James Webb Space Telescope Reveals New Insights into Sub‑Neptune Exoplanets

Astronomers using the James Webb Space Telescope (JWST) have reported several breakthroughs in the study of sub‑Neptune exoplanets. A team led by Sagnick Mukherjee at Arizona State University showed that high‑altitude clouds composed of vaporized rock and salts can act as a thermal blanket, raising temperatures in the lower atmosphere by more than 1,000 °C and influencing the conditions at the boundary with the planetary interior. Separate modeling work by researchers at the University of Chicago, including Collin Cherubim, found that the sub‑Neptune TOI‑270 d may conceal large amounts of water beneath a hydrogen‑rich layer, overturning earlier ideas that such worlds have well‑mixed interiors. In a related JWST observation, helium escaping from the rocky planet LHS 1140 b was detected, providing the strongest evidence yet that an Earth‑like planet in another star’s habitable zone retains an atmosphere. Together, the studies suggest that sub‑Neptunes possess complex interior structures, hidden water reservoirs, and that atmospheres can be identified on rocky worlds, expanding our understanding of planetary formation and habitability beyond the Solar System.