Photos reveal Pluto’s fresh face

IOWA CITY - Pluto long has been presumed to be like a ball of ice. But now for the first time in human history, scientists don't have to rely on a presumption.

Nearly a decade after it launched from Earth, the New Horizons spacecraft flew by the distant 'dwarf planet” Tuesday morning, and NASA released high-resolution images Wednesday it captured from about 7,700 miles away.

Scientists were surprised by what they saw.

'We thought, and my guess would have been, that it would look a lot like Europa - a big ball of ice,” University of Iowa astronomy professor Robert Mutel said, referring to Jupiter's sixth-closest moon made up of mostly silicate rock and a water-ice crust.

'But these first images are totally different,” Mutel said. 'It looks like there might be active geology, which is the last thing anyone thought.”

Many more images are expected to trickle in over the coming weeks and months - keeping the entire scientific community, including UI astronomers, captivated.

'We didn't really expect to see so much surface definition,” according to Mutel, who was not alone in his shock at the 'youthful” icy mountains revealed by the first close-up photos.

New Horizons principal investigator Alan Stern called the photos - revealing a mountain range with peaks rising up to 11,000 feet and evidence the surface might still be geologically active - a 'home run” and 'just mind blowing,” according to NASA.

Pluto was still considered the solar system's ninth planet when New Horizons was launched in 2006. But it was reclassified as a 'dwarf planet” after the discovery of other Pluto-like spheres orbiting in the Kuiper belt, the region beyond the eighth planet, Neptune. The objects are believed to be remnants from the formation of the solar system 4.6 billion years ago.

The first photos indicate Pluto's mountains probably were formed no more than 100 million years ago - making them 'mere youngsters,” according to NASA.

In fact, the shots of both Pluto and its largest moon, Charon, have scientists now believing their surfaces are among the youngest ever seen in the solar system.

That's what stood out to UI physics professor Jasper Halekas, who is lead investigator on an instrument aboard another NASA mission - its Mars Atmosphere and Volatile Evolution spacecraft, or MAVEN.

'If you look up at our moon, you see a surface scarred by craters, reflecting its bombardment by impactors over 4 billion years,” Halekas said. 'On Pluto and Charon, there's no hint remaining of that kind of bombardment. … That seemingly implies that these planets are - or were recently - geologically active, and that is absolutely fascinating.”

Pluto was the last major unplumbed body in the solar system, and Mutel said the flyby marks what could be the final exploration of totally uncharted territory in the foreseeable future.

'This is the last major unknown discovery that we have sent a spacecraft close to,” he said. 'We are not doing this anymore. This is it.”

The new information will shape research into the origins of the solar system and inform the next generation of students and scientists.

'We only have one flyby, and those images will be in text books - or whatever replaces them - for hundreds of years,” Mutel said. 'It's not likely we will go back to Pluto any time soon.”

Reuters contributed to this report.