Earth, the water planet. Its lakes, rivers, and oceans hold a crucial element for life. Earth-orbiting satellites help us track and better understand how this water moves around the globe. #WorldWaterDay Groundwater – hidden from plain sight – is a vital source of water that can be difficult to track. The GRACE-FO mission detects subtle changes in Earth’s gravity caused by the movement of water, like from groundwater and polar ice. Our favorite fruits, veggies, and grains depend on water. NASA m