When a drought hits, the ground dries out, rivers shrink, and plants wilt. But how do you know exactly how much water has vanished from a vast area? Ordinary instruments can't cover an entire continent. So scientists sent two satellites into space that fly in tandem and measure Earth's gravitational pull.
If there's less water beneath the satellites, gravity weakens, and the satellites drift slightly apart. By tracking these tiny changes in distance, they weighed the La Plata basin in South America. It turned out that during the 2008–2009 drought, the region lost 248 gigatons of water. That's like stripping a layer of water 12 centimeters thick from an area the size of Argentina and Uruguay combined.
Now this method helps monitor droughts worldwide. The satellites have become scales that feel a continent slimming down, and they warn when it's time to store water.
The deficit of 248 gigatons of water is equivalent to a layer 12 centimeters thick spread over an area comparable to the combined territory of Argentina and Uruguay.
The idea of weighing water from space echoes Arthur C. Clarke's novel 'The Fountains of Paradise,' where orbital engineers use gravitational anomalies to build a space elevator.