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

Figure 6

Photomicrographs of polished petrographic thin sections of DSDP 418A basaltic glass pillow margins, highlighting various igneous petrographic features. The photomicrographs shown in (a, c) and (d—“inset”) are taken in cross polarized light (crossed nicols), whereas (b) and (d) are in plane polarized light (uncrossed nicols). (a-b): sample DSDP-418A-75-3[120–123]. (c-d): sample DSDP-418A-68-3[40–43]. Note that (a) and (b) depict the same petrographic area. cpx: clinopyroxene; FG: fresh basaltic glass; glm: glomerocryst; h: artificial hole in the petrographic section; OZ: oscillatory zoned plagioclase; plg: plagioclase phenocryst; Sk: skeletal plagioclase crystal.

(a)

(b)

(c)

(d)