Pluto’s mountains may be more like icebergs in the ocean than mountains on Earth. Made of water ice, these big blocks of material are probably floating on a “sea” of nitrogen ice, Moore revealed. In some regions, these mountains are as large as the Rockies but are still buoyant enough to rise high above denser nitrogen and carbon monoxide ices. “Even the largest mountains of Pluto could simply be floating,” Moore said during his presentation.

Near the western edge of the ice field known as Sputnik Planum, giant sheets of water ice can be fractured and rearranged, producing what Moore refers to as “anarchic terrain.” Jumbled chains of angular blocks, some as much as 25 miles (40 kilometers) across and 3 miles (5 kilometers) high, form mountains that stretch chaotically near the otherwise smooth, young plain.

Fans of Golden Age science fiction great Edmond Hamilton recall the Marching Mountains from the 1940 novel Calling Captain Future, which provides a map showing the perpetual circle followed by these geographical behemoths.

(Map of Edmond Hamiltons Captain Future Pluto)

CURT nodded. He was peering toward the towering white masses that loomed up vaguely ahead. "Those are the Marching Mountains, Grag," he told the robot. "Remember them?"

Grag nodded uneasily. "Yes, I don't like them."

"My people too are afraid of them," Tharb confessed. "They have often times destroyed the towns of my tribe."

The Marching Mountains of Pluto, one of the greatest natural wonders of the System, were soon almost below them.

This particular range was a vast wall of ice, a thousand feet high, that advanced with a shifting, flowing movement over the ice-fields in a southwestward direction. The crackling, crashing roar of its progress reached their ears as a deafening cannonade.

Mountains of ice, marching! The Marching Mountains were really vast glaciers, that moved at a speed many times faster than any glacier of Earth. Around and around this frigid planet eternally, their mighty ranges moved like ponderous, walking white giants.

"Master, above us!" Grag yelled suddenly.

A dark space cruiser, with the black disk of the Legion of Doom on its bows, was diving down on them.

"Ambush!" Curt cried, his gray eyes suddenly blazing. "I might have known--"

He swept their flier aside with a lightning movement. It was too late. The guns of the cruiser blasted atomic fire.

The whole flier rocked sickeningly as its tail and rocket-tubes were blasted away. Then it plunged toward the ice hundreds of feet below, while the Legion cruiser zoomed up and away.

"We're going to fall in front of the Marching Mountains!" cried Tharb wildly. "It is certain death!"

Update: Thanks to Winchell Chung of Project Rho for the tip on this story AND a great text quote! End Update.