Like a pair of figure skaters clasping hands around a common centre of mass, Pluto and Charon make for a fascinating couple in this new image from the New Horizons, which was taken on 8 July and includes colour information collected by the spacecraft’s Ralph instrument. Believed to be born from a collision that happened billions of years ago, the dwarf planet and its largest moon don’t really look much like siblings given their different appearances.
“These two objects have been together for billions of years, in the same orbit, but they are totally different,” says Alan Stern of the Southwest Research Institute (SwRI), who is New Horizons’ Principal Investigator.
In this high-contrast image, bright and dark features dominate Pluto’s surface. Charon on the other hand has a dark polar region that interrupts its generally much more uniform and light grey terrain. On the dwarf planet’s moon, the reddish materials that give Pluto its pop of colour are absent from Charon. What’s more, the exotic ices like frozen nitrogen, methane and carbon monoxide that’s been discovered on Pluto, can’t be found anywhere on its frozen water- and ammonia-based companion. The 750 mile-across world, which is about half the diameter of its parent, contains equal measures of rock and water ice.
The brighter areas on Charon are suspected to be impact craters. “If we see impact craters on Charon, it will help us see what’s hidden beneath the surface,” says the mission’s Geology, Geophysics and Imaging (GGI) team leader Jeff Moore of NASA’s Ames Research Center. “Large craters can excavate material from several miles down and reveal the composition of the interior.”
John Spencer also of SwRI and GGI’s deputy team leader says of Pluto’s moon: “Charon is now emerging as its own world. Its personality is beginning to really reveal itself.”