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arXiv 1802.10422astro-ph.EP
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3.5 Gyr火星气候演变模型中火星大气损失对雪融化潜力的影响

Effect of Mars Atmospheric Loss on Snow Melt Potential in a 3.5-Gyr Mars Climate Evolution Model

Megan Mansfield, Edwin S. Kite, Michael A. Mischna

备注：
12 pages, 8 figures, accepted to JGR Planets
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摘要：

后诺亚纪火星古河道表明，大约3.5 Gya后火星表面存在液态水（Irwin等人，2015; Palucis等人，2016年）。为了探索CO $_{2}$分压和结晶度的变化对地表水存在可能性的影响，我们建立了一个零维表面能平衡模型。我们结合这个模型与物理上一致的轨道历史跟踪条件在过去的3.5 Gyr的火星历史。我们发现，对于对应于$dP/dt \propto t^{-3.73}$或更快的指数损失率的大气压力，允许熔化，但是如果我们假设由火星大气和挥发性演化（MAVEN）任务进行的初始测量所计算的速率在$0.5 σ$范围内，则我们假设由MAVEN测量的所有逸出的氧气都来自大气CO $_{2}$（Lillis等人，2017; Tu等人，2015年）。假设在每个火星年最温暖的部分期间有最佳的融化条件，以这种损失率融化与西方河流网络形成的选定关键地质约束相匹配（Irwin等人，2015; Stopar等人，2006; Kite等人，2017年a，b）。大气压力对表面能的影响比火星平均湿度的变化更大。这些结果表明，MAVEN对大气损失的初步测量结果与大气损失是将火星从允许融化的气候转变为不允许融化的气候的主要过程相一致（Jakosky等人，2017年），但如果$<2$ Gya古通道得到证实，或者如果MAVEN测量的大部分逃逸氧气来自H $_{2}$ O，则需要非CO $_{2}$升温。

英文摘要：

Post-Noachian Martian paleochannels indicate the existence of liquid water on the surface of Mars after about 3.5 Gya (Irwin et al., 2015; Palucis et al., 2016). In order to explore the effects of variations in CO$_{2}$ partial pressure and obliquity on the possibility of surface water, we created a zero-dimensional surface energy balance model. We combine this model with physically consistent orbital histories to track conditions over the last 3.5 Gyr of Martian history. We find that melting is allowed for atmospheric pressures corresponding to exponential loss rates of $dP/dt \propto t^{-3.73}$ or faster, but this rate is within $0.5 σ$ of the rate calculated from initial measurements made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, if we assume all the escaping oxygen measured by MAVEN comes from atmospheric CO$_{2}$ (Lillis et al., 2017; Tu et al., 2015). Melting at this loss rate matches selected key geologic constraints on the formation of Hesperian river networks, assuming optimal melt conditions during the warmest part of each Mars year (Irwin et al., 2015; Stopar et al., 2006; Kite et al., 2017a,b). The atmospheric pressure has a larger effect on the surface energy than changes in Mars's mean obliquity. These results show that initial measurements of atmosphere loss by MAVEN are consistent with atmospheric loss being the dominant process that switched Mars from a melt-permitting to a melt-absent climate (Jakosky et al., 2017), but non-CO$_{2}$ warming will be required if $<2$ Gya paleochannels are confirmed, or if most of the escaping oxygen measured by MAVEN comes from H$_{2}$O.

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