Moving Hills

NASA just presented an intriguing, but rational, explanation for one of the most recent space mysteries to date—Pluto’s moving hills.

Pluto’s complex terrain features a hill cluster located in the great ice plain that was once called the Sputnik Planum, at the “heart” of Pluto. The hills vary in size, from one to a dozen km/miles wide, and are largely considered as proof of Pluto’s multifaceted geology.

But what’s even more interesting is that hills, unlike the ones found on our planet, are not stationary.

"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." Image Credit: NASA/JHUAPL/SwRI

NASA’s explanation? These hills that were discovered based on New Horizon’s latest mission data, are actually icebergs. This explanation makes a lot of sense—except the surface that these ice hills are floating on is also supposedly on ice.

How does ice float on ice?

Ice-on-ice movement is a theory that NASA’s New Horizon’s team has been running with for a little over a month.

The theory proposes that we are actually seeing two different types of ice—nitrogen ice that is common on the planet and water ice. Nitrogen ice is significantly more dense than water ice, which then allows the ice hills movement as it “floats” on.

Think of it in kind of the same way icebergs move across the Arctic Ocean.

So what’s next for the team now that one of Pluto’s greatest geological mysteries has been solved? NASA has announced that New Horizons will look into figuring out how and why gobs of nitrogen are moving down the dwarf planet's surface.

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