New details of Pluto's largest moon Charon are revealed in this image from New Horizons' Long Range Reconnaissance Imager (LORRI), taken late on July 13, 2015 from a distance of 289,000 miles (466,000 kilometers) in a picture released by NASA in Laurel, Maryland, July 15, 2015. [Photo/Agencies]

New Horizon's first close-up, which covered a patch of ground about 150 miles (241 km) near Pluto's rugged equatorial region, even has scientists wondering if the icy world is still geologically active.

"Pluto has so much diversity. We're seeing so many different features ... there's nothing like it," New Horizons scientist Cathy Olkin told reporters at Johns Hopkins University Applied Physics Lab where the mission control center is located.

Another surprise was Pluto's primary moon, Charon, which was believed to be geologically dead. Instead, New Horizons found troughs, cliffs and giant canyons - all evidence of internal processes.

"Charon just blew our socks off," said Olkin.

So far only a fraction of the thousands of pictures and science measurements collected by New Horizons during its traverse through the Pluto system have been relayed. The data will be transmitted back to Earth over the next 16 months.

"I don't think any one of us could have imagined that it was this good of a toy store," said New Horizons' lead scientist Alan Stern.