| Abstract |
Recent observation revealed several exoplanets with masses ranging from Earth to Neptune and radii more extensive than that of the Earth. These planets possess a unique atmosphere with mass fractions ranging from 1 % to 30 %, reflecting diversity in the atmospheric mass fractions. Such diversities are supposed to be caused by the differences in the formation processes of exoplanets. Especially in the later stage of their formation, planets experience giant impact events causing the atmospheric escape. We perform smoothed particle hydrodynamic simulations to reveal the impact-induced atmospheric escape for young super-Earths with 10 % to 30 % of the atmospheric mass fraction. We find that the kinetic energy of the escaped atmospheric mass is almost proportional to the sum of the kinetic impact energy and self-gravitational energy released from the merged core. We evaluate the relationship between the kinetic energy of the escaped mass and the escaped atmospheric mass fraction. The present study provides strong constraints on the formation scenarios of observed rocky planets. Since a giant impact event removes the primordial atmosphere efficiently, observed rocky planets with atmospheres must have formed before the protoplanetary disk dispersal. |
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