[8] However, a recent study of the planet's internal structure informed by observations taken with the James Webb Space Telescope suggests that a "waterworld" composition is implausible and the planet is more likely to host a thick gaseous envelope consisting of hydrogen, helium, water and other volatile chemicals such as methane or carbon dioxide.

[9] It is a mini-Neptune, meaning it is larger than Earth but is significantly smaller (in mass and radius) than the gas giants of the Solar System.

Through a comparison with theoretical models, the density in turn provides limited but highly useful information about the composition and structure of the planet.

[1][13] Due to the relatively small size of GJ 1214 b's parent star, it is feasible to perform spectroscopic observations during planetary transits.

[1][13] Water planets could result from inward planetary migration and originate as protoplanets that formed from volatile ice-rich material beyond the snow-line but that never attained masses sufficient to accrete large amounts of H/He nebular gas.

[13] In January 2025, spectroscopic analysis of GJ 1214 b revealed its atmospheric contents to be metallic, with carbon-dioxide acting as an aerosol, suspended above it.

[23] This layout was noted to be similar to that of a "Super-Venus," although further analysis is needed to confirm whether the weak elemental readings are not a statistical anomaly.

[24] GJ 1214 b was first detected by the MEarth Project, which searches for the small drops in brightness that can occur when an orbiting planet briefly passes in front of its parent star.

In early 2009, the astronomers running the project noticed that the star GJ 1214 appeared to show drops in brightness of that sort.