Early Wednesday morning, in the icy cold and pitch black of the Antarctic winter, a small Canadian plane touched down near the South Pole and evacuated two sick workers in a daring rescue mission.
It was only the third ever staged at the South Pole during the southern hemisphere's winter.
A Twin Otter turboprop plane retrieved the sick workers from the Amundsen-Scott research station, about 820 feet from the geographic South Pole, a spokesman for the US National Science Foundation, Peter West said.
The plane's crew and a medical team had made the 10-hour journey to the South on Tuesday night to reach two unidentified patients, whose medical condition could not be treated on site.
The planes picked up the patients and touched back down at Rothera, a British base in Antarctica about 1,500 miles away from the South Pole station, Wednesday Eastern time. The plane then flew to Puerta Arenas, Chile, landing Wednesday night, CNN reported.
The NSF operates the Amundsen-Scott station and organized the rescue mission last week given the condition of the first patient, which was not disclosed for privacy reasons.
"It was really an emergency," West said.
It later became apparent that the second worker also needed to be evacuated.
Two Twin Otter planes flew from Calgary, Canada on June 14 to start their long journey to the South Pole.
“They had to fly down from Calgary to Colorado, Colorado to Ecuador, Ecuador to Chile, Chile to Rothera, where they prepared for the flight,” West said.
One plane waited at Rothera as an emergency back-up while the other flew to the South Pole.
The planes, operated by the Canadian company Kenn Borek Air, are specially designed to operate in extremely cold temperatures and run missions to the Arctic during North America’s summer.
The sick workers are employed by the US company Lockheed Martin and were to be taken to a hospital in South America.
The Amundsen-Scott base was home to 48 people who work on-site throughout the austral winter, which spans February through October.
Near the world's southernmost point, workers spend this period withstanding nearly complete darkness and dramatically low temperatures. On Tuesday, when the rescue plane landed, the thermometer dropped to -76 degrees Fahrenheit.
It was only the third time that such a rescue operation has been launched in the middle of winter.
In 2001, the only doctor at the Amundsen-Scott station was suffering from a life-threatening pancreatic condition and required urgent evacuation. A second medical evacuation was carried out in 2003.
In 1999, the US station's doctor Jerri Nielsen treated herself for breast cancer for months before the weather improved and she could be flown off the base in the Antarctic spring.
West said such evacuation missions are dangerous because of the extreme cold during the Antarctic winter, but also the near-total darkness.
"There are lights at the station, and they did light the runway, but nonetheless over the continent, which is the size of the US and Mexico combined, there are very few navigational aids,” West said.
Research projects at the Amundsen-Scott station include monitoring long-term levels of carbon dioxide in the atmosphere.
The station also operates two telescopes that observe "cosmic microwave background" radiation — the faint light signature left by the Big Bang — to study the origins of the universe, dark energy and dark matter.
The World's Carolyn Beeler contributed reporting to this story.