Wisps of volcanic gas, rather than photosynthesis, may energize rare microbes eking out an existence on the Martian-like flanks of the tallest volcanoes in South America’s Atacama Desert.
This newly discovered handful of bacteria, fungi and rudimentary organisms called archaea have not been formally identified, but DNA analysis has revealed that they are very different from anything else known to science.
“Genetically, they're at least 5 percent different than anything else in the DNA database of 2.5 million sequences," said Ryan Lynch, a doctoral student at the University of Colorado, Boulder, who cultured the Atacama microbes in the lab.
When Lynch and his colleagues searched specifically for chlorophyll or genes known to be involved in photosynthesis, they came up dry. That’s when they realized that some of these bugs might utilize completely new forms of metabolism.
In a recent report in the Journal of Geophysical Research-Biogeosciences, Lynch and his co-authors suggest that the microbes may extract energy and carbon from wisps of gases such as carbon monoxide and dimethylsulfide that sometimes drift in the air. The process wouldn't give the bugs a high-energy yield, Lynch said in a press release, but enough could add up over time to be meaningful.
Clearly, it’s a tough way to make a living. The research team found fewer than 20 species per gram of Atacama mountain soil. By comparison, a single gram of normal soil is home to thousands of species.
Such low diversity is unusual when you consider how efficiently microbes usually get around. They can get caught up in winds, sucked up into clouds, and transported great distances from their point of origin before falling back to the ground in droplets of rain or flakes of snow.
Then again, the Atacama volcanoes are at the extreme edge of inhospitable. Rising to altitudes of more than 19,685 feet, their rocky flanks rarely experience lasting precipitation. Much of the sparse snow that falls sublimates back to the atmosphere soon after it hits the ground. What is more, the atmosphere is breathlessly thin, ultraviolet radiation is twice as intense as it is at lower altitudes, and temperatures are extreme—ranging by more than 100 degrees Fahrenheit in a single day.
"This environment is so restrictive, most of those things that are raining down are killed immediately," said Lynch’s adviser, microbial ecologist Steve Schmidt. "There's a huge environmental filter here that's keeping most of these things from growing."
In related research, Schmidt is teaming up with astrobiologists to model what past conditions were like on Mars. With their rocky terrain, thin atmosphere and high radiation, the Atacama volcanoes are some of the most similar places on Earth to the Red Planet.
"If we know, on Earth, what the outer limits for life were, and they know what the paleoclimates on Mars were like, we may have a better idea of what could have lived there," he said.
Photo: Steam Rising From Geysers and Fumaroles, El Tatio, Atacama, Chile (Getty)