“The observation of nitrogen dioxide gas on a habitable planet could potentially indicate the presence of an industrialized civilization”, said Ravi Kopparapu of NASA’s Goddard Space Flight Center in a press release.
His team is publishing a preliminary study on the subject this month. Nitrogen dioxide gas (NO2) is a gas released in all types of combustion. It could therefore be considered as a marker, a sort of “technosignature”.
Traces visible 30 light years away
NO2 would be detected by observing the light reflected by an exoplanet as it revolves around its star. If we assume an Earth-like planet orbiting a Sun-like star, a civilization producing the same amount of NO2 as ours would be detected up to about 30 light years away with about 400 hours of observation. But that will require the development of a super powerful telescope.
The problem is that NO2 can also be produced by natural phenomena like with volcanoes, for example. “On Earth, around 76% of NO2 emissions are due to industrial activity”, said Giada Arney of NASA Goddard, co-author of the article. It will not be the only obstacle. The presence of clouds and aerosols would also lead to false positives. But more advanced models should make it possible to sort it out.
Source: Goddard Space Flight Center