There's no priority mail in Antarctica. Supplies must be delivered the old fashioned way, by caravan. Instead of horses and wagons, however, the supplies are loaded atop skis and pulled by a tractor across the snow and ice.

This week, France's Pleiades satellite photographed an Antarctic caravan from its vantage 430 miles above Earth's surface. The 1,000-foot-long convoy can be seen as a dark sliver, stretching across the white landscape.

It takes 10 days for the caravan to trek supplies 620 miles from the coastal outpost of Dumont d'Urville to the Concordia research station. The uphill trek sees the heavy-duty tractors ascend nearly two miles in elevation. After three days of unpacking, the caravan heads back toward the coast -- an eight-day, downhill trip.

The Concordia research station is jointly operated by France and Italy but hosts scientists from across Europe. Scientists there conduct research in a variety of fields, from glaciology to biology. It is an ideal location to study climate change, as well as make astronomical observations.

Because of its unique landscape and sunless winters, the European Space Agency uses the venue to study the effects of isolation on the station's crew.