Water is regarded as the second most important source of life, behind air, which most organic life requires constantly. The oldest water in the world is found in Canada, specifically the Kidd Creek mine in northern Ontario. In 2016, researchers discovered what is thought to be the oldest water, estimated to be at least 2 billion years old, but more likely 2.7 billion. The circumstances at the mine's bottom have been ideal for preserving the water. This ancient water was discovered at a depth of 2.5 kilometers (1.5 miles) because the Kidd Creek mine is the world's deepest basal metal mine, holding numerous metal minerals such as copper, zinc, and silver.