NASA's New Horizons probe on 'Pluto's doorstep'

In this file photo, an artist's rendering of NASA's New Horizons probe is shown ahead of its first-ever flyby of Pluto.

NASA's New Horizons probe is nearing the end of a historic journey to study one of our solar system's most controversial subjects: Pluto.

On July 14, the spacecraft will perform the first-ever flyby of the dwarf planet, passing a little over 12,000 kilometres from the surface. The mission hopes to provide new close-up imagery of the frozen world.

"We are so looking forward to what we are about to do," Alan Stern, principal investigator for New Horizons, told CTV News.

"We've come such a long way and we are on Pluto's doorstep," he added.

So far, the probe, which was launched in 2006, has already sent some spectacular and eye-opening visuals back to Earth.

Earlier this week, NASA revealed time-lapse photographs taken of Pluto and its largest moon, Charon, between June 23 and June 29. The colour images exposed some startlingly new details about the dwarf planet's surface.

"We see a bright region in Pluto's north pole, so it might be a polar (ice) cap," said Cathy Olkin, deputy project scientist for New Horizons.

"We're looking to get closer and investigate that further," she added.

Scientists also want to get a better look at several mysterious dark spots that are unlike anything they've ever encountered.

The spots appear to be evenly spaced and roughly 500 kilometres in diameter.

"Pluto looks like no other world in our solar system," New Horizons mission scientist Marc Buie said in a post on NASA's website.

"We're already seeing a remarkable amount of detail, and the complexity continues to increase as the images get better," he added.

Photographs taken by New Horizons earlier this week also confirmed that Pluto is the solar system's other "Red Planet."

While Mars' red terrain is famously tinted by iron oxide, Pluto's reddish-brown colour is likely caused by hydrocarbon molecules called tholins. Tholins are formed when cosmic rays and solar ultraviolet light interact with the methane in Pluto's atmosphere and on its surface.

"Pluto's reddish colour has been known for decades, but New Horizons is now allowing us to correlate the colour of different places on the surface with their geology and soon, with their compositions," said Stern in a post on NASA's website.

Some scientists have speculated that the dwarf planet could have rings, but so far the probe's images suggest it does not.

Pluto has long been a source of contention among scientists. Discovered by an American astronomer in 1930, it was originally considered the ninth planet from the sun.

However, it status as a full-fledged planet fell into question over the next 75 years as many scientists argued over its tiny diameter and mass, when compared to other objects in the solar system.

With a diameter of 2,302 km, it is only about two-thirds the size of Earth's moon.

In 2006, Pluto was demoted to dwarf planet status when the International Astronomical Union created an official definition for the term.

Scientists with the New Horizons mission hope to shed new light on some the dwarf planet's greatest mysteries, and potentially put to bed old arguments.

"When you go somewhere new … you'll learn something you probably could never even imagine. And that's part of the excitement of this mission," said Hal Weaver, project scientist for New Horizons.

With a report from CTV News' John Vennavally-Rao