In the Northern Hemisphere, the spring equinox promises warmer days and green plants. But for researchers at NOAA's South Pole Atmospheric Baseline Observatory, Sunday March 20 marks the start of the austral autumn, the last time they see the sun for six months.

The National Science Foundation’s Atmospheric Research Observatory illuminated by the sun approaching South Pole sunset in 2014. (Image credit: NOAA-LT Joseph Phillips)