Wood's Vessel Elements on Mars

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 Rectangular Vessel Elements in Wood: Clarifying the Morphology

Recent observations from Mars images suggest that rectangular microstructures might represent biological remains, specifically cross-sections of vessel elements. A key question then arises: can vessel elements be rectangular in transverse section?

Anatomical and Botanical Evidence

Yes, vessel elements can appear rectangular in cross-section under certain conditions. While many vessel elements are roughly circular when cut transversely, they can also appear oval, elliptical, polygonal, or rectangular, especially in tightly packed wood tissue.

Why Rectangular Shapes Occur

• Cell Packing: In dense woods, the pressure from adjacent cells can flatten vessel elements slightly, making them look rectangular.

• Developmental Deformation: Immature wood or wood under stress (e.g., in response to compression or tension) can show flattened vessel lumens.

• Species-Specific Traits: Certain hardwoods exhibit more angular or polygonal shapes depending on the anatomical arrangement and secondary wall thickening.

Visual Examples

Schematic and real microscopic images from botanical sources support this:

• Quercus (oak) transverse sections sometimes show rectangular or flattened pores.

• Teaching materials from SIU Plant Anatomy Lab show polygonal and rectangular vessel pores.

• Studies like PMC9291787 discuss developmental flattening of wood elements.

Martian Implications

In the context of Martian imagery (e.g., NASA Perseverance image SIF_1610_0809873848), red arrows highlight square and rectangular structures between 60 and 120 microns wide, comparable to Earth vessel elements. The 4 cm-wide image allows this estimation.

These observations strongly support a plausible biogenic interpretation:

• Size match: 60–120 µm is consistent with terrestrial vessel element diameters (15–800 µm).

• Shape justification: Rectangular cross-sections are documented in botanical literature.

Conclusion

The claim that “vessel elements cannot be rectangular” is false or at least oversimplified. Rectangular vessel elements are anatomically possible, especially under natural compression or species-specific development. The Martian features, therefore, do not contradict what is seen in fossil wood on Earth.

These findings add weight to the hypothesis that some Martian microstructures may represent fossilized biological remains like wood cells, and not just mineralogical phenomena.

Prepared with references to primary literature and botanical teaching sources. Figure sourced from:
https://www.flickr.com/photos/fossil_lin/54757989865/sizes/o/
Image Credit: NASA/JPL-Caltech, enhanced with Zeke filter by L. Lin.

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