Tanker Escort (IMAGE) U.S. National Science Foundation Caption The USCGC Polar Star escorts a tanker through the sea ice of McMurdo Sound. Credit U.S. Coast Guard Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.