Scientists have released the first up-close images ever of Pluto and its big moon Charon. And they say they're amazed.
The long-awaited images were unveiled in Maryland, home to mission operations for NASA's New Horizons spacecraft.
Nasa spokesman Dwayne Brown said: "Yesterday, America's space program took another historic leap for humankind. Today, the New Horizons team is bringing what was previously a blurred point of light into focus."
The latest spectra from New Horizons Ralph instrument reveal an abundance of methane ice, but with striking differences from place to place across the frozen surface of Pluto. Photo / NASA
A zoom-in of Pluto reveals an icy range about as high as the Rockies. To the scientists' great surprise, there are no impact craters. On Charon, deep troughs and canyons can be seen.
The images were collected as New Horizons swept within 7,700 miles of Pluto on Tuesday, becoming Pluto's first visitor in its 4.5 billion-year existence.
Nasa said the giant mountains likely formed 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.
That suggests the close-up region, which covers less than one percent of Pluto's surface, may still be geologically active today.
Like the rest of Pluto, this region would presumably have been pummeled 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.
"We now have an isolated small planet that is showing activity after 4.5 billion years," said Alan Stern, New Horizons' principal investigator. "It's going to send a lot of geophysicists back to the drawing board."
Jeff Moore of New Horizons' Geology, Geophysics and Imaging Team, 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.
GGI deputy team leader John Spencer of the Southwest Research Institute said: "This may cause us to rethink what powers geological activity on many other icy worlds."
The mountains are probably composed of Pluto's water-ice "bedrock".
Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Instead, a stiffer material, most likely water-ice, created the peaks.
The image shows youthful mountains rising from the dwarf planet's icy surface. Photo / Nasa
"At Pluto's temperatures, water-ice behaves more like rock," said deputy GGI lead Bill McKinnon of Washington University, St Louis.
John Spencer, a New Horizons science team member, said that the team has yet to find an impact crater in any of the scans, suggesting Pluto is very compared to the solar system.
The team also announced that the "heart" feature of Pluto will now be known as the Tombaugh Regio, after Clyde Tombaugh, the discoverer of Pluto.
Scientists had been waiting with bated breath for the closest images of dwarf planet Pluto to be sent back to earth.
Unmanned Nasa spacecraft New Horizons passed within 12,500km of the dwarf planet yesterday, after a journey of more than 4.8 billion km over more than nine years.
The closest images seen from the space probe so far were taken at a distance of more than 760,000km - but they have already wowed scientists, showing Pluto has a Mars-like reddish hue.
They also revealed Pluto's crater-covered landscape and an enigmatic blue heart-shaped feature on its surface which has already taken off on the internet.
It was very different to the icy ball covered in nitrogen snow many imagined, said Auckland Stardome Observatory and Planetarium astronomer Grant Christie.
An image from one of Pluto's moons, Charon, indicated tectonic activity taking place - raising questions about energy forces on the dwarf planet and whether water pockets existed.
The variety of the terrain was striking for Pluto experts, Dr Christie said.
"All of those sorts of questions are things they will be keen to explore and find out," he said.
"This is probably the last - apart from moons of Uranus and Neptune - piece of major real estate that we'll be able to reach for a while."
When New Horizons launched in 2006 Pluto was still a planet, but a few months later it was downgraded to a dwarf planet. It is now known officially as "asteroid number 134340".
Dr Christie said the Nasa probe was collecting so much information it would take 18 months to download, but he expected a hungry public would be fed as many images as possible soon.
He was also cautious about reading too much into the apparent red colour of Pluto until more testing was performed on the chemical makeup of the surface.
Dr Christie said he didn't think Pluto would be as red as Mars. Instead, it might be more of a pinkish hue.
