There are roughly 100 billion galaxies in the universe. Each houses an incalculable number of planets, but how do you find them across this vastness? There are some biosignatures that scientists look for in the atmosphere — with chemical compounds like oxygen and methane being a marker that life could exist here on the Earth, for instance. But astronomers believe there’s another indicator that could signal the presence of life in space: nitrous oxide, more affably known as the laughing gas.
“There’s been a lot of thought put into oxygen and methane as biosignatures. Fewer researchers have seriously considered nitrous oxide, but we think that may be a mistake,” said astrobiologist Eddie Schwieterman at the University of California, Riverside on Tuesday. Schwieterman, along with a team of astrobiologists, worked on a paper published in The Astrophysical Journal this week. Their research suggests that the current roster of chemical compounds is insufficient in our search for life.
Put simply, it means the presence of nitrous oxide in distant worlds could indicatelife — effectively widening the lens through which we look for extraterrestrial life on planets outside our solar system.
So far, laughing gas has been an unsuspect indicator. Nitrous oxide, N2O, is generated by microorganisms on Earth. So much so that organisms transform other nitrogen compounds into N2O through a metabolic process that gives them cellular energy. “In a fish tank, these nitrates build up, which is why you have to change the water,” Schwieterman explained. A small amount of nitrous oxide is generated by lightning too.
But so far, the concentration of nitrous oxide in our atmosphere has beenrather limited, which deters astrobiologists from using the 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 could be produced by living beings. A series of experiments further placed this planet around stars in distant galaxies, accounting for geographical events and other contingencies. The researchers then determined how much of the laughing gas could be detected from the Earth, say, from the observatory at the James Webb Space Telescope (JWST).
Arguably, given that laughing gas in itself isn’t found in abundance in Earth’s atmosphere, the likelihood of its presence in other distant worlds feels rather limited. But “this conclusion doesn’t account for periods in Earth’s history where ocean conditions would have allowed for much greater biological release of N2O. Conditions in those periods might mirror where an exoplanet is today,” Schwieterman said.
Interestingly, back in 2010, a separate team of researchers also batted for using laughing gas to detect life on Mars. They compared the Don Juan pond in Antarctica with the lakes found on Mars. In Antarctica, the water was rich with nitrite, and on reacting with minerals in volcanic rock, nitrous oxide was produced. Similarly, given the similarities on account of geology and sub-zero temperatures of both the lakes, laughing gas could be an important component on Mars too.“This could be an easy way to ‘sniff’ around the surface of Mars looking for pockets of sub-surface brine that might be hotspots for extreme microbial life,” one of the researchers had said then.
The laughing gas presents a hint of an answer in our search for life on distant planets. The scientists at JWST could perhaps be more conscious of looking at biomarkers beyond the usual roster; perhaps the nearby star system Trappist-1 could be a starting point too. Even if nitrous oxide fails to guarantee life, it could be a laughing matter quickly brushed away.
