The U.S. Coast Guard Cutter Polar Star freed the fishing vessel Antarctic Chieftain Friday night after it had become icebound approximately 900 miles northwest of McMurdo Sound, Antarctica, according to a Coast Guard news release.

After rendezvousing with the Antarctic Chieftain, the crew of Polar Star took the the 207-foot Australian-flagged fishing vessel in a stern tow. With both ships surrounded by 12-to-15-f00t thick ice covered with two feet of snow, the tow was slower and much more hazardous than towing in open water. Upon reaching a polynya, or small area of open water, the Antarctic Chieftain was able to check the extent of the damage to her propeller blades and determine whether she could proceed using her own engines. While Maritime New Zealand reports that Antarctic Chieftain is now underway, the two ships will still have to head north through another 60 miles of ice.

Rescue Coordination Center (RCC) New Zealand asked Polar Star to respond to the Antarctic Chieftain’s request for assistance. The 150-person crew of Polar Star, homeported in Seattle, Washington, was deployed to McMurdo Station, Antarctica, as part of Operation Deep Freeze, providing logistical support to the U.S. Antarctic Program (USAP), managed by the National Science Foundation. RCC New Zealand, which is responsible for all major maritime and aviation search and rescue missions within New Zealand’s search and rescue region, is managed by Maritime New Zealand.

The 399-foot Polar Star is the nation’s only heavy icebreaker capable of operating in the thick Antarctic ice for a mission such as breaking out the Antarctic Chieftain or clearing McMurdo Sound for the annual resupply of McMurdo Station, and only recently returned to service after a long refit.