
This illustration shows cross-sections of the Earth and the exoplanet Kepler-138d. Measurements of Kepler-138d’s density suggest it could have a water layer that makes up more than 50% of its volume, to a depth of about 1,243 miles (2,000 kilometers). Credit: Benoit Gougeon (University of Montreal)
This illustration shows cross-sections of the Earth and the exoplanet Kepler-138d. Measurements of Kepler-138d’s density suggest it could have a water layer that makes up more than 50% of its volume, to a depth of about 1,243 miles (2,000 kilometers).