Recurring Slope Lineae Formation on Changing Slopes.

Abstract:

Recurring Slope Lineae (RSLs) and other associated dark streaks appear in the southern mid-latitudes on the martian surface during the spring to summer months. Gullies commonly emerge from bedrock and form from volatile thawing and associated sediment transportation and deposition. All of these forms involve the movement of fluids and associated sediments on variable slopes. The objective of this research is to generate subsurface flows, resembling those of liquid brines, under regolith at slope angle ranges that represent those on which RSLs and gullies occur on Mars. RSLs are generally found on steeper slopes. The higher slopes ranged from 25°-30° and lower slopes 12°-18°.

As the slope increased, the total channel and apron length increased. There was a significant increase from the lower to higher slopes. The maximum width of the channel decreased as the slopes increased. Lower slopes produced a more dendritic channel pattern; an alcove, the main channel and an apron with two diverging branches. However, the higher slopes produced channels with more variability in the fluvial features. Lobes diverged from the main channel at varying distances from the water source. Channel walls were more distinct, along with formation of natural levees. Increases in fluid viscosity, produces a more singular channel.

From these observations we conclude that lower slopes are more conducive to RSL formations from their basic geomorphology. Higher slopes produce more distinct morphologies associated with fluvial erosion that are more similar to gullies. The effect of viscosity also appears to alter the morphologies of the flow features. Understanding the origin of these fluvial features can lead to greater understanding of fluids on Mars.