The only functional U.S. icebreaker reached the northernmost point ever for a U.S. surface ship on a winter mission.

Before noon on Christmas Day, the heavy icebreaker Polar Star reached the latitude of 72 degrees 11 minutes North — the furthest north a U.S. surface vessels has sailed in winter — before turning to head south for a port call in Dutch Harbor, the U.S. Coast Guard said.

By the time the ship reached its turnaround point, about 80 miles away from Utqiaġvik, Alaska, it was sailing in complete darkness — something unusual for the crew of a ship that usually operates in year-round daylight of Antarctic summer while the Arctic is plunged into polar night.

Those milestones come as part of a rare winter Arctic mission for the U.S. Coast Guard, which — with few polar-capable icebreakers remaining in its fleet — has mostly operated in during polar summers in recent years. Read more at ArcticToday.