Experiments reveal extreme water generation during planet formation

The most abundant type of planet discovered in the Galaxy has no analogue in our Solar System and is believed to consist of a rocky interior with an overlying thick H₂-dominated envelope. Models have predicted that the reaction between the atmospheric hydrogen and the underlying magma ocean can lead to the production of notable amounts of water. However, the models suffer from the current lack of experimental data on the reaction between hydrogen and silicate melt at high pressures and temperatures. Here we present new experimental results designed to investigate this interaction. Laser heating diamond anvil cell experiments were conducted between 16 GPa and 60 GPa at temperatures above 4,000 K. We find that copious amounts of hydrogen dissolve into the silicate melt with a large dependence on temperature rather than pressure. We also find that the reduction of iron oxide leads to the production of marked amounts of water along with the formation of iron-enriched blebs. Altogether, the results indicate that the typical processes attending planet formation will result in substantial water production with repercussions for the chemistry and structure of the planetary interior as well as the atmosphere.