New Hubble Maps of Pluto Show Surface Changes
This is the most detailed view to date of the entire surface
of the dwarf planet Pluto, as constructed from multiple NASA
Hubble Space Telescope photographs taken from 2002 to 2003. The center disk (180 degrees) has a mysterious bright spot
that is unusually rich in carbon monoxide frost. Pluto is so small and distant that the task of resolving the surface is as
challenging as trying to see the markings on a soccer ball 40 miles away.
Credit: NASA, ESA, and M. Buie (Southwest Research Institute). Photo No. STScI-PR10-06a|
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› Image with scale
› Full photomap
› View video of Pluto rotating (Credit: NASA, ESA, and M. Buie/Southwest Research Institute)
NASA today released the most detailed set of images ever taken of the distant
dwarf planet Pluto. The images taken by NASA's Hubble Space Telescope show an
icy and dark molasses-colored, mottled world that is undergoing seasonal changes
in its surface color and brightness. Pluto has become significantly redder,
while its illuminated northern hemisphere is getting brighter. These changes
are most likely consequences of surface ices sublimating 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. The dramatic change in color apparently
took place in a two-year period, from 2000 to 2002.
The Hubble images will remain our sharpest view of Pluto until NASA's New
Horizons probe is within six months of its Pluto flyby. The Hubble pictures are
proving invaluable for picking out the planet's most interesting-looking
hemisphere for the New Horizons spacecraft to swoop over when it flies by Pluto
Though Pluto is arguably one of the public's favorite planetary objects, it is
also the hardest of which to get a detailed portrait because the world is small
and very far away. Hubble resolves surface variations a few hundred miles
across, which are too coarse for understanding surface geology. But in terms of
surface color and brightness Hubble reveals a complex-looking and variegated
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 that is present on Pluto's surface, leaving behind a dark and red
When Hubble pictures taken in 1994 are compared with a new set of images taken
in 2002 to 2003, astronomers see evidence that the northern polar region has
gotten brighter, while the southern hemisphere has gotten darker. These changes
hint at very complex processes affecting the visible surface, and the new data
will be used in continued research.
The top picture was taken in 1994 by the European Space
Agency's Faint Object Camera. The bottom image was taken in
2002-2003 by the Advanced Camera for Surveys. The dark band
at the bottom of each map is the region that was hidden from view
at the time the data were taken. Credit: NASA, ESA, and M. Buie (Southwest Research Institute) Photo No. STScI-PR10-06b|
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The images are allowing planetary astronomers to better interpret more than
three decades of Pluto observations from other telescopes, says principal
investigator Marc Buie of the Southwest Research Institute in Boulder, Colo.
"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
The Hubble pictures underscore that Pluto is not simply a ball of ice and rock
but a dynamic world that undergoes dramatic atmospheric changes. These are
driven by seasonal changes that are as much propelled by the planet's 248-year
elliptical orbit as its axial tilt, unlike Earth where the tilt alone drives
seasons. The seasons are very asymmetric because of Pluto's 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 that the mass of the
atmosphere doubled over that time. This may be due to warming and sublimating
nitrogen ice. The new Hubble images from 2002 to 2003 are giving astronomers
essential clues about how the seasons on Pluto work and about the fate of its
The images, taken by the Advanced Camera for Surveys, are invaluable to planning
the details of the New Horizons flyby in 2015. New Horizons will pass by Pluto
so quickly that only one hemisphere will be photographed in the highest possible
detail. Particularly noticeable in the Hubble image 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," says
Buie. 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 will also help New Horizons scientists better calculate the
exposure time for each Pluto snapshot, which is important for taking the most
detailed pictures possible," says Buie. With no chance for re-exposures,
accurate models for the surface of Pluto are essential in preventing pictures
that are either under- or overexposed.
The Hubble images are a few pixels wide. But through a technique called
dithering, multiple, slightly offset pictures can be combined through
computer-image processing to synthesize a higher-resolution view than could be
seen in a single exposure. "This has taken four years and 20 computers operating
continuously and simultaneously to accomplish," says Buie, who developed special
algorithms to sharpen the Hubble data.
The Hubble research results appear in the March 2010 issue of the
Astronomical Journal. Buie's science team members are William Grundy of Lowell
Observatory in Flagstaff, Ariz., and Eliot Young, Leslie Young, and Alan Stern
of Southwest Research Institute in Boulder, Colo.
Buie plans to use Hubble's new Wide Field Camera 3 to make further Pluto
observations prior to the arrival of New Horizons.
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA's Goddard Space
Flight Center manages the telescope. The Space Telescope Science
Institute conducts Hubble science operations. The institute is operated
for NASA by the Association of Universities for Research in Astronomy,
Inc. in Washington, D.C.
› Additional background information about
Pluto from Southwest Research Institute