If aliens blanket their planets with powerful greenhouse gases like we do, we might be able to tell.
That’s according to a recent thought experiment in which scientists identified five “artificial” greenhouse gases that, when abundant enough, can be detected in the atmospheres of certain exoplanets using existing technology, incl The James Webb Space Telescope (JWST).
Gases that include fluorinated versions of methane, ethane, propane, etc Earth are known to be some of the most effective and persistent heat-trapping gases that humans emit during various industrial manufacturing processes, such as those used to manufacture semiconductors. Since these substances don’t occur naturally in large quantities — at least as far as Earth’s chemistry is concerned — their detection in an exoplanet’s air would signal the presence of a technologically advanced species, the researchers say.
On Earth, these gases are dangerous pollutants, and limiting their emissions is essential to the fight against humans climate change. However, their presence in an alien atmosphere is not necessarily bad news.
“For us, these gases are bad because we don’t want to increase warming,” study lead author Edward Schwieterman of the University of California, Riverside, said in a recent paper. declaration. “But they would be good for a civilization that might want to prevent an impending ice age or terraform an otherwise uninhabitable planet in their system, as humans have suggested. Mars.”
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Such deliberate climate modification to create an Earth-like environment is known as terraforming. The idea of ​​terraforming Mars has appeared in almost every science fiction story, and in recent years scientists have also proposed similar approaches to support long-term colonization. Ideas for warming Mars include thawing some of the ice at the planet’s poles and releasing carbon dioxide trapped on its surface to prop up the planet’s thin atmosphere like a warm blanket. However, some remain skeptical of the concept. For example, Paul Sutter, an astrophysicist at SUNY Stony Brook and a Space.com contributor, wrote in a 2021 article that this type of terraforming effort probably won’t workAnd that’s mainly because Mars probably doesn’t contain enough carbon dioxide to produce a decent warming trend.
Recently, Schwieterman and his colleagues simulated planet v TRAPPIST-1 systemwhich is a family of seven stone planets about 40 light years far from Earth in the constellation of Aquarius; several of them are considered potentially habitable. The planet TRAPPIST-1f, for example, orbits its host star every nine days within its planet habitable zone.
If aliens were to terraform such a planet, scientists found that JWST could identify five greenhouse gases. One of them, sulfur fluoride, has a warming potential 23,500 times that of carbon dioxide. A tiny amount of this gas, which has a lifetime of at least 1,000 years, is enough to thaw an icy planet to the point where life-supporting liquid water flows to its surface, scientists say. (Life as we know it, to be clear).
“The long lifetime makes these gases excellent technological signatures to systematically search for compared to shorter-lived signals,” study co-author Daniel Angerhausen of ETH Zürich said in another paper. declaration. “These signatures could even survive their civilization if their geoengineering experiments failed.
Other similar fluorinated gases can hang around in an Earth-like atmosphere for up to 50,000 years, so “they don’t need to be replenished very often to maintain a hospitable climate,” Schwieterman said in a statement.
That means extraterrestrial life on frigid planets beyond ours Solar System pumps a lot of greenhouse gases into their atmospheres to make their worlds more habitable, our existing telescopes could detect them. Even if only one out of every million gas molecules absorbed infrared radiation from its host star, it would produce a clear signature detectable by JWST and others spaceSchwieterman and his team found the telescopes.
“You wouldn’t need a special effort to look for these technosignatures if your telescope is already characterizing the planet for other reasons,” Schwieterman said. “And it would be wonderful to find them.
These findings are described in paper published June 25 in The Astrophysical Journal.