NASA probe detects 'polar cap' on distant Pluto

For the first time, images from NASA's New Horizons spacecraft are revealing bright and dark regions on the surface of faraway Pluto - the primary target of the New Horizons' close flyby in mid-July this year.

The images reveal that the dwarf planet has broad surface markings - some bright, some dark - including a bright area at one pole that may be a polar cap.

"As we approach the Pluto system, we are starting to see intriguing features such as a bright region near Pluto's visible pole, starting the great scientific adventure to understand this enigmatic celestial object," explained John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington, DC.

"As we get closer, the excitement is building in our quest to unravel the mysteries of Pluto using data from New Horizons," he added in a statement.

The images were captured from within 113 million km using the telescopic Long-Range Reconnaissance Imager (LORRI) camera on New Horizons.

A technique called image deconvolution sharpened the raw, unprocessed images beamed back to the Earth.

Also captured in the images is Pluto's largest moon, Charon, rotating in its 6.4-day long orbit.

The exposure times used to create this image set -- a tenth of a second -- were too short for the camera to detect Pluto's four much smaller and fainter moons.

Since it was discovered in 1930, Pluto has remained an enigma.

It orbits our Sun more than about five billion km from the Earth.

Researchers have struggled to discern any details about its surface.

These latest images allow the mission science team to detect clear differences in brightness across Pluto's surface as it rotates.

"After travelling more than nine years through space, it is stunning to see Pluto, literally a dot of light as seen from the Earth, becoming a real place right before our eyes," added Alan Stern, New Horizons principal investigator.

The images the spacecraft return will dramatically improve as New Horizons speeds closer to its July rendezvous with Pluto.

New Horizons will pass approximately 12,500 km above Pluto's surface this summer.