# Exoplanets Without Lots of Water Cant Maintain Their Carbon Cycles - Date: 2026-04-20 - Category: Space & Aerospace Earth may be the rare water-rich outlier, not the template. New research puts a number on the minimum ocean mass an arid planet needs to sustain its climate: 20 to 50 percent of Earths. Below that, even worlds in the habitable zone can go Venus-mode. ---