NASA releases more New Horizons photos of Pluto

NASA has released more images of Pluto after the spacecraft New Horizons made its historic flyby of the dwarf planet earlier in the week.

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One photo shows a carbon monoxide-rich area within the Tombaugh region, Pluto's vast heart-shaped feature.

"There is no other carbon monoxide concentration [on Pluto] like this," said Alan Stern, principal investigator of the New Horizons team. "It's a very special place on the planet."

NASA released other high-resolution images of the icy dwarf planet on Wednesday, a day after the flyby, showing mountains on Pluto and canyons on the largest of its five moons, Charon.

Some of the ice mountains are comparable in size to some of the smaller Rocky Mountains. Charon's canyons may be up to nine kilometres deep.

The lack of craters on both Pluto and Charon suggests the two are still geologically active.

A closeup of a crater-free area named Sputnik Planum was released during Friday's briefing. Scientists believe Pluto's plains may be less than 100 million years old.

Sputnik Planum is adjacent to a set of mountain ranges, illustrating the "stark contrasts on Pluto in terms of the geology," Stern told reporters.