THE LITTLE COLORADO RIVER AT GRAND FALLS, ARIZONA: A VALUABLE TERRESTRIAL ANALOG IN INVESTIGATING THE RATES AND NATURE OF FLUVIAL EROSION ON MARS

The Little Colorado River at Grand Falls, Arizona, is an intermittently active dryland fluvial system that is eroding through soft sedimentary rock with little vegetation covering the falls. This location is an ideal analog environment to fluvially modified landscapes on Mars, as its intermittent behavior is likely representative of the intermittent nature of fluvial processes early in Martian history. In this study, we highlight how investigating the short-term erosion dynamics and rates at Grand Falls can help to shed new light on the nature and rates of fluvial erosion on Mars.

The majority of investigations into the rates and nature of fluvial erosion on both Earth and Mars have focused on long-term erosion rates averaged over hundreds or thousands of years, as the kinematics and nature of fluvial erosion is difficult to characterize in real-time. At Grand Falls, erosion rates are sufficiently high that modern technologies can directly identify and quantify the extent and nature of erosion. The intermittent activity of the Little Colorado River at Grand Falls also allows for direct measurement and sampling. The U.S. Geological Survey has a long history of hydrological monitoring on the Little Colorado River, allowing for erosion dynamics to be directly related to hydrological activity when erosion occurs.

Here we will characterize the unique properties of Grand Falls that make it a valuable terrestrial analog environment. We will also highlight the specific suite of measurements that will be necessary to accurately quantify and characterize the rates and nature of fluvial erosion and relate them to measured hydrology. Lastly, we will identify and discuss key similarities to specific Martian fluvial systems, showing how results from detailed studies at Grand Falls could be directly compared to Martian surface observations in an effort to refine models of fluvial erosion rates and dynamics.