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

a.

b.

Xe+

3D

30 μm

20 μm

100 µm10 µm

c.

500 μm
10 μm

20 μm

Phyl

5 µm

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

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

Slice 248

Slice 255

Slice 283

Slice 269

Slice 292

Slice302

OP

Phyllosilicate

1 µm

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

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

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

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

MEYS

CR(LM2023042)

andEuropeanRegional

Development

Fund-ProjectUP

CIISB(No.

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