Greenhouse gases can help us find advanced alien civilisations, scientists say

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Scientists have identified a set of greenhouse gasses which could be used as a marker to look for advanced alien civilisations with the potential to transform entire planets to make them habitable.

While greenhouse gasses cause global warming and must be controlled on Earth, they may be used intentionally to make other worlds hospitable.

“For us, these gases are bad because we don’t want to increase warming. But they’d be good for a civilization that perhaps wanted to forestall an impending ice age or terraform an otherwise uninhabitable planet in their system,” study co-author author Edward Schwieterman from the University of California Riverside explained.

Researchers have identified a set of gasses that can be detected even at low concentrations in planets outside our solar system using existing technology such as Nasa’s James Webb Space Telescope.

Since these gases do not naturally occur in significant quantities, finding them in other worlds could be signs of technology use by aliens, or a type of technosignature, scientists say.

These gasses include fluorinated versions of methane, ethane, and propane, along with gases made of nitrogen and fluorine or sulfur and fluorine.

While on Earth, they are used in industrial applications such as making computer chips, in space they may be used to systematically look for intelligent life forms, researchers say.

For instance, a subset of these gasses is Sulfur hexafluoride, which has 23,500 times the warming power of carbon dioxide.

Even a relatively small amount of this gas could heat a freezing planet to a point where it could start having liquid water on its surface, the study noted.

“With an atmosphere like Earth’s, only one out of every million molecules could be one of these gases, and it would be potentially detectable. That gas concentration would also be sufficient to modify the climate,” Dr Schwieterman said.

These molecules are also exceptionally long-lived and can persist in an Earth-like environment for up to 50,000 years.

Some of these fluorinated compounds also absorb infrared radiation which could be detectable with space-based telescopes.

“You wouldn’t need extra effort to look for these technosignatures, if your telescope is already characterizing the planet for other reasons. And it would be jaw-droppingly amazing to find them,” Dr Schwieterman said.