Wet Mars implications of revised scaling calculations for Evros Vallis

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Abstract
In this paper we report the results of our investigation of Evros Vallis, a martian late Noachian dendritic valley network centered at ∼12°E, 12°S. The study area is located SSW of Schiaparelli and SE relative to Meridiani Planum. After establishment of the valley system, the region underwent extensive erosion and tectonic activity, which partly obliterated and modified Evros Vallis's original features. We used Mars Global Surveyor Mars Orbiter Laser Altimeter, Mars Odyssey Thermal Emission Imaging System, and Mars Express High Resolution Stereo Camera imagery and altimetry data to carry out observations and morphometric analysis of the system, and applied network scaling parameters to our measurements of valley widths, slopes, lengths and drainage areas. We obtained the following results: (a) Hack's law exponent n=1.02; (b) width–area scaling exponent b=0.21; and (c) slope–area scaling exponent θ=0.23. These values are different from those previously derived from analysis of the eastern extent of the valley system. We found that network scaling is not applicable to the investigation of Evros Vallis, a conclusion that may be relevant also to other martian network valleys. The concave-up 790 km-long profile of the main valley suggests that a classic equilibrium status was reached. Our findings are in agreement with models of a warmer and wetter martian climate at the end of the Noachian.

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