Scientists on planet rapture over surprise Pluto pictures
Scientists have told of their delight after new pictures from the Nasa spacecraft New Horizons on its successful fly-past of Pluto revealed some major surprises.
The images show there is a range of mountains rising as high as 11,000ft (3,353m) above the surface of the icy planet.
And Pluto's largest moon, Charon, has a canyon estimated to be four to six miles (6.4km-9.7km) deep, plus a range of cliffs and troughs stretching about 600 miles (966km) from left to right.
The mountains on Pluto are from no more than 100 million years ago - mere youngsters relative to the 4.56-billion-year age of the solar system - and may still be in the process of building, said Jeff Moore, of New Horizons' Geology, Geophysics and Imaging Team (GGI).
That suggests the region they are in, which covers less than 1% of Pluto's surface, may still be geologically active today.
Nasa experts base the youthful age estimate on the lack of craters there. As with the rest of Pluto, this region is thought to have been hit by space debris for billions of years and would have once been heavily cratered - unless recent activity had given the region a facelift, erasing those pockmarks.
Mr Moore said: "This is one of the youngest surfaces we've ever seen in the solar system."
Unlike the icy moons of giant planets, Pluto cannot be heated by gravitational interactions with a much larger planetary body. 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.
The mountains are thought to be composed of the planet's water-ice "bedrock".
On Charon, there is also a lack of craters, suggesting a relatively young surface that has been reshaped by geological activity.
Cathy Olkin, of the New Horizons team, told a news conference at mission control in Baltimore, Maryland: "Charon just blew our socks off when we had the new image. We've been thrilled all morning, the team has been abuzz - 'Look at this, look at that'."
She said that in the north of Charon there was a darkish area and scientists were referring to it informally as Mordor - presumably a reference to the region in JRR Tolkien's The Lord Of The Rings.
"From the north east to the south west, a series of troughs and cliffs. This is a huge area, it could be due to internal processing. The canyon is four to six miles deep. I find that fascinating, it's a small world with canyons, cliffs, and dark regions that are still slightly mysterious to us."
The mountains on Pluto could stand up respectably against the Rocky Mountains or other mountain ranges on Earth, the experts said.
Alan Stern, principal investigator for New Horizons, said: "I certainly didn't expect Charon to show such a range and variety of terrain, as this shows us."
The pictures come from nearly three billion miles (4.8 billion km) away after New Horizons' epic mission - the closest encounter ever with the dwarf planet.
Pluto has been shown to have a surprising Mars-like reddish hue, with an enigmatic heart-shaped feature on its surface that has already become its calling card on the internet.
New Horizons has taken more than nine years to reach Pluto, carrying with it the ashes of the astronomer who discovered the remote icy object in 1930.
When the mission was launched, the aim was to reach the outermost of the Sun's family of nine planets. Seven months into the probe's epic journey, international astronomers downgraded Pluto's status to "dwarf planet".
But despite its small size - just over two-thirds the diameter of the Earth's moon - Pluto looks and behaves like a fully fledged planet, having an atmosphere and no less than five moons of its own.
Pluto is so far away that its light takes more than four hours to reach the Earth, making communication with New Horizons an exercise in patience.
The 720 million-dollar (£461 million) probe is the size of a baby grand piano and, after launching on January 19 2006, it reached an Earth-relative velocity of 36,373mph (58,537kph), making it the fastest space vehicle in history.