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Martian Recurring Slope Lineae (RSL)

Recurring Slope Lineae (RSL) are dark, narrow streaks that appear on steep, warm Martian slopes during late spring and summer, fade in winter, and reappear the following year. Three scientists discuss the mechanism responsible for these features:

*Scientist 1*
RSL are caused by the seasonal flow of liquid brine (salty water). The Martian regolith contains hygroscopic salts (such as perchlorates) that absorb water vapor from the atmosphere in a process called deliquescence. During the warmer seasons, these salts absorb enough moisture to dissolve into liquid brines, lowering the freezing point of water and allowing liquid to flow downslope, darkening the soil.

*Scientist 2*
RSL are dry granular flows, or mini-avalanches of sand and dust, requiring no liquid water. The streaks appear on slopes that are at or near the angle of repose (the steepest angle at which granular material remains stable). Seasonal heating by sunlight increases the temperature of the dark dust particles, causing expansion and removing thin layers of adsorbed atmospheric gas between grains. This destabilizes the dust, causing it to flow downslope and expose darker subsurface material.

*Scientist 3*
RSL are caused by the discharge of shallow subsurface aquifers. Underneath the Martian surface, thin lenses of water ice exist. During the peak of summer warmth, geothermal heat combined with seasonal solar heating melts these ice lenses. The resulting fresh water breaches the surface, flowing down the slopes and darkening the regolith before rapidly evaporating into the thin Martian atmosphere.

Based on the passage, match each scientist to the primary source or mechanism they hypothesize is responsible for the formation of Recurring Slope Lineae (RSL).