Weird planets may be the best place to look for strange alien life, according to new research

Scientists have searched for alien life for years, but space is huge, and technology has limits, making it hard to find answers. Traditionally, researchers have focused on finding planets similar to Earth, believing that conditions mirroring our own would be the best place to look for life.

However, a new study suggests that an entirely different type of planet could provide clearer evidence of living organisms.

Instead of focusing on Earth-like planets, scientists have identified a unique biosignature gas that could reveal life in environments that are vastly different from our own.

This discovery shifts the search toward larger, ocean-covered planets with thick hydrogen atmospheres, known as hycean planets, where certain microbes could potentially thrive.

Gases could be key indicators

The recent study, led by researchers from the University of California, Riverside, explored the unexpected gases that may signify life on exoplanets.

The research was focused on methyl halides, compounds made of a carbon and three hydrogen atoms bonded to a halogen, such as chlorine or bromine.

On Earth, these gases are produced by bacteria, marine algae, fungi, and certain plants.

Hycean planets and extraterrestrial life

Detecting these biosignatures presents challenges. Exoplanets similar to Earth are too small and dim for the James Webb Space Telescope (JWST) to observe effectively.

Instead, researchers suggest targeting hycean planets, which are larger and in orbit around small red stars.

These bodies are covered in deep oceans, and enveloped in thick hydrogen atmospheres. Though humans cannot survive on these planets, some microbes might.

“Unlike an Earth-like planet, where atmospheric noise and telescope limitations make it difficult to detect biosignatures, hycean planets offer a much clearer signal,” explained Eddie Schwieterman, UCR astrobiologist and co-author of the paper .

Practical approach to finding life

Scientists believe looking for methyl halides on hycean planets is a practical strategy, given current technology.

“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,” said Michaela Leung, UCR planetary scientist and first author of the paper.

Finding these gases could also be more efficient than searching for other biosignatures.

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

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

Detecting life from vast distances

Methyl halides exist on Earth in small amounts, but hycean planets could have atmospheric conditions that allow these gases to accumulate. This makes detection easier from vast distances.

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

The study builds on previous research into biosignature gases, including dimethyl sulfide.

Methyl halides stand out due to their strong absorption of infrared light and their ability to accumulate in hydrogen-rich atmospheres.

While JWST is currently the most powerful tool for this search, future missions could enhance detection.

The proposed European LIFE mission, expected to launch in the 2040s, may confirm these biosignatures in less than a day.

“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.”

Expanding the search for extraterrestrial life

Researchers plan to extend their investigations to other planetary types and biosignature gases.

They have already studied gases from extreme environments on Earth, such as the Salton Sea, which emits halogenated compounds like chloroform.

“We want to get measurements of other things produced in extreme environments on Earth, which could be more common elsewhere,” Schwieterman said.

Direct sampling of exoplanet atmospheres remains out of reach, but advances in telescope technology and observational techniques could change that.

“Humans are not going to visit an exoplanet anytime soon,” Schwieterman said. “But knowing where to look, and what to look for, could be the first step in finding life beyond Earth.”

The study is published in The Astrophysical Journal Letters.

Image Credit: NASA, ESA, CSA, Joseph Olmsted/STScI

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