Abstract Valley networks are ancient drainage systems incised on the southern hemisphere of Mars, and stand as evidence that liquid water once sculpted its surface. The duration of valley network activity and the sources of water are key questions in deciphering the timing of water stability on early Mars, but remain poorly constrained. In this study we address two questions: Did Martian valley networks evolve for sufficiently long to establish their own erosional basins, or do their profiles primarily reflect landscape pre-incision topography? And were these valleys precipitation-fed or spring-fed? Our analysis uses the theoretical framework built to describe the shape of steady-state river profiles on Earth to compare and analyze the concavity of 62 valley network longitudinal profiles on Mars. Using non-linear fits to valley profiles we evaluate the degree to which valley networks are consistent with fluvial steady-state. The fit enables the identification of valley network concavity index and area-discharge exponent, which we then interpret in terms of the theoretical framework to discuss valley network maturity and water source. Our results show that the majority of valley networks do not have concave or even smooth profiles, and did not substantially modify their surrounding landscape. We observe disparity in concavity indexes of valley networks belonging in the same integrated basins, indicating different stages of landscape evolution and lack of synchronous valley development. However, our results identify six valley networks consistent with fluvial steady-state and areally uniform precipitation.

中文翻译：

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火星山谷网络是否显着改变了景观？

摘要 山谷网络是在火星南半球切开的古老排水系统，是液态水曾经雕刻其表面的证据。山谷网络活动的持续时间和水源是破译早期火星上水稳定时间的关键问题，但仍然缺乏约束。在这项研究中，我们解决了两个问题：火星山谷网络是否进化了足够长的时间来建立自己的侵蚀盆地，或者它们的剖面是否主要反映了切割前的地形？这些山谷是降水补给还是春季补给？我们的分析使用建立的描述地球稳态河流剖面形状的理论框架来比较和分析火星上62个谷网纵向剖面的凹度。使用非线性拟合山谷剖面，我们评估山谷网络与河流稳态一致的程度。该拟合能够识别河谷网络凹度指数和面积流量指数，然后我们根据理论框架对其进行解释，以讨论河谷网络成熟度和水源。我们的结果表明，大多数山谷网络没有凹面甚至平滑的轮廓，并且没有实质性地改变其周围的景观。我们观察到属于同一综合盆地的山谷网络的凹度指数存在差异，表明景观演化的不同阶段和缺乏同步的山谷发展。然而，我们的结果确定了与河流稳态和区域均匀降水一致的六个山谷网络。