Sub-Neptune planets, often billed as possible "water worlds," may be more desert than deep sea, according to a new study.
For years, scientists thought these planets, which are larger than Earth but smaller than Neptune, could form far from their stars, sweeping up ice beyond the so-called "snow line." As the planets migrated inward, scientists have thought that ice might melt into oceans hidden beneath hydrogen skies. Such hypothetical worlds were dubbed "Hycean planets," a blend of "hydrogen" and "ocean."
