Scientists knew Mercury was shrinking. They didnt know the true extent.

The solar system's smallest planet has suffered significant shrinkage, drawing up 30 percent more than scientists even previously estimated. Mercury, which orbits closest to the sun, is a tiny rocky world that has continuously leaked heat into space since its sizzly formation 4.5 billion years ago. As its heavy iron core cools, the entire planet shrinks, like a grape transforming into a raisin in the sun. Its outer crust buckles and cracks around it, but on a planet scale, those surface wri