The Coast Guard Cutter Polar Star, the United States' only operational heavy icebreaker, transits an ice field in the Southern Ocean en route to the Antarctic Chieftan, a disabled fishing vessel near Antarctica, Feb. 13, 2015. Polar Star's crew is participating in a multinational rescue operation for the Antarctic Chieftan's crew. Polar Star's crew has been underway in Antarctica in support of Operation Deep Freeze 2015, part of the U.S. Antarctic Program, managed by the National Science Foundation. (U.S. Coast Guard photo by Petty Officer 1st Class George Degener)