The Coast Guard Cutter Polar Star moves through pack ice Dec. 28, 2019, about 200 miles north of McMurdo Station, Antarctica. The 43-year-old Polar Star is the nation's only heavy icebreaker, and the crew is heading to McMurdo Station to escort refuel and resupply ships through the ice, which can be as thick as 10 feet. This year marks the 64th iteration of the operation known as Operation Deep Freeze. U.S. Coast Guard photograph by Senior Chief Petty Officer NyxoLyno Cangemi