Shanghai Astronomical Observatory Astrophysics Colloquium

Title：On the formation of water oceans in rocky exoplanets with hydrogen atmospheres

Speaker: Darius Modirrousta-Galian (Shanghai Jiao Tong University)

Time：3:00 pm Oct. 23th (Thursday)

Tencent Meeting：46822606747 password: 6360

Location: Lecture Hall, 3rd floor

Abstract：

It has been suggested that some rocky exoplanets could form substantial water inventories through oxidation reactions between their primordial hydrogen-rich atmospheres and underlying magma oceans. Here we investigate this hypothesis using a coupled atmosphere–magma ocean model. We find that large-scale water formation is unlikely for two reasons. First, any water formed from oxidation reactions in the magma ocean would quickly outgas because of the water-poor atmosphere above. Second, the top boundary layer of the magma ocean becomes stable against convection because the oxidation reactions produce metallic iron, which sinks to the core. This iron loss makes the top boundary layer significantly more buoyant than the rest of the magma, thus becoming stable against mixing. Our results suggest that hydrogen dissolution is unlikely to play a major role in the formation of oceans in rocky exoplanets.

CV：

Darius Modirrousta-Galian, an astrophysicist from London, United Kingdom, is currently an Associate Professor at the School of Physics and Astronomy at Shanghai Jiao Tong University, a Tsung-Dao Lee Scholar at the Tsung-Dao Lee Institute, and a Visiting Research Fellow at Yale University in the United States.

He obtained his Bachelor’s degree in Astrophysics and his Master’s degree in Planetary Science from University College London. He then pursued his Ph.D. at the University of Palermo and the Italian National Institute for Astrophysics. During his doctoral studies, he conducted theoretical research on planets and exoplanets as a Visiting Researcher at the California Institute of Technology under the supervision of Professor David Stevenson. After earning his Ph.D., he worked as a Postdoctoral Researcher at Yale University, focusing on the loss of volatiles and redox evolution on the early Earth in collaboration with Professor Jun Korenaga.

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