The recent sinking of the MS Explorer cruise ship in Antarctica has spotlighted the dangers of operating passenger vessels in remote polar areas.

The ice-reinforced Explorer was a veteran of the polar cruise-ship trade. It had made dozens of voyages to the Arctic and Antarctic since 1969, safely transporting thousands of tourists to see penguins and polar bears, glaciers and icebergs, though the ship was evacuated at least twice after Antarctic groundings. The Canadian-owned ship sank Nov. 23 after hitting submerged ice. Its 100 passengers and 54 crew were all rescued.

But experts note that the crews of such ships must deal with floating ice, unpredictable weather and substandard nautical charts — all of which can create life-threatening situations.

"These are warning signals," says Jim Barnes, executive director of the Washington, D.C.-based Antarctic and Southern Ocean Coalition. "You add up the incidents, and I think it's clear that standards need to be strengthened to reduce risks to human safety and the environment."