Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

Figure 9

Petrographic and SEM study of the alpha-recoil track etch-tunnel (ARTET) zone at the glass-palagonite interface (in polished petrographic thin section). (a–d): sample DSDP-418A-75-3[120–123]; (e–o): sample DSDP-418A-68-3[40–43]. The images shown in (a, b, e–g, i, and j) are BSE images, while (c, d, h, k, and l) are secondary electron images. Note: (c) and (d) are close-ups from Figure 7(c). Pink dots in (d, h, k, and l) represent hypothetical ARTs—note the striking similarity in size between the real etch-tunnels and the ARTs. Photomicrographs (taken in plane polarized light) in (m–o) show the same petrographic area shown in (e–l). ART: alpha-recoil track; ARTETs: alpha-recoil track etch-tunnels; cf: corrosion front; ETZ: etch-tunnel zone; f₁: early fractures associated with palagonite; FG: fresh basaltic glass; GP: granular palagonite ART alteration; ip: initial palagonite; iz: intermediate zone (between the etch-tunnel and palagonite zones); P: palagonite zone; plg: plagioclase; Var.: varioles.

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