Images sent by NASA’s New Horizons spacecraft shows Pluto’s blue atmospheric hue, and the planet has frozen water. NASA shared the images on Thursday, showing the dwarf planet’s atmospheric hue that is in a kind of cobalt blue.
The haze is likely to be made up of red or gray particles, and the blue tint shows that they are small enough, allowing them to scatter light like the Earth’s sky. A blue sky occurs after sunlight is scattered by small particles. These particles are tiny nitrogen molecules on Earth, and on Pluto they appear to be larger, but they are small sootlike particles called tholins.
“Who would have expected a bluesky in the Kuiper Belt? It’s gorgeous,” said Alan Stern, New Horizons principal; investigator.
“Tholins” are small tar or soot-like particles that are formed when nitrogen and methane break apart in ultraviolet light and recombine into new, complex macromolecules, responsible for the red coloring on Pluto’s surface. The great red spot on its moon Charon is also formed by the same process. These particles are believed to have formed high up in Pluto’s atmosphere, creating the amazing blue scatter. The term “tholins” was coined by Carl Sagan in 1979, and according to Sarah Horst of Johns Hopkins University, these particles can block UV rays in the atmosphere.
Apart from the blue skies discovery, NASA also reported about small patches of exposed water ice. Though ice is present all over the planet, most of the H2O places are covered by ices made of other molecules. The research team said that the water ice seemed to corelate with parts of the planet tinted red by tholins Silvia Protopapa, a science team member from the University of Maryland, College Park said that they don’t understand the relationship between water ice and the reddish tholin colorants on Pluto’s surface.[ Source ]