Great Lakes on the USA/Canada border, seen from space. The Great Lakes cover an area of almost 250,000 square kilometres, making them the largest expanse of fresh water in the world. Lake Michigan is at upper centre, with Lake Superior above and left of it. The other lakes (Huron, Ontario and Erie) are under cloud to the right of Lake Michi- gan. This image was taken by the space shuttle Discovery during mission STS-105 in August 2001.