“Strongest Sign Yet”: Telescope Detects Possible Signs of Life on Distant Planet K2-18 b

In a groundbreaking find, scientists detect gases on exoplanet K2-18 b—produced on Earth only by life—offering the most compelling evidence yet of potential alien biology.

April 17, 2025 | In what may be a historic moment in the search for life beyond Earth, scientists using the James Webb Space Telescope (JWST) have detected strong traces of two biologically linked gases—dimethyl sulfide (DMS) and dimethyl disulfide (DMDS)—in the atmosphere of K2-18 b, a distant exoplanet located 124 light-years away in the Leo constellation.

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Both gases are known on Earth to be exclusively produced by living organisms, primarily marine microbes like phytoplankton. While the discovery is not confirmation of extraterrestrial life, it is the strongest biosignature yet observed outside our solar system, researchers say.

“This is a transformational moment in the search for life beyond the solar system,” said lead scientist Nikku Madhusudhan of the University of Cambridge. “We have entered the era of observational astrobiology.“

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🌍 K2-18 b: A “Hycean” World With Potential for Life

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• Type: Sub-Neptune exoplanet
• Size: 8.6 times the mass of Earth, 2.6 times its diameter
• Orbit: In the “habitable zone” of a red dwarf star
• Distance: 124 light-years away
• Atmosphere: Hydrogen-rich, contains carbon dioxide, methane, and now possibly DMS/DMDS
• Class: Likely a Hycean world – an ocean-covered planet with a hydrogen atmosphere

“We’re talking about microbial life, possibly like what we see in Earth’s oceans,” Madhusudhan noted. “Multicellular or intelligent life is unlikely to be detected at this stage.“

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🧪 Why DMS and DMDS Are Significant

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• On Earth:
  DMS and DMDS are produced only through biological activity—primarily by marine microbes.
• On K2-18 b:
  Detected at concentrations thousands of times higher than Earth’s levels
• Statistical Confidence:
  99.7%, meaning only a 0.3% chance the signal is a fluke
• Significance:
  Strong biosignatures, yet scientists urge caution and call for repeat observations and further testing

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🔭 How the Discovery Was Made: The Transit Method

The Webb telescope observed K2-18 b using the transit method—analyzing starlight filtered through the planet’s atmosphere as it passed in front of its host star. This helped identify chemical signatures with high precision.

Previously, JWST also detected methane and carbon dioxide in the planet’s atmosphere—carbon-based compounds considered essential to life.

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🧠 Expert Reactions and the Road Ahead

“We must be very careful to test the data as thoroughly as possible,” said Christopher Glein, Principal Scientist at the Southwest Research Institute, noting that further validation is essential.

“It’s a big ‘if’. No one should prematurely claim we’ve found life,” added Madhusudhan. “We still need to rule out abiotic (non-biological) processes that might explain these signals.“

Madhusudhan emphasized that future observations should:

1. Repeat and confirm the signals to push statistical certainty closer to one in a million.
2. Explore alternative chemical mechanisms that may produce the same gases without involving life.

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🌌 A New Era in the Hunt for Life

K2-18 b now joins a growing list of promising candidates for harboring life outside our solar system. The JWST’s latest discovery doesn’t prove life exists—but brings humanity closer than ever to answering the age-old question: Are we alone in the universe?

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📌 Tags:

K2-18b, James Webb Space Telescope, life on exoplanet, alien biosignatures, DMS gas in space, exoplanet discovery, habitable zone planets, microbial life, space science news, Hycean world