Planet K2-18b: Everything You Need To Know About The ‘Alien’ Planet

Scientists may have found signs of life on an exoplanet 124 light years away – or they may not. Welcome to the very cautious world of space science.

It’s the kind of headline that makes your inner space nerd sit up: researchers have detected potential biosignature gases on K2-18b, a distant planet orbiting a red dwarf star 124 light years from Earth. The catch? No one’s popping champagne just yet.

The study, led by Professor Nikku Madhusudhan and published in Astrophysical Journal Letters, picked up hints of dimethyl sulphide (DMS) or dimethyl disulphide (DMDS) in the planet’s atmosphere. On Earth, these gases are produced almost exclusively by living organisms—specifically, marine microbes. So naturally, the whispers of alien life began.

Image @Omari Williams via Pinterest

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But before you start imagining seaweed-scented alien oceans, let’s talk science.

The detection was made using NASA’s ultra-fancy James Webb Space Telescope, which can analyse the atmospheres of far-off planets using infrared light. In this case, researchers focused on Hycean planets—a newly recognised class of water-covered worlds with hydrogen-rich atmospheres. K2-18b is one such planet, making it a prime candidate for this type of biosignature search.

Here’s why it’s interesting: DMS and DMDS are considered promising biosignatures. They don’t tend to hang around in atmospheres without a reliable source, and their production from non-living processes (aka abiotic pathways) is tricky to pull off. The researchers argue that the levels they detected on K2-18b would be hard to explain without something alive producing them.

Still, there are caveats. Big ones.

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For starters, the telescope can’t distinguish between DMS and DMDS—they have almost identical infrared fingerprints. Plus, without knowing more about the planet’s environment (does it have a surface? water? a solid crust?), it’s hard to say what these molecules actually mean. We don’t even know for sure if K2-18b could support life, let alone that it does.

And while the study hints that abiotic processes are unlikely to produce the gas levels detected, that doesn’t mean they’re impossible. As the authors themselves note, DMS has even been spotted on a lifeless comet before.

Image @WWD via Pinterest

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To their credit, the team behind the study aren’t claiming definitive proof. They’re calling for a “dedicated community effort” to explore the findings further, test for false positives, and refine our understanding of life-friendly chemistry.

As Professor John Barbur from City St George’s, University of London, puts it: detecting DMS is exciting, but “the discovery of a new colour”—oops, wrong study. (Still, he’s just as sceptical here.)

So, is there life on K2-18b? Maybe. Maybe not. The real win is how far we’ve come in being able to ask the question—and get even a hint of an answer.