• Cheers and whoops as Nasa probe makes historic fly-by
• Data from New Horizon shows Pluto is red like Mars
• More images of dwarf planet to be released later today

Astonishing images taken from Nasa's New Horizon's spacecraft have shown for the first time that Pluto is red like Mars.

Scientists were expecting to find a dark, icy world, but the first close up shots sent back from the probe show a rusty tint.

Nasa posted a stunning new image of Pluto on Instagram, taken by New Horizons from a distance of 476,000 miles, the closest ever picture of Pluto taken by Nasa as it approached the new red planet.

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It clearly shows the dwarf planet's surprising Mars-like reddish hue, and the enigmatic heart-shaped feature on its surface that has already become Pluto's calling card on the internet.

The nine-year mission to Pluto reached its climax on Tuesday when New Horizons flew close to the dwarf planet before journeying into the Wild West of space - the Third Zone. Nasa scientists played The Final Countdown, by 1980s rock band Europe, to mark the historic occasion (the US is the only nation to have visited every planet in the solar system).

When New Horizons launched in 2006 Pluto was still a planet, but just a few months later it was downgraded to a dwarf-planet or 'plutoid' and is now known officially as 'asteroid number 134340'

Its arrival should have marked the completion of mankind's quest to map the Solar System. Instead it will be remembered as the beginning of the exploration of 'The Third Zone' also known as the mysterious Kuiper Belt, a huge unchartered band of planetary debris left over from the solar system's formation 4.56 billion years ago.

At the Applied Physics Laboratory (APL) at Johns Hopkins University in Maryland, mission control staff and visitors clapped, cheered and waved American flags, chanting "USA, USA" in an outpouring of patriotic emotion.

Nasa administrator Charles Bloden said that the team had been astounded when the first images came back revealing a red planet.

"It's not an icy planet. It's red. How can the surface be red? The geological world is excited about something they didn't even think they would be involved in. Geologists are marvelling at the colour and thinking how can that be so far away from the Sun.

"We're calling Pluto a planet, technically it's a dwarf planet. I call it a planet, but I'm not the rule maker. It's a big day for Nasa. The US today has become the first nation to visit every planet in our Solar System.

"We wanted to demonstrate that we could navigate the last known planet in our Solar System. That is an incredible tehcnological achievement.

NASA’s New Horizons spacecraft is speeding towards Pluto for the first-ever flyby on July 14, 2015. Scientists are eager to collect data on the dwarf planet’s chemical and atmospheric makeup, and the Ralph spectrometer will do just that. Instrument scientist Dennis Reuter discusses Ralph, Pluto, and exploration of our solar system’s last frontier, the Kuiper Belt. Source: NASA Goddard/Youtube

"I expected to see some cold, grey icy planet. It has reddish tint, not unlike Mars. That's facinating. We continue to be mesmerised by this incredible planet and its moons."

Experts believe the colour arises from the chemical action of sunlight generating red compounds in the atmosphere that then fall on the surface.

Over the last few weeks the probe has sent back tantilising images as it moved ever closer to Pluto revealing unusual features dubbed 'the whale' and 'the heart.'

The probe will pass straight over the heart-shaped feature just 7,800 miles from the surface, at 30,800 mph taking pictures and a range of other measurements.

It then carries on into the Kuiper Belt, and will eventually leave the Solar System, a feat only achieved by Voyager so far.

The first 'phone home' message from New Horizons is expected at 2am BST on Wednesday morning and the first images rare expected to be released at around 8pm that evening. British company e2v has provided the camera for the mission.

Dr Alan Stern, principal science investigator at New Horizons sais: "It feels good. So many people put so much work into this around the country. It's a moment of celebration. We have completed the initial reconnaisance of the Solar System, started under President Kennedy.

"The spacecraft is currently doing its job taking measurements and we are going to have it check back in with us tonight and that's when we will find out if it completed its job successfully."

Other photos taken from a million miles away revealed evidence of cliffs, craters and chasms larger than the Earth's Grand Canyon.

Speaking at APL, former astronaut John Grunsfeld, associate administrator of Nasa's Science Mission Directorate, said: "It's just amazing. This is truly a landmark in human history. People often think the success of missions like this is about engineers, the hardware, but the real key is team work, and that's what Nasa excels at.

"We're celebrating the moment New Horizons had its closest approach to Pluto, but we're not talking to the spacecraft; it's doing its job. Tonight we're going to get the signal, the ping, (telling us) that it made it through the system and it's ready to start sending us a treasure trove of data."

New Horizons was the fastest spacecraft to ever launch and is partly powered by nuclear energy. It is also working on its own without instructions from mission control because the communication lag is so great.

And it is carrying the ashes of the scientist who discovered Pluto, Clyde Tombaugh. Tombaugh died on January 17 1997, nine years and two days before New Horizon's launch, but one of his final requests was for his ashes to be sent into space.

A small container carrying his remains is affixed to the inside of the upper deck of the probe bearing the inscription: "Interred herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's 'third zone'"

New Horizons has already answered one basic question about Pluto, its precise size. Scientists used photos from the spacecraft's telescopic camera, the Long Range Reconnaissance Imager (Lorri), to determine that the dwarf planet is somewhat larger than previously thought, having a diameter of 1,473 miles.

The result confirms that Pluto is larger than any other known solar system object beyond the orbit of Neptune.

Mission scientist Dr Bill McKinnon, from the University of Washington, said: "The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest."

Close up images taken by New Horizons are expected to show surface features just 50 metres across.

British astronomer Brendan Owens, from the Greenwich Royal Observatory in London, said: "This is really unexplored territory. The images of Pluto we got previously have been only a few pixels across, just showing areas of light and dark on this world.

"Now we're getting up close and personal, something that has never been done before. This whole region is hard for astronomers to explore because we rely on light, and at that distance so little sunlight falls on these objects that you have very little data to work with.

"Learning about the composition of Pluto may give us more of a handle on the make-up of the solar system."

"What Nasa's doing with New Horizons is unprecedented in our time ... the last picture show for a very, very long time."

Pluto has a thin atmosphere of nitrogen, methane and carbon dioxide, which expands as the dwarf planet's elongated 248-year orbit takes it closer to the Sun, causing icy material on its surface to vaporise.

Since its discovery, only a third of Pluto's year - the time it takes to complete one orbit of the Sun - has passed.

Scientists believe the dwarf planet may bear signs of past volcanic activity and could even have liquid water beneath its frozen surface.

Because of its elliptical 248 year orbit the mission has been timed so that probe needed only travel the shortest distance.

When Pluto was discovered in 1930, a competition was held to find a name for the new planet.

Eleven-year-old Venetia Burney chose Pluto because it was dark and far away, like the god of the underworld. She received a £5 (NZ$11) as a reward.