The fingerprint of Martian channelized flows: A reconstruction of Mars' early climate through new methods from physical geomorphology

Abstract:

We present a new methodology to characterize Martian valley networks and to understand their origin in terms of key underlying erosion processes. We use high resolution Mars image data to classify diagnostic geometric properties of valley networks in terms of five independent parameters. The minimum valley width, valley aspect ratio and branching angle are related to the dynamics of fluvial or glacial erosion and interactions between these flows with Mars’ topography. The stream order and fractal dimension are statistical measures of valley network complexity. Applied to 45 channel networks on Earth, an empirical principal component analysis algorithm distinguishes features related to glaciers, sub-glacial channels and varied fluvial systems in a way that is consistent with predictions from theoretical scaling analyses. Applying our method to Mars, we expand our analysis to include topography produced by lava flows and we identify features reliably related to erosion by wet- and dry-bottomed glaciers and by surface runoff, as well as features related to the emplacement of lava flows. Interestingly, we also identify a class of valley network with a mechanical origin that is not clearly associated with Earth-like fluvial or glacial processes. Significantly, the spatial distribution of valley networks related to glacial and fluvial processes varies with latitude and longitude, as well as with geological age with implications for the evolution of Mars’ average climate over time, the likelihood of periodic ice ages, and for the nature and time-variability of the planet’s hydrological cycle. We also explore ways to apply the same methodology to build understanding of the surface processes underlying the formation of the enigmatic channel networks on Titan