Halley Research Station is a research facility in Antarctica on the Brunt Ice Shelf operated by the British Antarctic Survey (BAS). The base was established in 1956 to study the Earth's atmosphere. Measurements from Halley led to the discovery of the ozone hole in 1985. The current base is the sixth in a line of structures and includes design elements intended to overcome the challenge of building on a floating ice shelf without being buried and crushed by snow. As of 2020, the base has been left unstaffed through winter since 2017, due to concerns over the propagation of an ice crack and how this might cut off the evacuation route in an emergency.