Estimation of the molecular composition and hydrogen escape rate of impact-induced steam atmospheres

我们在这个项目中取得了三个主要成果。首先是关于撞击导致的行星大气的分子组成。计算结果显示，金星和超级地球周围的M型恒星将拥有富含CO-H2的大气层，火星和地球将拥有富含CH4的大气层。其次是类地行星的氢气逸出率。计算结果表明，氢的逸出速率在很大程度上取决于蒸汽大气在吸积后是否凝结成海洋，并决定是否会形成类似地球的潮湿行星或类似金星的干燥行星，包括其内部。三是撞击实验和撞击脱气挥发分的质谱分析。实验结果表明，K/PG碰撞会产生足以使海洋表层酸化的酸雨，从而可能导致K/PG的大量灭绝。

We obtained three main results in this project. First is on the molecular compositions of impact-induced planetary atmospheres. Calculation results revealed that Venus and super Earth's around M-type stars would have CO-H2-rich atmosphere and Mars and Earth would have CH4-rich atmosphere.Second is on hydrogen escape rate from terrestrial planets. Calculation results indicate that hydrogen escape rate depends greatly on whether or not a steam atmosphere would condense to an ocean after accretion and determines whether an Earth-like wet planet or Venus-like dry planet, including its interior, would form. Third is impact experiments and mass spectroscopic measurements of impact-degassed volatiles. Experimental results show that the K/Pg impact would generate acid rain sufficient to acidify the ocean surface layer, which may lead to the K/Pg mass extinction.