Wood Fibrils from Asteroid Ryugu

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Original Caption Summary:
Figure 1c shows high-resolution TEM imagery of a Ryugu particle (C0068), interpreted by the original authors as a saponite–serpentine intergrowth. The image highlights two distinct sets of lattice fringes: 0.7 nm (serpentine) and 1.1 nm (saponite), attributed to phyllosilicate lamellae formed by aqueous alteration.

Critical Reanalysis

Upon magnification (800%) and detailed inspection, the structures highlighted in Figure 1c are found to strongly resemble nanometer-scale fibrils—repeating, interconnected strands with vertical alignment. This configuration mirrors the ultrastructure of secondary cell walls in terrestrial wood, particularly in tracheids and vessel elements.

In the image:
– Red arrows and rectangles identify nano-fibrils grouped in vertical bundles.
– The spatial continuity between fibrils suggests biological templating.
– The morphology is inconsistent with randomly intergrown clays or typical abiotic phyllosilicates.

Why Not Just Saponite and Serpentine?

While the mineralogical assignment by the original authors (saponite and serpentine) is chemically plausible, the regular alternation of lamellae at precise intervals of 0.7 nm and 1.1 nm is uncharacteristic of known abiotic processes. No current mineralogical models or synthetic analogs reproduce such rhythmic, bidirectional lamellae with biological-like architecture.

In contrast, biological cell walls—particularly the S2 layer of wood cells—commonly exhibit nanolamellae of similar dimensions, composed of alternating crystalline cellulose fibrils and hemicellulose/lignin matrices.

Comparative Evidence

Implications

This reinterpretation opens the possibility that the structures observed in Ryugu particle C0068 are not merely mineralogical artifacts, but rather fossilized nanostructures—preserved remnants of wood-like biological material. Given that asteroids cannot produce wood autonomously, such features may have been delivered to Ryugu via Martian ejecta or another ancient planetary fragment.

Reference: Devonian vessel elements Diagrams of vessel elements

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