The energetic molecule perchlorate is rocket fuel and, it turns out, food for ancient microbes. Given that deposits of the stuff have been found wherever robots look on Mars, could the chlorine compound—poisonous to the development of humans—be serving as Martian life's lunch?
A team of Dutch researchers show in the April 5 edition of Science that an archaeon—as the name implies, an old type of microbe distinct from bacteria—can grow quite happily on perchlorate. Archaeoglobus fulgidus takes the perchlorate in, gains energy by transforming it into highly reactive chlorite and moves on. Thriving in volcanic vents beneath the sea as well as other superhot areas of Earth, such as oil reservoirs or places where hot rock turns water to steam, A. fulgidus and other microbes like it might be the reason there's not more rocket fuel lying around on our planet.
This is the first archaeon known to feed on perchlorate but it is not the first microbe found to do so. Some bacteria can manage the same trick and even boast a special enzyme to help them rapidly break down the resulting chlorite, which is otherwise damaging to cells. The byproduct of that breakdown, however, is oxygen, which A. fulgidus cannot tolerate. It survives the potential onslaught by relying on sulfur compounds naturally present in its environment to react away the chlorite, a symbiotic relationship between life and non-life chemistry.
It's possible, then, that A. fulgidus is one of the most primeval forms of life on the Earth, evolving potentially even before oxygen-producing photosynthesis. The rise of that modern atmosphere-creating process may have driven A. fulgidus's ancestors to the dark, deep, hot places of the globe.
As for Mars, the surface of the red planet is certainly too cold for this bug to survive, which may explain why there's so much rocket fuel lying around. But discovery of the microbe raises the possibility that rocket propellant could serve as fuel for some other life form there, perhaps deep beneath the perchlorate-bearing surface.