Russian news reports say two manned submarines have touched the bottom of Lake Baikal, the world's deepest body of fresh water. The Interfax and ITAR-Tass news agencies on Tuesday cited expedition organizers as saying that the Mir-1 and Mir-1 submersible vehicles descended more than a mile (1,680 meters) to reach the bottom of the vast Siberian lake. Scientists taking part in the mission are expected to conduct a host of geological and biological tests of Baikal. The lake is a UNESCO World Heritage site that is home to more than 1,700 species of plants and animals. It is the world's largest freshwater lake by volume.