Third vessel heads to rescue passengers on Akademik Shokalskiy, trapped in Antarctic ice A longer trip than they thought: Passengers on the Akademik Shokalskiy gather on the ice. The operators of a ship stricken in the Southern Ocean are facing a multimillion-dollar expense bill, as a third vessel began a rescue attempt five days after the tourist ship became trapped in sea ice. A group of scientists, explorers and tourists aboard the Russian ship Akademik Shokalskiy have been stuck about 1500 nautical miles south of Hobart since Christmas Eve. On Christmas Day, the Australian Maritime Safety Authority requested the Aurora Australis and two other ships, a Chinese and French icebreaker, sail to assist the Akademik Shokalskiy. Trapped: The view from the bridge of the Aurora Australis. The Australis, an Australian-flagged vessel, cut short its mission to resupply the Casey station in Antarctica and was due to reach the area at about 11pm on Sunday Sydney time. Two smaller icebreakers had earlier been unable to break through the ice. Under the Treaty of the Safety of Life at Sea, vessels are required to respond to a distress message, with the costs incurred a matter for the ship owners after the event, a spokesperson for the Australian Maritime Safety Authority said. Rob Massom, an expert in sea ice at the Australian Antarctic Division and Climate Change and Ecosystems Co-operative Research Centre, said it was not unknown for sea ice to form into tight-packed ice very quickly. It formed from freezing of the surface of the ocean at minus 1.8 degrees, Dr Massom said. "Although it's summertime, the ice can blow around and the area can change very quickly, causing ships to get penned in the ice," he said. Sea ice packs could also raft up on top of each other, doubling the thickness of the ice and forming pressure ridges several metres thick, he said. Sea ice could occur anywhere around the cost of Antarctica, but that particular area had changed due to the calving of icebergs - when icebergs break away from the land ice and float away. The summer was the safest time for tourist ships to go to Antarctica, Dr Massom said. The Akademik Shokalskiy does not have the capacity to cut through sea ice. The Aurora Australis can cut through ice more than a metre thick. An AMSA spokesperson said that if the Aurora Australis could not battle through the ice, the trapped passengers might have to be removed by helicopter.