Listening practice: The satellites that weigh water

Today, let us listen to a story about water that is almost invisible. It is not a bright river on a map, and it is not a blue lake that tourists can photograph. It is groundwater, the water stored in soil and rock below our feet. NASA says the original GRACE mission, a pair of U.S. and German satellites launched in two thousand two, changed the way scientists watch this hidden part of the water cycle. Instead of measuring water only where people can place wells or gauges, GRACE followed tiny changes in Earth's gravity. Those changes helped scientists see where water was being stored, where it was moving, and where it was disappearing.