Water production on exoplanets revealed by pressure experiments
by Clarence Oxford Los Angeles CA (SPX) Nov 20, 2025
Researchers led by Lawrence Livermore National Laboratory postdoctoral scientist Harrison Horn have demonstrated a pathway for producing water on sub-Neptune exoplanets. The team recreated the boundary conditions between hydrogen atmospheres and magma cores using a laser-heated diamond-anvil cell.
Horn stated, "Our experiments are the first to look at interactions between hydrogen and silicates at the pressure-temperature conditions expected at their interface in sub-Neptune exoplanets. We show that water does not need to come from further out in the solar system. It can be produced within a planet itself."
The study focused on sub-Neptune exoplanets, which have radii between two and four times that of Earth and represent some of the most common planet types observed by NASA's Kepler mission. Many sub-Neptunes orbit closely to their host stars, which has led scientists to consider them rocky and dry due to high temperatures. Previously, scientists assumed water present on these planets arrived through cometary or asteroidal impacts, or via planetary migration from cooler regions.
The new experiments contradict those theories, revealing that at high pressure and temperature conditions, molten silicates can react with atmospheric hydrogen. This reaction produces oxygen, which interacts with hydrogen to yield substantial water. The quantity of produced water depends on each planet's composition and interface conditions.
The findings indicate that dry sub-Neptunes may become wet through this internal mechanism, rather than external delivery or migration, challenging and expanding current models of planetary formation. Horn commented, "These results help further our understanding of how planets form, a rapidly growing field in the era of space- and ground-based telescope exoplanetary search efforts."
Water production on exoplanets revealed by pressure experiments
by Clarence OxfordLos Angeles CA (SPX) Nov 20, 2025
Researchers led by Lawrence Livermore National Laboratory postdoctoral scientist Harrison Horn have demonstrated a pathway for producing water on sub-Neptune exoplanets. The team recreated the boundary conditions between hydrogen atmospheres and magma cores using a laser-heated diamond-anvil cell.
Horn stated, "Our experiments are the first to look at interactions between hydrogen and silicates at the pressure-temperature conditions expected at their interface in sub-Neptune exoplanets. We show that water does not need to come from further out in the solar system. It can be produced within a planet itself."
The study focused on sub-Neptune exoplanets, which have radii between two and four times that of Earth and represent some of the most common planet types observed by NASA's Kepler mission. Many sub-Neptunes orbit closely to their host stars, which has led scientists to consider them rocky and dry due to high temperatures. Previously, scientists assumed water present on these planets arrived through cometary or asteroidal impacts, or via planetary migration from cooler regions.
The new experiments contradict those theories, revealing that at high pressure and temperature conditions, molten silicates can react with atmospheric hydrogen. This reaction produces oxygen, which interacts with hydrogen to yield substantial water. The quantity of produced water depends on each planet's composition and interface conditions.
The findings indicate that dry sub-Neptunes may become wet through this internal mechanism, rather than external delivery or migration, challenging and expanding current models of planetary formation. Horn commented, "These results help further our understanding of how planets form, a rapidly growing field in the era of space- and ground-based telescope exoplanetary search efforts."
Research Report:Building wet planets through high-pressure magma-hydrogen reactions