A day on Charon
On approach to the Pluto system in July 2015, the cameras on NASA's New Horizons spacecraft captured images of the largest of Pluto's five moons, Charon, rotating over the course of a full day. The best currently available images of each side of Charon taken during approach have been combined to create this view of a full rotation of the moon.
Charon – like Pluto – rotates once every 6.4 Earth days. The photos were taken by the Long Range Reconnaissance Imager (LORRI) and the Ralph/Multispectral Visible Imaging Camera from July 7-13, as New Horizons closed in over a range of 10.2 million kilometers. The more distant images contribute to the view at the 9 o'clock position, with few of the signature surface features (such as the cratered uplands, canyons, or rolling plains of the informally named Vulcan Planum) visible. The side New Horizons saw in most detail, during closest approach on July 14, 2015, is at the 12 o'clock position.
These images and others like them reveal many details about Charon, including how similar looking the encounter hemisphere is to the so-called “far side” hemisphere seen only at low resolution – which is the opposite of the situation at Pluto. Dimples in the bottom (south) edge of Charon's disk are artifacts of the way the New Horizons images were combined to create these composites. NASA / JHUAPL /SwRI