HUNTING for aliens is now a little easier as scientists discover a new sign that gives away life on far-off planets.

Importantly, this new signal teases the presence of alien life on distant worlds that look nothing like Earth.

The new clue is a set of gases that can be detected in the atmosphere of exoplanets – worlds beyond our solar system.

These gases are “rarely considered in the search for extraterrestrials”, according to the University of California, Riverside.

Even better, these gases could be picked up with existing space hardware: the James Webb Space Telescope.

The JWST launched in late 2021 and has been probing the skies to study the origins of the universe, galaxies, stars, and exoplanets that could support life.

Scientists say that it would be able to detect a group of gases called methyl halides.

On Earth, they’re mostly produced by bacteria, marine algae, fungi, and some plants, the researchers revealed.

But when scientists are hunting for methyl halides in space, the exoplanets that look like Earth are too “small and dim” to be spied by the JWST.

So JWST would need to look for bigger exoplanets that orbit small red stars.

These Hycean planets would have deep world-spanning oceans and thick atmospheres made up of hydrogen.

Humans wouldn’t be able to live on these worlds – but alien microbes could “thrive”.

“Unlike an Earth-like planet, where atmospheric noise and telescope limitations make it difficult to detect biosignatures, Hycean planets offer a much clearer signal,” said UCR astrobiologist Eddie Schwieterman.

Now scientists think that we should be looking for methyl halides on these Hycean worlds.

It could give us a key clue that life is lurking beneath their dense hydrogen atmospheres.

“Oxygen is currently difficult or impossible to detect on an Earth-like planet,” said Michaela Leung, a planetary scientist at UCR.

“However, methyl halides on Hycean worlds offer a unique opportunity for detection with existing technology.”

FAST FINDS

These gases aren’t the only sign of extraterrestrial life that alien-hunters could spot.

But scientists say that they might be an easier option.

“One of the great benefits of looking for methyl halides is you could potentially find them in as few as 13 hours with James Webb,” said Leung.

“That is similar or lower, by a lot, to how much telescope time you’d need to find gases like oxygen or methane.

“Less time with the telescope means it’s less expensive.”

ALIEN WORLDS

Earth has life forms that produce methyl halides – but it’s only found in low concentrations in our atmosphere.

By contrast, Hycean planets have a very different kind of atmosphere and host star.

So the gases could build up in the atmosphere, potentially making them detectable from “light years away”.

“These microbes, if we found them, would be anaerobic,” Schwieterman explained.

“They’d be adapted to a very different type of environment.

“And we can’t really conceive of what that looks like, except to say that these gases are a plausible output from their metabolism.”

E.T. HOPE

JWST isn’t the only way that we can track down these gases either.

The proposed European LIFE mission that would launch in the 2040s could confirm signs of these gases in “less than a day”, the scientists say.

“If we start finding methyl halides on multiple planets, it would suggest that microbial life is common across the universe,” Leung said.

“That would reshape our understanding of life’s distribution and the processes that lead to the origins of life.”

And Schwieterman added: “Humans are not going to visit an exoplanet anytime soon.

“But knowing where to look, and what to look for, could be the first step in finding life beyond Earth.”

This research was published in the Astrophysical Journal Letters.