Where did Earth’s oceans come from? That question has intrigued researchers for centuries. Unraveling the origin and evolution of the oceans is a greater challenge than it is for landforms. In the latter case, solid materials (rocks) that formed billions of years ago are still in place and can be studied to determine their age and evolution. Water that makes up the oceans presents a different problem. That water existed at one point in Earth’s history almost entirely in the form of water vapor in the atmosphere, and at other times, it existed at least partially in the form of snow and ice. Determining the precise amount of water present at any one time in Earth’s history, and its location and boundaries, is, therefore, a challenging task.View More Where did Earth’s oceans come from?