Scientists find unusual gas on exoplanets, could be the biggest clue in alien hunt

Could alien life exist on planets nothing like Earth? Scientists think a surprising new method could unravel this mystery.

Researchers from the University of California, Riverside, suggest that certain gases detected in the atmospheres of exoplanets could be key indicators in the search for extraterrestrial life.

These planets, which exist outside our solar system, can be observed using a James Webb Space Telescope (JWST), the largest telescope currently in space.

Methyl halides are gases of a methyl group, which bears a carbon and three hydrogen atoms bonded to a halogen atom such as chlorine or bromine. On Earth, they are mainly produced by bacteria, marine algae, fungi, and certain plants.

A key challenge in detecting these gases is that Earth-like exoplanets are too small and faint to be observed with the JWST. Instead, the most technically advanced telescope would have to focus on larger exoplanets orbiting small red stars.

Hunting for life beyond Earth

These exoplanets are called the Hycean planets, which are characterized by deep global oceans and thick hydrogen-rich atmospheres.

While these worlds would be uninhabitable for humans, they could provide a suitable environment for certain microbes to 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,” paper co-author Eddie Schwieterman said.

The researchers believe that the search for methyl halides on Hycean planets could be an ideal strategy for looking for extraterrestrial life.

“Oxygen is currently difficult or impossible to detect on an Earth-like planet. However, methyl halides on Hycean worlds offer a unique opportunity for detection with existing technology,” Michaela Leung, the first author of the paper, said

The researchers said that looking for such gases is easier than searching for other types of biosignature gas on other planets.

“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,” Leung said.

The researchers noted that the required telescope time to detect methyl halides is comparable or significantly lower than needed to identify gases like oxygen or methane. They added that requiring less telescope time makes the search more cost-effective.

A chemical clue in exoplanet atmospheres

On the Earth, Methyl halides exist only in the trace. However, due to the unique atmospheric composition of Hycean planets and proximity to small red stars, these gases could build up to much higher concentrations—potentially making them detectable from light-years away.

Researchers explained that any microbes in such environments would likely be anaerobic, but their metabolic processes would produce these gases.

The study expands on previous research exploring biosignature gases, including dimethyl sulfide, another life indicator. However, methyl halides stand out due to their strong infrared absorption properties and the likelihood of their accumulation in hydrogen-rich atmospheres.

The researchers noted that discovering methyl halides on multiple planets could suggest microbial life is widespread in the universe.

Researchers plan to expand their work to other planetary environments and gases, using Earth’s extreme locations, like the Salton Sea, as analogs.

The researchers believe that while direct sampling of exoplanet atmospheres remains out of reach, advances in telescope technology could bring humanity closer to discovering alien life.

“Humans won’t visit an exoplanet soon,” Schwieterman said, “but knowing where to look is the first step in finding life beyond Earth.”

The study is published in The Astrophysical Journal Letter.