Laughing gas found in space could mean life


According to researchers at UC Riverside, laughing gas is typically absent from the list of substances astrobiologists use to look for life on worlds orbiting other stars.

Biosignatures are chemical components in a planet's atmosphere that may be indicative of life, and they frequently include gases that are abundant in our planet's atmosphere right now.

"The role of oxygen and methane as biosignatures has received considerable attention. Nitrous oxide has received less attention from researchers, but we believe that may be a mistake "affirmed astrobiologist Eddie Schwieterman of the Department of Earth and Planetary Sciences at UCR.

In a piece that was just published in The Astrophysical Journal, this result and the modelling efforts that led to it are described in full.

To get there, Schwieterman led a group of scientists who calculated the maximum amount of nitrous oxide that life on an Earth-like planet could theoretically emit. After that, they created simulations of that planet orbiting various types of stars and calculated the quantities of N2O that could be picked up by a telescope like the James Webb Space Telescope.

"You may theoretically identify nitrous oxide at amounts comparable to CO2 or methane in a star system like TRAPPIST-1, the closest and best system to examine the atmospheres of rocky planets," Schwieterman said.

Nitrous oxide, or N2O, is a gas that is produced in a variety of ways by living things. Other nitrogen molecules are continuously converted by microorganisms into N2O through a metabolic process that can produce useful cellular energy.

"Nitrogen waste products are produced by life, and some microbes turn them into nitrates. You must change the water in a fish tank since these nitrates accumulate there "explained Schwieterman.

But under the correct circumstances in the ocean, certain bacteria can turn those nitrates into N2O, according to Schwieterman. Following that, the gas seeps into the atmosphere.

N2O can be found in an environment and still not be a sign of life in some situations. This was taken into account in the modelling of Schwieterman's group. For instance, lightning can produce a small amount of nitrous oxide. However, lightning also produces nitrogen dioxide, giving astrobiologists a hint that the gas was produced by non-living meteorological or geological processes.

Others who have thought about N2O as a biosignature gas frequently come to the conclusion that it would be impossible to detect at such a distance. This conclusion, according to Schwieterman, is based on current N2O concentrations in the Earth's atmosphere. Some people think this is because there isn't much of it on this planet, which is packed with life. "This result ignores instances in Earth's past when ocean conditions would have permitted for a significantly higher biological emission of N2O. Conditions throughout those times may have mirrored an exoplanet's current environment, "added Schwieterman.

According to Schwieterman, common stars like K and M dwarfs emit a light spectrum that is less effective than our sun at dissolving the N2O molecule. When these two effects are combined, the estimated concentration of this biosignature gas on a populated world could be significantly raised.

Daria Pidhorodetska, Andy Ridgwell, and Timothy Lyons, as well as researchers from Purdue University, the Georgia Institute of Technology, American University, and the NASA Goddard Space Flight Center, were part of the research team.

Since the James Webb telescope may soon be transmitting data about the atmospheres of rocky, Earth-like planets in the TRAPPIST-1 system, the research team feels that now is the right time for astrobiologists to take alternate biosignature gases like N2O into consideration.

If we seek for it, we might detect this biosignature gas, thus we wanted to put this theory forth to demonstrate that. It would be challenging to find elsewhere as well.

Reference:  Astrophysical Journal

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