Images sent back by NASA’s New Horizons spacecraft last week reveal that pluto has blue atmospheric hazes and water ice on its surface.

Regions of exposed water ice highlighted in blue.

Pluto’s blue haze layer captured by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC).

The colour of the haze are caused by tholins, grey or red coloured particles that scatter blue light in the atmosphere.“That striking blue tint tells us about the size and composition of the haze particles,” science team researcher Carly Howett said in a statement . “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.”The tholin particles form high in the atmosphere, and are broken apart by ultraviolet sunlight. Particles eventually reform as they fall to Pluto’s surface, adding to its red coloring. The numerous exposed small patches of water ice detected by New Horizons appear bright red in recent colour images.“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.”“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 spacecraft is 3.1 billion miles (5 billion kilometers) from Earth on course for a small Kuiper Belt object (KBO) known as 2014 MU69. NASA recently released photos that reveal close-ups of Pluto's arctic mountain ranges, glaciers, and streams of frozen nitrogen . You can get an idea of what it’s like to fly through the atmosphere of the dwarf at low altitude.Image Credit: NASA/JHUAPL/SwRI

Jenna Pitcher is a freelance journalist writing for IGN. You can follow her on Twitter