Due to the limitations presented by our culture’s fledgling space travel technology, simply going to a planet orbiting another star isn’t a practical way of determining whether or not there’s any life there. Instead, researchers are using indirect methods of looking for extra-solar life, such as the conditions presented by the planet’s host star in relation to it’s orbit, the presence of an atmosphere, temperature, and so on. Now, a research team has devised a list of signature gases that astronomers can look for, that might be produced when a potential extraterrestrial organism metabolizes.

Biology on our own planet produces it’s own waste elements, such as plants producing oxygen, and animals producing methane, to name but two examples, but the research team, led by Massachusetts Institute of Technology’s Sara Yeager, have come up with a list of gases that could be produced by life forms with biologies that might be vastly different to our own. They used a simple principle, looking at elements that were stable when exposed to water, but remained chemically reactive when under standard atmospheric temperature and pressure.

The list itself is quite exhaustive — it’s comprised of 14,000 molecules — but could be a useful tool in helping researchers narrow down the search for extrasolar life. Detecting different elements in the atmospheres of other planets is an existing technique, and can use space-based telescopes to extend the range of this detection to exoplanets.

“This work reminds me of Darwin’s voyage aboard The Beagle, exploring the vast diversity of life by sailing around the world,” says Nancy Y. Kiang, with NASA’s Goddard Institute for Space Studies.

“In the search for life beyond our planet, we are currently at a similarly exciting, early but rapidly evolving stage of exploration as the discovery of exoplanets accelerates. Instead of netting strange creatures from the bottom of the sea, the authors here have searched and found thousands of curious, potentially biogenic gas molecules. These will inspire a new body of research into identifying also larger molecules, investigating their origin and fate here, and their potential expression on exoplanets as signs of life.”