Astrobiology Images

• Figure 1. Biogenic-looking features in ALH84001 Martian meteorite (A, D, & F) and similar features in the Columbia River Basalts (B, C, E & G). The features in the Columbia River basalt samples were produced when rock chips were submersed in bacteria-containing well-water from the basalt formations in a culturing laboratory experiment. Identical control experiments using sterilized water did not produce any similar features. The similarity of the ALH84001 features to the Columbia River biogenic features supports our interpretation that the features in ALH84001 were formed by bacteria.
• Figure 2. Closeup [field emission scanning electron microscope (FE-SEM)] of a triplet structure within the martian meteorite Nakhla with a 20 nanometer wide filament extending from the apex of a terminal sphere. The spheres appear to be partially submerged within biofilm or a later generation of "iddingsite" clay.
• Figure 3. Field emission scanning electron microscope (FE-SEM) image of spheroidal features in the martian meteorite Shergotty with smectite-like clay coatings. These features and spheroidal features observed in Nakhla [Figure 2] are both similar to features in samples cultured from Columbia River Basalt [Figure 4].
• Figure 4. Field emission scanning electron microscope (FE-SEM) images of spherical features in bacteria-containing samples from Columbia River Basalt. Such features were absent from sterile controls (Thomas-Keprta et al., 1998. Their morphology is similar to that of features in martian meteorites Nakhla [Figure 2] and Shergotty [Figure 3].