“For exoplanet astronomy, one of the biggest things we want to do is find evidence for life. I don’t want us to be in the situation where we’re the boy who cried wolf.”

-Kreidberg, Director at the Max Planck Institute for Astronomy

The search for alien life has been fueled by our rapidly advancing space technology and humanity’s perennial curiosity for what is beyond. A hunt for another pale blue dot. Planetary science stands at the forefront of extraterrestrial research with telescopes like JWST and Euclid unraveling paradisiacal crevices of our universe through their futuristic infrared technology. At the pedestal of this astrobiological movement stands the recently sensationalized K2-18b, a sub-Neptune planet, 124 light years away[11], that is the centrepiece of today’s intergalactic banquet. Particularly after 2025, observations by the James Webb Space Telescope (JWST) detected potential biosignatures, including dimethyl sulfide (DMS) and dimethyl disulfide (DMDS). These findings, led by Nikku Madhusudhan’s team at the University of Cambridge, invigorated discussions about K2-18b as a candidate “Hycean” world—a novel class of planets with hydrogen-rich atmospheres and liquid water oceans[4].

Today, I will be discussing the science behind chemical biomarkers of life and how the sci-comm industry has glamorized K2-18b’s findings, transforming nuanced results into what I term “bite-sized exobiology gummy bears” (oversimplified nuggets of science). Through a scientific lens, I will explore the Hycean hypothesis, abiotic DMS pathways, and Madhusudhan’s contributions, critiquing the rhapsodization of exobiology and its implications for scientific discourse.

The Hycean Hypothesis:

Discovered in 2015 by NASA’s Kepler mission, K2-18b is an exoplanet approximately 8.6 times Earth’s mass and 2.6 times its diameter[1]. Positioned in the habitable zone, where stellar flux permits liquid water, it became a prime target for atmospheric characterization. In 2019, Hubble Space Telescope observations revealed water vapor, sparking interest in its habitability. Subsequent JWST observations in 2023, using NIRISS and NIRSpec, confirmed methane and carbon dioxide at 1% and 0.1% abundances[3][4]. By April 2025, JWST’s MIRI found the DMS signal to 10-15 parts per million which is about a thousand times what we find on Earth[5]. 

Now you might ask, why is dimethyl sulfide this particularly enchanting? Why not some other carbon compound like cyanide, perhaps? (Warning: Cyanide is actually poisonous, making this a horrible rhetorical question.) DMS is a compelling biosignature candidate because, on Earth, it is primarily produced by marine phytoplankton[1][12] via enzymatic cleavage of dimethylsulfoniopropionate. Madhusudhan’s team modeled a biological scenario requiring microbial productivity 100–1000 times Earth’s, plausible for a Hycean world with nutrient-rich oceans. Their photochemical models, incorporating sulfur cycling, predict DMS stability in Hydrogen-rich atmospheres, enhancing its detectability. 

But. The abiotic pathways of DMS production cannot be ruled out. The absence of expected photochemical byproducts, such as ethane in the JWST spectra raises doubts about biological DMS production, as ethane is typically co-produced in methane-rich atmospheres[7]. On comets like 67P, DMS is produced abiotically,  likely due to gas-phase reactions of methyl and thio (SH) compounds. UV-driven photochemistry could bring out the birth of DMS from methane and hydrogen sulphide which is also an equally probable possibility considering the detected methane and inferred sulphur reservoirs[13]. These pathways challenge the biosignature cultural movement of sci-comm media, as emphasized by astrobiologist Eddie Schwieterman, who noted the need for “contextual molecules” like ethane or sulphur dioxide to distinguish biological from abiotic DMS[14].

Exobiology Gummy Bears:

While the research in itself is groundbreaking and exciting, sci-comm media outlets play a pivotal role in translating complex research for public consumption. Yet something we all know is that cautious science doesn't make news. 

Credit: Magnilion, Getty Images 

Media has transformed K2-18b’s complex findings into what I like to call bite-sized exobiology gummy bears—colorful, easy, and make sure you only read the headline and never actually end up opening the article. Instagram science narratives lean heavily on the emotional appeal of discovering extraterrestrial organisms, evoking images of turquoise oceans teeming with life despite the data’s limitations. Caveats that are paramount to scientific inquiry like the low statistical importance of the DMS signal are acknowledged in the original study but are often purposefully ignored or omitted in popular articles. 

Such rhaposidization has dichotomous implications. While buzz about space science is always good for justifying funding for telescope projects like the Nancy Grace Roman Telescope. But at the same time it risks disillusionment of the notion of finding intelligent creatures intergalactically. The 2020 phosphine detection on Venus, later disputed, serves as a cautionary tale of how biomarkers are not strong enough evidence of life. Second, sensationalization can distort scientific priorities, pressuring researchers to chase high-profile biochemistry over less glamorous but equally important studies, such as characterizing sub-Neptune’s unique atmospheres.

For K2-18b, future JWST observations, estimated to require 16–24 hours, will be critical to achieving five-sigma significance and testing the Hycean hypothesis. Until then, the scientific community must resist the temptation to "cry aliens," as astronomer Laura Kreidberg cautioned[2].

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