Scientists have just figured out the means by which a certain type of microbe can convert urine into hydrazine. Yes, that's right: these tiny bugs chow down on your pee, and then poop out honest to goodness rocket fuel.
Anammox bacteria are capable of ingesting ammonium, which can be found in, you know, pee, and through a complex process, they can convert it into hydrazine, which is a type of rocket fuel. The space shuttle, for example,
uses used hydrazine to power its maneuvering thrusters as well as its auxiliary power units.
We've known about these little bugs for a long time, but it was just recently that scientists figured out how they do what they do. The how part is important because left to their own devices, anammox bacteria aren't particularly efficient, meaning that you'd need to go on a serious bender to give the microbes enough, uh, resources to produce any significant amount of hydrazine.
Scientists at Radboud University Nijmegen in the Netherlands have pieced together the crystal structure of the protein complex that anammox bacteria rely on to do this handy little conversion, meaning that it might be possible to amp the bacteria enough to start producing hydrazine in useful volumes. Combined with that astronaut poop power cell and a long-duration food source, trips to Mars (and beyond) are starting to look a lot more feasible.