New Horizons Space Probe: What Surprised Scientists the Most About Pluto

— -- Three months after the world got its closest look ever at Pluto, the New Horizons science team has released their first research paper detailing the space probe's early findings from its close encounter with the dwarf planet.

Published today in Science Magazine, the paper paints a fascinating portrait of the mysterious world on the edge of the solar system. Among the most stunning discoveries for scientists were Pluto's geological diversity and the activity still taking place on the dwarf planet's surface.

“The Pluto system surprised us in many ways, most notably teaching us that small planets can remain active billions of years after their formation," principal investigator Alan Stern said in a statement. "We were also taught important lessons by the degree of geological complexity that both Pluto and its large moon Charon display."

At 4.5 billion years old, scientists did not expect to find an active dwarf planet, but New Horizons captured a trove of evidence upending this belief.

Curiously, in the western lobe of Pluto's now-famous heart-shaped region, nicknamed Sputnik Planum, the team found evidence of methane ice and carbon monoxide ice, in addition to the water ice that was announced last week. The smoothness of the region indicates to scientist the area must still be active enough to erase craters that have formed.

New Horizons also took a close look at Pluto's largest moon, Charon, finding tectonic activity and a mysterious dark polar region. Researchers also looked at the first images of Nix and Hydra, the smallest of Pluto's five moons, and found they are more reflective than its largest, Charon. One explanation is a coating of surface water ice on the two tiny moons, according to researchers.

NASA has so far downloaded 15 percent of the data from New Horizons, which in the middle of a year-long data dump. Traveling at the speed of light, signals take 4.5 hours to travel 3 billion miles to reach Earth. With data downlinking at a rate of approximately 1 to 4 kilobits per second, it's expected the entire trove of science from the July 14 flyby will take one year to be transmitted back to Earth.