Radar images previously revealed thousands of buried glacier-like formations in the planet’s northern and southern hemispheres. That data has now been incorporated into computer models of ice flow to determine the glaciers’ size and hence how much water they contain. “We have looked at radar measurements spanning 10 years back in time to see how thick the ice is and how it behaves. A glacier is, after all, a big chunk of ice and it flows and gets a form that tells us something about how soft it is. We then compared this with how glaciers on Earth behave and...