Story by Tim Newcomb • POP MECH
The use of biosignatures in the search for space-based life should include nitrous oxide, researchers say.
The presence of laughing gas—or N2O—can signify the presence of living organisms.
Nitrous oxide may be easier to see with current technology than previously thought.
Don’t laugh off the potential value in finding nitrous oxide (N2O) in space atmospheres—scientists say the laughing gas could be a key biosignature in the search for life beyond our own planet.
Add in that our current technology (looking at you, James Webb Space Telescope) is adept at locating N20, and it’s clear why researchers at the University of California, Riverside want us to take laughing gas seriously.
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In a paper published earlier this month in The Astrophysical Journal, researchers from UCR’s Department of Earth and Planetary Sciences, including astrobiologist Eddie Schwieterman, say we’ve focused plenty on oxygen and methane as biosignatures, but skipping out on nitrous oxide “may be a mistake.”
As scientists study exoplanets in the search for extraterrestrial life, they strain for a view of biosignatures, typically the same gases found in abundance in Earth’s atmosphere— because, well, they’re what we personally know can support life. But Schwieterman and his team used simulations to show that with different stars from the sun we know and love, the biosignature search could well include N2O. Better yet, the James Webb Space Telescope could easily detect the colorless gas, famously used as a dental anesthetic and in preparing homemade whipped cream.
“In a star system like TRAPPIST-1, the nearest and best system to observe the atmosphere of rocky planets, you could potentially detect nitrous oxide at levels comparable to CO2 or methane,” Schwieterman says in a news release.
Living organisms create N2O in a variety of ways, continually transforming other nitrogen compounds into nitrous oxide via a metabolic process that can yield useful cellular energy. “Life generates nitrogen waste products that are converted by some microorganisms into nitrates,” Schwieterman says. “In a fish tank, these nitrates build up, which is why you have to change the water. However, under the right conditions in the ocean, certain bacteria can convert those nitrates into N2O. The gas then leaks into the atmosphere.”
Sure, the UCR team knows that in some circumstances, an atmosphere containing N2O doesn’t necessarily indicate life—lightning, for example, produces N2O. But the team believes that in these cases, plenty of other gases would exist that show the N2O is a geological process, not something from a living organism.
In the past, researchers have pooh-poohed the idea of looking for nitrous oxide, simply because they said it would be tricky to see. But that idea is based on the fact that Earth’s atmosphere isn’t heavy in N2O.
Nitrous oxide—commonly known as “laughing gas”—is a colorless gas, stored in liquid form, that dentists use to produce anesthetic effects in patients undergoing surgeries like wisdom teeth removal. It’s also sold in bulk in tiny cylinders to help bakers give homemade whipped cream its oomph. Now, scientists say it’s a biomarker that could signal life forms on distant exoplanets.
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“This conclusion doesn’t account for periods in Earth’s history where ocean conditions would have allowed for much greater biological release of N20,” Schwieterman says. “Conditions in those periods might mirror where an exoplanet is today.”
Consider that our sun does a fine job of breaking up N2O molecules compared to some other less-impressive celestial bodies, like dwarf stars K and M, that don’t have as powerful a light spectrum to break up the molecules. It’s then possible that nitrous oxide molecules could hang on quite a bit longer on those stars.
This all led the team—which included folks from Purdue University, the Georgia Institute of Technology, American University, and the NASA Goddard Space Flight Center—into the belief that now is the time for astrobiologists to consider N2O as an alternative biosignature.
“We wanted to put this idea forward,” Schwieterman says, “to show it’s not out of the question we’d find this biosignature gas if we look for it.”
“This conclusion doesn’t account for periods in Earth’s history where ocean conditions would have allowed for much greater biological release of N20,” Schwieterman says. “Conditions in those periods might mirror where an exoplanet is today.”
Consider that our sun does a fine job of breaking up N2O molecules compared to some other less-impressive celestial bodies, like dwarf stars K and M, that don’t have as powerful a light spectrum to break up the molecules. It’s then possible that nitrous oxide molecules could hang on quite a bit longer on those stars.
This all led the team—which included folks from Purdue University, the Georgia Institute of Technology, American University, and the NASA Goddard Space Flight Center—into the belief that now is the time for astrobiologists to consider N2O as an alternative biosignature.
“We wanted to put this idea forward,” Schwieterman says, “to show it’s not out of the question we’d find this biosignature gas if we look for it.”
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