Up to a mile high, the mountains sit in the southwest portion of Pluto’s Tombaugh Regio (Tombaugh Region), more popularly known as its "heart."
It became clear, based on higher resolution images taken as New Horizons got closer and closer to Pluto, that the "heart" wasn't all one feature, but was divided into several regions with very different texture and reflectivity.
Now we're seeing just how broken that heart is: The mountain ranges found in the western portion of the Tombaugh Regio are a sharp contrast to what lies just a bit east. In the Sputnik Planum (Sputnik Plain), the frozen surface is smooth, suggesting that geologic activity has resurfaced the area quite recently.
This new image shows how dynamic Pluto is as a planet. To the left, we can see a dark, crater-marked surface -- a surface that must be billions of old, perhaps nearly as old as the solar system itself. But on the other side of the mountains sits the frozen, smooth Sputnik Plain, a patch of surface that can't be more than 100 million years old.
“There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west,” Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team, said in a statement. “There’s a complex interaction going on between the bright and the dark materials that we’re still trying to understand.”