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Last-modified: 2022-05-26 () 16:01:50 (27m)
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astro-phߥʡ轵12:00鳫ŤƤޤϢChanoul Seo ůϯ һΡ

Schedule & History

2021ǯ 2020ǯ 2019ǯ 2018ǯ 2017ǯ 2016ǯ 2015ǯ 2014ǯ

1 4/14 15:00-All membersSelf-introductionƣ
2 4/28 15:00-Masahiro Ikoma (NAOJ)Five key questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
3 5/10 15:00-Sho Shibata (University of Zurich)Exploring formation pathways of gas giant planets using planetesimal accretionTuesdayŲ
4 5/19 15:00-Kenji Furuya (NAOJ)Different degree of nitrogen and carbon depletion in protoplanetary disksŲ
5 6/2 15:00-Tatsuya Yoshida (Tohoku University)Hydrodynamic escape of reduced proto-atmospheres on Earth and Marsƣ
X 7/5 15:00-Hidenori Genda (ELSI)TBDTuesday
5/10 Sho Shibata (University of Zurich), Exploring formation pathways of gas giant planets using planetesimal accretion
The composition of gas giant planets is a useful tracer of planet formation. Recent observations of gas giant planets suggest that planetesimal accretion had occurred in their formation stage. In our previous studies, we found that large amount of planetesimals can be captured by a protoplanet when the protoplanet migrates into the region which we call as sweet spot for planetesimal accretion. In this talk, we will apply the theory of sweet spot to the formation of close-in gas giant planets and Jupiter and Saturn. We will discuss the formation history of those planets using the planetesimal accretion process.
6/2 Tatsuya Yoshida (Tohoku University), Hydrodynamic escape of reduced proto-atmospheres on Earth and Mars
Earth and Mars likely have obtained reduced proto-atmospheres enriched in H2 and CH4 through impact degassing from planetary building blocks and gravitational capture of the surrounding nebular gas during accretion. Such reduced proto-atmospheres are expected to have been lost by hydrodynamic escape, but their fluxes and timescale for hydrogen depletion remain highly uncertain due to the ambiguity in the radiative loss of energy and chemical processes in escaping outflows. Here we develop a one-dimensional hydrodynamic escape model which includes radiative and chemical processes for a multi-component atmosphere and applied to the reduced proto-atmospheres on Mars and Earth to estimate the atmospheric escape rates and propose possibly atmospheric evolutionary tracks that are consistent with the isotopic compositions and amounts of the surface volatiles. We find that the hydrodynamic escape is suppressed due to the energy loss by the radiative cooling both on Earth and Mars. The escape rate decreases more than one order of magnitude than that of the pure H2 atmosphere when the mixing ratio of CH4 is high. As a result, the duration of the reduced hydrogen-rich environment becomes longer, implying that the early atmospheres played important roles in producing organic matters linked to the emergence of living organisms. The suppression of the hydrodynamic escape by the radiative cooling is more significant on Earth due to the larger gravity and higher temperature in the escaping outflow. The difference in the hydrodynamic escape may have contributed to the difference in the amounts and isotopic compositions of the surface volatiles between Earth and Mars.