In September, the New Horizons team released a stunning but incomplete image of Pluto’s crescent. Thanks to new processing work by the science team, New Horizons is releasing the entire, breathtaking image of Pluto.
This image was made just 15 minutes after New Horizons’ closest approach to Pluto on 14 July 2015, as the spacecraft looked back at Pluto toward the Sun. The wide-angle perspective of this view shows the deep haze layers of Pluto’s atmosphere extending all the way around Pluto, revealing the silhouetted profiles of rugged plateaus on the night (left) side. The shadow of Pluto cast on its atmospheric hazes can also be seen at the uppermost part of the disc. On the sunlit side of Pluto (right), the smooth expanse of the informally named icy plain Sputnik Planum is flanked to the west (above, in this orientation) by rugged mountains up to 11,000 feet (3,500 metres) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. Below (east) of Sputnik, rougher terrain is cut by apparent glaciers.
The backlighting highlights more than a dozen high-altitude layers of haze in Pluto’s tenuous atmosphere. The horizontal streaks in the sky beyond Pluto are stars, smeared out by the motion of the camera as it tracked Pluto. The image was taken with New Horizons’ Multi-spectral Visible Imaging Camera (MVIC) from a distance of 11,000 miles (18,000 kilometres) to Pluto. The resolution is 700 metres (0.4 miles).
Mapping Pluto’s ‘Broken Heart’
The Youngest Crater on Charon?
New Horizons scientists have discovered a striking contrast between one of the fresh craters on Pluto’s largest moon Charon and a neighbouring crater dotting the moon’s Pluto-facing hemisphere.The crater, informally named Organa, caught scientists’ attention as they were studying the highest-resolution infrared compositional scan of Charon. Organa and portions of the surrounding material ejected from it show infrared absorption at wavelengths of about 2.2 microns, indicating that the crater is rich in frozen ammonia – and, from what scientists have seen so far, unique on Pluto’s largest moon. The infrared spectrum of nearby Skywalker crater, for example, is similar to the rest of Charon’s craters and surface, with features dominated by ordinary water ice.
Using telescopes, scientists first observed ammonia absorption on Charon in 2000, but the concentrations of ammonia around this crater are unprecedented.
“Why are these two similar-looking and similar-sized craters, so near to each other, so compositionally distinct?” asked Will Grundy, New Horizons Composition team lead from Lowell Observatory in Flagstaff, Arizona. “We have various ideas when it comes to the ammonia in Organa. The crater could be younger, or perhaps the impact that created it hit a pocket of ammonia-rich subsurface ice. Alternatively, maybe Organa’s impactor delivered its own ammonia.”
Both craters are about the same size — roughly 5 kilometres (3 miles) in diameter — with similar appearances, including bright wisps or rays of ejected material, or ejecta. One apparent difference is that Organa has a central region of darker ejecta, though from the map created with data from New Horizons’ Ralph/LEISA instrument, it appears that the ammonia-rich material extends beyond this dark area.
“This is a fantastic discovery,” said Bill McKinnon, deputy lead for the New Horizons Geology, Geophysics and Imaging team from Washington University in St. Louis. “Concentrated ammonia is a powerful antifreeze on icy worlds, and if the ammonia really is from Charon’s interior, it could help explain the formation of Charon’s surface by cryovolcanism, via the eruption of cold, ammonia-water magmas.”