The Physical Properties of Carbonaceous Asteroids
Daniel Britt
University of Central Florida
The rendezvous and sampling of asteroids 162173 Ryugu and 101955 Bennu have opened a new window on carbonaceous
asteroid physical properties. Both objects have the structure of low-density rubble piles [1], with surfaces that are extremelyrough, covered in starkly angular blocks and boulders, and depleted in fine particle sizes and dust [2]. The returned Ryugu
material is similar to CI carbonaceous chondrites [3] and Bennu is likely either CI or CM-like materials. The surface of Ryugu
exhibits very low thermal conductivity and high porosity [4]. What does this imply for the link between the physical propertiesof carbonaceous asteroids and hydrated carbonaceous meteorites?
The mineralogy these objects are dominated by phyllosilicates, primarily serpentines and saponite [3]. For Ryugu theserpentines are the magnesium-rich endmember similar to CI mineralogies. For Bennu the serpentine mineralogy is still
unknown but may be the iron-rich endmember Cronstedtite. One major characteristic of serpentines is a strong negative
excursion in the coefficient of linear thermal expansion in the range of 200°-250° K [5]. This effect is shown in Figure 1 for
five CM carbonaceous chondrites. Since the carbonaceous materials are basically conglomerates that include some very
dissimilar minerals, this negative thermal expansion excursion in serpentines may be key to understanding their surface
properties as they evolve in the inner solar system. Cobbles and boulders exposed on the surfaces of carbonaceous asteroids
will undergo extreme temperature excursions as they rotate into the Sun and then are exposed to deep space. All the minerals
in the conglomerates will expand and contract according to their thermal expansion coefficients. For most minerals the
expansion is a linear, positive function of temperature. However, for carbonaceous chondrites the serpentines and otherphyllosilicates will expand, contract, and then expand again in a course of their heating and subsequent cooling. This willproduce an extreme energetic effect on the mineral grain boundaries, essentially pushing them apart, contracting to open space,
and then pushing apart again. The overall effect will be to weaken the conglomerate and induce increasing porosity into what
appear to be coherent cobbles/boulders. This will leave the surface covered with boulders and cobbles that are extremely
friable, porous, and weak. Because the effect is limited to the penetration depth of the rotational thermal pulse, it may be that
only the surface materials are significantly weakened by this process. Cobbles buried at some modest depth and do not undergo
temperature excursions may retain significantly more coherence and strength than the surface material.
One important observation is the lack of small particle size and dusty materials in the surface regolith. With the stresses
induced by the thermal excursions, it would be expected that at least some of the boulder and cobble material would
disaggregate to form a dusty regolith. However, the surface
appears much like a “desert pavement” where active
processes extract the fine materials from the surface andarmor it with particle sizes too large to be moved by theactive processes. Active ejection processes have been
observed on Bennu with rocks as large as 10 cm being
ejected. Because of the low gravity, fine particle sizes arelikely to be entrained in the solar wind once ejected,
resulting in a depletion of fines on the surface. Below thesurface on both Ryugu and Bennu sampling activities
revealed horizons more enriched in fine materials [1].

Figure 1. Thermal Expansion Coefficient for CM carbonaceous chondrites

References[1] Sugita S. et al 2019. Science 364: 252 [2] Michikami T. et al. 2019. Icarus 331: 179. [3] Yokoyama T. et al. 2022. Science
10.1126/science.abn7850 [4] Gott M. et al. 2019 Nature Astronomy 3(11): 971. [5] Opeil C. et al. 2020. MAPS
10.1111/maps.13556. [6] Lauretta D. et al. 2019 Science 366:6470.

New theoretical results on asteroid regolith specific heat, cohesion and heat transfer,and a revisit of comet 67P surface strength
J. Biele1, M. Grott2, S. Ulamec1, J. Knollenberg2, J.-B. Vincent2
1
German Aerospace Center, DLR-RB/MUSC Cologne, Germany
2German Aerospace Center, DLR-PF, Berlin, Germany
We report and discuss on some of our recent theoretical advances on asteroid regolith specific heat cP, van der Waals-force
between regolith particles, and heat transfer in the regolith. We also report on the strength of comet surface material, includinga refined model of its size dependence and wide variability depending on the degree of “cementation” (sintering) and a reappraisal of some particularly low and high strength values for comet 67P reported earlier in the literature. Thermal andmechanical properties are correlated.
Specific heat
Surface temperature models could be impacted by the drastic decrease in cP(T) values toward low temperatures; thermal
models generally assume lunar basalt calorimetric properties, which are not well known outside the data range 90 K to 350 K.
Indeed, ‘knowledge of specific heat variability as a function of temperature and bulk material composition remains largely
under-constrained for the need of planetary thermal modelers’[1].
In particular, the specific heat capacity of geological materials
relevant to solar system body surfaces below room temperature is
not particularly well constrained and the thermal modelingcommunity only has a limited set of adequate ready-to-use cP(T)trends for planetary surface temperature modeling. - We provide
the means to calculate synthetic cP(T) from a known bulk
composition, for almost any solar system material from 10 K to1000 K, and additionally a method to predict the specific heat curve
beyond the temperature range measured, even if the composition isnot (well) known. [2]Van-der-Waals force[3] have calculated the pull-of force due to van der Waals interaction, and due to capillary bridges, between particles with selfaffine fractal (random) roughness, which is realistic. They have shown that surface roughness, if big enough, results in aninteraction (VdW) force which is independent of the size of the particles, in contrast to the linear size dependency expected forparticles with smooth surfaces (simple JKR, DMT). For fractured rock particles a realistic surface roughness reduces the pullof force between micrometer sized particles by a factor of ∼ 100, and even more for larger particles, it is of the order of 0.1 – 1
nN. This means that the dependence of cohesive strength (or tensile
strength, in N/m²) of the granular medium on particle size is due tothe increase in the number of particle-particle contacts (per unit
area) alone. A decrease in particle size only increases the number ofcontacts without changing the strength of the particle-particle
adhesive bond. The small-particle glue idea, figure 1, of [4] is agood one! This results also affects the predicted (high) porosity of
granular media in micro-gravity, since the granular Bond number isvery different now.
Figure 1. The big particles (fragments) in an asteroid could be kept together by a matrix of smaller particles. Effective yield stress of rubble
pile asteroids of order (or less than) σY ≈ 25 Pa.

Heat transfer
Thermal conductivity k of granular media and porous rocks seemed well explained by classical theories (Maxwell equations,Stefan-Boltzmann radiative transfer, contact mechanics like Hertz or JKR theory). All those classical thermal conductivity
theories operate with models from the 19th century (Maxwell, Fourier, Stefan-Boltzmann law, Hertz) and completely neglect
phonons and quantum mechanics! We are revising the underlying assumptions, and find that most are doubtful.

Figure 2 Cartoons
depicting idealized (leftand right) and realistic
contact (middle)

Rough irregular rock (silicate) particles do not form strong contacts when granular, not much phonon conduction across point
contacts, JKR not applicable at all, heat transfer by near-field evanescent EM waves at least equally important, (NFRHT)~1/R0.8-dependence. Radiative conduction is not ∝ T3 either, if grains are not well conducting (non-isothermality);different regime if void scale <= thermal wavelength λT ≈3000/T µm K (radiative transfer, dense media scattering andtransmission, Planck not valid if particle size < λT); Most assumptions on porosity dependence, in particular of krad, were
wrong [5, 6]. Porous rock effective conductivity (meteorites) as function of porosity in not Maxwell „swiss cheese“, much
lower values at medium porosities  rather weakly cemented/sintered ex granular matter. Cracks, percolating and closepores, .. no theory is available! We are working both theoretically and experimentally to understand this better [7, 8].
Revisit of Comet Surface Strength
For comet 67P, we have re-analyzed the data for the apparently exceptional 67P Abydos site, where originally a lower limit ofseveral MPa for compressive strength was suggested. We use a correlation going back to Digby [9, 10] between strength,
Young’s module and thermal conductivity for weakly sintered porous media; our revised value for compressive strength is 28–
690 kPa on the 5–30 cm scale, still representing the probably most competent material on the comet, potentially with a reduced
porosity compared to the average 70–80%. The size effect law [11] for quasi-brittle failures bridging the small-size asymptotic
strength (compressive or tensile) and the power law ~1/d1/2 of LEFM seems to apply for cometary and meteoritic material: thestrength of very small lab samples cannot be simply extrapolated to larger sizes!

References[1] Piqueux, S., et al., Journal of Geophysical Research: Planets, 2021. 126(11): p. e2021JE007003. [2] Biele, J., et al.,International Journal of Thermophysics, 2022. 43(9): p. 144, DOI: 10.1007/s10765-022-03046-5. [3] Persson, B.N.J. and J.
Biele, Tribology Letters, 2022. 70(2): p. 34, DOI: 10.1007/s11249-022-01570-x. [4] Scheeres, D.J., C.M. Hartzell, and P.
Sanchez, Icarus, 2010. 210, DOI: 10.1016/j.icarus.2010.07.009. [5] Ryan, A.J., et al., Journal of Geophysical Research:
Planets, 2020. 125(2): p. e2019JE006100, DOI: 10.1029/2019je006100. [6] Ryan, A.J., et al., JGR Planets, 2022: p.
e2022JE007191. [7] Persson, B.N.J. and J. Biele Applied Physics Letters, 2022, submitted. [8] Biele, J., et al., 44th COSPAR
Scientific Assembly. Held 16-24 July, 2022. 44: p. 186. [9] Digby, P., Journal of Applied Mechanics, 1981. 48(4): p. 803-808.
[10] Grott, M., et al., Nature Astronomy, 2019. 3(11): p. 971-976. [11] Bažant, Z.P., Archive of Applied Mechanics, 1999.
69(9-10): p. 703-725, DOI: 10.1007/s004190050252.

Comparison of Thermal Inertia between Ryugu Sample and Carbonaceous Chondrites
Takuya Ishizaki1, Hosei Nagano2, Satoshi Tanaka1, Tatsuaki Okada1, Naoya Sakatani1, Tomoki Nakamura3, Ryohei Fujita2,
Abdulkareem Alasli2, Tomoyo Morita3, Mizuha Kikuiri3, Kana Amano3, Eiichi Kagawa3, Hisayoshi Yurimoto4, Takaaki
Noguchi5, Ryuji Okazaki6, Hikaru Yabuta7, Hiroshi Naraoka6, Kanako Sakamoto1, Shogo Tachibana8, 1, Sei-ichiro Watanabe2,
Yuichi Tsuda1
1
Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
2
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan
3
Tohoku University,2-1-1, Katahira, Aoba-ku, Sendai, Miyagi 980-8578, Japan
4
Hokkaido University, 5, Kitahachijonishi, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
5
Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto, Kyoto 060-0810, Japan
6
Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, Fukuoka 812-8581, Japan
7
Hiroshima University, 1-3-2 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan
8
The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Introduction: According to the general planetary formation scenario, the Solar System bodies evolved over a long period oftime through repeated collision, fragmentation, and aggregation of planetesimals formed in the solar nebula. Thermal evolution,
which induces various physicochemical reactions such as aqueous alteration, thermal metamorphism, and volcanism, is
important for the evolution of planets. The temperature history inside the planetesimals followed in thermal evolution can vary
greatly depending on when and how large they agglomerate and effective thermal conductivity. Therefore, it is essential for thetheory of planetary system formation to know the thermal conductivity of asteroids and meteorites, especially those that arethought to have existed since the early stages of planetary system formation.
The Ryugu sample brought back in 2020 by Hayabusa2 was found to be a primitive Ivuna-type carbonaceous chondrite, which
is close to the average composition of the Solar System [1]. Although it is expected that the physical properties of Ryugu,
including thermal conductivity, will be analyzed in detail, most of the measurements of physical properties of meteorites havebeen performed on relatively easily available ordinary chondrites [2–4], because they require more samples than chemical andpetrological evaluations. Therefore, there has been no method that can evaluate thermal conductivity of limited amount ofsamples such as Ryugu samples. In this study, we developed a lock-in thermography (LIT) periodic heating method that canmeasure the thermal diffusivity of small sample of several mm scale without contact [5]. Then we measured the anisotropic
distribution of thermal diffusivity for five types of Ryugu samples. Additionally, Thermal inertia was evaluated using reported
density and specific heat and compared with values reported for other carbonaceous chondrites.
Samples and Methodology: In this study, six samples of C0002-plate 3, C0002-plate 4, C0025, C0033, A0026 and A0064
were evaluated. C0002-plate 3 and C0002-plate 4 are flat plates cut out from C0002, and the others have granular shape. A spot
on the sample is periodically heated using a laser and the temperature response is measured by LIT to obtain the phase lag
distribution on the sample surface. The thermal diffusivity is analyzed from the gradient of the phase lag according to thisequation; 𝐷 = 𝜋𝑓 / (𝑑𝜃/𝑑𝑟)2 . Here, D is thermal diffusivity, f is heating frequency, θ is phase lag and r is distance from heating
point. Thermal inertia, which is expressed as the product of the square root of thermal diffusivity, density, and specific heat, wasevaluated based on the reported density and specific heat. The heating frequency was selected according to the sample size to
avoid the influence of reflected temperature waves at the sample edge, and then measurements were performed at 2, 1, 4, 4, 4,
and 20 Hz for C0002-plate 3, C0002-plate 4, C0025, A0026, C0033, and A0064, respectively. C0002-plate 3, C0002-plate 4 andA0064 were measured under vacuum, and C0025, A0026, and C0033 were measured under atmospheric pressure because thevacuum environment was not available at that time yet. C0002-plate 4 was also measured under atmospheric pressure.
Results and Discussion: Figure 1 shows the phase lag distribution and the thermal diffusivity distribution of C0002-plate 3
as a representative of all samples. And the mean, maximum, minimum, and maximum to minimum ratio of the thermal diffusivity
distribution for each sample are summarized in Table 1. C0002-plate 3 is known to have cracks in the evaluation region (in the
direction of 105-195 deg), and it can be seen that the thermal diffusivity decreases significantly in the direction of the cracks.
The other samples also show various thermal anisotropy. The results of C0002-plate 4 measured under both vacuum andatmospheric pressure show that the thermal diffusivity becomes larger, and the thermal anisotropy becomes smaller underatmospheric pressure. The thermal anisotropy seems to be caused by cracks inside the sample. Heterogeneity of mineralcomposition or microporosity may also affect. The returned Ryugu samples were found to have various mineral compositions
and conglomerate-like structures [6].

Table 1. Measurement results of thermal diffusivity.
SampleC0002-3
C0002-4(Vacuum)
C0002-4(1 atm)
C0025
A0026
C0033

Average,
mm2/s
0.28 ± 0.07

Max/ Min,
mm2/s
0.75/ 0.02

Max/Minratio
38.0

0.33 ± 0.08

1.05/ 0.07

15.0

0.45 ± 0.12

0.60/ 0.31

1.94

0.56 ± 0.10
0.51 ± 0.02
0.58 ± 0.11

1.12/ 0.36
0.60/ 0.34
0.82/ 0.27

3.11
1.76
2.96

C0002-3 (Vacuum)
Phase lagFigure 1. Phase lag and thermal diffusivity distribution of
C0002-plate 3.

The obtained thermal diffusivity was then converted to thermal inertia using specific heat and bulk density, and a plot of therelationship with bulk density is shown in Figure 2. Error bars for thermal inertia indicate maximum and minimum values. The
bulk densities of these samples are 1820, 1740, 1650, 2260, and 1870 kg/m3 respectively, and the specific heat of 865 J/(kg⋅K)
measured in the initial analysis was used as a representative value [6]. In addition, Figure 2 also shows plots of the thermal inertia
of carbonaceous chondrites reported so far (Cold Bokkeveld (CM2), Jbilet Winselwan (CM2), Murchison (CM2), Murray (CM2),
NWA 7309 (CM2), NWA 5515 (CK4), Allende (CV3), Kainsaz (CO3.2)) [4, 7]. The plots are shown in light blue for themeasurements taken in vacuum and in purple for those taken at atmospheric pressure. The thermal inertia at atmospheric pressure
becomes larger than that at vacuum pressure because the thermal diffusivity becomes larger due to the air-filled cracks.
The averaged values of the thermal inertia of 748-1475 J/(s1/2m2K) obtained in this measurement is significantly larger thanthat observed value of 300±100 J/(s1/2m2K) [8] by the thermal infrared imager (TIR) onboard Hayabusa2. On the other hand,some of the minimum values corresponded to the observed values. This suggests that the value of thermal inertia may differ
depending on the measurement scale. In this measurement, the thermal diffusivity was evaluated in the region of several hundredsof micrometers long as thermal diffusion length, but the TIR observations were made at depths down to several centimeters
because the thermal inertia was analyzed using the diurnal variation of the surface temperature due to the 7.6-hour rotation periodof asteroid Ryugu. Therefore, it is possible that large-scale cracks caused by meteor impacts and thermal stresses on a scalelarger than several hundreds of micrometers are widely developed in the rocks and boulders of Ryugu
The Ryugu sample seems to be the lowest-density category when compared to carbonaceous meteorites, and the thermal inertia
values appear to follow a correlation trend with the bulk density of carbonaceous chondrites. However, if the bulk density of the
Ryugu sample were 2236 kg/m3, which is the average of the five CM2 densities, the average thermal inertia of the Ryugu sample
would be 1132 J/(s1/2m2K), which is almost identical to the average CM2 value of 1191 J/(s1/2m2K). This means that the only
substantial difference between Ryugu and CM2 is the bulk density, and the product of thermal conductivity and specific heat arealmost the same. Since the thermal conductivity generally decreases when the bulk density decreases due to porosity, it is possiblethat the thermal conductivity of Ryugu's matrix is larger than that of CM2. Further validation will be conducted by evaluating
additional carbonaceous chondrites including CI chondrites, which are closest to Ryugu.

Thermal inertia, W/(s1/2m2K)

3000
2500

CO3.2
Kainsaz

2000
1500

CM2

C0025
C0002-P4

A0026
1000
500
0
1600

JbliletWinselwan

A0064
C0002-P3

C0033

CK4

CM2

NWA 5515(@ 200 K)

NWA 7309

CM2

Cold Bokkeveld

CM2

MurrayVacuum1 atm

CM2

Murchison

Soini et al., 2020
Opeil et al., 2020

C0002-P4
1800

2000

CV3

Allende(Error range of thermal inertia means max. and min. value)
2200

2400

2600

2800

3000

3200

Bulk density, kg/m3
Figure 2. Thermal inertia vs. bulk density of Ryugu samples and carbonaceous chondrites.

References[1] T. Yokoyama et al., Science abn7850 (2022). [2] K. Yomogida et al., J Geophys Res. 88 (1983) 9513–9533. [3] M. Beech
et al., Planet Space Sci. 57 (2009) 764–770. [4] A.J. Soini, et al., Meteorit Planet Sci. 55 (2020) 402–425. [5] T. Ishizaki et al.,Int J Thermophys. 43 (2022). [6] T. Nakamura et al., Science abn8671 (2022). [7] C. Opeil et al., Meteor Planet Sci. 55(8)(2020) E1–E20. [8] T. Okada et al., Nature. 579 (2020) 518–522.

Thermal properties of asteroid Ryugu from global, local, and micro-scale observations and thepossible formation and evolution scenario of Ryugu
Tatsuaki Okada1,2, Satoshi Tanaka1,2, Naoya Sakatani1, Yuri Shimaki1, Takehiko Arai3, Hiroki Senshu4, Hirohide Demura5,
Tomohiko Sekiguchi6, Toru Kouyama7, Masanori Kanamaru2, Takuya Ishizaki1
1Institute of Space and Astronautical Science, JAXA, Japan, 2University of Tokyo, Japan, 3Maebashi Institute of Technology,
Japan, 4Chiba Institute of Technology, Japan, 5University of Aizu, Japan, 6Hokkaido University of Education, Asahikawa,Japan, 7National Institute of Advanced Industrial Science and Technology, Japan..
Thermophysical properties of C-type asteroid 162173 Ryugu have been investigated through remote sensing using the
Thermal Infrared Imager (TIR)[e.g., 1-3], on the surface using the radiometer MARA on MASCOT lander [4,5], and theanalysis of return sample [e.g.,6,7]. The global average and the local distribution of thermal inertia were mapped by TIR, withthe typical value of 200 to 400 J m-2 kg-1 s-0.5 (tiu, hereafter) [1], which is lower than that of typical chabonaceous chondrite
meteorites of 600 to 1000 tiu [8]. Surface boulders and their surroudings have almost the same thermal inertia, indicating thatmost of boulders are consisted of materials with high porosity (pores and cracks in them) and not completely consolidated, andthe surroundings are covered with boulders and rocks (not sandy regolith) [1], which was confirmed during the descentoperations. The flat diurnal temperature profiles observed at the afternoon local time indicate the very rough surface [1].
Considering the thermal model with rough surface [9], the thermal inertia and roughness are derived simultaneously [2]. Upclose observations by TIR during the descent operations suggested that boulders have a variety of thermal inertia, with morethan 80 % of them having 200 to 400 tiu, while some portions have very low (<100 tiu) or very high (>600 tiu) thermal inertias[3]. They are identified as “Hot Spots” and “Cold Spots”, because they are observed exceptionally hotter or colder comparedwith their surroundings [1,3]. The surface experiment by MARA indicated the simiar thermal inertia for a single boulder [4],so that the rough boulders should be the representative material on the asteroid. Multi-band radiometry by MARA indicates thesimilarity to aqueously altered carbonaceous chondrites (CI or CM) but not like heated carbonaceous chondrites [5].
The average thermal properties of returned samples show the thermal inerita almost similar to that of typicalcharbonaceous chondrites for <100 µm scale [6,7], although the thermal inertia (or more directly the thermal diffusivity) in the
direction where cracks exist indicate much lower, consistent with the thermal inertia by remote sensing by TIR or surface
measurements by MARA. The return samples are not always representative as the intact surface on Ryugu regaring thephysical properties, since fragile portions of them might have been broken during impact sampling as well as during the severe
shock and vibration in the return capsule when entry to Earth. The return samples seem to be consisted of more consolidated
parts of Ryugu surface materials with flatter surface, instead of fragile and porous features observed as cauliflower-like crambyboulders on Ryugu. The return sample are more like CI chondrites in mineralogy, chemistry, and textures but with darker,
more porous and fragile characteristics [10,11]. The difference of thermal inertia between larger scale (> 1mm) and a smallerscale (<0.1 mm) might attribute to the existing cracks and pores inside of boulder materials. A formation scenario of Ryugu
will be shown to explain the history of Ryugu formation and evolustion or even a planetary formation.
Our scenario is like this: 1) porous dust with ices of volatile species (water and CO2) were accumulated to form aplanetesimal in the outer solar system. 2) Aqueous alteration occurred by internal heating due to radioactivity of Al26 but notheated to drive strong thermal metamorphism. Materials were more altered at the innermost region to consolidate almost equal
to typical carbonaceous chondrites, but less altered at the outermost region to leave the materials so porous and fragile. 3) The
parent body migrated to inner region of the Solar System, 4) Impact fragmentation of parent body, sometimes by S-type bodies[12]. 5) Degassing of volatiles by sublimation due to exposre to space, to make freeze-dry porous materials. 6) Reaccretion offragmented rocks and boulders with high porosity by low degree of consolidation and freeze-dry and formation of a rubble pilebody. Most of surface boulders are occupied by those from the inner region of the parent body as the representative boulders,
while relatively porous boulders originated from the outermost region are the “hot spots” and relatively consolidated boulders
originated from the innermost region are the “cold spots”. 7) Some uppermost surface processes by spaceweathering.
References[1] Okada T. et al, 2020. Nature 579, 518-522. [2] Shimaki Y. et al., 2020. Icarus 348, 113835. [3] Sakatani N. et al. 2021.
Nature Astron. 5, 766-774. [4] Grott M. et al. 2019. Nature Astron. 3, 971-976. [5] Hamm M. et al. 2022. Nature Comm. 13,364. [6] Nakamura T. et al. 2022 Science abn8671. [7] Ishizaki T. et al. This issue, [8] Flynn, GJ, 2018. Chem. Erde. 78, 269298. [9] Senshu H. et al. 2022. Intl J. Thermophys. 43, 102. [10] Yada T. et al. 2022. Nature Astron.6 214-220. [11] Pilorget etal. 2022. Nature Astron. 6, 221-225. [12] Tatsumi E. et al. 2021. Nature Astron. 5, 39-45.

Evidence of Permafrost Processes in C-asteroid Regoliths
M. Zolensky1, T. Nakamura2, T. Mikouchi3, H. Yurimoto4, T. Noguchi5, R. Okazaki6, H. Yabuta7, H. Naraoka6, K. Sakamoto8,
S. Tachibana3, S. Watanabe9, and Y. Tsuda81
ARES, NASA Johnson Space Center, Houston, TX 77058, USA (michael.e.zolensky@nasa.gov); 2Tohoku University, Miyagi
980-8578, Japan; 3The University of Tokyo, Tokyo 113-0033, Japan; 4Hokkaido University, Sapporo 060-0819, Japan; 5Kyoto
University, Kyoto 606-8502, Japan; 6Kyushu University, Fukuoka 819-0395, Japan; 7Hiroshima University, HigashiHiroshima 739-8526, Japan; 8ISAS/JAXA, Sagamihara 252-5210, Japan; 9Nagoya University, Nagoya 467-8501, Japan.
Introduction: C-complex asteroids have suffered a wide variety of physical processing, some of which are not very obvious.
Carbonaceous chondrites experienced and recorded a very wide range of chemical and physical processing in both nebular andasteroidal settings [1-7], resulting in the following textures: brecciation, flattened chondrules and foliation (CV and CM
chondrites in particular), carbonate and phyllosilicate veins (CI, CM, CV3 dark inclusions), local alignment of matrix
phyllosilicates (CR2, CI, CM), and shearing (mylonitization) around lithic fragments. Many of the extensively alteredcarbonaceous chondrites contain rounded to elliptical aggregates of phyllosilicates, carbonates, spinels (chromite andmagnetite), Fe-Ni sulfides, and embayed olivines and pyroxenes, generally ascribed to impact shock or static burial pressures[6,7]. However, it is probable that even in the wettest regions of an asteroid dry periods were experienced during the periodic
breaching of an icy surficial rind [8], which could have occurred during impacts or "volcanic" venting of gas and heat from theinterior (this assumes internal heating). Thus, there should have been multiple wet-dry cycles experienced by these regolith or
immediately subsurface materials. We have previously suggested that all the deformation features mentioned above would
have arisen naturally from cycles of wet-dry and, more critically, freeze-thaw environmental conditions (permafrost) inasteroid regoliths [5]. Here we detail two related textures observed in CI chondrites, including asteroid Ryugu samples(essentially CI chondrite), consistent with permafrost processes.
Permafrost Processes in Regoliths: It is well-known to soil scientists that conditions of radically alternating humidity canhave important morphologic and petrologic consequences [9]. Grains and lithic clasts can become rotated, crushed and drawn
out into linear features (shearing). Porosity (including contraction and shearing cracks) and other bulk physical properties willvary in a dramatic manner. Easily altered materials will be dissolved while more resistant materials will be pulverized andmixed into matrix. These effects would be most pronounced for the C1-2 lithologies where the swelling clay saponite can befound in abundance, including the CI chondrite meteorites and asteroid Ryugu samples. Another important process to beconsidered is periodic growth and melting of ice crystals in the regolith [10-11]. The positive molal volume change during
crystallization of water will induce oriented microfabrics to develop in the regolith, normal to the direction of ice crystal
growth. Thus, masses of platy grains (in this case phyllosilicates, especially saponite flakes) will develop a pronounced
compaction and preferred alignment. This process will recur for each freezing episode. Since the orientation of the growing ice
mass will vary for each succeeding generation of growth, the eventual result will be to impart a particular, invasive, regolith
fabric consisting of sheets of aligned clays for each generation, which will appear as anastomosing strings of phyllosilicateswith roughly aligned basal directions in polished or thin sections (Figure 1). Our study has revealed that such textures arecommon in the CI chondrites.
Ice crystal growth could explain the preferred alignment of saponite observed in some Ryugu samples (see Figure 6b of[12]). However, a more likely explanation for this particular texture is mobilization of saponite flakes during wet, water
saturated episodes, and deposition of these flakes onto the surface of underlying rock fragments under the force of gravity.
These features are termed “silt caps”, and these are a common feature of permafrost soils [11,13]. Of course, a majordifference between permafrost processes on earth as compared to asteroids is the greatly reduced gravity on the latter.
However, mass wasting is usually observed on small bodies including asteroids (including Ryugu and Bennu) and comet
nuclei [14,15], so gravity-driven processes operated on the Ryugu parent body. Growth and collapse of subsurface asteroidal
icicles would also impart cyclical changes in bulk regolith porosity, induce rotation and movement of crystals and lithic
fragments through frost heaving, and consequent shearing [11]. This process could also account, to some degree, for theflattened chondrules observed in some carbonaceous chondrites (especially CMs).
Conclusions: We therefore suggest that cyclical, indigenous environmental processes, rather than impact gardening, could be
responsible for some of the late-stage petrologic characteristics of wet carbonaceous chondrites, and Ryugu samples. We notethat this suggestion has also recently been proposed by another group [16]. Bulk petrographic features of additional Ryugu
samples and carbonaceous chondrites should be investigated more systematically in order to test this idea, especially samples
rich in clays such as saponite.
References: [1] Moskovitz et al. (2013) Icarus 224, 24; [2] Vilas (2008) Ap. J. 135, 1101–1105; [3] Lazaro et al. (2012) A&A
549, L2; [4] Zolensky et al. (2022) MAPS 57, MAPS.13909; [5] Zolensky (1995) Meteoritics 30, 606-607; [6] Sneyd et al.
(1988) Meteoritics 23, 139-149; [7] Scott et al. (1992) GCA 56, 4281-4293; [8] DuFresne and Anders (1962) GCA 26, 10851114; [9] Nahon (1991) Introduction to the Petrology of Soils and Chemical Weathering, pp. 122-133; [10] Van Vliet and Fox(2018) Frost Action. In Interpretation of Micromorphological Features of Soils and Regoliths, 2nd Ed., Elsevier; [11] Zhang etal. (2021) The Influence Mechanism of Freeze-Thaw on Soil Erosion: A Review. Water 13, 1010; [12] Nakamura T. et al.,(2022) Science 377, 10.1126/science.abn8671; [13] Menzies and Ellwanger (2011) Boreas 40, 271-288; [14] Jawin et al.

(2020) JGR Planets 125, Issue 8; [15] Steckloff and Samarasinha (2018) Icarus 312, 172-180; [16] Nakamura E. et al. (2022)
Proceedings of the Japan Academy, Series B 98, 227-282.

Figure 1. Ivuna CI chondrite, in cross polars. Two views of the same area in different rotation angles showing two distinct
directions of phyllosilicate (yellow stringers) preferential orientations (arrows). Views measure 2 mm in longest dimension.

Modeling of aqueous alteration in the parent body of the asteroid Ryugu

1

A. Tsuchiyama1,2, J. Matsuno1 and M. Matsumoto3
Research Organization of Science and Technology, 2CAS, Guangzhou Institute of Geochemistry, 3Tohoku University

The mineralogy, petrology and chemical properties of the samples collected from the asteroid 162173 Ryugu by the
Hayabusa2 spacecraft show that the samples correspond to CI meteorites not affected by terrestrial weathering (e.g., [1-3]). The
parent body of Ryugu were formed by accretion of minerals, organics, and ice, and aqueous alteration occurred by reaction ofmelted ice with the minerals and organics [1]. The major lithology of the Ryugu samples consists mostly of hydrous
phyllosilicates (serpentine and saponite), carbonates, FeS and magnetite which precipitated from liquid (melted ice) during theaqueous alteration. Least- and less-altered lithologies, where some anhydrous minerals, such as olivine, remained unaltered or
partially altered, were also observed [1]. Model chemical equilibrium of the aqueous alteration was calculated in an appropriate
condition (e.g., 40oC based on oxygen isotope equilibrium [2] and ice of H2O + 0.08 CO2 based on CO2-bearing fluidinclusion[1]) as a function of the initial water/rock ratio (in mass), W/R, and found that the mineral assemblages are almost
consistent with the least-altered, less-altered and altered major lithologies at W/R of 0.06 to 0.1, 0.1 to 0.2, and 0.2 to 0.9,
respectively [1]. The order of precipitation of minerals in the major lithology was also estimated from the included and enclosed
relations among these minerals [4].
We understood the outline of the aqueous alteration by the Ryugu sample initial analysis as mentioned above. However, we
still do not know how the aqueous alteration occurred and ceased; for example, how liquid was present, and precipitation
occurred from the liquid. Therefore, in this study, we performed a modeling of the aqueous alteration by reference to the minerals
and their assemblages and the chemical composition of the Ryugu samples.
In the present model, we made the following assumptions to simplify the problem; (1) the system Mg-Fe-Si-Ca-O-S-C-H istaken into consideration with the bulk chemical composition of CI [5] that is unchanged during the alteration except for O(oxidation or reduction permitted). (2) The starting material is composed of anhydrous minerals, amorphous silicate, organics,
and CO2-H2O ice. Olivine, metallic Fe, and FeS are considered for the anhydrous minerals. We adopted Mg# (Mg/(Mg+Fe) inmole) of 0.99 for olivine, which was observed in least- and less-altered lithologies [6]. Material similar to GEMS (glass
embedded with metal and sulfide) is considered for amorphous silicate based on the observation in the least-altered lithology [1].
This GEMS-like material (GLM) is assumed to have the mean GEMS composition of [7]. We consider relatively oxidized GLM,
where only nanoFeS particles (without nanoFe) are embedded in FeO-bearing amorphous silicate. Thus, the Mg# of theamorphous silicate becomes 0.612 to maintain the mean GEMS composition. The density of GLM is assumed to be 3 g/cm3. (3)We consider only IOM as organics. The chemical composition of IOM is adopted from [8] and its density is assumed to be 1.3
g/cm3. IOM is not changed by the alteration. (4) The ice CO2/H2O ratio is 0.08 as proposed by [1]. The ice melts to form CO2bearing water. The temperature is 40oC proposed by [2] and the pressure is less than ~50 bar for a 50-km-radius parent body [1].
In these conditions, the melted ice is a liquid state (not fluid) and the densities of H2O and CO2 are almost constant (1 g/cm3 [9]and 1.04 g/cm3 [10], respectively). (5) The aqueously altered products are serpentine, saponite, FeS, magnetite, and dolomite.
The Mg#’s of serpentine and saponite are 0.85 based on the Ryugu sample analysis [1]. Dolomite is only considered as acarbonate although other carbonates (magnesite and calcite) are present in the Ryugu samples. (6) GLM stats to react with liquid
to form serpentine and saponite first, and simultaneously the same proportion of Fe as that of altered GLM becomes magnetite.
If the GLM is completely altered, olivine starts to react with liquid. (7) GLMs and the phyllosilicates (serpentine and saponite)
have nano-sized pores (nanopores) based on the TEM observation of the Ryugu samples [1]. Any other pores are not present in
the initial state, but the space that used be as ice acts as micron-sized pores (micropores). (8) The water/rock ratio, W/R, is definedas the mass ratio of water (or ice) to whole of the other materials including IOM.
The amounts of the formula weights of the phases (minerals, IOM and liquid) were calculated to have elemental balanceamong the chemical compositions of the phases and the bulk chemical compositions, and their volumes were obtained from thedensities of the phases. This calculation is similar to the CIPW norm calculation, and chemical equilibrium was not considered.
We made calculation for a case where the initial IOM volume is 10% with respect to solid phases and the porosities of thenanopores in both GLM and phyllosilicates are 40%.
In the initial state, the modes of olivine, Fe, FeS (nanoFeS in GLM not included), GLM with nanopores, and IOM arecalculated to be 17.2, 2.5, 4.9, 67.4, and 8.1 vol.%, respectively, to have the elementary balance (Fig.1 at W/R = 0). We changed
the initial water/rock ratio (in mass), W/R, as a parameter. The final mineral assemblages after the complete reaction with liquid
were calculated with different W/R. Changes in the volumes of the phases are shown in Fig. 1. In the range of W/R = 0 to 0.10
(Stage-1 in Fig. 1), mainly saponite and minor amounts of serpentine and magnetite form from GLM and Fe, and H2O in liquidis completely consumed. CO2 in liquid is also completely consumed to form dolomite, and therefore no liquid remains in thisstage after the aqueous alteration. GLM and Fe are completely consumed at W/R = 0.10. With further increase in W/R, olivine
starts to react with water, and serpentine forms by consuming some saponite together with olivine to accommodate their Mg/Si
ratios (W/R = 0.10 to 0.12, Stage-2 in Fig. 1). Olivine is completely consumed at W/R = 0.12, and no liquid remains in this stage
too. In W/R > 0.12, some liquid remains after complete reaction with GLM, Fe and olivine, and the volumes of magnetite,saponite, serpentine, and FeS are constant (W/R = 0.12 to 0.19, Stage-3 in Fig. 1). The volume of dolomite increases by
consuming CO2 in liquid, and no CO2 remains in liquid in this stage. In W/R > 0.19 (Stage-4 in Fig. 1), some CO2 remains inliquid because [C] > 2[Ca] and the volume of dolomite is constant. Stage-1, Stage-2 and Stages-3 and -4 roughly correspond theleast-altered, less-altered, and altered major lithologies, respectively, in terms of their mineral assemblages. The modes ofdolomite, magnetite, saponite with nanopores, serpentine with nanopore, FeS, and IOM in Stage-4 are 2.0, 4.3, 31.3, 48.1, 8.1,
and 6.2 vol.%, respectively. These are similar to those of the main lithology [1]. The relation of W/R and stages are also roughly
consistent with the chemical equilibrium calculation of [1]. The boundary between Stages-2 and -3 (W/R = 0.12) corresponds to
W/R = 0.18 in [1]. This difference is derived from the rough calculation in the present model. The broad similarities suggest thatthe present model roughly reflects the equilibrium although the model itself does not consider equilibrium.
As a next step, we calculated the proportions of liquid filling pores. The total volume of the bulk material consisting ofminerals, IOM, and pores (nanopore in GLM and/or phyllosilicates and micropore after ice) increases by the aqueous alterationfrom the initial volume (minerals, IOM, nanopore in GLM, and ice) by ~10 – 20%. Because such volume increase would notoccur for asteroids, we assumed that the initial bulk volume maintains constant by collapsing some of micropores. Liquid (ifpresent) occupies the remaining pores. Fig. 2 shows the liquid proportion filling pores, f, and the total porosity including liquid,f, as a function of W/R for the initial state before aqueous alteration. As we assumed liquid preferentially fills nanopores due tocapillarity, with increasing W/R, f(nanopore) increases first, and then f(micropore) increases after f(nanopore) reaches 100 %.
For the final state after aqueous alteration (Fig. 3), similar behavior of f’s can be seen, but f(nanopore) and f(micropore) are 0 %in Stages-1, and -2. These results showed that liquid partially occupies only nanopores if W/R is small, and even if W/R is large,
macropores are not fully filled with liquid, suggesting that pores are not fully filled with liquid during aqueous alteration. The
bulk density of Ryugu samples was determined to be 1.79 g/cm3, indicating the porosity of 31 % if we compared with the grain
density of CI meteorites [1]. If the porosity has not changed from the end of aqueous alteration to present, f of 31 % corresponds
to W/R of 0.19 (Fig. 3), where 100 % of nanopores and 61 % of micropores are filled with liquid, respectively, before thealteration (Fig. 2), and 55 % of nanopores and 0 % of micropores are filled with liquid, respectively, after the alteration (Fig. 3).
These suggest that aqueous alteration in the Ryugu parent body should occur through dissolution and reprecipitation in conditions
where not so much water present.

Figure 1. The volumes of phases after
aqueous alteration at different water/rockratio, W/R.

Stage-2
Stage-1 Stage-3

100

80

80

60

60

40

40

20
0
0

micropore
nanoporepore (average)
porosity

0.2

0.4
0.6
W/R (mass)

0.8

20
0
1

Figure 2. Liquid proportion filling poresand porosity before aqueous alteration.

Stage-4
f-III_ver4b_10_99

100

100

80

80

60

60

40

40

20
0
0

micropore
nanoporepore (average)
porosity

0.2

0.4
0.6
W/R (mass)

0.8

20
0
1

Porosiry (including liquid), φ (%)

100

Liquid proportion filling pore, f (%)

Stage-4

Porosiry (including liquid), φ (%)

Liquid proportion filling pore, f (%)

Stage-2
Stage-1 Stage-3

Figure 3. Liquid proportion filling poresand porosity after aqueous alteration.

References[1] Nakamura T. et al. 2022. Science. 10.1126/science.abn8671. [2] Yokoyama T. et al. 2022. Science
10.1126/science.abn7850. [3] Ito M. et al. 2022. Nature Astron. 10.1038/s41550-022-01745-5. [4] Tsuchiyama A. et al. 2022.
85th Annual Meeting of The Meteoritical Society 2022 6221.pdf. [5] Lodders K. et al. 2009. Landolt–Bornstein (Berlin:
Springer), 42. [6] Mikouchi T. et al. 2022. 85th Annual Meeting of The Meteoritical Society 2022 6180.pdf. [7] Keller L.P.
and Messenger S. 2011. Geochim. Cosmochim. Acta 75:5336. [8] Alexander C.M.O’D. et al. 2007. Geochim. Cosmochim.
Acta 71:4380. [9] Xiaoyan Ji. et al. 2005. Ind. Eng. Chem. Res. 44:8419. [10] Longhi J. et al. 2005. Geochim. Cosmochim.
Acta 6: 529.

Chemical abundances in Ryugu, nugget effect, and cosmic composition
Nicolas Dauphas1, Tetsuya Yokoyama2, Ryota Fukai3, Tomohiro Usui3, Shogo Tachibana4, Maria Schönbächler5, Andrew M.
Davis1, Hisayoshi Yurimoto6, The Hayabusa2-initial-analysis chemistry team, The Hayabusa2-initial-analysis core.
1
Origins Lab, Dept. of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, USA
2
Dept. of Earth & Planetary Sciences, Tokyo Institute of Technology, Japan
3
Dept. of Solar System Sciences, ISAS, JAXA
4
Dept. of Earth and Planetary Science, University of Tokyo, Japan
5
Inst. für Geochemie und Petrologie, ETH Zürich, Switzerland
6
Dept. of Earth and Planetary Sciences, Hokkaido University, Japan
Approximately 99.86% of the mass of the solar system is locked up in the Sun, which is largely inaccessible and whose
composition is only known through spectroscopy and analysis of solar wind. Much of our knowledge of the chemical and isotopic
compositions of the bulk solar system comes from analysis of meteorites, and among those CI (Ivuna-type) carbonaceouschondrites, which contain most elements except the most volatile ones in proportions that match estimates from solar photosphereobservations [1,2]. CI chondrites are rare and most of them have been in meteorite collections for many decades (the largest one,
Orgueil, fell in 1864), where they have been exposed to moisture, airborne and handling contaminants. The Hayabusa2 mission
sampled ~5.4 g of pristine material from Ryugu, a Cb-type asteroid [3]. Laboratory analyses of the returned sample show that
Ryugu is related to CI chondrites and probably originated from the outskirts of the solar system [4-7]. The only known
contaminant for Ryugu samples is Ta in the projectile used to liberate dust and fragments from Ryugu's surface [8]. Given theirpristine nature, Ryugu samples are ideally suited to constrain the composition of outer-solar system material, which we take asa proxy for the solar composition. A caveat to estimating the solar composition using Ryugu or CI chondrites is that these may
contain extraneous refractory dust compared to other inner solar system objects. This was most clearly demonstrated with rareearth elements (REEs), as carbonaceous chondrites all show Tm anomalies relative to non-carbonaceous chondrites [9,10],
presumably due to the presence of refractory dust with a group II REE pattern characterized by large positive Tm anomalies
produced by evaporation/condensation processes in the solar nebula [11]. At this stage, it is unclear if the Sun would contain thesame complement of refractory dust as CI chondrites, or if inner solar system objects are more representative.
3

3

1.5

1%

1

CI

-do
lom

0.5
0
0

0.5

1
(Rb/Sr)N

1.5

ite

2

-do
lom

(Fe/Mn)N

2

2.5

ite

(Mn/Cr)N

6%

m
olo
+d

2.5

1.5
1
0.5

ite

2

m
olo
+d

0
0

0.5

ite

1
(Rb/Sr)N

1.5

2

Fig. 1. Correlations between Mn/Cr, Fe/Mn, and Rb/Sr ratios. The yellow star is the CI composition. The red points
are bulk fragment measurements for Ryugu [4,7]. The curves are calculated mixing curves between bulk CI anddolomite in CI chondrites [12,13].
Yokoyama et al. [4] and Nakamura E. et al. [7] reported high precision chemical composition analyses of Ryugu fragments
by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), the gold standard for such analyses. Those
measurements show that Ryugu has almost unfractionated chemical abundances relative to CI chondrites, strengthening the casefor a link between Cb-asteroid and CI chondrites. The fragments analyzed are relatively small (from ~0.2 to ~30 mg) and show
significant departures relative to CI chondrites that are unrelated to volatility. This is true even in the largest fragments analyzed,
which show significant enrichments in REEs, Ca, Sr, Ba, P, and Mn [4]. Chemical abundance variations have been seen
previously in chondrites that presumably reflect heterogeneous distribution (and unrepresentative sampling) of phases highly
enriched in some elements [9]. This is known as a nugget effect and represents a limit in the precision that can be attained inbulk rock analyses. Carbonate and phosphate phases have been found in Ryugu samples [4,6,7] and could be responsible for thechemical variations seen in bulk fragment analyses.

A nugget effect for REEs associated with the presence of phosphate was identified in carbonaceous and ordinary chondrites[9]. There are several telltale signatures of such a nugget effect. The first one is that in elemental ratio plots, "bulk" analyses
should define mixing curves between the true bulk and the mineral composition. In ordinary and carbonaceous chondrites, thepresence of phosphate nuggets was identified as a negative correlation between La/Lu ratios and Eu/Eu* (=observed
Eu/interpolated Eu) anomalies (phosphates in ordinary chondrites have high La/Lu and negative Eu/Eu* anomalies) [9]. The
phosphates in Ryugu lack these characteristic features and are more difficult to detect [7]. Ryugu fragments are rich in dolomite,
which has high Mn/Cr, low Rb/Sr, and low Fe/Mn. In Fig. 1, we plot CI-normalized Mn/Cr and Fe/Mn against Rb/Sr. As shown,
the ratios are correlated, and the variations observed can be well explained by admixture or removal of dolomite at the percent
level. Another telltale signature of a nugget effect is that the dispersion in elemental ratios should decrease as the inverse of thesquare root of the mass of sample homogenized [9]. As shown in Fig. 2, the dispersions in elemental ratios are consistent with asampling problem associated with a nugget effect. The dispersion in elemental ratios can be calculated if the nugget size,
abundance, and composition are known [9]. Because these are poorly constrained for carbonates, we calculated instead thedispersion for the smaller fragments digested and calculated the predicted dispersion for larger masses. Having established that
unrepresentative sampling of carbonate is likely responsible for the dispersion in specific elemental ratios, we can predict the
expected dispersion if large sample masses are digested. We thus estimate that for 1 g of Ryugu sample homogenized/digested,
the dispersion (2s) of the bulk Mn/Cr and Rb/Sr ratios will be better than ~±5%. Elements that are not concentrated in specificminerals will be much less affected by this uncertainty. Our analysis shows that much of the dispersion in chemical composition
between Ryugu grains is a due to non-representative sampling of mineral phases highly enriched in some elements. This artifact
can be remediated by homogenizing a larger sample mass (~1 g), which is important to constrain the "cosmic" composition, andtest if previous estimates based on CI chondrites are reliable.
0.5
0.3

Log10 (Rb/Sr)N

Log10 (Mn/Cr)N

0.4
0.2
0.1
0
-0.1
-0.2
-0.3
0.001

0.01
0.1
Sample mass (g)

1

0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
0.0001

0.001
0.01
0.1
Sample mass (g)1Fig. 2. Elemental ratios sensitive to carbonate nugget effects against mass homogenized/digested. If a nugget effect ispresent, we would expect the dispersion to decrease as the inverse of the square root of the mass of sample
homogenized/digested (black envelope) [9]. As shown, this seems to be the case.
References. [1] Lodders, K., 2021. Space Science Reviews, 217, 1. [2] Asplund M. et al. 2021. Astronomy & Astrophysics
653, A141. [3] Yada T. et al. 2022. Nature Astronomy 6:214. [4] Yokoyama T. et al. 2022 Science eabn7850. [5] Ito, M et al.
2022. Nature Astronomy, 1, https://doi.org/10.1038/s41550-022-01745-5. [6] Nakamura T. et al., 2022. Science, eabn8671. [7]Nakamura E. et al. (2022) Proceedings of the Japan Academy, Series B 98, 227. [8] Sawada H. et al. 2017. Space Science
Reviews, 208, 81. [9] Dauphas, N. and Pourmand, A., 2015. Geochimica et Cosmochimica Acta, 163, 234. [10] Barrat, J.A.,
Dauphas, N., et al., 2016. Geochimica et Cosmochimica Acta, 176, 1. [11] Hu, J. Y., et al. (2021). Science Advances, 7(2),eabc2962. [12] Endreß, M. and Bischoff, A., 1996. Geochimica et Cosmochimica Acta 60, 489. [13] Macdougall, J.D., et al.
1984. Nature, 307, 249.
The Hayabusa2-initial-analysis chemistry team: T. Yokoyama, K. Nagashima, I. Nakai, E.D. Young, Y. Abe, J. Aléon,
C.M.O'D. Alexander, S. Amari, Y. Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B.-G. Choi, N.
Dauphas, A. M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M. K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe,
G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, A. Ishikawa, M. Ito, S. Itoh, N. Kawasaki, N. T. Kita, K. Kitajima, T. Kleine, S.
Komatani, A. N. Krot, M.-C. Liu, Yuki Masuda, K.D. McKeegan, M. Morita, K. Motomura, F. Moynier, A. Nguyen, L. Nittler,
M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y.
Terada, T. Usui, S. Wada, M. Wadhwa, R.J. Walker, K. Yamashita, Q.-Z. Yin, S. Yoneda, H. Yui, A.-C. Zhang, H. Yurimoto.
The Hayabusa2-initial-analysis core: S. Tachibana, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H.
Yabuta, H. Yurimoto, Y. Tsuda, S. Watanabe.

Abundance and properties of Ryugu diffuse organic matter
Rhonda Stroud1,2, Bradley De Gregorio2, Jens Barosch3, Larry Nittler1,3
The Hayabusa2-initial-analysis Organic Macromolecule Team and Core Team1
School of Earth and Space Exploration, Arizona State University, USA,
2
Materials Science and Technology Division, US Naval Research Laboratory, USA,
3
Earth and Planets Laboratory, Carnegie Institution of Washington, USA

Initial Analysis studies have revealed that Ryugu regolith particles contain abundant organic carbon (3 wt%) [1,2],
and that organic matter has the same range of morphologies as previously observed in primitive chondrites, including
solid and hollow nanoglobules, nanodiamonds, dense, irregularly shaped particles, and diffuse materials with poorlydefined boundaries [3]. The diffuse organics form coatings on and fill the space between mineral grains, and intercalate
into phyllosilicates. Because the diffuse carbon can be very thin (single nm) and intimately mixed with the nanoscale
minerals, especially phyllosilicates, it is below the spatial limit for many techniques. Many analyses focus instead on
globules or other organic particles > 200 nm. However, the diffuse carbon represents a substantial portion, possibly
50% or more, of the total organic carbon, and must be considered for a complete understanding of the Ryugu organics.
To better understand the abundance and properties of diffuse carbon, we used correlated scanning transmission x-ray
microscopy (STXM), scanning transmission electron microscopy (STEM) and nanoscale secondary ion mass
spectrometry (NanoSIMS) to examine samples from Chambers A and B.
Figure 1A shows a bright-field STEM image montage of a focused ion beam (FIB) lift-out section from particle
A108-?? pressed into a Au mount for NanoSIMS analysis. The BF STEM image shows a mixture sulfides andphyllosilicates with domain sizes of 10s to 100s of nm, but no discernable carbonaceous particles. However, STEMbased energy dispersive x-ray spectroscopy (EDS) mapping of the section Fig. 1B reveals carbon distributed
throughout. Quantification of the C:Si molar ratio with Cliff-Lorimer routines for areas > 1µm2 for no visible
nanoglobules indicate values of ~ 0.8 ±0.3. Similar STEM-EDS analysis of additional FIB sections shows comparable
C:Si ratios, confirming that a large portion of the organic carbon is present as diffuse matter rather than globular
carbon in general, not only in this specific particle. However, it is difficult to obtain a precise determination of fractionof the diffuse vs. particulate carbon because the ability to resolve individual organic carbon particles < 100 nm depends
greatly on the sample preparation and analysis conditions. In 100-nm thick FIB sections such as this, amorphous
carbon particles as large as 50 nm could be hidden in images by the greater intensity variation of the phyllosilicatesand sulfides, and only revealed by spectroscopy.
Measurement of the carbon K edge x-ray absorption near edge structure (XANES) with STXM can provide theaverage functional chemistry distribution of the diffuse carbon (Fig. 1D, Fig. 1E). Notably, there are four prominent
peaks in the diffuse carbon spectrum from regions across this FIB section, with the typical aromatic (C=C), ketone(C=O), carboxyl (COOH) groups commonly seen in chondritic IOM, plus the CO3 carbonate peak. Although thecarbonate peak is very intense, the additional x-ray absorption peaks associated with crystalline carbonates are absent.
In addition, the STEM-EDS shows Ca is absent, and no signs of Fe or Mg carbonate nanocrystals are observed in the
STEM images. XANES spectra extracted from smaller ROIs show variability in the relative intensity of the fourfunctional groups and in some cases distinct aliphatic-rich regions can be found (Fig.1D blue box, 1E blue spectrum).
To better constrain the nature of the diffuse carbon, it is also helpful to analyze samples of particle prepared byultramicrotome and as demineralized acid-insoluble organic matter (IOM) isolates. Those date are discussed but notshown here due to space constraints, but will be presented at the meeting. Some, but not all, of the diffuse organic
matter is preserved in the IOM samples, and comprises the fine-grained porous material referred to as “fluffy”, distinct
from the nanoglobules. Notably, the prominent carbonate peak, easily observed in the FIB sections, is not present in
the IOM XANES data. The CO3 peak is present though difficult to measure in the XANES data from microtomed

particles. Electron energy loss spectroscopy in the STEM, coupled with EDS, shows the carbonate peak is associatedwith organic carbon in direct contact with phyllosilicates. This suggests that different portions of the diffuse IOM
have distinct chemical origins, with the molecular carbonate signature possibly due to reaction of C-rich fluids withphyllosilicates.

Figure 1. A Bright field scanning transmission electron
microscope image montage of a FIB section from particle 108xx. B. Energy dispersive x-ray spectroscopy composite
elemental map of C, Si, Au and Ga. The Au is the substrate,and Ga from FIB carbon deposition. C. Extracted sum spectrum
from the area outlined in white in (C). D. Scanningtransmission x-ray absorption microcopy image of the FIB
section at 288.9 eV. E. Extracted normalized spectrum in
optical density units from representative regions, revealing
pervasive molecular carbonate chemistry and localizedenhancement in aliphatic content.

References[1] Yokoyama T et al. 2022. Science abn7850. [2] Yabuta H. et al. 2022. Abstract #2241. 53d LPSC. [3] Stroud R.
M., et al. 2022. Abstract #2052. 53d LPSC.
The Hayabusa2-initial-analysis Organic Macromolecule Team and Core Team: H. Yabuta, G. D. Cody, C.
Engrand, Y. Kebukawa, B. De Gregorio, L. Bonal, L. Remusat, R. Stroud, E. Quirico, L. R. Nittler, M. Hashiguchi,
M. Komatsu, E. Dartois, J. Mathurin, J. Duprat, T. Okumura, Y. Takahashi, Y. Takeichi, D. Kilcoyne, S. Yamashita,
A. Dazzi, A. Deniset-Besseau, S. Sandford, Z. Martins, Y. Tamenori, T. Ohigashi, H. Suga, D. Wakabayashi, M.
Verdier-Paoletti, S. Mostefaoui, G. Montagnac, J. Barosch, K. Kamide, M. Shigenaka, L. Bejach, T. Noguchi, H.
Yurimoto, T. Nakamura, R. Okazaki, H. Naraka, K. Sakamoto, S. Tachibana, S. Watanabe, and Y. Tsuda

Sulfur-XANES of intact Ryugu grains and the isolated IOM
H. Suga1, Y. Tamenori1, H. Yabuta2, H. Yurimoto3, T. Nakamura4, T. Noguchi5, R. Okazaki6, H. Naraoka6, K. Sakamoto7,
S. Tachibana8, S. Watanabe9, Y. Tsuda7, and the Hayabusa2-initial-analysis IOM team1
Japan Synchrotron Radiation Research Institute (JASRI/SPring-8),1-1-1 Kouto, Sayo, Hyogo pref. 679-5198 Japan,
2
Hiroshima University, Japan, 3Hokkaido University, Japan, 4Tohoku University, Japan, 5Kyoto University, Japan, 6Kyushu
University, Japan, 7JAXA, Japan, 8Univ. of Tokyo, Japan, 9Nagoya University, Japan.
Introduction: The Hayabusa 2 spacecraft was launched on December 2014 to collect samples of the near-Earth C-type(carbonaceous) asteroid (162173) Ryugu [1]. This mission aims to investigate the origin and evolution of the early Solar
System and life. In December 2020, the spacecraft returned 5.42 g of the Ryugu surface samples to the Earth [2]. The initialsample analysis team and the JAXA phase2 curation found that the elemental compositions, mineralogy, and organic chemistryof asteroid Ryugu were identical to those of CI chondrites [e.g., 3-6].
A variety of sulfur-bearing organic molecules have been identified from both soluble organic matter (SOM) andinsoluble organic matter (IOM) in carbonaceous chondrites [e.g., 7-9]. Sulfur has a wide range in oxidation states from -2 to+6, so it can be used as a cosmochemical indicator of redox conditions; therefore, it contributes to elucidating the formation oforganic molecules in the early Solar System. X-ray Absorption Near Edge Structure of Sulfur (S-XANES) can be used toestimate oxidation states of sulfur from a large chemical shift, and the chemical species can be discussed by the spectral profile.
In this study, we conducted the S-XANES analysis on intact Ryugu grains and the isolated IOM to determine the sulfur
composition.
Samples and Method: The Ryugu aggregate samples A0109-21 and C0057-1&2 were selected for S-XANES measurements.
The acid treatment protocol of IOM isolation is described in [3] in detail. The intact Ryugu grains and the isolated IOM wereanalyzed by non-destructive bulk S K-edge XANES analysis at BL27SU in SPring-8.
Results and Discussion: Sulfur-XANES spectra were obtained from the intact Ryugu grains and the isolated IOM. The
spectral profile of the intact grains is composed of the dominant peak around 2470.4 eV and broad spectra ranging from 2475.0
to 2484.0 eV. The peak of 2470.4 eV corresponds to the inorganic sulfide (S1-) [8]. Compared with the spectral profile ofstandard materials in the previous study [e.g., 10], it corresponds to pyrrhotite, a common sulfide in Ryugu [5]. In addition, apeak derived from sulfate (S6+) was observed at 2482.6 eV from A0109-21.
The S-XANES spectra of Ryugu IOM were entirely different from those of the intact grains. The peak around 2472.0
eV corresponding to organic sulfides (C-S-S-C, C-S-C) was the most prominent from the spectra of Ryugu IOM. The shoulder
feature at 2474.3 eV is consistent with the presence of heterocyclic sulfur (S0) [9]. The broad profile ranging at 2477.0–2484.0
eV could be a mixture composed of oxidized organic sulfur species; such as sulfonate (R-SO2O-R’), sulfone (R-SO2-R’), andsulfites (R-SO3) [8]. A moderate peak of sulfates was also observed, which is likely to be correspond to organic sulfate (R-OSO3) because inorganic sulfate compounds should have already been dissolved from the Ryugu samples during acid treatment
to extract IOMs. No significant difference was found between IOMs extracted from A0109 and C0057.
The spectral shapes of the isolated Ryugu IOM were broadly similar to those of IOM from carbonaceous chondrites[8,9], except that the peak derived from inorganic sulfide was not detected from the Ryugu IOM. In particular, moderate
abundances of heterocyclic sulfur and oxidized organic sulfur functional groups in Ryugu IOM were closer to those in IOM
isolated from CM rather than that of CI. CI experienced a higher temperature (100–150 °C) than CM, and heterocyclic sulfur
and oxidized organic sulfurs in them are the aqueous alteration products related to the alteration temperature [8]. Our study
shows that Ryugu experienced as low temperature as CM chondrites during the parent body aqueous alteration, which isconsistent with the discussion by [5].
Conclusion: In this study, organic sulfur functional groups were identified from the IOM isolated from Ryugu samples by SXANES. Our results indicate that reductive organic sulfur components, i.e., organic sulfides (C-S-S-C, C-S-C), are dominantrelative to oxidized organic sulfurs in Ryugu IOM. Ryugu IOM experienced low-temperature parent body aqueous alteration.
References[1] Tachibana S. et al. 2014. Geochemical Journal 48:571–587. [2] Yada T. et al. 2022. Nature Astronomy 6:214–220. [3]Yabuta, H. et al. 2022, Science, under review. [4] Yokoyama T. et al. 2022. Science, eabn7850. [5] Nakamura T. et al. 2022.

Science, abn8671. [6] Ito M. et al. 2022. Nature Astronomy, https://doi.org/10.1038/s41550-022-01745-5. [7] Schmitt-Kopplin
Ph. et al. 2010. PNAS 107:2763–2768. [8] Orthous-Daunay FR. et al. 2010. Earth and Planetary Science Letters 300:321–328.
[9] Bose M. et al. 2017. Meteoritics & Planetary Science 52:546–559. [10] Suga H. et al. 2021. Minerals 11:514.
The Hayabusa2-initial-analysis Organic Macromolecule and Core Teams: H. Yabuta, G. D. Cody, C. Engrand, Y.
Kebukawa, B. De Gregorio, L. Bonal, L. Remusat, R. Stroud, E. Quirico, L. R. Nittler, M. Hashiguchi, M. Komatsu, E. Dartois,
J. Mathurin, J. Duprat, T. Okumura, Y. Takahashi, Y. Takeichi, D. Kilcoyne, S. Yamashita, A. Dazzi, A. Deniset-Besseau, S.
Sandford, Z. Martins, Y. Tamenori, T. Ohigashi, H. Suga, D. Wakabayashi, M. Verdier-Paoletti, S. Mostefaoui, G. Montagnac,
J. Barosch, K. Kamide, M. Shigenaka, L. Bejach, T. Noguchi, H. Yurimoto, T. Nakamura, R. Okazaki, H. Naraoka, K.
Sakamoto, S. Tachibana, S. Watanabe, and Y. Tsuda

Investigating the noble gas and nitrogen relationship between Ryugu and othercarbonaceous chondrites
M. W. Broadley1, D. J. Byrne1, E. Füri1, L. Zimmerman1, B. Marty1 R. Okazaki2, T. Yada3, F. Kitajima2, S. Tachibana3,4, K.
Yogata3, K. Sakamoto3, H. Yurimoto5, T. Nakamura6, T. Noguchi7, H. Naraoka2, H. Yabuta8, S. Watanabe9, Y. Tsuda3, and the
Hayabusa2 Initial Analysis Volatile Team
1

Université de Lorraine, CNRS, CRPG, F-54000 Nancy France,, 2Kyushu University, Japan. 3Institute of Space andAstronautical Science, JAXA, Japan, 4University of Tokyo, Japan, 5Hokkaido University, Japan, 6Tohoku University, Japan,
7
Kyoto University, Japan, 8Hiroshima University, Japan, 9Nagoya University, Japan.
The Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) successfully returned surface material from theC-type asteroid (162173) Ryugu to Earth. This material has now been classified as closely resembling CI-type chondrites,
which are the most chemically pristine meteorites. The analysis of material from the surface of Ryugu therefore provides aunique opportunity to analyze the volatile composition of material that originated from a CI-type asteroid [1] withoutcomplications arising from terrestrial contamination. Given their highly volatile nature, the noble gas and nitrogen inventoriesof chondrites are highly sensitive to different alteration processes on the asteroid parent body, and to terrestrial contamination.
We investigated at CRPG Nancy (France) the nitrogen and noble gas signature of two grains collected from the first andsecond touchdown sites [2] to provide an insight into the formation and alteration history of Ryugu. We find that theconcentration of trapped noble gas in the Ryugu grains is greater than the average composition of previously measured CI
chondrites. The trapped noble gases are primarily derived from phase Q, although a significant contribution of presolar
nanodiamonds Xe-HL is noted. The large noble gas concentrations coupled with a significant contribution of presolar
nanodiamonds suggests that the Ryugu grains may represent some of the most primitive unprocessed material from the earlysolar system.
In contrast to the noble gases, the abundance of nitrogen and δ15N composition of the two Ryugu grains are lower than the
average CI chondrite value. We attribute the lower nitrogen abundances and δ15N measured in this study to the preferential
loss of a 15N-rich phase from our grains during aqueous on a parent planetesimal. The analyses of other grains returned from
Ryugu have shown large variations in nitrogen concentrations and δ15Nindicating that alteration fluids heterogeneouslyinteracted with material now present on the surface of Ryugu. Finally, the ratio of trapped noble gases to nitrogen is higher
than CI chondrites, and is closer to refractory phase Q and nanodiamonds. This may indicate that Ryugu experienced aqueousalteration that led to the significant loss of nitrogen likely from soluble organic matter hosted in our two grains without
significant modification of the noble gas budget, which is primarily hosted in insoluble organic matter and presolar diamonds
and is more resistant to aqueous alteration.
References[1] Yokohama et al. 2022 Science DOI: 10.1126/science.abn7850. [2] Okazaki et al. Science, Accepted.

Nitrogen isotopes in Ryugu return samples revealed by the stepwise combustion analysis,in comparison with CI falls and Antarctic finds
Ko Hashizume1, Akizumi Ishida2, Ayano Chiba1, Ryuji Okazaki3, Toru Yada4, Fumio Kitajima3,
Hisayoshi Yurimoto5, Tomoki Nakamura2, Hiroshi Naraoka3, Takaaki Noguchi6, Hikaru Yabuta7, Shogo Tachibana8,
Sei-ichiro Watanabe9, Kanako Sakamoto4 and Yuichi Tsuda4
1Faculty of Science, Ibaraki University, 2Department of Earth Science, Tohoku University, 3Department of Earth and Planetary Sciences,

Kyushu University, 4Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 5Department of Earth andPlanetary Sciences, Hokkaido University, 6Division of Earth and Planetary Sciences, Kyoto University, 7Department of Earth and Planetary
Systems Science, Hiroshima University, 8UTokyo Organization for Planetary and Space Science, The University of Tokyo, 9Department ofEarth and Environmental Sciences, Nagoya University

Nitrogen isotope ratio is a powerful tool in cosmochemistry to decipher theorigin and evolution of planetary materials. The nitrogen isotope ratio 15N/14N,
usually expressed by the delta notation, δ15N ≡ [(15N/14N)/(15N/14N)AIR - 1] x1000 (‰), exhibits large variations among different meteorites (Fig. 1). The
isotope ratio of nitrogen, being a typical volatile element, is particularly useful
to constrain the formation and evolution processes of planetary atmosphere for
Earth and other rocky planets. Viable Earth formation models assume that
CI/CM-like volatile-rich carbonaceous chondrites may have contributed as oneof the important volatile sources for Earth, if not entirely on the source for the
rocky body of this planet. CI chondrites, the most volatile-rich chondritic groupknown so far, exhibit δ15N values typically around +40 ‰. The higher δ15N
values for the CI chondrites than for the present Earth atmosphere may impose
important constraints on the formation and evolution history of the Earthatmosphere.
The texture and mineralogical composition of Ryugu samples are similar to
CI chondrites. Three fall meteorites categorized as CI chondrites, Alais, Ivuna
and Orgueil, have been studied so far for nitrogen isotopes. However, recent
search on the vast stock of Antarctic meteorites has revealed that there exist
several Antarctic meteorites which exhibit similar texture and mineralogicalcomposition with the fall CI chondrites. Though similar, these potential CI
Antarctic meteorites still exhibit marked difference from the CI falls, particularly
from the volatile-element points of view: The majority of phyllosilicates are
dehydrated in these Antarctic CI meteorites, while the phyllosilicates of CI falls
mostly remain hydrated [4]. Fig. 2 compares bulk nitrogen isotope composition
of Ryugu samples with those of CI chondrites, falls (Alais, Ivuna and Orgueil)
and an Antarctic find (Y-980115). Interestingly, the δ15N values are correlatedwith the nitrogen concentrations: lower the concentration, lower the δ15N value.
Note that this correlation is not compatible with the one we normally expect tooccur by Rayleigh-distillation type devolatilization process, nor by addition of aterrestrial contamination at different degrees. Apparently, an unknown isotope
fractionation (or mixing) effect in the nitrogen isotope composition has emerged
among the CI-chondrite family.
The stepwise analyses may provide isotope “fingerprints” to compare theidentities of planetary materials. By this method, we may distinguish possible
endmembers co-existing in the samples. Fig. 3 demonstrates the usefulness of
this method, for example, by the profiles obtained from a Ryugu bulk sample,
compared with the one for CI chondrite Orgueil. These profiles provide
information, not only the bulk δ15N value and bulk N and C concentrations, but
include points such as, (a) presence of a nitrogen component easily combustible
at low (>200oC) temperatures with δ15N < +10 ‰, (b) a component released

Fig 1. Bulk nitrogen isotope composition among
different meteorites. Compilation by Hashizume(2015) [1]. Important isotope data beyond thisrange include protosolar composition (-380 ‰;Marty et al, 2011 [2]) or cometary range (+600 +1000‰; Marty et al, 2016 [3])Fig 2. Bulk nitrogen isotope composition
of Ryugu samples and CI chondrites.
Ryugu data labelled A0105-07 and C010607 are reported in [5] (Ibaraki data);
A0105-05 and C0106-06 in [6] (Nancy
data); A0106 in [7] (JAMSTEC data). The
other solid marks are literature bulk data
for CI chondrites from [8-13]. Open marks(Ivuna and Y-980115) are sums of
unpublished stepwise combustion data
recently acquired at Ibaraki Univ.

spike-wise at ~500oC with δ15N « 0 ‰, which is inferred to be hosted by presolar
nano-diamonds, (c) one released at 600-800oC exhibits a plateau δ15N value of+17‰, and (d) finally the one released at 1100oC and above with a δ15N value as
low as -20‰. Apparently, nitrogen in Ryugu consist of several components with
distinct origins. The combustion profile of Orgueil, though shows partially similar
isotope signature with Ryugu, for example the one presumably from presolar
microdiamonds, exhibits generally δ15N higher than Ryugu by several tens of ‰,and higher N concentrations. The differences are particularly prominent at low
temperature range below 600oC, which is generally considered to be the range
where N from the organic matter is released. Seemingly the organic matter with
δ15N values as high as +60‰ is missing in Ryugu, which could correspond to the“missing component” inferred by comparing the bulk composition for samples
belonging to the CI chondrite family (Fig. 2). It is worth to note that, though themissing component could be inferred to be an organic component from the
combustion temperature, it seems to be decoupled with the bulk of carbon, andcould be a component with a peculiar chemical composition with much higher N/Cratios than the bulk composition.
In this presentation, we will compare the stepwise combustion profiles
obtained for Ryugu, with those of Ivuna and Y-980115 recently obtained using thesame facility equipped at Ibaraki University. Though part of the Ryugu data
(A0105-07 and C0106-07) exhibit similar bulk nitrogen concentrations and δ15N
values with Y-980115, we will demonstrate that the combustion profiles appear
quite different, possibly suggesting that the N isotope evolution mechanism could
be different between these two kinds of CI-like samples.

Fig 3. Comparison of stepwise combustion
profiles for Ryugu sample C0106-07 (bttm)
obtained at Ibaraki Univ, and literature data
[11] for Orgueil (top). The concentrations
are plotted in arbitrary unit, although theareas of the bars between different
temperature ranges, and also between thetwo samples for the same element correctly
represent the relative concentrations.

References[1] Hashizume K. 2015. In “Encyclopedia of Astrobiology” doi:10.1007/978-3-642-27833-4_1065-3. [2] Marty B. et al.
Science 332:1533. [3] Marty B. et al. 2016. Earth and Planetary Science Letters 441:91. [4] King AJ. et al. 2019. Geochemistry79:125531. [5] Okazaki R. et al. 2022. Abstract #1348. 53rd LPSC.[6] Byrne DJ. et al. 2022. Abstract #2096. 53rd LPSC. [7]Naraoka H. et al. 2022. Abstract #1781. 53rd LPSC. [8] Kerridge JF. 1985. Geochimica et Cosmochimica Acta 49:1707. [9]Robert F. & Epstein S. 1982. Geochimica et Cosmochimica Acta 46:81. [10] Yang J. & Epstein S. 1983. Geochimica et
Cosmochimica Acta 47:2199. [11] Grady MM. et al. 2002. Meteoritics & Planetary Science 37:713. [12] Pearson VK. et al.
2006. Meteoritics & Planetary Science 41:1899. [13] Chan QHS. et al. 2016. Earth, Planets and Space 68:7.

Visible to Near-Infrared Spectrophotometry of C0002 Powder Samples of Asteroid 162173 Ryugu
in Comparison with ONC-T and NIRS3 Instruments Onboard Hayabusa2 Spacecraft
T. Hiroi1, R. E. Milliken1, K. M. Robertson1, C. D. Schultz1, K. Amano2, T. Nakamura2, H. Yurimoto3, T. Noguchi4, R.
Okazaki5, H. Yabuta6, H. Naraoka5, K. Sakamoto7, S. Tachibana8, T. Yada7, M. Nishimura7, A. Nakato7, A. Miyazaki7, K.
Yogata7, M. Abe7, T. Okada7, T. Usui7, M. Yoshikawa7, T. Saiki7, S. Tanaka7, T. Fuyuto9, S. Nakazawa7, S. Watanabe10, Y.
Tsuda7, S. Sasaki11, H. Kaiden12, K. Kitazato13, M. Matsuoka14, and E. Tatsumi15
1
Brown University, 2Tohoku University, 3Hokkaido University, 4Kyoto University, 5Kyusyu University, Japan, 6Hiroshima
University, 7JAXA Institute of Space and Astronautical Science, 8University of Tokyo, 9Kanagawa Institute of Technology,
10
Nagoya University, 11Osaka University, 12National Institute of Polar Research, 13University of Aizu, 14National Institute ofAdvanced Industrial Science and Technology, 15Instituto de Astrofisica de Canarias.
Samples and Spectrophotometric Measurements
Powder samples of the largest sampled stone C0002 of asteroid
162173 Ryugu returned by Hayabusa2 mission were loaned for visible
and near-infrared (VNIR) spectrophotometric studies. The powder
samples were produced by physical-strength measurements and werepartially contaminated with a glue (glycol phthalate). Part of thepowder was washed with acetone, which turned it into a fine powder(<125 µm estimate). Large glue fragments were handpicked from theremaining coarse powder (125-500 µm estimate) and a bulk powder
sample was produced by combining the two powder samples.
Bidirectional VNIR reflectance spectra (0.3-2.6 µm) of the samples
were measured at NASA Reflectance Experiment Laboratory (RELAB)
using its bidirectional reflectance spectrometer at the standard viewing
geometry of 30° incidence and 0° emergence angles, and theirphotometric properties were measured at a limited number of viewing
geometries. The photometric property of a Labsphere Spectralon
standard was measured relative to the standard viewing geometry at 550
nm in wavelength.
Biconical Fourier-transform infrared (FTIR) reflectance spectra (1100 µm) of the samples were measured in a dry-air purged environment.
The VNIR and FTIR spectra were combined at 2.5 µm in wavelength byscaling the FTIR reflectance to the VNIR reflectance.

Fig. 1. Phase-angle dependency of reflectances of C0002
powder samples at 550 nm in wavelength.

Spectrophotometric Analyses
Phase-angle dependency of the powder samples at 550 nm inwavelength is plotted in Fig. 1, and VNIR-FTIR spectra up to 4 µm are
Fig. 2. VNIR-FTIR spectra (0.3-4 µm) and photos ofplotted in Fig. 2 along with sample photos under a microscope. The C0002 powder samples. Cup diameter is 4 mm.
phase curve in Fig. 1 shows much brighter albedo and lower inclination
than those obtained by ONC-T measurements in proximity of asteroid
Ryugu [1]. It may be due to the difference between the flatter surfaceof the powder sample compared with the rough asteroid surface that
includes shadows. Further photometric modeling analysis is warranted.
The OH and H2O absorption bands near 3 µm in spectra shown in
Fig. 2 were analyzed in the same manner as [2]. Natural log
reflectance spectra of the powder samples were fit with a linear-inwavelength continuum background and Gaussians (in wavenumber)over the wavelength range of ~2.6-3.6 µm (variable depending onspectral shape). One of the results (fine powder) is shown in Fig. 3.
Because the first two Gaussian bands (labeled as 1 and 2 in Fig. 3) are
believed to be characteristic of carbonaceous chondrite classes [2], their Fig. 3. Gaussian fitting of C0002 fine powder spectrum.

Band 1 centers and Band 1 / Band 2 strength ratios are plottedin Fig. 4. Ryugu C0002 powders all plot very close tounheated CI1 chondrites and Ivuna heated up to 400°C. This
result is consistent with previous studies of Ryugu being
mostly unheated CI1 chondrite [e.g., 3], and low-degree
heating may not be detected by this method.
Comparison with ONC-T and NIRS3 Observations
Shown in Fig. 5 is a plot of linear combinations of the
VNIR-FTIR spectra of the C0002 fine and coarse powder
samples to match average spectra of representative (butdifferent) areas of Ryugu acquired by ONC-T and NIRS3.
Most of the ONC-T band reflectance values, overall spectral
shape, and 2.7 µm absorption band strength could be matched.
However, when the 2.7 µm band region is closely
examined, there are significant mismatches between the NIRS3
and C0002 spectra. The NIRS3 spectrum shows absorption
bands at 2.65 and 2.81 µm which are absent in C0002 spectrum.
If this is not due to NIRS3 data calibration errors, there may besome unstable phases lost during the sample recovery.
Another mismatch is the 2.7 µm band center position.
Fig. 6 shows the NIRS3 spectrum and the modeled C0002
spectrum with its wavelength resolution matched with that of
NIRS3 spectrum (18 nm). While the NIRS3 spectrum (openblack squares) shows the band center at around 2.72 µm
asymmetrically expanded toward the longer wavelength, themodeled C0002 powder spectrum (solid purple circles) shows
the band center clearly at a shorter wavelength near 2.71 µm.
When the C0002 powder spectra are artificially shifted toward
the longer wavelength by 6 nm before resampling for the
NIRS3 resolution, the resulting modeled spectrum (open purple
circles) matches with the NIRS3 spectrum much better. A
difference in band position is consistent with spectra of ejecta
from an artificial crater showing shorter 2.7 µm band positions[4].
Summary and Discussion
If the C0002 powder samples represent the average surface
material of asteroid Ryugu, this study indicates that the global
space weathering may have occurred mainly by solar wind thatcaused the 2.7 µm absorption band center to be shifted toward a
longer wavelength [e.g., 5].
If such space weathering
occurred, the 2.7 µm band strength and the visible spectra
measured with ONC-T might have been altered as well. This
would influence the physical interpretation of the model fits
shown in Fig. 5.
References[1] Tatsumi E. et al. 2020. A&A 639:A83. [2] Hiroi T. et al.
2021. Polar Science 29:100723. [3] Yokoyama T. et al. 2022.
Science 10.1126:7850. [4] Kitazato K. et al. 2021. Nature
Astronomy 5:246. [5] Lantz C. et al. 2015. A&A 577:A41.

Fig. 4. Band 1 center vs. Band 1 / Band 2 strength ratio of C0002
powder samples plotted with hydrous carbonaceous chondrites(modified from [2]).

Fig. 5. Comparison of C0002 powder spectra with ONC-T andNIRS3 data.

Fig. 6. Matching of the 2.7 µm absorption band feature between
the modeled C0002 powder spectra and NIRS3 spectrum in Fig. 5.

Reflectance spectrum of Ryugu grains and their acid-extracted residues in the UV–VIS range
K. Yumoto1, H. Yabuta2, S. Sugita1,
The Hayabusa2 initial analysis IOM team, and the Hayabusa2 Initial Analysis Core team1
Univ. of Tokyo, Japan.
2
Hiroshima Univ., Japan.
Introduction: Reflectance spectrum in the ultraviolet to visible (UV–VIS) range is among the most frequently used wavelength
range for observations of main-belt C-complex asteroids. Furthermore, distinctive spectral differences (e.g., spectral slope,absorption at UV) have been reported among C-complex asteroids [1]. However, their interpretation is not necessarilystraightforward. This is because the UV–VIS spectrum is controlled by various physical (e.g., grain size) and/or chemical (e.g.,mineralogy) state of the reflector. Thus, it is difficult to translate the UV–VIS spectral properties into physically andmineralogically well-defined constraint(s) on asteroid materials.
Studies on the UV–VIS spectra of samples returned from asteroid Ryugu may help us resolve this problem. This is because
the physical/chemical state of the returned samples have been studied in detail and pre-processing of the samples allows us tocontrol the sample state (e.g., extraction of certain minerals by acid treatments). Remote sensing by the Optical Navigation
Camera (ONC) onboard Hayabusa2 revealed a dark/flat and homogeneous UV–VIS spectrum on the surface of Ryugu [2]. The
dark/flat nature of the spectrum was confirmed by initial description of the returned samples [3, 4]. However, grain-to-grain
spectral variation was substantially higher than those observed by remote sensing [5]. The variation in reflectance has been
attributed to specular reflections caused by micro-scale facets, which were not resolved by remote sensing [5]. Such a result
suggests that the texture of grains and abundance of opaque minerals with high reflectivity in the UV–VIS range can highly
affect the reflectance of C-complex asteroids. However, the specific (sets of) minerals and/or organic matter that affect the
spectra of returned samples have not been identified yet.
In this study, we compared the UV-VIS spectra of intact Ryugu grains with those of acid-extracted residues to evaluate
how insoluble organic matter (IOM) contribute to Ryugu’s dark and flat spectrum.
Samples and methods: We measured the UV–VIS spectra of returned samples with and without acid treatments that dissolve
specific minerals: intact (i.e., un-extracted) grains, HCl-extracted residues, and HCl/HF-extracted residues. All samples wereallocated to and processed by the Hayabusa2 IOM team. We measured 50 intact grains from aggregate samples A0106, A0108,
and C0109 and 35 grains in the HCl-extracted residues from A0108. Minerals, such as carbonates, sulfides, and magnetite areremoved by HCl extraction, and the residue mainly comprises of phyllosilicates and IOM. We also measured 19 grains in the
HCl/HF-extracted residues from C0002 and C0107. HCl/HF extraction only leaves IOM within the residue. The sizes of all
grains ranged from ~10 µm to 200 µm except for one ~1 mm intact grain from A0108.
The UV–VIS spectra were measured by a high-resolution multi-band spectrometer developed at the University of Tokyo.
The spatial resolution is ~2 µm at 550 nm with a 300 µm × 300 µm field of view. The spectrometer is equipped with 25 narrow(10 nm width) band-pass filters from 230 to 1000 nm. Energy of the light power was
reduced (30 µW at 550 nm) to avoid sample alteration. A standard diffuse reflector with99% reflectance (Spectralon/Labsphere) was used for radiometric calibration.
Results and Discussion: The reflectance image of the largest grain measured in this study
is shown in Fig. 1. Areas with high reflectance in Fig. 1 are specular reflections. Such
specular reflections were also observed in acid-extracted residues. These photometriceffects were not corrected in our analysis but reflectance from the entire grain (within thedashed curve in Fig. 1) were integrated to obtain the average reflectance for each grain.
The spectrum of a typical grain for each of the three mineralogic composition type is shownin Fig. 2. These spectra show that mineralogy have a significant effect on the 1) reflectance,
2) UV absorption feature, and 3) VIS spectral slope as follows.
Fig 1 Reflectance image of the
1. Reflectance: Though reflectance has large grain-to-grain variation, Fig. 2 shows largest grain (from A0108)
that phyllosilicate + IOM residues (i.e., HCl-extracted residues) have a measured in this study. The dashedsignificantly darker reflectance. Such correlation of reflectance with mineralogy curve shows the rim of the grain.
provides insights into the reason for the dark nature of carbonaceous materials. Our result implies that the mixing stateof phyllosilicates with IOMs may be important in effectively darkening the carbonaceous material. However,reflectance of acid-extracted residues can be affected by physical and/or chemical alteration caused by the extraction
process. Characterization of such alteration is needed to verify the implication of our result.
2. UV absorption feature: Fig. 2 shows that though spectra of intact grains are flat throughout the UV–VIS range, spectraof acid-extracted residues show a broad UV absorption centered at ~300 nm. The absorption shape of IOM in Ryugu
samples, which is characterized by steepening of the spectral slope from VIS to UV, is consistent with those in
Murchison meteorites [6]. Meteoritic studies show that such UV absorption may be caused by abundance of C-H bonds
in organics [7] or deficit of magnetite [8]. Since acid extraction removes magnetite and increases the concentration of
IOM in the residues, our result is consistent with both hypotheses.
3. VIS slope: Fig. 2 shows that IOMs exhibit a redder slope in the VIS range. Such trend is consistent with measurementsof IOMs in carbonaceous meteorites [6, 9].
These correlation of the spectra with demineralization can be clearly observed in Fig. 3; residues have deeper UV absorption
and IOMs have redder VIS slope. This result suggests that variations in UV absorption and spectral slope observed among Ccomplex asteroids [1] may represent difference in relative abundance of organics to other acid-soluble minerals.
Conclusion: We measured the UV–VIS spectra of Ryugu returned samples and their acid-extracted residues to evaluate how
IOM contributes to the dark and flat spectra of Ryugu. Our results show that a variation of constituting minerals/organics,
especially demineralization of opaque minerals with higher reflectivity and increase in concentration of IOM, has a significant
effect on the reflectance, UV absorption feature, and VIS slope of Ryugu returned samples. This result implies that spectral
variation in the UV–VIS range observed among C-complex asteroids may represent chemical variation such as abundance oforganics and other acid-soluble minerals.

Fig 2 (Left) Average reflectance spectrum for each of the mineralogic composition. (Right) Reflectance spectrum after normalization
at 550 nm. The patch represents the standard error observed among grains.

Fig 3 Correlation plot between UV and VIS spectral slope. Each plot shows the spectrum for each grain measured in this study.
References: [1] Bus & Binzel (2002). Icarus, 158(1), 146-177. [2] Sugita et al. (2019). Science, 364(6437), eaaw0422. [3]Yada et al. (2021) Nat. Astron., 6(2), 214-220. [4] Cho et al. (2022). PSS, 221, 105549. [5] Yumoto et al. (2022). JpGU,#C002365. [6] RELAB, PDS Geosciences Node Spectral Library. [7] Hendrix et al. (2016) MAPS, 51(1), 105-115. [8] Hendrix
et al. (2019). GRL, 46(24), 14307-14317. [9] Kaplan et al. (2019). MAPS, 54(5), 1051-1068.

Nano-infrared spectroscopy of Ryugu samples using AFM-IR measurement
Van T. H. Phan1, Pierre Beck1, Rolando Rebois1 and Takaaki Noguchi2, the Hayabusa2-initial-analysis Sand team.
1

Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), France
2
Kyoto University, Division of Earth and Planetary Science, Kyoto, Japan

Introduction: In late 2020, samples of Ryugu (C-type) were collected from its asteroid and returned to Earth, led by theJapan Aerospace Exploration Agency (JAXA), thought to be similar in composition to CI chondrites 1. Understanding how andunder what conditions the organic matter interacted with inorganic phases, is a key step in hypothesizing the mechanism ofaccreted organic matter. This “fresh” carbonaceous material allows us to investigate the best preservation sample without
terrestrial impact 2. In addition, the “bulk” Ryugu samples also show some spectral reflectance bands corresponding to the NHrich compounds 3. Altogether, our study aims to characterize the minerology, organic matter and the possible N-bearing
molecule. To gain insight into fine meteorites matrices containing an interplay of ingredients at the sub-micro scale, it requires
analytical techniques with the sub micrometer spatial resolution to separate their composition and understand theirpetrographic relations. Infrared spectroscopy (IR) is an effective method and a non-destructive technique for molecular-atomic
scale vibrations of organic and inorganic compounds in the extra-terrestrial materials 4,5. However, conventional IR
spectrometers use mirror-based optics to focus the beam on the sample and thus the spatial resolution is limited by thediffraction limit. This IR diffraction limitation can be overcome by using AFM-IR (Atomic Force Microscopy-Infrared
Spectroscopy), based on the combination of infrared spectroscopy and atomic force microscopy to efficiently distinguishspectral signatures of the different constituents 6,7.
Our study aims to characterize two different grains of Ryugu that can be affected by the weathering space prepared by“Min-pet fine team” (Sand team)8 as crushed sample between two diamond windows, as well as two different Orgueil samples:
one comes from the Paris Museum (Orgueil Museum) and the another one expected “fresher” kept in the sealed flask (Orgueil
Flask) from collection of M. Bizzaro. Here, we report the comparison of AFM-IR results between Ryugu and Orgueil as a CI
chondrite both in minerology and organic structure.
Samples preparation and methods: Two grains of Ryugu (P0032 and P0038), received from the Sand initial analysis
team, were prepared by crushing 10 – 20 µm fragments between two diamond windows. As with Ryugu, the Orgueil Museum
and Orgueil Flask samples were also pressed down to the appropriate thickness for AFM-IR measurement. Before AFM-IR
analysis, all samples were performed the micro-FTIR analysis to select the region of interests (ROI).
IR spectroscopy and AFM-IR measurement: The micro-infrared spectra were first analyzed with a Bruker Hyperion
3000 infrared microscope. The nano-IR measurements were obtained with a Bruker nanoIR3s at IPAG (Grenoble, France),
which includes an AFM probe capable of scanning the sample and generating topographic images at nm vertical resolution.
The AFM-IR measurement can be performed in two acquisition modes: AFM and chemical imaging, and local, single point IR
spectrum. First, the wavenumber is fixed and the tip moves along the surface to obtain the AFM topography and IR absorption
at the given wavenumber. Second, the position of the tip is fixed and the IR laser is tuned to the possible spectral range (2000 –700 cm-1 with the APE laser at IPAG) which provides the local absorption spectrum at the point of interest 6.
Results and Discussion: We are able to characterize two bulk grains of Ryugu with the region of interest 5×5 µm2 (grain
P0032) in the in Figure 1 and the ROI of 3×3 µm2 (grain P0038) in Figure 2.

Figure 1. AFM-IR of a 5×5 µm2 region of interest (ROI)
acquired with the NanoIR3s at IPAG (Grenoble, France)of grain P0032. Left images: AFM image, the AFM-IR
images of 1720 (red), 1450 (blue), 1100 (yellow), 1000
cm-1 (green) corresponding to C=O, carbonate, sulfate andSi-O; and RGB (red, green, blue) composition image fromthe combination of three AFM-IR absorption images: 1720,
1450 and 1000 cm-1 respectively. Right panel: comparisonof local AFM-IR spectra on the carbonate rich area (inblue), and the phyllosilicate area (in green) withphyllosilicate signature of Orgueil Flask, µ-FTIR spectraof Ryugu, calcite and dolomite minerals.

In the first grain, P0032, AFM-IR images at different wavenumber were obtained at 1720, 1450, 1100 and 1000 cm-1 inthe left panel corresponding to carbonyl (C=O), carbonate, sulfate and phyllosilicate (Si-O), respectively (Figure 1). The threemaps of 1720, 1450 and 1000 cm-1 wavenumber were overlaid in the RGB composite image, allowed us to identify the twodifferent domain compositions in the mapped area: the green area can be distinguished by a strong absorption at 1000 cm-1
attributed to the presence of phyllosilicate; the blue/purple area shows a strong absorption at 1450 cm-1 related to carbonate.
Numerous spectra were obtained across this ROI shown in the right panel and compared to AFM-IR spectra of Orgueil Flask,
dolomite, calcite and µ-FTIR of the same P0032 grain. Spectrum A, the average of hundreds of spectra in the green region
shows signature at 1020 cm-1 corresponding to phyllosilicate (e.g., saponite, serpentine). Compared to the Orgueil
phyllosilicate spectra, Ryugu is lack of a sulfate signature at 1100 cm-1. However, we observed that some purple areas havestronger absorption at 1100 cm-1 and AFM-IR spectra also confirm the two peaks at 1100 and 840 cm-1 (B spectrum). This
Ryugu sample was collected in the fine-grained fraction, affected by space weathering 8, the phyllosilicate-rich region can be
modified. C spectrum in the blue region suggests the presence of carbonate with two strong signatures at 1440 and 860 cm-1,
all indicative of dolomite or calcite.
In the second Ryugu grain, P0038, we first collected the different images at 1720 (red), 1450 (blue) and 1000 cm-1
(green) in ROI of 20×20 µm2 and overlaid them in the RGB composite image in the upper left panel. We found a ~ 1µmdiameter globule with strong absorption at 1720 cm-1 corresponding to C=O in the organic material (Figure 2). Therefore, theROI of 3×3 µm2 was selected to obtain the different images at 1720, 1600, 1450 and 1000 cm-1. The RGB composite(combined between the images at 1720, 1450 and 1000 cm-1) show an organic globule in red with strong absorption at 1720
cm-1. Later, the contact AFM-IR spectra also confirm the presence of organic matter with two distinct features at 1720 and
1610 cm-1 corresponding to C=O and C=C, respectively. Although the AFM-IR images only show the strong organic
appearance, the AFM-IR spectra of organic globule still mixes with the minerals. Compared to the organic matter obtained at
Orgueil described in 9, the Ryugu organic material is more aromatic. The more diffuse organic may present in this ROI but still
finely mixed with phyllosilicate.

Figure 2. AFM-IR of a 3×3 µm2 region of interest (ROI)
acquired with the NanoIR3s at IPAG (Grenoble, France) ofgrain P0038 from the RGB image of 20×20 µm2 region on theupper left panel. Right images: AFM image, the AFM-IR
images of 1720 (red), 1600 (pink), 1450 (blue), 1000 cm-1
(green) corresponding to C=O, C=C, CO3/CH2 bend, and Si-O;
and RGB (red, green, blue) composition image from the
combination of three AFM-IR absorption images: 1720, 1450
and 1000 cm-1, respectively. Lower left panel: comparison of
local AFM-IR spectra on the organic globule (red), and thephyllosilicate area (green) with organic matter of Orgueil andµ-FTIR spectra of Ryugu.

Conclusion: The complete results and discussion of this study will be presented at the conference. So far, we confirm
that the AFM-IR technique allows us to disentangle the IR signatures of phyllosilicate, carbonate and organic matter in Ryugu
at the sub-micron scale. In minerology, compared to Orgueil, the sulfate signatures almost absent from the phyllosilicate, butsome modifications in Si-O-rich areas were observed. In the organic structure, the weak organic signature is diffuse andsignificantly intermixed with phyllosilicate, similar to the diffuse organic of Orgueil. A 1 µm-organic globule was also
observed with clear C=O and C=C features in its structure. This organic matter globule is more aromatic compared to theorganic matter in Orgueil meteorites.
Reference: [1] Yokoyama T. et al. 2022 Science (80). [2] Yada T. et al. 2021 Nat Astron. [3] Pilorget C. et al. 2022. Nat
Astron. [4] Orthous-Daunay FR. et al. 2013. Icarus. [5] Phan VTH. et al. 2021. Spectrochim Acta - Part A Mol Biomol
Spectrosc. [6] Dazzi A, Prater CB. 2017. Chem Rev. [7] Mathurin J. et al. 2019. Astron Astrophys. [8] Noguchi T. et al. 2022.
Abstract #1747. 53rd LPSC. [9] Phan VTH. et al. 2022. Meteorit Planet Sci.

Multi-scale variations of the ~2.7µm feature in Ryugu samples, observed by MicrOmega
1

Le Pivert-Jolivet, T.; 1,2Pilorget, C.; 1Brunetto, R.; 1Bibring, J.-P.; 3Nakato, A.; 1Hamm, V.; 3,4Hatakeda, K.; 1Lantz, C.;
Loizeau, D.; 1,5Riu, L.; 3Yogata, K; 1Baklouti, D.; 1Poulet, F.; 1Aléon-Toppani, A.; 1Carter, J.; 1Langevin, Y.; 3,6Okada, T.;
3
Yada, T.; 3,6Usui, T. and the MicrOmega ISAS Curation Team

1

1

IAS, Université Paris-Saclay, CNRS, France, 2Institut Universitaire de France, 3Institute of Space and Astronautical Science,
Japan Aerospace Exploration Agency, 4Marine Works Japan, Ltd, 5ESAC, ESA, Madrid, Spain, 6University of Tokyo, Bunkyo,
Tokyo 113-0033, Japan

Hayabusa2 is the first space mission to study and collect samples from a C-type asteroid. In December 2020, the spacecraft
brought back to Earth ~5.4g of materials from the surface of asteroid (162173) Ryugu. The samples were collected from two
different sites TD1 and TD2 [1] at the surface of the asteroid. The second touchdown was performed near the artificial crater
created by the small carry-on impactor [2] to collect both surface and subsurface materials. The samples were delivered to
JAXA (Japan Aerospace eXploration Agency) Extraterrestrial Curation Center for preliminary analyses. They were extracted
from chambers A and C, corresponding to TD1 and TD2 respectively, weighed and analyzed in a controlled N2 environment
by an optical microscope, a FTIR, and MicrOmega, a near-infrared (0.99-3.65 µm) hyperspectral microscope. MicrOmega
acquires images of 256x250 pixels with a spatial resolution of 22.5 µm. The total field of view covers ~5.7x5.7mm² [3]. The
first spectral characterization of the bulk samples within the Curation Facility [4,5] showed that the grains are extremely dark
and exhibit absorption features at 2.72 µm, 3.1 µm and 3.4 µm due to phyllosilicates, NH-rich compounds, and organics and/or
carbonates respectively. The ~2.7 µm feature was also observed on the asteroid’s surface by the NIRS3 spectrometer [6]. In
addition to the bulk samples, observations of individual grains, extracted from the bulks, were performed with MicrOmega.
We investigate here the variations of the ~2.7 µm feature at different scales, from the millimeter scale to the hundred microns
scale, on 177 grains (typical size 1-7 mm) from chambers A and C.
In order to extract an average spectrum of each grain but also to delimit the region of interest to study the spectral
heterogeneities inside the grains, we developed a procedure using thermal emission maps measured by MicrOmega. First, eachgrain was isolated from the rest of the field of view (the sample holder) thanks to their difference in terms of thermal emission.
Then, we performed a study of the ~2.7µm band at two different scales. On one hand, all pixels within the mask where
averaged to obtain the millimeter scale spectrum of each grain. On the other hand, to better understand the variations at
millimeter scale, we looked at smaller scales (<200 µm) to highlight possible heterogeneities within the grains. Two spectral
parameters were calculated to characterize the ~2.7 µm OH feature: the peak position was estimated using a gaussian fit, andthe band depth was calculated between the minimum of reflectance and a linear continuum.
At millimeter scale, the position of the ~2.7 µm OH feature is consistent with the position found in highly aqueously alteredcarbonaceous chondrites [7]. Contrary to the bulk spectra where the ~2.7 µm OH feature was very similar between the twochambers [5], the position of the band varies within an interval of 10 nm at individual grain scale and the peak position
distribution varies between the two chambers: there is an excess of grains from chamber A with a position at longer
wavelength. Another difference is that the band depth of the grains varies within a larger range in chamber A than in chamber
C. The analysis at smaller scales (<200 µm) is still ongoing and will be presented at the time of the conference.
We will discuss the spectral differences between the collected grains, in particular between chambers A and C, and what
information they carry about the composition of phyllosilicates and the space weathering processes affecting Ryugu’s surface
materials. Indeed, the OH feature position can change with the Mg/Fe ratio in phyllosilicates [8]. Moreover, space weatheringexperiments on carbonaceous chondrites [9] have shown that the band position was shifted towards longer wavelength after
irradiation. The slight variation of band position we observe at the grain scale is consistent with the shift observed on Ryugu’s
surface spectra, between the artificial crater and the surrounding surface [10]. We expect that the smaller scale analysis will
give hints on the involved processes.
References[1] Tachibana et al. (2020) LPS XXXXXI Abstract #2027. [2] Arakawa et al. (2017) Space Sci. Rev. 208, 187-212. [3] Bibringet al. (2017) Space Sci. Rev. 208, 401-412. [4] Yada et al. (2022) Nat Astron, 6, 214-220. [5] Pilorget et al. (2022) Nat Astron,

6, 221-225. [6] Kitazato et al. (2019) Science, 364, 272-275. [7] Takir et al. (2013) M & PS 48, 1618-1637. [8] Besson andDrits (1997), CCM, 45, 158. [9] Lantz et al. (2017) Icarus 285, 43-57. [10] Kitazato et al. (2021) Nat Astron, 5, 246-250.

Organics in Ryugu samples, from MicrOmega and FTIR analyses within the ISAS curation facility
1

Bibring, J.-P.; 2,3Hatakeda, K.; 1Brunetto, R.; 1Baklouti, D.; 1Carter, J.; 1,4Pilorget, C.; 1Loizeau, D.; 2Yogata, K; 2,5Okada, T.;
2
Yada, T.; 2,5Usui, T. and the IAS and ISAS MicrOmega Curation Team.
1

IAS, Université Paris-Saclay, CNRS, France; 2Institute of Space and Astronautical Science, Japan Aerospace Exploration
Agency; 3Marine Works Japan, Ltd; 4Institut Universitaire de France; 5University of Tokyo, Bunkyo, Tokyo 113-0033, Japan

Within the ISAS/JAXA facility, in which all samples collected by the Hayabusa 2 JAXA are maintained preserved from any
terrestrial contamination [1], the MicrOmega instrument [2] has analyzed bulk samples from both collection sites, spread onto
6 main dishes, as well as hundreds of grains extracted from them. Two features show up in the NIR (0.99 µm to 3.6 µm)
spectra of essentially all grains, as acquired by MicrOmega: one, peaked around the 2.7 µm, is diagnostic of OH stretch,primarily within the matrix material [3] while a second one, at ~3.4 µm, is due to either or both carbonates [4] and organics [5].
This paper focusses on the later one, with updated results and interpretation.
Most of the ~3.4 organics-related features within MicrOmega spectra are peaked at 3.42 µm, diagnostic of CH2 asymmetricstretch, with less significant CH3 absorption, around 3.38 µm (asymmetric) nor 3.45 (symmetric), pointing at aliphatic
methylenic moieties, with high CH2/CH3. MicrOmega spectra of a number of grains exhibit several other features, in a variety
of intensities, often coupled with the 3.42 µm and/or among themselves, primarily peaked around 2.9 µm, 3.05 µm, 3.25 µm,
3.55 µm. The candidate functional groups they are diagnostic of, are: aldehyde, alcohol, organic acid, amine and amide, andaromatics. The recent spectral upgrade of the FTIR within the curation facility, ranging up to 8.5 µm, has demonstrated,through preliminary analyses of the larger grain of the collection (C9000, > 1 cm wide), the potential of joined
MicrOmega/FTIR measurements on the same grain.
Specifically, the FTIR provides means to discriminate between distinct potential compounds in two spectral domains: 5.2-6.2µm, and 6.8-7.8 µm. Noticeably, C=O bonds (absorptions peaked at ~5.8 µm) can be distinguished from C=C bonds(absorptions peaked at ~6.2 µm). In addition, in a few spots, a critical feature shows up around 4.7 µm, potentially tracing
nitrile (-C≡C-) or cyanate (O=C=N-). In addition to N-rich compounds, P-rich bonds [6] could be confirmed and characterized
by FTIR.
We shall review all measurements performed up to now, by both MicrOmega and the upgraded FTIT within the curation
facility, and discuss them in the frame of the evolution of the pristine organic constituents within Ryugu.
References[1] Yada et al. (2022) Nat Astron, 6, 214-220[2] Pilorget et al. (2022) Nat Astron, 6, 221-225[3] LePivert et al. 2022, this symposium[4] Loizeau et al. 2022, this symposium[5] Carter et al. (2022) 53rd LPSC contrib. N°1495[6] Pilorget et al. 2022, this symposiumMicrOmega detections of carbonates in Ryugu returned samples within the Hayabusa2 JAXA
Extraterrestrial Curation Center
Loizeau, D.1; Pilorget, C.1; Riu, L.2; Brunetto, R.1; Bibring, J.-P.1; Nakato, A.3; Aléon-Toppani, A.1; Hatakeda, K.3; Yogata,K.3; Carter, J.1; Le Pivert-Jolivet, T.1; Yada, T.3; Okada, T.3; Usui, T.3; Langevin, Y.1; Lantz, C.1; Baklouti, D.1; Miyazaki, A.3;
Nishimura, M.3; Nagashima, K.3; Kumagai, K.3; Hitomi, Y.3; Sugiyama, Y.3; Abe, M.3; Saiki, T.3; Tanaka, S.3; Nakazawa, S.3;
Tsuda, Y.3; Watanabe, S.4;
1
Institut d'Astrophysique Spatiale, Université Paris-Saclay, CNRS, France, 2ESAC, ESA, Madrid, Spain,
3
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan,
4
Nagoya University, Nagoya 464-8601, JapanThe Ryugu samples brought back by the Hayabusa2 spacecraft in December 2020 have been delivered to the JAXA
Extraterrestrial Curation Center [1, 2]. Bulk samples and then sub-bulks and individual grains have been picked up and stored
into sapphire dishes, weighted, and analyzed with an optical microscope, FTIR spectroscopy, and MicrOmega hyperspectral
imaging [3] for initial description within the curation facility [2]. The MicrOmega instrument used in the JAXA Extraterrestrial
Curation Center is a NIR hyperspectral microscope. This configuration allows a mineralogical characterization of pristine
Ryugu samples, as they have never been exposed to terrestrial environment.
MicrOmega has a total field of view of 5 mm x 5 mm, with resolution of ~22.5 µm/pixel in the focal plane. It covers the
spectral domain from 0.99 µm to ~3.6 µm. Its capabilities enable the identification of organic matter and of different minerals
in the returned samples [4]. Initial analyses with MicrOmega were first made on the bulk samples from chambers A and C of
the Hayabusa2 returned capsule, and then on extracted individual grains and sub-bulks, each stored in their sapphire dishes.
For this study, we analyzed MicrOmega data of ~180 extracted individual grains (a few mm in size) and 14 sub-bulks (allobserved with MicrOmega within the Curation Center in 2021). This is a unique opportunity for mapping mineral and organic
species over a very large set of samples from Ryugu.
In the spectral domain of MicrOmega, carbonates have a strong characteristic double absorption band in the 3.3-3.5 µm area,accompanied by two other weaker bands around 2.5 and 2.3 µm. The exact spectral position of these bands varies with thecation content of the carbonate. Iron-bearing carbonates also show a strong absorption below 1.5 µm.
Detections of carbonates were made in grains included in the bulk samples from both chambers A and C. In the bulks, somesmall detached grains seem to be entirely carbonate-rich and are up to ~450 µm, down to <50 µm in size. In larger, extracted
grains, carbonate inclusions are also detected, with sizes up to >500 µm in a 3mm-sized grain, and down to <50 µm.
Spectrally, two carbonate populations are detected: many detections, mostly <100 µm in size, have spectral bands centered at
2.30, 2.50, and 3.30-3.43 µm, similar to CaMg(CO₃)₂ dolomite; and few detections, mostly >100 µm, have bands at 2.32, 2.51,
3.31-3.45 µm together with a strong absorption <1.5 µm, similar to (Mg,Fe)CO3 breunnerite. We also report 3 small detections(<50 µm in size) with spectra with bands at 3.35-3.48 µm, similar to CaCO3 calcite. Both dolomite and breunnerite-like areas
are detected in samples from both chambers, but we record more detections from chamber C than from chamber A.
The largest detection was made on grain C0041, covering ~0.25 mm², or ~10% of the visible surface of the grain. This grain is
one of the grains with “White regions” as described in [5]. The carbonate inclusion shows a complex morphology with threebranches, 100s µm long, around a main area. Spectra of this detection are breunnerite-like.
Another large and complex carbonate inclusion was detected in grain C0181. In this example, bright carbonate detections
surround a darker, 300 µm long carbonate inclusion that seem to correspond to a single crystal where both bright and darkcarbonates correspond to breunnerite-like spectra.
Carbonates detected by MicrOmega are distributed in two main populations both different in composition and size/morphology,
questioning the formation process or processes that led to this two populations. We did not detect any spatial transition fromdolomite to breunnerite, that would have indicated a possible gradient during a single formation event. We propose two distinct
formation processes: dolomites may have formed within small pores in the precursor material, limiting their size, very early inthe solar system [6], while breunnerite may have formed in fractures between grains, possibly after an impact on Ryugu’s
parent body, or even triggered by the impact. At what scale these processes were distinct in time is still questionable.
References[1] Tachibana S. et al. (2021) LPS, XXXXXII, Abstract #1289. [2] Yada T. et al. (2021) Nature Astronomy 6, p.214-220. [3]
Pilorget et al. (2021) Nature Astronomy 6, p.221-225. [4] Pilorget C. and Bibring J.-P. (2014) PSS 99, 7-18. [5] Nakato A. et al.
(2021) 8th Hayabusa Symposium. [6] McCain K. A. et al. (2022) 85th METSOC annual meeting.

Oxygen and carbon isotope compositions of Ryugu’s carbonates: Constraints on the conditions ofaqueous alteration
Wataru Fujiya1, Noriyuki Kawasaki2, Kazuhide Nagashima3, Conel M. O’D. Alexander4, Hisayoshi Yurimoto2, The
Hayabusa2-initial-analysis chemistry team, and The Hayabusa2-initial-analysis core.
1
Ibaraki University, 2Hokkaido University, 3University of Hawai‘i at Mānoa, 4Carnegie Institution for Science
The Hayabusa2 spacecraft collected CI-chondrite-like materials from the near-Earth asteroid 162173 Ryugu [1]. Ryugu
materials are mainly composed of secondary minerals that formed by aqueous alteration, e.g., phyllosilicates, carbonates,
sulfides, and oxides. In this study, we performed in-situ O and C isotope measurements of calcite (CaCO3) and dolomite(CaMg(CO3)2) in Ryugu samples A0058 and C0002 as well as the Ivuna meteorite to investigate the conditions of the aqueousalteration. We used secondary ion mass spectrometry (SIMS; CAMECA ims-1280HR) at Hokkaido University with a suite of
dolomite-ankerite standards [2] and a calcite standard “UWC3” [3].
The 18O values of the calcites (24‰ to 46‰) in C0002 and Ivuna show a larger variation than those of the dolomites in
C0002, A0058, and Ivuna (26‰ to 31‰) (Fig. 1). The average 17O value of the C0002 and Ivuna calcites is 1.37 ± 0.40‰(2SE). The 17O values of the C0002, A0058, and Ivuna dolomites are systematically lower than those of the calcites, and theaverage 17O value of the dolomites (0.26 ± 0.23‰, 2SE) is closer to the whole-rock values of two Ryugu samples [4] (0.30‰
and 0.58‰). Like the 18O values, the dolomites in A0058, C0002, and Ivuna have a relatively narrow range of 13C values
from 67‰ to 75‰ (Fig. 2). On the other hand, the 13C values of the calcites in C0002 and Ivuna are highly heterogeneous,
ranging from 65‰ to 108‰, and they are commonly higher than those of the Ryugu and Ivuna dolomites.
If, when the carbonates precipitated they were in O and C isotope equilibrium with the aqueous fluid, their O and C isotope
compositions would have been determined by the mass dependent equilibrium isotopic fractionation, which depends on
temperature, between carbonates and water for O, and that between carbonates and dissolved CO32− (and other dissolved Cbearing chemical species) for C [5]. Thus, the O and C isotope compositions of carbonates would reflect those of water and
CO32− as well as their formation temperatures. The 18O variation of ~22‰ observed in the Ryugu calcites (Fig. 1) corresponds
to formation temperatures that varied from 0 °C to 150 °C. However, the lack of a correlation between 18O and 13C values
implies that variable formation temperatures alone cannot explain the observed 18O and 13C variations (Fig. 2). Rather it
seems likely that both the 18O value of water and the 13C value of CO32− varied temporally. Because the 17O values of thefluids likely decreased as water-rock interaction progressed [6], the calcites with systematically higher 17O values shouldhave formed from less “evolved” fluids and likely crystallized earlier than the dolomites (Fig. 1).
It seems likely that the temporal variation in the 13C values of the C reservoirs and in their chemical speciation occurred
due to a change of O fugacity (fO2). Oxygen fugacity varied along with the production of H2 via the oxidation of Fe in metaland silicates by H2O and the subsequent escape of H2 from the system. To see how the 13C values of carbonates will changewith varying fO2, we consider a rather simple model, where gaseous CO 2 and CO and carbonates (and dissolved CO2, HCO3−,
and CO32−) are in C isotopic equilibrium and the CO2/CO ratio increases with increasing fO2. At first, the CO2/CO ratio may
have been characterized by that of the accreted ices, which may be around unity or higher as observed in cometary ices [7]. We
assume that the 13C value of the bulk gas (CO2+CO), 13Cbulk, is constant regardless of the CO2/CO ratio. Because the C
isotopic fractionation factor between CO2 and CO is positive at any temperature, e.g., 93‰ at 0 °C [8], both the 13C values of
CO2 and CO will decrease monotonically with increasing fO2 to keep 13Cbulk constant, and the 13C values of carbonates will
also decrease (Fig. 2). In this context, the dolomites with lower 13C values likely formed at higher fO2 and/or temperature thanthe calcites. This, combined with the O isotope signatures of the carbonates, implies that the calcites formed during prograde
alteration over wide ranges of fO2 and temperature, whereas the dolomites formed later from peak temperature to retrograde
cooling when the aqueous fluids and silicates approached O isotope equilibrium [9].
References:[1] Yokoyama T. et al. Science, 10.1126/science.abn7850 (2022) [2] Śliwiński M. G. et al. Geostand. Geoanal. Res. 40, 173184 (2016). [3] Kozdon R. et al. Chem. Geol. 258, 327-337 (2009). [4] Tang H. et al. Sci. Adv., submitted. [5] Alexander, C.
M. O’D. et al. Meteorit. Planet. Sci. 50, 810-833 (2015). [6] Clayton R. N. & Mayeda T. K. Earth Planet. Sci. Lett. 67, 151161 (1984). [7] Ootsubo T. et al. Astrophys. J. 752, 15 (2012). [8] Richet P. et al. Ann. Rev. Earth Planet. Sci. 5, 65-110(1977). [9] Nagashima et al. this meeting.

Figure 1. Oxygen isotope compositions of the calcite
and dolomite grains in Ryugu and Ivuna samples.

Figure 2. Comparison between C and O isotope
compositions of the calcite and dolomite grains in
Ryugu and Ivuna samples. A putative evolutionary
trend of 18O and 13C values is shown by thegreen arrow.

The Hayabusa2-initial-analysis chemistry team: T. Yokoyama, K. Nagashima, Y. Abe, J. Aléon, C.M.O'D. Alexander, S.
Amari, Y. Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T.
Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T.
Iizuka, T.R. Ireland, A. Ishikawa, M. Ito, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.C. Liu, Yuki Masuda, K.D. McKeegan, M. Morita, K. Motomura, F. Moynier, I. Nakai, A. Nguyen, L. Nittler, M. Onose, A.
Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui,
S. Wada, M. Wadhwa, R.J. Walker, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, H. Yurimoto.
The Hayabusa2-initial-analysis core: S. Tachibana, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H.
Yabuta, H. Yurimoto, Y. Tsuda, S. Watanabe.

Extraterrestrial Amino Acids and Amines Identified in Asteroid Ryugu Samples Returned by the
Hayabusa2 Mission
Eric T. Parker1, Hannah L. McLain1,2,3, Daniel P. Glavin1, Jason P. Dworkin1, Jamie E. Elsila1, José C. Aponte1,2,3, Hiroshi
Naraoka4, Yoshinori Takano5, Shogo Tachibana6,
The Hayabusa2-initial-analysis SOM team, The Hayabusa2- initial-analysis core1
Astrobiology Analytical Laboratory, Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD
20771, U.S.A.
2
Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center,Greenbelt, MD 20771, U.S.A.; 3Department of Physics, The Catholic University of America, Washington, D.C. 20064, U.S.A.;
4
Department of Earth and Planetary Science, Kyushu University, Nishi-ku, Fukuoka, 819-0395, Japan; 5Biogeochemistry
Research Center (BGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, 2370061, Japan; 6UTokyo Organization for Planetary and Space Science (UTOPS), The University of Tokyo, 7-3-1 Hongo, Tokyo
113-0033, Japan
Analyses of amino acids and aliphatic amines were performed on the hot water extracts of two asteroid Ryugu
samples returned by the JAXA Hayabusa2 mission. The two samples were A0106, which was comprised of surface material,
and C0107, which was comprised of both surface and possible subsurface material. Prior to amino acid analysis, portions ofeach sample extract underwent acid vapor hydrolysis, while other portions remained unhydrolyzed to allow for a respective
comparison between bound and free amino acids. Subsequently, these extracts were derivatized with o-phthaldialdehyde/Nacetyl-L-cysteine, a chiral, fluorescent tag that enhances analytical specificity and sensitivity for primary amines, and thenanalyzed using ultrahigh performance liquid chromatography with fluorescence detection and high-resolution mass
spectrometry. Prior to the analysis of aliphatic amines, separate portions of each sample extract were derivatized with
AccQ•Tag, a florescent tag that is insensitive to salts and targets primary amines and select secondary amines, and thenanalyzed by ultraperformance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. The
analyses performed here focused on the abundances and relative distributions of amino acids and aliphatic amines, as well as
determining the enantiomeric compositions of detected chiral amino acids. For contamination control and backgroundsubtraction purposes, procedural and analytical blanks were processed and analyzed in parallel with the Ryugu samples.
In total, 13 amino acids were detected and quantitated here. Five additional amino acids were tentatively identified,but not quantitated. Abundances of individual amino acids of the C2 – C6 variety were measured to vary between 0.02 and 15.8
nmol g-1. Among those amino acids identified, several were non-protein amino acids that are uncommon in biology. These
included β-aminoisobuytric acid (β-AIB) and β-amino-n-butyric acid (β-ABA), which were measured to be racemic or very
nearly racemic, suggesting that these species were likely to be indigenous to the sample and extraterrestrial in nature. While
trace quantities of select protein amino acids were found to be enriched in the L-enantiomer, elevated abundances of racemic,
free alanine were observed, indicating that the Ryugu sample studied here were exposed to minimal terrestrial contamination.
The analyses of aliphatic amines revealed four species of the C1 – C3 variety, which were identified and measured
above background levels. These aliphatic amines were methylamine, ethylamine, isopropylamine, and propylamine, in order ofdescending abundances. These aliphatic amine species were individually measured at abundances ranging from 0.05 – 34.14
nmol g-1 in the unhydrolyzed hot water extracts of Ryugu samples A0106 and C0107.
It has been reported that Ryugu samples are chemically similar to CI-type chondrites [1,2]. However, the abundancesand relative distributions of amino acids and aliphatic amines in Ryugu are strikingly different from those of CI1.1/2.0 Orgueil.
More specifically, CI1.1/2.0 Orgueil contains upwards of 5.6x the total abundance of amino acids as Ryugu, and more than 5x
the total abundance of aliphatic amines as Ryugu. These observed abundance differences could be caused by discrepancies inalteration conditions experienced by the parent bodies of Orgueil and Ryugu, or variabilities in original parent body chemical
conditions. Additionally, it is plausible the lower overall abundances of amino acids and amines in the near-surface samples
collected by Ryugu may be due to the loss of these compounds, or their volatile precursors, via such factors as space
weathering and solar heating in a hard vacuum environment. These possible loss mechanisms are worthy of further exploration.
Regarding amino acid distributions observed in Ryugu, α-amino acids, which could have been generated by the Strecker
cyanohydrin synthesis, were identified, along with β-, γ-, and δ-amino acids. Examples of the latter included C3 – C5 straightchain n-ω-amino acids. The observed amino acid distribution indicates that more than one formation mechanism occurred on
the Ryugu parent body and was responsible for the amino acids reported here. Lastly, the analytical techniques used here were
sufficiently sensitive to detect and quantify the target analytes under the limited sample mass conditions of the current work,
which offers strong evidence that these methods will likely perform similarly well when applied to the analyses of amino acids
and aliphatic amines in asteroid Bennu samples returned by the NASA OSIRIS-REx mission in September 2023.

References[1] Yada, T. et al. (2022) Nature Astronomy, 6, 214-220. [2] Yokoyama, T. et al. (2022) Science, eabn7850.
The Hayabusa2-initial-analysis SOM team: Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Kenji Hamase, Aogu
Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L.
McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Philippe Schmitt-Kopplin, Norbert Hertkorn, Alexander Ruf,
Francois-Regis Orthous-Daunay, Cédric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, Saburo
Sakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa,
Yasuhiro Oba, Yoshito Chikaraishi.
The Hayabusa2-initial-analysis core: Shogo Tachibana, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji
Okazaki, Kanako Sakamoto, Hikaru Yabuta, Hisayoshi Yurimoto, Yuichi Tsuda, Sei-ichiro Watanabe.

Carbon dust, from the ISM to the Solar System

1

E. Dartois1
Institut des Sciences Moléculaires d’Orsay (ISMO), UMR8214, CNRS, Université Paris-Saclay 91405 Orsay Cedex, France

The spectral signatures of interstellar medium dust grains reveal a great diversity of allotropes. Astronomical observations giveaccess to the molecular functionalities of these solids, setting constraints on the composition of organic solids and molecules in
the cycling of matter in the Galaxy. Some of these grains and molecules can be reproduced in the laboratory. Other signatures
still await for more precise identification of their carriers phases. Laboratory analogues help in constraining their physicochemical composition and evolution under the harsh galactical radiation environments. This talk will particularly focus on dust
materials from the far space environments, from diffuse ISM to protoplanetary disks. We’ll present some commonalities anddifferences between materials found in the Solar System, protoplanetary disks and Interstellar dust.

Figure 1.

Interstellar carbon allotropes (from Dartois et al. 2019).

References[1] Dartois, E., Charon, E., Engrand, C., Pino, T., Sandt, C. 2020. Mechanochemical synthesis of aromatic infrared band
carriers. The top-down chemistry of interstellar carbonaceous dust grain analogues. Astronomy and Astrophysics 637.
doi:10.1051/0004-6361/202037725[2] Dartois, E. 2019. Interstellar carbon dust. C, 5(4), 80.
[3] Dartois, E. and 17 colleagues 2015. Interstellar and interplanetary solids in the laboratory. Bulletin de la Societe Royale
des Sciences de Liege 84, 7–14.