Using data from the Ralph spectral composition mapper that flew aboard NASA’s New Horizons spacecraft, planetary researchers have detected water ice deposits exposed on the surface of the dwarf planet Pluto.

“Understanding why water appears exactly where it does, and not in other places, is a challenge that we are digging into,” said New Horizons team member Dr Jason Cook, of the Southwest Research Institute.

According to the scientists, large expanses of the planet don’t show exposed water ice, because it’s masked by other, exotic ices across most of Pluto.

A curious aspect of the discovery is that the regions showing strong water ice spectral signatures correspond to regions that are bright red in the enhanced-color images of the dwarf planet.

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

In the New Horizons image above, regions with exposed water ice are highlighted in reddish color.

The strongest signatures of water ice occur along Virgil Fossa, just west of Elliot crater on the left side of the image, and also in Viking Terra near the top.

A major outcrop also occurs in Bare Montes towards the right of the image, along with numerous much smaller outcrops, mostly associated with impact craters and valleys between mountains.

New Horizons is currently 3.13 billion miles (5.04 billion km) from our planet and 65.1 million miles (104.8 million km) beyond Pluto, with all systems healthy and operating normally.