The first ever close up images of the dwarf planet Pluto and its largest moon Charon have been released by scientists and they reveal a giant surprise.
A range of young mountains, rising as high as 3500m, have been discovered near Pluto's equator, above the surface of the icy body.
Scientists say the mountains most likely formed no more than 100 million years ago, making them comparatively youthful to the 4.56 billion-year-old solar systems they sit within.
The long-awaited images were part of a mission by NASA's unmanned New Horizons spacecraft which passed within 12,500km of the dwarf planet yesterday.
This followed a journey of more than 4.8 billion km over nine years.
The close-up image was taken about 1.5 hours before New Horizons' closest approach to Pluto, when the spacecraft was 77,000 km from the surface of the planet.
Jeff Moore of New Horizons' Geology, Geophysics and Imaging Team (GGI), said the age of the mountains is estimated by the lack of craters in the area.
"This is one of the youngest surfaces we've ever seen in the solar system," Moore said.
Scientists say Pluto is unable to be heated by gravitational interactions with a much larger planetary body and that some other process must be generating the mountainous landscape.
"This may cause us to rethink what powers geological activity on many other icy worlds," said GGI deputy team leader John Spencer, of the Southwest Research Institute.
He said the mountains were likely formed by Pluto's water-ice "bedrock".
"At Pluto's temperatures, water-ice behaves more like rock,” said deputy GGI lead Bill McKinnon of Washington University, St. Louis.
Scientists also said the "heart" feature of Pluto will now be known as the Tombaugh Regio, after Clyde Tombaugh, the discoverer of Pluto.