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For decades, scientists have searched the stars for signs of alien life — scanning distant planets for the presence of water, oxygen, and Earth-like conditions. But what if we’ve been looking for the wrong clues all along?
A new study suggests that we should widen our lens and start searching for a different set of chemical signatures — methyl halides — in the atmospheres of planets far different from our own. And the exciting part?
The Chemical Clues We’re Overlooking
Researchers at the University of California, Riverside (UCR) have identified a group of gases that are rarely considered in the search for extraterrestrial life: methyl halides. These compounds — such as methyl chloride or methyl bromide — are naturally produced by life on Earth, specifically by marine algae, bacteria, fungi, and some plants.
While they may sound exotic, methyl halides are surprisingly common in Earth’s atmosphere, particularly around ocean environments. Yet until now, they’ve largely been ignored as potential biosignatures in the search for life on other planets.
Why? Because most of our focus has been on planets that resemble Earth. But that may be a mistake.
Earth-Like Planets Are Harder to Observe
Ironically, Earth-like planets — the ones we assume are most likely to host life — are incredibly difficult to observe in detail.
That’s because they’re typically small and dim, especially when compared to the stars they orbit. Instruments like the James Webb Space Telescope (JWST), while powerful, struggle to capture detailed atmospheric data from such faint targets.
“Right now, detecting oxygen on an Earth-like planet is extremely challenging or even unfeasible,” explains Michaela Leung, a planetary scientist at the University of California, Riverside (UCR). So while Earth analogs may indeed be teeming with life, our technology just isn’t quite ready to confirm it — yet.
This is where another type of planet takes center stage: the Hycean planet.
Enter the Hycean Planets: Giant Ocean Worlds with Hydrogen Skies
Hycean planets are a newly theorized class of exoplanets that are bigger than Earth, have deep global oceans, and are wrapped in a thick hydrogen-rich atmosphere. The word “Hycean” combines “hydrogen” and “ocean,” and these planets are quickly emerging as top contenders in the quest to find alien life.
They don’t resemble Earth in the traditional sense. Their atmospheres are too thick for humans to breathe, and their gravity and chemical makeup may be completely alien to us. But that doesn’t mean life couldn’t exist there.
In fact, these planets could offer ideal conditions for microbial life to thrive beneath their dense atmospheric layers, possibly in nutrient-rich oceans warmed by internal or stellar heat.
Even better? These worlds are more accessible for observation compared to Earth-like planets.
“Compared to Earth-like planets, where atmospheric interference and telescope constraints complicate the detection of biosignatures, Hycean planets provide a much stronger and clearer signal,” says Eddie Schwieterman, an astrobiologist at UCR.
