Pluto's White, Dark-Orange and Charcoal-Black Terrain Captured by NASA's Hubble

WASHINGTON -- NASA has released the most detailed and dramatic images
ever taken of the distant dwarf planet Pluto. The images from NASA's
Hubble Space Telescope show 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," says principal investigator
Marc Buie of the Southwest Research Institute in Boulder, Colo.

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. The Hubble images are
invaluable for picking the planet's most interesting hemisphere for
imaging by the New Horizons probe.

New Horizons will pass by Pluto so quickly that only one hemisphere
will be photographed in detail. Particularly noticeable in the Hubble
images is a bright spot that has been independently noted to be
unusually rich in carbon monoxide frost. It is a prime target for New
Horizons. "Everybody is puzzled by this feature," Buie said. New
Horizons will get an excellent look at the boundary between this
bright feature and a nearby region covered in pitch-black surface
material.

"The Hubble images also will help New Horizons scientists better
calculate the exposure time for each Pluto snapshot which is
important for taking the most detailed pictures possible," Buie said.
With no chance for re-exposures, accurate models for the surface of
Pluto are essential for properly exposed images.

The Hubble images surface variations a few hundred miles across that
are too coarse for understanding surface geology. But in terms of
surface color and brightness, Hubble reveals a complex-looking world
with white, dark-orange and charcoal-black terrain. The overall color
is believed to be a result of ultraviolet radiation from the distant
sun breaking up methane present on Pluto's surface, leaving behind a
dark and red-carbon-rich residue.

The Hubble images are a few pixels wide. Through a technique called
dithering, multiple, slightly offset pictures are combined through
computer-image processing to synthesize a higher-resolution view than
can be seen in a single exposure.

"This has taken four years and 20 computers operating continuously and
simultaneously to accomplish," Buie said. Buie developed the special
algorithms to sharpen the Hubble data. He plans to use Hubble's new
Wide Field Camera 3 to make additional observations prior to the
arrival of New Horizons.

For Hubble information and images, visit:

http://www.nasa.gov/hubble

Source: NASA