Living on the Edge

Chile’s Atacama Desert is one of the driest places on Earth. Portions of this desert can go years without experiencing any rainfall. In fact, the Atacama is so dry that NASA has used the region to test Mars landers. Even in this seemingly inhospitable environment, though, scientists are still finding evidence of life. With little to no water, life, in the form of cyanobacteria, has been found to actually extract water out of minerals in the rocks, according to research from the University of California - Irvine,  Johns Hopkins University, and UC Riverside.

The name of this hardy cyanobacteria which lives inside rock (called endolithic bacteria) is Chroococcidiopsis. The research team first noticed a pattern that whenever this bacteria was found in the Atacama, both the minerals gypsum and anhydrite were often present in the rock sample, as well. The mineral gypsum is a water-containing calcium sulfate-based mineral. The hypothesis was that these bacteria extracted the water content from the gypsum and converted it to the dehydrated mineral, anhydrite. This was confirmed when small samples of the rock were exposed to both arid and moist conditions in the lab. For the rock samples in the moist conditions, the bacteria didn't produce anhydrite, as they just extracted what water they needed from the environment. However, the bacteria in the arid conditions behaved just like they did in the Atacama, excreting organic acids to effectively mine the rock for its water content.

The case of the Atacama's Chroococcidiopsis shows that even though a rocky surface might appear devoid of life above the surface, below the surface, even in the seeming absence of water, life may thrive. These extremophiles on Earth provide more evidence that we may someday find life in the seemingly inhospitable conditions on Mars or beyond.