29. Nanobacteria on Earth?
Because we know so little about Mars, we can only try to understand its life by comparing it with Earth life, by trying to find life in Earth environments that may be similar to martian environments. The possible fossils in ALH 84001 lived inside a volcanic rock, but unfortunately very little is known about micro-organisms that live in rocks, or bacteria as small as the objects in ALH 84001 (slides #26 and #28). One area of active research is understanding life in the Columbia River basalt lava rocks of eastern Washington State. Dr. Todd Stevens and Dr. James McKinley of Pacific Northwest Laboratories have recently published evidence that bacteria live kilometers underground in these rocks, completely isolated from the Earth's surface. These bacteria thrive and produce methane gas with only water and basalt rock as their food and fuel.
This electron microscope image shows possible bacteria from a deep underground sample of the Columbia River basalts, from an area that showed chemical evidence of living bacteria. The filament near the image center is approximately 2 micrometers long and 0.1 micrometer in diameter — as long as the possible martian fossil in slide #25, but a little slimmer. The filament is near a few spheres that are 0.1–0.25 micrometers in diameter. These shapes could all be methane-producing bacteria, or they could be mineral growths (clays and asbestos minerals) that happen to be shaped like filaments and spheres. Detailed chemical studies, difficult at such small sizes, will be needed to confirm or deny that these shapes really are micro-organisms.
D. McKay, NASA/JSC