The Chinese research vessel and icebreaker Xue Long broke free from ice and was back in the open waters off Antarctica on Tuesday. Zhang Jiansong /Xinhua/Landov hide caption

toggle caption Zhang Jiansong /Xinhua/Landov

The U.S. Coast Guard icebreaker Polar Star, seen here in 1999, has been sent to help free Russian ship Akademik Shokalskiy and Chinese icebreaker Xue Long, which are gripped by Antarctic ice. U.S. Coast Guard Handout Photo/Reuters /Landov hide caption

toggle caption U.S. Coast Guard Handout Photo/Reuters /Landov

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