NASA’s New Horizons Spacecraft Finds Red Ice and Blue Skies On Pluto

Pluto has blue skies and bright red water ice, NASA has announced, after receiving new images from the first spacecraft ever to visit the dwarf planet.

The New Horizons probe sent the first colour images of Pluto back to the American space agency last week.

The sky’s striking blue tint is the result of the way that light reflects off tiny particles called tholins.

“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” said Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI).

“A blue sky often results from scattering of sunlight by very small particles. 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,” said science team researcher Carly Howett, also of SwRI.

The particles themselves are likely grey or red in colour and form high up in the atmosphere.

Along with the blue haze, the New Horizons spacecraft also detected numerous small, exposed regions of water ice on the dwarf planet.

“Large expanses of Pluto don’t show exposed water ice,” said science team member Jason Cook, of SwRI, “because it’s apparently masked by other, more volatile ices across most of the planet. Understanding why water appears exactly where it does, and not in other places, is a challenge that we are digging into.”

Curiously, the ice appears to be red in colour and scientists aren’t quite sure why.

“I’m surprised that this water ice is so red,” says Silvia Protopapa, a science team member from the University of Maryland. “We don’t yet understand the relationship between water ice and the reddish tholin colorants on Pluto’s surface.”

The New Horizons space probe was launched in 2006, finally reaching Pluto in July 2015, making it the very first spacecraft to explore the distant planet.

Image credit: NASA/JHUAPL/SwRI