Newly computer-processed images of Pluto taken by the Hubble Space Telescope depict the planet as a dynamic world that undergoes dramatic atmospheric changes produced by its seasons and not just a ball of ice and rock, NASA said Thursday.

The images depict an icy and dark molasses-colored world that is highly mottled and whose northern hemisphere is now getting brighter.

The new Hubble shots, taken from 2002 to 2003, reveal rapid variations on Pluto's surface propelled by the world's extreme seasons, lead investigator Marc Buie, of the Southwest Research Institute in Boulder, Colorado, revealed today at a press briefing.

"Around the solar system, the only things whose surfaces change by a notable amount are Earth and Mars", said astronomer Mike Brown of Caltech. "Pluto has even more dramatic changes than anything else".

The new images are hoped to pose as a vital role in targeting the New Horizons planetary probe, which was launched in 2006 and will swing by Pluto on July 14, 2015.

Buie fetched a better resolution pictures, cobbling together a network of 20 homemade computers that worked continuously for four years to produce the high-resolution pictures. Working on a limited budget, Buie was able to develop the computers for about $450 apiece.