Page 37 - (DK) Eyewitness - Mars

DISAPPEARING ICE CAP
In winter, carbon dioxide in the Martian
atmosphere freezes, much of it joining the
North Polar cap, which grows larger. The
first image—October 1996 on Earth—is
early spring on Mars, with the cap at its
greatest. Warming temperatures melt the
cap, shown smaller in the late-spring middle
image, and smallest in summertime. The great
ring of dark sand dunes encircling the North
October 1996 January 1997 March 1997 Polar cap is now fully exposed.

CLIFFS OF SOLID ICE
This three-dimensional
representation of the North
Polar cap appears like a great
island of icy cliffs. The image was
constructed by combining Viking
orbiter photographs with
topographic data from Mars
Global Surveyor’s Laser Altimeter.

Layers of ice, patterns of snow

The surface of the North Polar cap resembles a sponge, while
the South Polar cap has large troughs and broad mesas. This
indicates the poles have very different climates. The northern
cap is warmer because it tilts sunward when Mars’s elliptical
orbit takes the planet closest to the Sun. In summer, the colder
southern cap melts less than does the northern cap.

ICE STACKED IN LAYERS
Mars has ice-bound soil and dust
DESIGNS IN SNOW ON MARS as deep as 10,000 feet (3.1 km).
Martian snow patterns take on bizarre forms, and scientists often nickname Some layers on this outcrop at the
them. The left image, from the North Polar region, is “Kitchen Sponge” North Polar cap are 30–100 feet
because of its closely spaced pits, which are about 5.5 feet (1.7 m) deep. The (9–30 m) thick. A single layer
wiggly designs, termed “fingerprints,” are curved troughs on the South Polar 33 feet (10 m) thick would take
cap. The next pattern, also from the south, is “Swiss Cheese.” 100,000 years to accumulate.

FUTURISTIC EXPLORATION
This painting by a space scientist shows
future astronauts using equipment to drill
into polar ice. These researchers take core
samples to study the different layers. In
this same way, tree rings, ice cores, and
sea-bottom cores are analyzed on Earth.
Core samples help scientists learn about
changes in a planet’s climate over great
time periods.

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