Episode Details

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So the whole world seems to have become very excited about the claim of a biosignature discovered in the atmosphere of the exoplanet K2-18b. And no sooner did those headlines hit the airwaves, astronomers came out in droves expressing skepticism and concerns. It feels a bit confusing to have two sides so certain of their position, and often the truth is more nuanced than either side will concede. So today, we're going to take a deep dive into K2-18b. You'll get the chance to hear both arguments and make up your own mind.

Written & presented by Prof. David Kipping. Special thanks to Nikku Madhusudhan and Ryan Macdonald for joining this episode.

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THANK-YOU to T. Widdowson, D. Smith, L. Sanborn, C. Bottaccini, D. Daughaday, S. Brownlee, E. West, T. Zajonc, A. De Vaal, M. Elliott, B. Daniluk, S. Vystoropskyi, S. Lee, Z. Danielson, C. Fitzgerald, C. Souter, M. Gillette, T. Jeffcoat, J. Rockett, D. Murphree, M. Sanford, T. Donkin, A. Schoen, K. Dabrowski, R. Ramezankhani, J. Armstrong, S. Marks, B. Smith, J. Kruger, S. Applegate, E. Zahnle, N. Gebben, J. Bergman, C. Macdonald, M. Hedlund, P. Kaup, W. Evans, N. Corwin, K. Howard, L. Deacon, G. Metts, R. Provost, G. Fullwood, N. De Haan, R. Williams, E. Garland, R. Lovely, A. Cornejo, D. Compos, F. Demopoulos, G. Bylinsky, J. Werner, S. Thayer, T. Edris, F. Blood, M. O'Brien, D. Lee, J. Sargent, M. Czirr, F. Krotzer, I. Williams, J. Sattler, B. Reese, O. Shabtay, X. Yao, S. Saverys, A. Nimmerjahn, C. Seay, D. Johnson, L. Cunningham, M. Morrow, M. Campbell, B. Devermont, Y. Muheim, A. Stark, C. Caminero, P. Borisoff, A. Donovan, H. Schiff, J. Cos, J. Oliver, B. Kite, C. Hansen, J. Shamp, R. Chaffee, A. Ortiz, B. McMillan, B. Cartmell, J. Bryant, J. Obioma, M. Zeiler, S. Murray, S. Patterson, C. Kennedy, G. Le Saint, W. Ruf, A. Kochkov, B. Langley, D. Ohman, P. Stevenson, T. Ford, T. Tarrants, A. Laroye, I. Venzor, R. Raszka, B. Gaalen, A. Taylor, D. Wedgewood, J. Alley, D. Aron, G. Thomsen, S. Shardool, B. Kingston, A. Phan Le, N. Voyton, N. Offor, A. Huch, J. Morrison & C. Fitzsimmons.

REFERENCES
► Madhusudhan et al. 2025, "New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI", ApJL, accepted: https://arxiv.org/abs/2504.12267
► Madhusudhan et al. 2023, "Carbon-bearing Molecules in a Possible Hycean Atmosphere", ApJ, 956, 13: https://arxiv.org/abs/2309.05566
► Schmidt et al. 2023, "A Comprehensive Reanalysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum", AAS Journals, submitted: https://arxiv.org/abs/2501.18477
► Madhusudhan et al. 2021, "Habitability and Biosignatures of Hycean Worlds", ApJ, 918, 1: https://arxiv.org/abs/2108.10888
► Wogan et al. 2024, "JWST observations of K2-18b can be explained by a gas-rich mini-Neptune with no habitable surface", ApJ, 963, 7: https://arxiv.org/abs/2401.11082
► Cooke & Madhusudhan 2024 , "Considerations for Photochemical Modeling of Possible Hycean Worlds", ApJ, 977, 209: https://arxiv.org/abs/2410.07313

#CoolWorlds #K218b #Biosignature

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