The first global maps of Pluto and its moon Charon are out. And they are putting a bookend on NASA’s New Horizons mission to the dwarf planet.
“From a completionist’s point of view, they are all the good data we have, stitched together into a coherent, complete mosaic,” says Ross Beyer. He is a planetary scientist at NASA’s Ames Research Center in Moffett Field, Calif. He and colleagues recently published the new maps in Icarus.
The charts focus on regions of Pluto and Charon where the New Horizons spacecraft snapped images from at least two angles. The spacecraft flew by the dwarf planet and its moon in 2015. By combining pairs of images, astronomers could see the height and depth of the different landscapes on Pluto and Charon.
These measurements add detail to already familiar physical features. For instance, the smooth plains of Pluto’s distinctive, heart-shaped ice sheet are known as Sputnik Planitia. The plains lie two to three kilometers (1.2 to 1.9 miles) below a rim that surrounds the region.
There’s an even bigger surprise, though. Pluto has a system of ridges and troughs that is 3,200 kilometers (2,000 miles) long. The ridges and troughs trace a single, long line across the dwarf planet. That streak may stretch all the way around the globe. This feature was only visible with all the data put together, Beyer says. The team doesn’t have a good explanation for its formation yet.
The findings appear online June 11 in Icarus.
Charon’s map confirmed that the moon is made up of two large zones. There are smooth plains in the southern hemisphere. And there are fractured blocks and canyons in the northern hemisphere. Beyer and colleagues report the finding online July 3 in a separate paper in the journal. Initially, scientists thought both terrains were at the same elevation. But the new map shows that the southern plains are situated a kilometer or two (0.6 to 1.2 miles) lower than the northern terrain.
“We don’t know quite why that is yet, but it sure is interesting,” Beyer says.
Other planetary scientists will use these charts to continue unearthing Pluto’s secrets. And Charon’s, too. “These maps really form the basis, the cartographic foundation, for anything any other scientist will do,” Beyer says.