(See description below)
Hubble's Closest View of Mars
NASA's Hubble Space Telescope snapped this
portrait of Mars within minutes of the planet's closest approach
to Earth in nearly 60,000 years. This image was made from a
series of exposures taken between 5:35 a.m. and 6:20 a.m. EDT
Aug. 27 with Hubble's Wide Field and Planetary Camera 2. In this
picture, the red planet is 34,647,420 miles (55,757,930 km) from
Earth.
This sharp, natural-color view of Mars reveals several prominent
Martian features, including the largest volcano in the solar
system, Olympus Mons; a system of canyons called Valles
Marineris; an immense dark marking called Solis Lacus; and the
southern polar ice cap.
Olympus Mons [the oval-shaped feature just above center] is the
size of Arizona and three times higher than Mount Everest. The
dormant volcano resides in a region called the Tharsis Bulge,
which is about the size of the U.S. and home to several extinct
volcanoes. The three Tharsis Montes volcanoes are lined up just
below Olympus Mons. Faint clouds are hovering over Arsia Mons,
the southernmost of these volcanoes.
The long, dark scar, below and to the right of the Tharsis Bulge,
is Valles Marineris, a 2,480-mile (4,000-km) system of canyons.
Just below Valles Marineris is Solis Lacus, also known as the
"Eye of Mars." The dark features to the left of Solis
Lacus are the southern highlands, called Terra Sirenum, a region
riddled with impact craters. The diameters of these craters range
from 31 to 124 miles (50 to 200 km).
The image was taken during the middle of summer in the Southern
Hemisphere. During this season the Sun shines continuously on the
southern polar ice cap, causing the cap to shrink in size [bottom
of image]. The orange streaks are indications of dust activity
over the polar cap. The cap is made of carbon dioxide ice and
water ice, but only carbon dioxide ice is seen in this image. The
water ice is buried beneath the carbon dioxide ice. It will only
be revealed when the cap recedes even more over the next two
months. By contrast, the Northern Hemisphere is in the midst of
winter. A wave of clouds covers the northern polar ice cap and
the surrounding region [top of image].
This view of Mars reveals a striking contrast between the
Northern and Southern hemispheres. The Northern Hemisphere is
home to volcanoes that may have been active about 1 billion years
ago. These volcanoes resurfaced the north's landscape, perhaps
filling in many impact craters. The Southern Hemisphere is
pockmarked with ancient impact craters, which appear dark because
many are filled with coarser sand-sized particles.
Mars and Earth make a "close encounter" about every 26
months. These periodic encounters are due to the differences in
the two planets' orbits. Earth goes around the Sun twice as fast
as Mars, lapping the red planet about every two years. Both
planets have elliptical orbits, so their close encounters are not
always at the same distance. In its close encounter with Earth in
2001, for example, Mars was about 9 million miles farther away.
Because Mars was much closer during this year's rendezvous, the
planet will appeared 23 percent larger in the sky. Mars will not
be this close again until 2287.
This photograph is a color composite generated from observations
taken with blue, green, and red filters. A total of 11 filters,
spanning a wide wavelength range—-from blue to near
infrared—-were used during the observations. The shorter
wavelengths show clouds and other atmospheric changes. The longer
wavelengths, including the near infrared, reveal Martian surface
features.