Venus once hosted oceans? New clues point to a watery past and a volcanic turn to a runaway greenhouse
Some climate models suggest Venus could have harbored liquid water and temperate conditions for up to about two billion years, aided by slow rotation that encouraged cloud cover; later widespread volcanic resurfacing may have vented CO2 and triggered a runaway greenhouse, leaving Venus far hotter than today. The evidence is debated—cloud behavior on a young Venus and the deuterium-to-hydrogen ratio offer clues but no consensus. Next-generation missions (NASA’s DAVINCI and VERITAS, and ESA’s EnVision) aim to study the atmosphere, surface, and history to help settle whether Venus ever had oceans or was always hot.