Previously, scientists have commonly used the detection of combinations of oxygen and methane within the atmospheres of exoplanets as indicators in the search for extraterrestrial Life because of the relevance of these components to biological life activities.
A new NASA study suggests that extraterrestrial technological civilizations are likely to cause similar pollution to their atmospheres as human industrial activities, and that it may be possible to determine the presence of technological civilizations on exoplanets by detecting the presence of polluting components in their atmospheres.
There are many pollutants emitted into the atmosphere from human industrial activities, and nitrogen dioxide is one of them. This study found that nitrogen dioxide gas in the atmosphere has a strong ability to absorb certain colors of visible light, and that the light reflected from the exoplanet’s atmosphere can be analyzed to determine the situation of nitrogen dioxide in the planet’s atmosphere.
This study suggests that the amount of nitrogen dioxide in an exoplanet’s atmosphere could be a potential indicator in the search for extraterrestrial technological civilizations. Nitrogen dioxide is one of the products of petroleum combustion, although non-industrial activities such as some biological activities, lightning and volcanic eruptions can also produce some of it.
On Earth, most of the carbon dioxide gas is a product of human activity – car exhaust and emissions from oil-fueled power plants, among others,” said NASA researcher Ravi Kopparapu. Within the lower atmosphere (10 to 15 kilometers above the ground), human activities produce the vast majority of nitrogen dioxide. Therefore, the amount of nitrogen dioxide on a habitable planet can be used as a potential indicator of the presence of an industrial civilization on it.”
So far, scientists have discovered more than 4,000 exoplanets and believe that some of them may have life on them, perhaps even life with technological civilizations. But because they are so far away from Earth, it is not feasible to send probes to fly to explore them, so scientists thought of using the powerful telescopes that are now available to peer and speculate about the interior of those worlds.
NASA said that this is the first study to suggest the use of nitrogen dioxide as an indicator of technological civilization to probe exoplanets.
The study built a model to analyze the range of exoplanet technology civilizations that can be detected at the farthest point with existing telescope technology. Their model shows that a planet like Earth orbiting the Sun, if the civilization on it produces the same amount of nitrogen dioxide as on Earth, can be detected from as far as 30 light years away, from 400 hours of observation data, using NASA’s most advanced telescope to be launched.
One light year is already a very long distance, equivalent to about 9.5 trillion kilometers. The nearest star to our sun is 4 light years away, and our galaxy is about 100,000 light years wide.