Nasa spacecraft New Horizons got a detailed look at Pluto .

Nasa spacecraft New Horizons got a detailed look at Pluto 

  NASA's New Horizons spacecraft is expected to fly by Pluto, the most distant planetary body ever explored.

After a journey of 9.5 years across 5.3 billion kilometres of space, Nasa's New Horizons spacecraft is about to give humanity its first detailed look at Pluto and its large moon Charon.

At 10.49pm NZ time on Tuesday, the spacecraft flew within 12,500 km of Pluto's surface, making its closest approach to the dwarf planet. It furiously collected data as it zipped past at 57,900 kmh .

The data will be relayed back to the tracking station in Australia, Canberra's Deep Space Communication Complex (CDSCC). Each piece of data will then take about four-and-half hours to transmit, with the full dataset taking about 15 months to complete — but the first high-resolution images should be available to the public on Friday or Saturday (NZ time).

An artist's impression of Nasa's New Horizons spacecraft encountering Pluto and its largest moon, Charon.

If the distant Kuiper Belt object has snow-capped mountains, steep crevasses and towering ice cliffs, as some scientists have predicted, New Horizons will see them.

READ MORE: Pluto is bigger than we thought

At the same time, other instruments aboard the spacecraft will take measurements to determine what the dwarf planet is made of, create temperature maps of its multicoloured surface, and search for auroras in its thin atmosphere.

The Australian tracking station, 35 km from the capital of Canberra, is part of Nasa's Deep Space network and is one of only three tracking stations in the world.

Early in the mission's planning stages, principal scientist Alan Stern and his colleagues decided that on the day of closest approach, all of the spacecraft's power should go toward gathering information, rather than beaming it across the solar system.

"On the day of the flyby, only engineering data comes down," Stern said. "On the 15th [16th, NZ time], the science data dump begins again."

He added: "To work on this mission, you have to really be into delayed gratification."


But even in the days before the flyby, when New Horizons was still more than 8 million kilometres from the Pluto system, the spacecraft was already sending back intriguing hints of discoveries to come.

Pluto's mottled surface looks more complex then anyone anticipated, Stern said, and he was surprised to see that the Texas-sized moon Charon had dark poles - something that has never been seen before in the solar system.
"It's almost an anti-polar cap," he said.
 In addition, scientists can now say with certainty that Pluto does not have dust rings around it like its neighbour, Neptune.

It also appears that Pluto does not have any additional moons beyond the five satellites Charon, Nix, Styx, Hydra and Kerberos that had already been spotted by Nasa's Hubble Space Telescope.

The New Horizons team is not saying what the revelations might mean.

"No answers yet," said Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology and a member of the team. "We are trying to take these interpretations very slowly and carefully, especially as new and closer data are arriving."

It may seem that 9.5 years is a long time to travel for a close flyby that will last for just a day, but Stern said that had always been Nasa's plan.

"The first visit to every planet is a flyby," he said. "It's a simpler mission - it costs less and you get the basic lay of the land."

In the meantime, the scientists, like the world, are just thrilled this moment has come.

"Alan (Stern) has been at this for a quarter of a century and I've been working on it for 15 years," said Glen Fountain, New Horizons' project manager. "I'm excited that we are finally here, and I'm just waiting to see that next image."