NASA’s New Horizons spacecraft has beamed back the first color image of Pluto’s atmosphere.
New Horizons looks toward the night side of Pluto and sees sunlight scattering through the periphery of the dwarf planet’s atmosphere and forming a ring of blue color. This image was generated by software that combines information from blue, red and near-infrared images to replicate the color a human eye would perceive as closely as possible. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
The thin atmosphere of Pluto rings its silhouette like a blue halo in this picture taken by New Horizons’ Ralph/Multispectral Visible Imaging Camera.
“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” said Dr Alan Stern of the Southwest Research Institute, principal investigator for New Horizons.
Pluto’s high-altitude haze is thought to be similar in nature to that seen at Titan, Saturn’s largest moon and the second-largest moon in the Solar System.
Particles in Pluto’s haze are small and likely gray or red, but the way they scatter blue light has gotten the attention of NASA researchers.
“That striking blue tint tells us about the size and composition of the haze particles,” said New Horizons team member Dr Carly Howett, also of the Southwest Research Institute.
“A blue sky often results from scattering of sunlight by very small particles,” she said.
“On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger – but still relatively small – soot-like particles we call tholins.”
The New Horizons team believes that tholins form high in the dwarf planet’s atmosphere.
This photo is a close-up from the one above. According to NASA scientists, complex chemical compounds called tholins give Pluto a distinctive blue haze. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
“UV sunlight breaks apart and ionizes nitrogen and methane molecules and allows them to react with one another to form more and more complex negatively and positively charged ions,” they explained.
“When they recombine, they form very complex macromolecules, a process first found to occur in the upper atmosphere of Titan.”
“The more complex molecules continue to combine and grow until they become small particles,” the scientists said.
“Volatile gases condense and coat their surfaces with ice frost before they have time to fall through the atmosphere to the surface, where they add to Pluto’s red coloring.”
New Horizons is currently 3.13 billion miles (5.04 billion km) from our planet and 64.1 million miles (103.2 million km) beyond Pluto. The spacecraft is healthy and all systems are operating normally.
