ELSI Seminar

Keiko Hamano
July 30, 2018

Diversity of planetary atmospheres originating during planet formation
Earth, Venus, and Mars are classified as the same category "terrestrial planets", but they have a quite different atmosphere and surface environment. A richer variety in planetary atmospheres is expected to be discovered on terrestrial exoplanets. One of the ELSI's main research goal is to clarify what makes a huge variety in planetary atmospheres and to address why and when Earth followed an evolutionary path to surface environment hospitable to life. I have been tackling this scientific goal, using theoretical modeling of the formation and evolution of planetary atmospheres during planet formation. Delivery, partitioning, and loss of volatile elements would occur simultaneously on terrestrial planets during their formation stage. All the processes would alter the mass and composition of early atmospheres, sometimes in a mutually linked way.

In this talk, I will present my research achievements on an interplay between planetary atmosphere and a magma ocean, impact delivery and loss of planetary atmospheres by impacts, and detectability of solidifying planets in extrasolar planetary systems. I will talk about the following research topics that I focus on in the coming years. 1) Understanding volatile budgets on proto-planets growing in a disk. I will do modeling of a proto-planet's atmosphere connecting to a protoplanetary disk and discuss potential fractionation of volatile elements by disk-gas circulation and dissolution to magmas. 2) Effects of high-pressure chemistry for evolution of an atmosphere and a magma ocean. Utilizing recent studies on ferric/ferrous iron speciation in silicate melt, I will address how volatile budgets can be affected by redox state and pressure at the base of a magma ocean, which would be relevant to the planetary mass. 3) Theoretical predictions on atmospheric evolution for exoplanets observations. I will explore how thermal and transmission spectra could change by outgassing of H2O from a magma ocean, based on our model.