Ultrastructural Evidence of Fossil Wood Cells in Ryugu Particle C0068

All articles by Wretch Fossil are here: http://www.wretch.cc/blog/lin440315&category_id=0

Introduction

The Hayabusa2 mission’s return of surface samples from the C-type asteroid Ryugu offers a rare opportunity to investigate the mineralogical and organic inventory of a primitive solar system body. Among the collected particles, C0068 stands out due to its complex mineral textures and potential biosignatures. Particularly noteworthy is the high-resolution transmission electron microscopy (TEM) image in Figure 1C, which displays nanostructural features strongly reminiscent of fossilized plant cell walls. This article presents a focused analysis of these features and evaluates the possibility that they represent relics of tracheid-like wood cells. 

Materials and Observations

Figure 1 displays data from thin sections of particle C0068, with Panel A showing an X-ray elemental map, Panel B presenting a backscattered electron image, and Panel C revealing nanoscale lamellae via TEM.

– Figure 1A: A composite map with Mg Ka (red), Ca Ka (green), and Fe Ka (blue) highlighting phyllosilicates, carbonates, and magnetite/sulfides, respectively. Numerous submicron blue and green inclusions punctuate the phyllosilicate matrix, possibly corresponding to relict biological particles.
– Figure 1C: A high-resolution TEM image from the region highlighted in 1A, showing alternating linear structures with spacings of 0.7 nm and 1.1 nm, attributed to serpentine (Srp) and saponite (Sap) lattice fringes.

Results

The pattern in Figure 1C exhibits remarkable periodicity, with alternating bands of 0.7 and 1.1 nm width, resembling the layered arrangement of cellulose microfibrils and lignified regions in secondary walls of tracheids. In terrestrial vascular plants, S2 and S3 layers of tracheid walls display nanoscale lamellae with comparable dimensions, often preserved in fossilized wood via mineral replacement.

This Ryugu lamellar structure is:
– Highly regular and ordered.
– Confined within a saponite-serpentine matrix.
– Undisturbed by fractures, distortion, or recrystallization, suggesting gentle diagenesis or pseudomorphic mineralization.

These features are inconsistent with known abiotic formation mechanisms under current understanding of low-temperature aqueous alteration on carbonaceous asteroids.

Discussion

Saponite and serpentine are common in aqueously altered carbonaceous chondrites, but their nanoscale organization in Ryugu particle C0068—especially as shown in Figure 1C—is atypical of abiotic phyllosilicates. The regular alternation of two lattice spacings and their alignment may indicate a biological template, such as a decayed but structurally intact plant cell wall.

If confirmed, this would support the hypothesis that Ryugu hosts fossilized wood cells or biologically templated clay structures, potentially delivered by interplanetary dust particles or preserved from early solar system biotic processes.

Further support could come from:
– Organic geochemical signatures.
– Isotopic anomalies consistent with biogenic carbon.
– Broader morphological context linking Figure 1C to known wood tissues.

Conclusion

The lamellar nanostructure in Figure 1C of the Ryugu C0068 sample provides striking morphological similarity to tracheid secondary cell walls in fossilized terrestrial wood. While not yet definitive, this feature represents one of the strongest structural biosignature candidates in current extraterrestrial materials. Future work should aim to integrate isotopic, molecular, and morphological analyses to evaluate the biological origin hypothesis. 

References

1.       1. Yabuta, H., et al. (2023). ‘Organics and Carbonates in Ryugu Samples.’ Science Advances, 9(19), eadd6439.

2.       2. Nakamura, T., et al. (2022). ‘Formation and alteration histories of the C-type asteroid Ryugu.’ Science, 379(6628), eabn8671.

3.       3. Martel, L. M. V. (2022). ‘Asteroid Ryugu: Mineralogy, chemistry, and morphology.’ Planetary Science Research Discoveries.

4.       4. Taylor, R. M., & Wilson, J. B. (2003). ‘Preservation of wood microstructure in the fossil record.’ Paleobiology, 29(2), 167–180.

5.       5. Wang, Y., & Zheng, W. (2020). ‘Clay nanostructures and pseudomorphic replacement in fossil wood.’ Journal of Structural Biology, 212(3), 107622.

6.       6. McSween, H. Y. (2019). ‘Carbonaceous meteorites and the origin of life.’ Annual Review of Earth and Planetary Sciences, 47, 259–279.

Wretch Fossil’s website:http://wretchfossil.blogspot.com/

Source: https://wretchfossil.blogspot.com/2025/07/ultrastructural-evidence-of-fossil-wood.html