A team of researchers has detected hydrogen sulfide (H₂S), water vapor (H₂O), carbon dioxide (CO₂), and carbon monoxide (CO) in the atmosphere of the Jupiter-mass exoplanet HD 189733b using data from the James Webb Space Telescope (JWST). These findings, based on transmission spectroscopy of the planet's transit, reveal a high atmospheric metallicity, approximately 3-5 times that of its host star. The detection of H₂S and the low carbon-to-oxygen ratio suggest that the planet formed from the accretion of water-rich icy planetesimals. The study also found a low upper limit on methane abundance, indicating a low carbon-to-oxygen ratio and supporting the planetesimal accretion formation pathway. The researchers used two complementary modeling approaches to interpret the data: a grid-based retrieval and a free retrieval method. The grid-based retrieval found a metallicity of 3-5 times stellar, while the free retrieval provided a better fit with more flexible model assumptions. The results indicate that HD 189733b has a sub-stellar C/O ratio and a high atmospheric metallicity, consistent with the accretion of water-rich icy planetesimals. The study also addressed potential systematic effects in the data, including instrumental ramp features and stellar spot crossings, and accounted for these in the analysis. The findings provide important insights into the atmospheric composition and formation history of HD 189733b.A team of researchers has detected hydrogen sulfide (H₂S), water vapor (H₂O), carbon dioxide (CO₂), and carbon monoxide (CO) in the atmosphere of the Jupiter-mass exoplanet HD 189733b using data from the James Webb Space Telescope (JWST). These findings, based on transmission spectroscopy of the planet's transit, reveal a high atmospheric metallicity, approximately 3-5 times that of its host star. The detection of H₂S and the low carbon-to-oxygen ratio suggest that the planet formed from the accretion of water-rich icy planetesimals. The study also found a low upper limit on methane abundance, indicating a low carbon-to-oxygen ratio and supporting the planetesimal accretion formation pathway. The researchers used two complementary modeling approaches to interpret the data: a grid-based retrieval and a free retrieval method. The grid-based retrieval found a metallicity of 3-5 times stellar, while the free retrieval provided a better fit with more flexible model assumptions. The results indicate that HD 189733b has a sub-stellar C/O ratio and a high atmospheric metallicity, consistent with the accretion of water-rich icy planetesimals. The study also addressed potential systematic effects in the data, including instrumental ramp features and stellar spot crossings, and accounted for these in the analysis. The findings provide important insights into the atmospheric composition and formation history of HD 189733b.