification of organic matter in the cycle of matterfrom the interstellar matter to the Solar System. It also motivates the research for these large compounds in other CCs

References[1] Sabbah et al. 2017. The Astrophysical Journal, 843, 34. [2] Sabbah et al 2022. The Astrophysical Journal, 931, 91.

FIB Tomography-STXM-TEM on organic material from Hayabusa-2 grain A0083.
H. G. Changela1, Y. Kebukawa2, L. Petera1, M. Ferus1 E. Chatzitheodoridis3, L. Nedjl4, R. Nebel1, Z. Hlavenkova5, J.
Moravcova5, P. Krepelka5, R. Holbova5, J. Novacek5, T. Samoril6,7, K. Sobotkova6, H. Tesarova6 and D. Zapotok8
1 J’Heyrovski Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czechia. 2 Tokyo Institute of Technology,
Tokyo, Japan. 3 National Technical University of Athens, Greece. 4 Bruno University of Technology, Czechia. 5 Central
European Institute of Technology Masaryk University, Brno, Czechia. 6 Central European Institute of Technology Nano, Brno,
Czechia. 7 TESCAN GROUP a.s., Brno, Czechia. 8 TESCAN USA Inc, Pennsylvania, USA. Email: changela@unm.edu
Introduction The success of the Hayabusa-2 mission provides unique insight into prebiotic evolution from a known asteroid
free from terrestrial contamination. Asteroid 16273Ryugu (Ryugu here on in) is of CI (Ivuna-type) composition, lacking any
distinct chondrules and calcium aluminium inclusions, and is composed mainly of secondary minerals including phyllosilicate,carbonates, (Fe, Ni) sulphides, Fe-oxides and phosphates [1]. Organic material (OM) also pervades Ryugu, characteristic of
OM found in primitive chondrite matrices. Micron to submicron organic particles (OPs) – macromolecular organic objects
completely surrounded by inorganic material – make up the major mass fraction of OM [e.g. 2], consistent with insolubleorganic matter (IOM). A volumetrically diffuse organic component aromatic-poorer and carboxylic-richer than OPs foundwithin chondritic hydrated silicates [3] also occurs in Ryugu [4]. This study is on a grain from the 1st touch-and-go (TAG) site
on Ryugu, characterising the distribution, functional chemical variation and mineral setting of OM in situ.
Samples & Methods Grain A0083 (Radegast here on in) is a 1.3 and 1.7 mm grain from Chamber A of the Hayabusa-2
collector TAG site. Radegast was prepared and analyzed taking an approach of minimal damage and material loss forcharacterisation. Radegast was picked up with vacuum tweezers and placed on a clean Au base with an ~2 mm divot, mounted
on an Al stub. An ~1.5 mm circular hole in clean Al foil was placed over the top of Radegast and fastened at the edge of thestub, exposing the grain out of the hole and securing it. This has the advantage that the grain can be turned over by lifting thefoil for any further characterization whilst leaving the grain intact. Focused Ion Beam (FIB) ~100 nm lamella of Radegast wereprepared for Scanning Transmission X-ray (STXM) and Transmission electron Microscopy (TEM). The TESCAN AMBERX
and LYRA3 at TESCAN GROUP and the Central European Institute of Engineering & Technology (CEITEC)-nano,respectively, were used to compare the effects of Xe+ plasma FIB with Ga+ FIB lamella preparation on the STXM
measurements of OM in the samples. To minimize sample information losses by destruction from the traditional FIB lamella
sample preparation, FIB tomography was performed from the edge of the grain during milling prior to lift-out. Grains of Ivuna
were also embedded in molten S for ultramicrotome using methods in [5]. 110 nm samples were cut using a Leica UC7 at
CEITEC-Muni to compare the STXM measurements between Xe-, Ga- FIB lamella and microtome samples. Scanning
Transmission X-ray Microscopy (STXM) measurements were made at BL 19A at the Photon Factory, Japan. S/TEM was
performed with the CEITEC-MUNI Thermofisher Talos F200C, and the J’Heyrovski Institute’s JEOL 2100.
Ga+

a.

b.

Xe+

3D

30 μm

20 μm

100 µm10 µm

c.

500 μm
10 μm

20 μm

Phyl

5 µm

Figure 1. BSE images of particle A0083 (Radegast). (a) Entire image of Radegast. Insets show various phases on the top of the particle. Blueand purple are Fe-Sulphides (probably hexagonal pyrrhotite) Yellow is Fe-oxides (magnetite). Pink is a mixture of minerals. Green rectangle
shows the region of tomography from the top edge of Radegast. (b) Tomography and Lamella liftout regions. Inset show the milled regions
for tomography and lamella liftout made between Ga+ (LYRA3) and Xe+ (AMBERX) FIB instruments. (c) A Coarse grained organic particle(arrowed) from 1st cross section of tomography volume.

Results & Discussion Radegast displays CI composition similar to samples from both TAG sites, suggesting widespread
alteration across the asteroid. Organic particles are mostly submicron with IOM morphology. Some coarser OPs identified in
the tomography completely surround phyllosilicate, suggesting post-formation of the primary mineralogy within them (Fig. 2).
Slice 240

Slice 248

Slice 255

Slice 283

Slice 269

Slice 292

Slice302

OP

Phyllosilicate

1 µm

Figure 2. FIB Tomography slices of a coarse-grained organic particle in Radegast.

Organic particles and diffuse OM are consistent between FIB and microtome samples of Ivuna (diffuse OM in microtome
samples have not been previously reported), implying that both Ga+ and Xe+ FIB preserve the functional chemistry of OPs
and diffuse OM (Fig. 3). Carbon-XANES shows that individual OPs in closer proximity to one another are more equilibrated,suggesting that the alteration recorded in the grain was a common process evolving them. They have aromatic-rich, 3-peak
spectra similar to the ‘aromatic’ particles in [4]. Notably, OPs in Ivuna are aromatic poorer, with lower aromatic/ketone ratios
than those in Radegast and other Ryugu samples. Aromatic-rich OPs are however in higher abundance in the CR1 GRO 95577[2] and Orgueil [3] than the type 2/3 carbonaceous chondrites. Diffuse OM (aromatic-poorer and aliphatic/carboxylic-richer
OM than OPs) in Radegast is also more similar to diffuse OM found in Ivuna (Fig. 3) and GRO 95577 [2], with higher
carboxyl/aromatic peak ratios than type 2/3. It is also similar by being in phyllosilicate rather than amorphous hydrated
silicates found in type 2/3 chondrites. SEM and TEM (Fig. 5) shows coarse and finer domains of phyllosilicate. Diffuse OM
occurs in both domains of phyllosilicate but is less concentrated in the coarse domains than the finer ones that are alsointermixed mostly with Fe and Fe,Ni-rich sulphides (Fig. 3a). HRTEM shows the coarse domains as mixed layers of serpentine
and smectite, consistent with previous studies [6].

Figure 3. STXM-TEM on Radegast. (a) HAADF
image of Xe+ prepared lamella. Inset is magnified
region where the C-XANES Stack was made, showing
a calcite grain adjacent to an OP. (b) C-XANES of
OPs and diffuse OM in Ivuna and Radegast. The OPin (a) is pink. Note the higher aromatic/ketone ratio of
OPs in Ryugu than in Ivuna.

Conclusion Organic material in Radegast evolved into aromatic-rich organic particles and aliphatic/carboxyl-rich diffuse OM
by alteration on Ryugu, similar to those found in type C1 planetary materials.
References [1] Nakamura T. et al. 2022 Science 379: eabn8671. [2] Changela. H. G. et al. 2018 Meteoritics & Planetary
Science 53:1006-1029. [3] Le Guillou C. et al. 2014 Geochimica Cosmochimica Acta 131: 368-392. [4] Yabuta H. et al. 2023
Science 679: 6634. [5] Noguchi T. et al. 2020 Life 10(8):135. [6] Ito M. et al. 2022 Nature Astronomy 6(10): 1-9.
Acknowledgements This research was funded by the Czech Science Foundation Project Reg. No. 21-11366S with financial support by
ERDF/ESF Centre of Advanced Applied Sciences (CZ.02.1.01/0.0/0.0/16_019/0000778). We acknowledge CF CryoEM of CIISB, Instruct-CZ
Centre,supported

by

MEYS

CR

(LM2023042)

andEuropean

Regional

Development

Fund-Project

UP

CIISB

(No.

CZ.02.1.01/0.0/0.0/18_046/0015974). We thank Takis Theodossiou of the Greek Meteorite Museum for the curation of the Ivuna meteorite.

New view on the paleomagnetic record of samples from asteroid Ryugu
1

C. Maurel1, J. Gattacceca1, M. Uehara1
CNRS, Aix Marseille Université, IRD, INRAE, CEREGE, Aix-en-Provence, France

The JAXA Hayabusa 2 mission returned ~5 g of material from the C-type asteroid Ryugu. Ryugu
material contains abundant magnetite and pyrrhotite, formed during aqueous alteration on its
parent body. The timing of aqueous alteration is not yet well constrained, with estimates ranging
between 1.8 and 6.8 Myr after CAI formation (Yokoyama et al., 2022; McCain et al., 2023). Given
these uncertainties, aqueous alteration on Ryugu’s parent body may have occurred during the
lifetime of the solar nebula magnetic field (i.e., up to ~5 Myr after CAI formation; Weiss et al.,2017). Magnetite and pyrrhotite may therefore carry a chemical remanent magnetization reflecting
the intensity of this field.
Rock magnetic and paleomagnetic data of Ryugu samples were recently published (Nakamura etal. 2022; Sato et al., 2022). The authors measured the NRM of two samples (0.425 mg and 1.556mg) and demagnetized the NRM using alternating fields (AF). They identified stable remanencecomponents in both samples up to 24 mT and 32 mT, respectively, which they interpreted as
evidence that Ryugu material experienced a 41- to 390-µT solar nebula field.
We conducted a new paleomagnetic investigation of two other Ryugu samples with mass 0.8 mg
and 20.8 mg. Data are very consistent among our two samples, but their mass-normalized NRM
intensities are 20 to 100 times weaker than the published ones. NRM demagnetization data exhibit
a poorly defined low-coercivity component up to ~8 mT, but become completely erratic at higher
AF field steps. A similar demagnetization behavior is found after applying anhysteretic remanent
magnetizations (ARM) acquired in bias fields up to 10 µT. For ARM bias fields of 20 µT and
greater, we can identify a component of the magnetization in the coercivity range 10-50 mT.
Although further analyses are being conducted, this favors the idea that the samples experienced
magnetic fields < 17 µT in intensity, assuming the sample acquired a chemical remanent
magnetization. This upper limit is compatible with both (i) the nebula field intensity estimatedfrom other meteorites with similar age of the NRM, and (ii) the absence of field.
We suspect that the samples used by Nakamura, Sato and colleagues may have been contaminatedby exposure to strong magnetic fields up to ~20 mT. We will discuss how such a contamination
can be identified using measurements that are non-destructive for the NRM. This highlights theneed for extreme caution to avoid magnetic contamination during handling of returned
extraterrestrial material. Our data show, however, that the samples were not remagnetized en masse
during sampling on the asteroid, in transit in the spacecraft or during curation preceding any
measurements.
We are very grateful to JAXA for the allocation of the Ryugu samples A0154 and C0005.

References
Yokoyama, T., et al. (2023) Science 379, eabn7850; McCain, K. A., et al. (2023) Nat. Astro. 7, 309-317;
Weiss, B. P., et al. (2017) Earth Planet. Sci. Lett. 468, 119-132; Nakamura, T., et al. (2022) Science 379,
eabn8671; Sato M., et al. (2022) J. Geophys. Res. Planets 127, e2022JE007405