NASA published the first color photos that show the atmosphere of the dwarf planet Pluto taken by the New Horizons space probe during its July 14, 2015 flyby. The previous images showed the haze in the atmosphere but not its colors so with the arrival of the new ones it was a surprise to find that Pluto’s sky is blue. Another discovery concerns the regions of water ice detected on the surface of the dwarf planet.

Alan Stern from Southwest Research Institute (SwRI), the principal investigator of the New Horizons mission, said that Pluto’s blue sky is gorgeous. He pointed out that this is an unexpected finding for an object in the Kuiper belt. Actually, the particles that create the haze are likely gray or red but the way they scatter blue light attracted the attention of the mission’s science team.

Science team researcher Carly Howett, also from SwRI, explained that the striking blue tint gives us information on the size and composition of the haze particles. A blue sky is often a result of the sunlight scattering by tiny particles. On Earth, they’re very small nitrogen molecules. On Pluto molecules appear to be larger: soot-like particles called tholins, compounds that are formed due to solar ultraviolet radiation starting from compounds such as methane or ethane.

Now the photos taken by the MVIC (Multispectral Visible Imaging Camera) instrument, one of the members of the small telescope Ralph that is part of New Horizons space probe’s payload, allowed us to see the color of Pluto’s atmosphere. Combining images at visible light from MVIC with the infrared spectroscopic ones of another component of Ralph, LEISA (Linear Etalon Imaging Spectral Array), it was possible to find deposits of water ice on the surface of the dwarf planet.

There were already several clues that there was water ice on Pluto but it’s often covered by other volatile compounds, which are also frozen, which mask it. For this reason, they identified several small areas of water ice but they take for granted that there are many others more difficult to identify.

Another curiosity about the water ice is that the regions where the spectroscopic analysis identified it is the same that correspond to the bright red color. Again, the color is given by the presence of tholins but the relationship between these compounds and water ice isn’t clear.

As always in the New Horizons mission, scientists will have to wait for the next pictures and other data transmitted by the spacecraft to try to map water ice on Pluto and better understand the distribution of the various materials on its surface. Pluto is proving an more and more a small world alive and also very colorful.