标题： 行星大气对冰质彗星撞击的响应 II：类地外行星模拟 显示英文标题

标题： The Response of Planetary Atmospheres to the Impact of Icy Comets II: exo-Earth Analogues

摘要： 地行星的轨道状态在其大气动力学、气候以及潜在可居住性方面起着重要作用。轨道还可能在塑造行星大气对冰质彗星撞击带来的物质输入的响应中发挥作用。为了研究这种响应，我们使用一个与3D地球系统模型WACCM6/CESM2耦合的彗星撞击和破裂模型，模拟了一个冰质彗星体对类地系外行星（即围绕类太阳恒星运行并具有昼夜循环的类地行星）的撞击。为了量化大气动力学在设定彗星撞击响应中的作用，我们将结果与之前一项研究进行比较，该研究调查了对潮汐锁定的类地系外行星的撞击。我们发现，行星的环流模式在塑造大气对冰质彗星撞击的响应中起着关键作用。在类地行星上形成的弱而多细胞的环流结构能够有效水平混合物质，但不能垂直混合，限制了水从深部破裂区域向高层大气的输送。反过来，这限制了低压下水的光解速率，减少了撞击后的成分变化幅度。它还由于低压下云冰形成减弱，从而导致散射减弱，降低了撞击的可观测性。尽管如此，行星整体成分的小幅变化仍能持续到准稳态，这加强了持续轰击可能有助于塑造类地世界的成分/可居住性的观点。 显示英文摘要

摘要： The orbital regime of a terrestrial planet plays a significant role in shaping its atmospheric dynamics, climate, and hence potential habitability. The orbit is also likely to play a role in shaping the response of a planetary atmosphere to the influx of material from an icy cometary impact. To investigate this response, we model the impact of an icy cometary body with an Earth-analogue exoplanet (i.e. an Earth-like planet orbiting a Sun-like star with a diurnal cycle) using a cometary impact and breakup model coupled with the 3D Earth-System-Model WACCM6/CESM2. To quantify the role that the atmospheric dynamics play in setting the response to a cometary impact, we compare our results with a previous study investigating an impact with a tidally-locked terrestrial exoplanet. We find that the circulation regime of the planet plays a key role in shaping the response of the atmosphere to an icy cometary impact. The weak, multi-celled circulation structure that forms on Earth-like planets is efficient at mixing material horizontally but not vertically, limiting the transport of water from the deep break-up site to higher altitudes. In turn, this limits the rate of water photodissociation at low pressures, reducing the magnitude of post-impact changes to composition. It also reduces the potential observability of an impact due to weakened cloud ice formation, and hence scattering, at low pressures. Despite this, small changes to the overall composition of the planet persist to quasi-steady-state, reinforcing the idea that ongoing bombardment may help to shape the composition/habitability of terrestrial worlds.