NASA releases a close-up photo of an area in the center-left of the heart feature of a young craterless plain which they name Sputnik Planum. It has a broken surface of irregularly-shaped segments, roughly 20 km (12 miles) across, bordered by what appear to be shallow troughs, some of which have darker material within them, while others are traced by clumps of hills that appear to rise above the surrounding terrain. Elsewhere, the surface appears to be etched by fields of small pits that may have formed by sublimation.
This terrain is not easy to explain. The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations.