Evidence for Wood-Cell-Like Structures in Martian Mudstones: Comparative Insights from Fossil Wood

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

Abstract

Recent observations of mudstone abrasion targets in Jezero crater (Perseverance rover, Apollo Temple at Cheyava Falls) have revealed abundant nodular features, colloquially termed “leopard spots.” PIXL elemental analyses demonstrate Fe–P enrichment in many of the rims of these nodules, consistent with Fe-phosphate minerals such as vivianite, while cores are enriched in Fe–S–Ni–Zn, consistent with greigite. SHERLOC Raman measurements additionally confirm the presence of organic carbon (G-band). Here, we present a comparative illustration juxtaposing these Martian nodules with well-documented structures in terrestrial fossil wood. We highlight morphological and mineralogical parallels that suggest some leopard-spot nodules may represent permineralized wood-cell remains rather than exclusively abiotic diagenetic products.

Figure 1. Comparative morphology of fossil wood cells and Martian leopard-spot nodules. Left: schematic of fossil wood in transverse (top) and longitudinal (bottom) view, showing cell walls, lumina, and pits. Right: SHERLOC/PIXL close-up (Apollo Temple abrasion target, Cheyava Falls, Jezero crater) highlighting nodules and reaction fronts. Green annotations indicate Fe–P enriched rims (vivianite-like); purple annotations indicate Fe–S–Ni–Zn enriched cores (greigite-like). Several nodules are alternatively interpreted as probable wood-cell remains.

The search for biosignatures in Martian sedimentary rocks has increasingly focused on mineral–organic associations. In Jezero crater, the Perseverance rover has documented abundant nodular features within clay-bearing mudstones. While the mission science team interprets these features as diagenetic reaction fronts, their abundance, morphology, and geochemical composition invite broader consideration. On Earth, vivianite commonly mineralizes within decaying organic tissues, including plant roots and wood, where reducing conditions and phosphate availability promote authigenic precipitation. This paper explores whether Martian nodules could reflect a similar process, with fossilized wood cells acting as templates for mineralization.

Methods

Two sources of imagery were employed:
1. Martian data: NASA/JPL-Caltech Mastcam-Z mosaics and SHERLOC/PIXL close-up images of the Apollo Temple abrasion target at Cheyava Falls, highlighting nodules and reaction fronts.
2. Terrestrial analogs: Transverse and longitudinal views of fossil wood microstructure, showing cell walls, lumina, and pits, serving as comparative reference points.

An annotated comparative figure was created to display structural similarities between Martian nodules and terrestrial wood cells.

Results

- Martian nodules (Panel c, Apollo Temple):
  – Rims: Fe–P enrichment (vivianite-like).
  – Cores: Fe–S–Ni–Zn enrichment (greigite-like).
  – Organic carbon (G-band) detected in adjacent Raman spectra.
  – Morphology: Rounded to oval cavities, 100–300 µm, arranged in clusters, superficially resembling transverse wood-cell lumina.

– Earth fossil wood (schematic analog):
  – Diagnostic structures: Consistent cell walls, central lumina, and intercellular pits.
  – Mineralization: Vivianite and other authigenic minerals commonly infill decaying cell lumina.
  – Morphological scale: Comparable dimensions (100–400 µm) to Martian nodules.

Discussion

The comparative figure highlights striking visual parallels between Martian leopard-spot nodules and terrestrial fossil wood anatomy. On Earth, vivianite rarely forms in isolation; it preferentially nucleates in organic-rich, reducing environments, including inside plant cells. The co-occurrence of Fe–P nodules, organic carbon, and redox-sensitive minerals (greigite) in Jezero mudstones suggests a microenvironment analogous to terrestrial organic diagenesis.

However, several caveats must be emphasized:
– The Martian nodules lack unambiguous secondary wall structures or pit fields diagnostic of wood.
– Abiotic nucleation of vivianite is chemically possible in Fe–P-rich sediments.
– Image enhancements and resolution limits complicate direct anatomical comparisons.

Thus, while suggestive, the evidence does not yet rise to the level of definitive proof. Future sample return and nanoscale analyses will be required to test whether these structures are mineral pseudomorphs of wood cells or purely abiotic concretions.

Conclusion

Our comparative analysis underscores the possibility that some Martian leopard-spot nodules at Cheyava Falls may represent permineralized wood-cell remains. Although abiotic explanations cannot yet be excluded, the consistent presence of Fe–P enrichment (vivianite-like rims), Fe–S (greigite-like cores), and organic carbon strengthens the case for biological templating. This figure aims to frame the debate: are we witnessing mineral diagenesis alone, or the fossilized vestiges of Martian wood tissue? 

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

Source: https://wretchfossil.blogspot.com/2025/09/evidence-for-wood-cell-like-structures.html