If aliens envelope their planets in powerful greenhouse gases like we do, we’d be able to tell.
That’s according to a recent thought experiment in which scientists identified five “artificial” greenhouse gases that, if abundant enough, could be detected in the atmospheres of some countries. exoplanets using existing technology, incl The James Webb Space Telescope (JWST).
Gases, which include fluorinated versions of methane, ethane, propane, etc earth are recognized as some of the most powerful and stable heat-trapping gases emitted by humans during various industrial production processes, such as those used to manufacture semiconductors, for example. Because these substances don’t form naturally in large quantities — at least if we look at Earth’s chemistry — their detection in an exoplanet’s air would signal the presence of technologically advanced species, scientists say.
On Earth, these gases are dangerous pollutants, and limiting their emissions is essential to human-led combat. climate change. Their presence in an alien atmosphere may not necessarily be bad news, however.
“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 recently. STATEMENT. “But they would be good for a civilization that perhaps wanted to prevent an impending ice age or terraform an otherwise uninhabitable planet in their system, as people have proposed for March.”
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Such deliberate climate modification to create an Earth-like environment is known as terraforming. The idea of ​​terraforming Mars has cropped up in almost every science fiction story, and in recent years, scientists have also proposed similar approaches to support long-term colonization. Ideas to warm Mars include melting some of the ice at the planet’s poles and releasing carbon dioxide trapped on its surface to support the planet’s thin atmosphere like a warm blanket. Although, some remain skeptical about the concept. For example, Paul Sutter, an astrophysicist at SUNY Stony Brook and contributor to Space.com, wrote in a 2021 article that this type of terraforming effort it probably won’t workmost importantly because Mars likely does not host enough carbon dioxide to cause a decent warming trend.
Recently, Schwieterman and his colleagues simulated a planet in TRAPPIST-1 systemwhich is a family of seven rocky planets about 40 light years away from Earth in the constellation of Aquarius; some of them are considered potentially habitable. The planet, TRAPPIST-1f, for example, orbits its host star every nine days within it residential area.
If aliens were to terraform such a planet, the researchers found that JWST could identify the five greenhouse gases. One of them, sulfur hexafluoride, has a warming potential that exceeds carbon dioxide by 23,500 times. Small amounts of this gas, which has a lifetime of at least 1,000 years, is enough to melt an icy planet to the point where life-sustaining liquid water flows to its surface, researchers say. (Life as we know it, to be clear).
“The long lifetime makes these gases excellent technological signatures to look for systematically compared to longer-lived signals,” study co-author Daniel Angerhausen of ETH Zürich said in another. STATEMENT. “These signatures could even survive their own civilization if their geoengineering experiments were to fail.”
Other similar, fluorinated gases can hang around in an Earth-like atmosphere for up to 50,000 years, so “they would not need to be replenished very often to maintain a hospitable climate,” Schwieterman said in the statement.
This means if extraterrestrial life on cold planets beyond ours solar system pumps a bunch of greenhouse gases into their atmospheres to make their worlds more habitable, our existing telescopes may be able to spot them. Even if just one in every million gas molecules absorbed infrared radiation from its host star, it would produce a signature telltale with JWST and others. ROOM-based telescopes, Schwieterman and his team found.
“You won’t need extra effort to look for these technological signatures if your telescope is already characterizing the planet for other reasons,” Schwieterman said. “And it would be incredibly amazing to find them.”
These findings are described in a paper published June 25 in The Astrophysical Journal.