This highest, driest, and coldest continent was referred to in the 17th century as Terra Australis Incognita—unknown southern land. Although the continent is still largely a mystery, what is known is that Antarctica's delicate ecosystem is in danger.

Scientists are studying environmental changes that have resulted in a vast decline in numbers of krill—tiny, shrimplike creatures that are the backbone of the food chain in the surrounding seas. As Antarctica becomes less isolated, the challenge will be to protect these ecosystems and the seals, penguins, and whales that rely on them.