Nature Study Finds Sub-Neptunes Can Make Water Internally Up to Tens of Percent by Weight
Updated
Updated · spacedaily.com · Jul 10
Nature Study Finds Sub-Neptunes Can Make Water Internally Up to Tens of Percent by Weight
1 articles · Updated · spacedaily.com · Jul 10
Summary
A 2025 Nature study found sub-Neptunes can generate substantial water deep inside the planet, rather than relying on icy comet or asteroid impacts from beyond a star system’s snow line.
Laboratory simulations by Dan Shim and Alona Vazan showed hydrogen-rich atmospheres reacting with molten silicate rock under extreme pressure and heat, pulling oxygen from the melt to form H2O.
The experiments suggest the process could convert a meaningful share of a planet’s mass into water—up to a few tens of percent by weight—far above earlier estimates.
That matters because sub-Neptunes and super-Earths are the most common planets detected, implying water could be a routine outcome of planet formation rather than a lucky delivery.
The study does not show those worlds have surface oceans: much of the water may stay trapped in deep magma and dense atmospheres, leaving open debates over planets such as K2-18b.
If planets can brew their own oceans, how does this rewrite our entire search for alien life?
Countless worlds may hide deep water, but could life ever escape these high-pressure, internal oceans to reach the surface?
Sub-Neptunes Forge Their Own Water: 2025 Discovery Redefines Exoplanet Habitability and Origins
Overview
A groundbreaking 2025 study revealed that sub-Neptune exoplanets can internally generate large amounts of water through high-pressure chemical reactions deep within their interiors. This discovery challenges previous theories that water on such planets mainly comes from external sources or is trapped in the mantle, often leaving surfaces dry. The new findings show that sub-Neptunes can have water content reaching several tens of percent by weight, fundamentally reshaping our understanding of how water-rich worlds form and exist beyond our solar system. This re-evaluation has major implications for the search for habitable planets and the potential for life beyond Earth.