Philips Atlas of the Universe

The Surface of Pluto

ATLAS OF THE UNIVERSE

T

he Hubble Space Telescope has allowed astronomers to

view the surface of Pluto as never before. Pluto had

always appeared as nothing more than a dot of light in

even the largest Earth-based telescopes because its disk

is much smaller than can be resolved from beneath the

Earth’s atmosphere.

Hubble imaged nearly the entire surface of Pluto, as it

rotated through its 6.4-day period, in late June and early

July 1994. These images, which were made in blue light,

show that Pluto is an unusually complex object, with more

large-scale contrast than any planet, except Earth. Pluto

itself probably shows even more contrast and perhaps

sharper boundaries between light and dark areas than is

shown in the images here, but Hubble’s resolution tends to

blur edges and blend together small features sitting inside

larger ones.

Pluto from Hubble. The

two smaller inset pictures

at the top are actual images

from Hubble (north at top).

Each square pixel is more

than 160 km (100 miles)

across. At this resolution,

Hubble discerns roughly

12 major ‘regions’ where

the surface is either bright

or dark. The larger images

(below) are from a global

map constructed through

computer image-processing

performed on the Hubble

data. The tile pattern is

an artefact of the image

enhancement technique.

Opposite hemispheres

of Pluto are seen in these

two views. Some of the

variations across Pluto’s

surface may be caused by

topographic features such

as basins, or fresh impact

craters. However, most of

the surface features unveiled

by Hubble, including the

prominent northern polar

cap, are likely produced

by the complex distribution

of frosts that migrate across

Pluto’s surface with its

orbital and seasonal cycles

and chemical byproducts

deposited out of Pluto’s

nitrogen–methane

atmosphere.

Map of Pluto’s surface,

assembled by computer

image-processing software

from four separate images

of Pluto’s disk taken with the

European Space Agency’s

(ESA) Faint Object Camera

(FOC) aboard the Hubble

Space Telescope. Hubble

imaged nearly the entire

surface, as Pluto rotated on

its axis in late June and early

July 1994. The map, which

covers 85 per cent of the

planet’s surface, confirms

that Pluto has a dark

equatorial belt and bright

polar caps, as inferred from

ground-based light curves

obtained during the mutual

eclipses that occurred

between Pluto and its

satellite Charon in the

late 1980s. The brightness

variations in this may be

due to topographic features

such as basins and fresh

impact craters. The black

strip across the bottom

corresponds to the region

surrounding Pluto’s south

pole, which was pointed

away from Earth when

the observations were

made, and could not

be imaged.

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