Atmospheric erosion and replenishment induced by impacts upon the Earth and Mars during a heavy bombardment
Atmospheric erosion and replenishment induced by impacts upon the Earth and Mars during a heavy bombardment
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DOI：
10.1016/j.icarus.2012.07.032
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发表时间：
2012-11-01
期刊：
影响因子：
3.2
通讯作者：
Motschmann, U.
中科院分区：
文献类型：
--
作者：
de Niem, D.;Kuehrt, E.;Motschmann, U.
用随机模型研究了地球和火星大气层遭受猛烈撞击的后果。主要结果是积累的优势。地球和火星的大气压力在加强轰击的过程中都在强烈增加。大气侵蚀的影响被认为是轻微的，关于逃逸在陨石进入，在不断扩大的蒸汽羽流，和喷射由于自由表面运动。初始大气表面压力如果与现代值相比较，结果是作为最终压力的不太重要的附加常数。撞击器保留和大气侵蚀参数化的比例律，兼容最近的数值模拟。在不同的模型和数值计算结果之间，分析了对撞击器尺寸、大气和行星参数的依赖性。随机模型的进料与净补给来源于撞击物材料和预先存在的大气气体的损失。主要输入参数是撞击物的总累积质量和彗星和小行星中大气分子的相对质量。撞击物集合的输入尺寸分布对应于目前观测到的主带小行星和KBO。速度分布取自Nice模型的动力学模拟。根据大型彗星撞击物的组成，地球可能会获得更大的大气层，表面压力只有几巴，主要是CO和CO2。对于火星来说，1-4巴的CO和CO2的积累需要一个10（24）g的小行星“晚期单板”，含有2%的亲大气物质。(C)2012 Elsevier Inc. All rights reserved.
Consequences of a heavy bombardment for the atmospheres of Earth and Mars are investigated with a stochastic model. The main result is the dominance of the accumulation. The atmospheric pressure is strongly increasing both for Earth and Mars in the course of an enhanced bombardment. The effect of atmospheric erosion is found to be minor, regarding escape during meteorite entry, in the expanding vapor plume, and ejection due to free-surface motion. The initial atmospheric surface pressure if comparable to the modern value turns out as a less important additive constant of the final pressure. Impactor retention and atmospheric erosion are parametrized in terms of scaling laws, compatible with recent numerical simulations. The dependence on impactor size, atmospheric and planetary parameters is analyzed among alternative models and numerical results. The stochastic model is fed with the net replenishment originating from impactor material and the loss of preexisting atmospheric gas. Major input parameters are the total cumulative impactor mass and the relative mass of atmophile molecules in comets and asteroids. Input size distributions of the impactor ensemble correspond to presently observed main belt asteroids and KBOs. Velocity distributions are taken from dynamical simulations for the Nice model. Depending on the composition of large cometary impactors, the Earth could acquire a more massive atmosphere, a few bars in terms of surface pressure, mostly as CO and CO2. For Mars accumulation of 1-4 bars of CO and CO2 requires an asteroidal 'late veneer' of the order of 10(24) g containing 2% atmophiles. (C) 2012 Elsevier Inc. All rights reserved.