From South African gold mines, to cooled seafloor lavas, these subsurface bugs have provided clues to the potential for life on Mars, and the diversity of possible fuel sources for life, including nuclear energy and toxic waste.
Similar Environments on Mars
Life on Mars may exist in "pillow lavas," volcanic rocks that are common on and below the terrestrial seafloor, according to Martin Fisk of Oregon State University. He and his colleagues have investigated the bacteria that live inside pillow lavas on Earth, and found that the microbes seem to be getting their energy from reactions between the glass in the rock and water.
Pillow lavas are likely to exist on Mars, Fisk said, and their unusual bulbous shape should make them easy to detect as researchers increase the resolution of photos taken of the planet's surface.
"On Earth, microbes live in the glass of pillow lavas. Mars could host life in similar volcanic rocks, although this would require the presence of 'primary producers' -- organisms that make organic matter from chemical energy and carbon dioxide," Fisk said. "We're currently working to identify those microbes in Earth's volcanic rocks."
Pillow lavas form as seawater rapidly cooled molten lava into volcanic glass. Because these glasses don't have internal crystal structures, the way minerals do, bacteria leave distinctively-shaped tracks as they bore minute holes into the glass.
"I sometimes joke that if NASA could get me a pillow lava, I could tell you if anything ever lived in it," Fisk said. He noted, however, that the rock would have to be well-preserved.
Life doesn't have to be from another planet in order to survive in seemingly inho