Figure 6
Characterization of possible microbial structures preserved in Target Area 2 (TA2) by using the ToF–SIMS molecular mapping capabilities. The image analysis follows the same morphological groups G1 to G8 adding one new group G9. Two different main structures defined by G1 and G9 are limited by a sharp boundary between them. The G1 microstructure is characterized by a strong intensity of different N- and S-bearing compounds that outline a diffuse filament network, whose primary composition would be large lipids such as ceramides. However, G9 shows a more massive filamentous mass that is traced by a high intensity in acylglycerides and FA fragments. G3 occurs as an independent group of microstructures that interlock both G1 and G9 microstructures. The RGB overlay shows two main microbial structures (G1 and G9) in which empty cavities would be occupied by a third microbial unit defined by G3. Interestingly, the G1 microbial structure is strongly mineralized by sulfate while G3 and G9 microstructures are mineralized by ferruginous materials, suggesting that they were formed in two separate mineralization episodes. The microbial structure and composition of G1 and G9 suggest that these groups could correspond to mineralized biofilms.
