With endless days inevitably come endless nights. The period during winter when supply vessels or aircraft are unable to access Antarctic bases is called “winterover.” At Palmer station, winterover is from April until August, and it is never dark for a full 24 hours because it lies north of the Antarctic circle. However at MacMurdo station further south and on the other side of the continent, winterover lasts from February to October with a significant period of total darkness. Rex, the research assistant for the meteorological instruments here, spent 12 months at MacMurdo. He described it to me as a magical ordeal: magical because of the beautiful phenomena he saw during the winter, but an ordeal for the mind and body. On a night (well day, but it was dark so night gives you a better mental picture) when the temperature was about -40F, a special thing happened. The air around him sparkled with miniscule ice crystals. They weren’t visible straight on, but through the corner of his eye he could see them catch the light, and then disappear. As Rex was recounting this phenomenon to me, his voice fell away and there was a silence. “The only word to describe it was….magical.” The aurora australis or southern lights, appear frequently as well. When solar particles collide with nitrogen and oxygen atoms in the atmosphere they “excite” them into a higher energy state. When the atoms eventually return to the unexcited, lower energy state, they lose the energy by emitting light. This light is what we call the aurora, with red and green colors emitted by oxygen, and red and blue colors emitted by nitrogen. Auroras are most visible at high latitudes because the earth’s magnetic field lines direct the solar wind particles toward the poles and increase the number of collisions there.
The greatest wonder Rex saw that winter however was something I had never heard of and occurs only in Antarctica. Nacreous clouds are formed in the spring when clouds of ice crystals high in the atmosphere are illuminated by the sun, which has not yet risen above the horizon. The ice crystals act as tiny prisms, scattering the light into all the colors of the rainbow. Rex said that he almost got frostbite because he was standing on a roof in rapt wonder for hours.
However, darkness and cold take a toll on the body. Apparently after living in such cold for an extended period of time, the brain stops making one of its neurotransmitters and actually slows down. It becomes difficult to focus, which gives Antarctic winter conversations a distinctive quality. People drift in and out and at any given time, there will be at least one person staring off into space. Looking back at the emails he wrote during that time, Rex can only conclude that he was in a different mental state. I am imagining a zombie-town Antarctic base with people wandering off across the dark ice, "frostee boy" soft-serve in hand. This is the reason that the United States Antarctic Program requires a psychological exam before wintering over, and employees are not allowed to stay on “the ice” for more than 14 months continuously.
One bright spot in all the darkness is the solstice, “Midwinter’s day,” when the bases from all 22 countries represented call each other, exchanging news and sharing group photos. However, trippy nacreous clouds notwithstanding I do not plan to spent a long night in Antarctica any time soon!