Astrobiologists use a lot of chemicals to look for life on planets around other stars, but some scientists think there's something missing.
Gases found in Earth's atmosphere today are typically included in chemical compounds in a planet's atmosphere that could indicate life.
Oxygen and methane have been used as biosignatures. Eddie Schwieterman is an astronomer in the Department of Earth and Planetary Sciences at the University of California, Irvine.
The conclusion is detailed in an article published in The Astrophysical Journal.
Schwieterman led a group of researchers that determined how much nitrous oxide could be produced on a planet like Earth. The amount of N 2 O that could be detected by an observatory like the James Webb Space Telescope was determined by the models they created.
"In a star system like TRAPPIST-1, the closest and best system to observe the atmospheres of rocky planets, you could potentially detect nitrous oxide at levels comparable to CO 2 or methane."
N 2 O can be created by a variety of ways, including by micro-organisms that transform other nitrogen compounds into N 2 O.
Nitrogen waste products are converted into nitrates by some organisms. Schwieterman said that the nitrates build up in a fish tank and need to be changed.
Schwieterman said certainbacteria can convert nitrates into N 2 O in the ocean. The gasses leak into the atmosphere.
N 2 O is not indicative of life under certain circumstances. The team of Schwieterman accounted for this. lightning creates a small amount of nitrous oxide. The nitrogen dioxide created by lightning is a clue as to why the gas was created.
It would be hard to detect N 2 O from so far away. Schwieterman said that the conclusion is based on the concentration of N 2 O in the atmosphere today. Because there isn't a lot of it on this planet, it's hard to find it elsewhere.
Schwieterman said the conclusion doesn't account for periods in Earth's history where ocean conditions would have allowed for more biological release of N 2 O.
Our sun is more effective at breaking up the N 2 O molecule than common stars like K and M dwarfs. The predicted amount of this biosignature gas could be greatly increased by these two effects.
The research team included scientists from a number of institutions, including the Georgia Institute of Technology.
The research team thinks now is a good time to consider alternative biosignature gases like N 2 O because the TRAPPIST-1 system may soon send information about the atmospheres of rocky, Earth-like planets.
Schwieterman said that they wanted to show that it was not out of the question that they would find biosignature gas.More information: Edward W. Schwieterman et al, Evaluating the Plausible Range of N2O Biosignatures on Exo-Earths: An Integrated Biogeochemical, Photochemical, and Spectral Modeling Approach, The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac8cfb Journal information: Astrophysical Journal