Comparative study between rivers in Tarim Basin in northwest China and Evros Vallis on Mars

Abstract

The morphometric characteristics of the Kaidu River and Keriya River in the extremely arid Tarim Basin, and the Evros Vallis on Mars were compared to study the formation of the dendritic Evros Vallis, which has great significance for exploring ancient climate of Mars. The following results were obtained: (a) the average sinuosities of Kaidu River, Keriya River, and Evros Vallis are 1.17, 1.35, and 1.32 respectively. (b) the average bifurcation ratios are 3.84, 4.73 and 3.43 respectively. (c) the average stream length ratios are 2.21, 3.86 and 2.08 respectively. (d) the stream frequencies are 0.017, 0.028 and 0.002 respectively. (e) the drainage densities are 0.195 km−1 and 0.217 km−1, and 0.048 km−1 respectively. (f) the stream gradients are 3.74‰, 7.03‰ and 1.63‰ respectively. (g) the stream fractal dimensions are 1.70, 1.0 and 1.68 respectively. Paleodischarge estimations at different stream segments of Evros Vallis support the hypothesis that the V-bend area that joints the eastern and western segments possibly has a tectonic origin. Geomorphological evidence (e.g., tributaries) from high-resolution images and stream morphometric parameters from a comparative analysis (e.g., concave upward longitudinal profile and stream fractal dimension) support previous hypothesis that Evros Vallis is a mature drainage system formed by precipitation-driven surface runoff. This drainage process occurred either in a continuously warm-wet climate that lasted long enough on early Mars or in regional hydrologic cycles consisting of precipitation and occasionally returned runoff in intermittently clement climates.