“Just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies. The misfit becomes the average. The Pluto-like objects are more typical in our solar system than the nearby planets we first knew.” -Alan Stern
When New Horizons approached the Pluto system last year, it discovered two vastly different worlds in Pluto and Charon. While Pluto had mountains, plains, ridges, and surface regions with vastly different properties, Charon looked more like our Moon: cold, airless, mostly uniform and full of craters.
As soon as we learned these two world were so different, the question of “why” was brought to the forefront. Yet the very same images hold clues: beneath Pluto’s volatile, ever-changing surface may lie a world that’s not so different from Charon. It’s only the easily sublimated molecules like nitrogen and methane that make the difference, and the reason Pluto has them exclusively is that it likely stole them from Charon a long time ago.