Washington: A team of researchers have demonstrated that frozen water in the form of snow or frost can melt to form debris flows on sunward-facing slopes of sand dunes in the Alaskan arctic at air temperatures significantly below the melting point of water.
The debris flows consist of sand mixed with liquid water, which cascade down steep slopes.
Southwest Research Institute (SwRI) scientists made their observations at the Great Kobuk Sand Dunes, in Kobuk Valley National Park, Alaska.
This site serves as an Earth-based cold-climate "analog" to dunes on Mars. Debris flows formed on days when air temperatures measured continuously by the team remained below the melting point of water.
Very few minutes of above-freezing ground surface temperatures are needed to locally melt frozen water and mobilize sand down steep slopes.
The scientists hypothesize that fresh patches of wind-deposited dark sand on bright white snow caused local hot spots to form where solar radiation was absorbed by the sand and conducted into the underlying snow.
This enabled meltwater to briefly form and sand to be mobilized despite subfreezing local air temperatures. A similar mechanism may be responsible for triggering debris flows on frozen Martian sand dunes.
The Alaskan debris flows formed at ground temperatures that may correspond to those occurring locally and seasonally on the surface of Mars, said hydrogeologist Dr. Cynthia Dinwiddie, a principal engineer in SwRI`s Geosciences and Engineering Division.
The Alaskan debris flows are morphologically similar to small, defrosting-related "dark dune spot" seepage flows that seasonally form in late winter on frost-covered Martian sand dunes.