Astronomers are used to looking at light from objects to learn about them, but sometimes the shadows are just as important.
The latest photo from NASA’s New Horizons was taken at a high phase angle, with the Sun behind the dwarf planet. In the image, which can be seen in full here, it is possible to spot the complex atmospheric haze layers, as well as the edge of the nitrogen ice plains (informally named Sputnik Planum) and the Norgay Montes at the top of the image.
One of the most interesting features is the cloud visible in the top right corner. An inset of this picture was released a few months ago in lower quality and since then it has kept astronomers wondering. The cloud appears to be tens of kilometers across and, according to atmospheric models for Pluto, it's made of methane.
A methane cloud over the Norgay Montes. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Pictures like this help scientists understand how Pluto’s atmosphere works. The New Horizons team was surprised to discover earlier this year that Pluto is losing less atmosphere than previously thought, which means it is dense enough to form winds, hazy layers, and clouds.
The bottom of the image shows some details about a large mountain range during the Plutonian night. A rugged topography appears backlit by the sun. Peaks with reliefs up to 5 kilometers (3 miles) high are interspersed with large valleys, providing more clues about the enigmatic geology of the dwarf planet.
New Horizons' Ralph/Multispectral Visual Imaging Camera (MVIC) took the image on July 14, 2015, about 19 minutes after closest approach. The probe was approximately 21,550 kilometers (13,400 miles) from Pluto and the image has a resolution of 430 meters (1,400 feet) per pixel.
New Horizons is currently flying towards its next target – a tiny 45-kilometer (28-mile) Kuiper belt object called MU69 – which it will reach on January 1, 2019.
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