Washington, Feb 5 (ANI): The most detailed images ever taken of the distant dwarf planet Pluto from NASA's Hubble Space Telescope have revealed an icy, mottled, dark molasses-colored world undergoing seasonal surface color and brightness changes.
Pluto has become significantly redder, while its illuminated northern hemisphere is getting brighter.
These changes are most likely consequences of surface ice melting on the sunlit pole and then refreezing on the other pole, as the dwarf planet heads into the next phase of its 248-year-long seasonal cycle.
Analysis shows the dramatic change in color took place from 2000 to 2002.
The Hubble pictures confirm Pluto is a dynamic world that undergoes dramatic atmospheric changes not simply a ball of ice and rock.
These dynamic seasonal changes are as much propelled by the planet's 248-year elliptical orbit as by its axial tilt.
Pluto is unlike Earth, where the planet's tilt alone drives seasons. Pluto's seasons are asymmetric because of its elliptical orbit.
Spring transitions to polar summer quickly in the northern hemisphere, because Pluto is moving faster along its orbit when it is closer to the sun.
Ground-based observations, taken in 1988 and 2002 show the mass of the atmosphere doubled during that time.
This may be because of warming and melting nitrogen ice.
The new Hubble images are giving astronomers essential clues about the seasons on Pluto and the fate of its atmosphere.
When the Hubble pictures taken in 1994 are compared to those of 2002 and 2003, astronomers see evidence that the northern polar region has gotten brighter, while the southern hemisphere darkened.
These changes hint at very complex processes affecting the visible surface.
The images will help planetary astronomers interpret more than three decades of Pluto observations from other telescopes.
"The Hubble observations are the key to tying together these other diverse constraints on Pluto and showing how it all makes sense by providing a context based on weather and seasonal changes, which opens other new lines of investigation," said principal investigator Marc Buie of the Southwest Research Institute in Boulder, Colorado.
These Hubble images, taken by the Advanced Camera for Surveys, will remain the sharpest view of Pluto until NASA's New Horizons probe is within six months of its flyby during 2015.
New Horizons will pass by Pluto so quickly that only one hemisphere will be photographed in detail. (ANI)