Pluto 'obviously a lot more complex' than many imagined

"The dwarf planet has sent a love note back to Earth via our New Horizons spacecraft" - Nasa has posted on Instagram

Stargazers are lapping up extraordinary images of Pluto beamed back to Earth by Nasa's New Horizons spacecraft.

Pictures snapped by the probe, as it approaches the dwarf planet in the far reaches of the solar system, have revealed Pluto's reddish tinge, similar to Mars.

They also show a landscape covered in craters and very different to the icy ball covered in nitrogen snow many imagined, Auckland's Stardome Observatory and Planetarium astronomer Grant Christie said today.

"It's obviously a lot more complex than that."

New Horizon's mission was proving exciting for those into planetary geology, as an image from one of Pluto's moons, Charon, indicated tectonic activity taking place.

"At the moment that's the thing that strikes the people that are experts on Pluto - the variety of the terrain.

"The processes on Pluto are so foreign to what we know about."

Signs of tectonic activity also raised questions about energy forces on the dwarf planet and even whether pockets of liquid water existed, Dr Christie said.

"All of those sorts of questions are things they will be keep 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."

And as New Horizons approached the dwarf planet, better images would give us an idea of what Pluto really looks like.

"These pictures that Nasa posted were taken during approach the day before. It was still a way away. Over the next 48 hours we'll see much better ones."

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.

"Exactly what they're going to show I don't know but I can't wait to see them."

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 he thought it might be more of a pinkish hue.

Scientists are now expecting to receive the latest images from New Horizon in the next few hours.

Earlier today Randy Wesson, from Nasa's jet propulsion lab, said this was the first time we had had an up-close encounter with Pluto.

"We're finding all sorts of interesting features - a few craters, which tells us it's a relatively young surface. We have a mysterious ... icy region near the equator," Dr Wesson told Radio New Zealand.

"We're going to write a book about Pluto when before it was just a smudge and the best we had was from the Hubble Telescope."

New Horizons had now flown past Pluto and was looking back at the solar system.

Because of its 200-watt power, it would take months to transmit all its data back to Earth, although "big, juicy" information would be available soon.