The dune field in Alaska that Dr. Dinwiddie and Southwest Research Institute colleague Don Hooper study sits on the boundary between boreal forests to the south and Arctic tundra to the north. Known as the Great Kobuk Sand Dune field, the sands were first formed during ice ages that occurred between 300,000 and 130,000 years ago.
Glaciers sculpted the Brooks Range to the north and left the sandy debris in the Kobuk River Valley. There, wind, meltwater, and more-recent ice ages would continue to rework the material to leave some 24 square miles of mobile dunes on the surface and another 250 square miles of sandy soils that don't get around much anymore.
NASA's small squadron of Mars orbiters revealed dunes in the planet's north polar regions, and they took enough images over a sufficient period of time to reveal that the dunes moved. But the pace was glacial, especially when compared with the movement of dunes in locations such as the Sahara Desert or the US Southwest.
Dinwiddie and colleagues looked to the Great Kobuk Sand Dune field for possible answers as to why Mars' polar dunes were such geophysical sloths – first exploring the Alaskan analogues via satellite remote-sensing, then in 2010, with a field trip in March, while temperatures still averaged about 5.5 degrees Fahrenheit and the dunes' top, mobile layer was still frozen solid.
During the field trip, the researchers noticed water coming up through the bore holes they had drilled but that had not yet reached deep into the dunes to tap the region's aquifer. Ground-penetrating radar and measurements of the ground's electrical resistance revealed evidence for a layer of liquid water just below the frozen mobile layer.