Roaming zones of precipitation on ancient Mars as recorded in valley networks

Authors

  • Monica R. T. Hoke,

    1. Department of Astrophysical and Planetary Science, University of Colorado at Boulder, Boulder, Colorado, USA
    2. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
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  • Brian M. Hynek

    1. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
    2. Department of Geological Sciences, University of Colorado at Boulder, Boulder, Colorado, USA
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Abstract

[1] The 10 largest valley networks in the Terra Sabaea, Arabia Terra, and Meridiani Planum regions of Mars were mapped, crater age dated, and analyzed by geomorphology, stream order, and drainage density to understand changes in fluvial erosion during early Martian history. All of these networks demonstrate characteristics consistent with formation by precipitation. Many appear to be in different stages of preservation, with both highly eroded and pristine valleys sometimes appearing in the same network. In some cases, the valley network morphologies and crater age dating indicate multiple periods of formation. The results from this research place precipitation-driven formation of the Martian valley networks in Terra Sabaea, Arabia Terra, and Meridiani Planum in the late Noachian and early Hesperian epochs (∼3.6–3.8 billion years ago). Our age estimates do not extend into earlier or later Martian history, and the spread in these ages indicates they did not all form or cease formation at the same time. The difference in age between the oldest and youngest valley networks in Terra Sabaea, Arabia Terra, and Meridiani Planum analyzed in this work is ∼210 ± 50 Ma. Within this range are valley networks that have distinctly separate ages and those that appear to be coeval. This research suggests the late Noachian and early Hesperian were characterized by roaming zones of precipitation that occurred during either continuously warmer and thicker atmospheric conditions or intermittently clement conditions, with precipitation occasionally returning to previously rainy regions and overall continuing near Meridiani Planum longer than in Terra Sabaea.

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