There Are Floating Hills of Ice in the ‘Heart’ of Pluto

http://www.nasa.gov/feature/pluto-s-mysterious-floating-hills http://www.nasa.gov/feature/nasa-s-new-horizons-a-heart-from-pluto-as-flyby-begins/

Hills of water ice on Pluto ‘float’ in a sea of frozen nitrogen and move over time like icebergs in Earth’s Arctic Ocean—another example of Pluto’s fascinating geological activity. NASA/JHUAPL/SwRI

Images from NASA’s New Horizons mission to Pluto show what may be water ice hills floating through a vast nitrogen ice plain that scientists have called the Sputnik Planum.

The Sputnik Planum ice plain is the western lobe of a heart-shaped region close to the dwarf planet’s equator. In the center of Sputnik Planum, floating hills cluster in groups observed to be up to 12 miles across. The Challenger Colles, another cluster located further north on the plain, measures 37 miles by 22 miles. 

Scientists believe that the hills are blocks of water ice---which is less dense than nitrogen-dominated ice---that float to the top of the plain.

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