section_path: Atmosphere and climate/Alternative scenarios
section_name: Alternative scenarios
paragraph_text: Alternative scenarios
  
  Detecting atmospheres around planets is difficult, and several reported findings are controversial. Barclay et al. 2021 suggested that the water vapour signal may be due to stellar activity, rather than water in K2-18b's atmosphere. Bézard et al. 2020 proposed that methane may be a more significant component, making up about 3–10% while water may constitute about 5–11% of the atmosphere, and Bézard, Charnay and Blain 2022 proposed that the evidence of water is actually due to methane, although such a scenario is less probable.