There are approximately 100 billion galaxies in the universe. Each is home to countless planets, but how do you find them across this vastness? There are biosignatures that scientists look for in the atmosphere – with chemical compounds like oxygen and methane being a marker that life could exist here on Earth, for example. But astronomers think there’s another indicator that could signal the presence of life in space: nitrous oxide, more popularly known as laughing gas.
“There has been a lot of thought about oxygen and methane as biosignatures. Fewer researchers have seriously considered nitrous oxide, but we think that may be a mistake,” the l Astrobiologist Eddie Schwieterman of the University of California at Riverside Schwieterman, along with a team of astrobiologists, worked on a paper published in The Astrophysical Journal this week. Their research suggests that the current list of chemical compounds is insufficient in our search for life.
In simple terms, this means that the presence of nitrous oxide in distant worlds could indicate life – effectively expanding the lens through which we search for extraterrestrial life on planets outside our solar system.
Until now, laughing gas has been an unsuspected indicator. Nitrous oxide, N2O, is generated by microorganisms on Earth. So much so that organisms convert other nitrogen compounds into N2O by a metabolic process that gives them cellular energy. “In an aquarium, these nitrates build up, which is why you need to change the water,” Schwieterman explained. A small amount of nitrous oxide is also generated by lightning.
But so far, the concentration of nitrous oxide in our atmosphere has been rather limited, which deters astrobiologists from using laughing gas as an indicator of life.
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The team explored this idea through a simulation model, creating a planet similar to Earth and determining how much nitrous oxide can be produced by living things. A series of experiments further placed this planet around stars in distant galaxies, taking into account geographical events and other contingencies. The researchers then determined how much laughing gas could be detected from Earth, for example from the observatory of the James Webb Space Telescope (JWST).
Arguably, since laughing gas itself is not found in abundance in Earth’s atmosphere, the likelihood of its presence in other distant worlds seems rather limited. But “this conclusion does not take into account periods in Earth’s history when oceanic conditions would have allowed a much greater biological release of N2O. The conditions of those periods could reflect where an exoplanet is today,” Schwieterman said.
Interestingly, in 2010 a separate team of researchers also fought for using laughing gas to detect life on Mars. They compared Don Juan’s pond in Antarctica with lakes found on Mars. In Antarctica, the water was rich in nitrite, and by reacting with the minerals in the volcanic rock, nitrous oxide was produced. Likewise, given the similarities due to the geology and sub-zero temperatures of the two lakes, laughing gas could also be an important element on Mars. an underground brine that could be a hotspot for extreme microbial life,” one of the researchers said at the time.
Laughing gas presents a hint of the answer in our search for life on distant planets. JWST scientists could perhaps be more aware of examining biomarkers beyond the usual list; perhaps the nearby star system Trappist-1 could also be a starting point. Even though nitrous oxide doesn’t guarantee life, it could be a quick laughing matter.