Fig. 1 Global distribution of data. Global distribution of data. Most of our data are for post–3.4 Ga rivers. Width (A) and wavelength (B) measurements. Some measurements are too close-spaced to be distinguished at this scale. We use k-means clustering of spatial locations of the data (see the Supplementary Materials) to identify 10 distinct groups, labeled 1 through 10. Each group is represented by circles of varying colors. Location of the Mars Science Laboratory (MSL) rover shown for reference. For comparison, the gray dots show the location of (mostly pre–3.4 Ga) valleys mapped by (11). The background is Mars Orbiter Laser Altimeter topography, clipped at elevations of −6 km (blue) and 8 km (red). Edwin S. Kite et al. Sci Adv 2019;5:eaav7710 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).