Pluto

Nasa’s New Horizons probe has spotted isolated water ice hills on the nitrogen ice glaciers of Pluto.

Measuring one to several kilometres, the hills are located in the vast ice plain called Sputnik Planumin side, Pluto’s ‘heart’.

They appear to be smaller versions of bigger and messy mountains situated on Sputnik Planum’s western border.

The hills prove Pluto’s plenteous geological activity.

Nasa in a statement said: "Because water ice is less dense than nitrogen-dominated ice, scientists believe these water ice hills are floating in a sea of frozen nitrogen and move over time like icebergs in the Earth’s Arctic Ocean.

"The hills are likely fragments of the rugged uplands that have broken away and are being carried by the nitrogen glaciers into Sputnik Planumin.

"The hills are likely fragments of the rugged uplands that have broken away and are being carried by the nitrogen glaciers into Sputnik Planumin."

"Chains of the drifting hills are formed along the flow paths of the glaciers."

On entering the cellular terrain of central Sputnik Planum, the hills become subject to convective motions of the nitrogen ice and are pushed to edges of the cells, making the hills form clusters of up to 20km.

New Horizons found a particularly large bunch of floating hills at the northern end, named Challenger Colles after the lost space shuttle Challenger, measuring 60km by 35km.

Hills at the northern end border with Pluto’s surrounding uplands, far from the cellular terrain. Scientists believe the hills have been beached because of the shallowness of the nitrogen ice.

New Horizons was launched in January 2006 to understand the composition and behaviour of Pluto’s atmosphere, big geological structures on the planet and its interaction with the particles ejected from the sun.

If successful, the mission will allow the US to complete initial reconnaissance of the solar system.


Image: Hills of water ice on Pluto float in a sea of frozen nitrogen and move over time like icebergs in the Earth’s Arctic Ocean. Photo: courtesy of Nasa / JHUAPL / SwRI.