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Hubble's Close Encounter with Mars
NASA's Hubble Space Telescope took this close-up
of the red planet Mars when it was just 34,648,840 miles
(55,760,220 km) away. This color image was assembled from a
series of exposures taken between 6:20 p.m. and 7:12 p.m. EDT
Aug. 26 with Hubble's Wide Field and Planetary Camera 2. The
picture was taken just 11 hours before the planet made its
closest approach to Earth in 60,000 years.
Many small, dark, circular impact craters can be seen, attesting
to the Hubble telescope's ability to reveal fine detail on the
planet's surface. One of the most striking is the 270-mile-
(450-km-) diameter Huygens crater, seen near the centerof the
image.
The two dominant dark swatches seen on this part of the planet
are classical regions labeled by early Mars observers. The
"shark-fin" shape to the right is Syrtis Major. The
horizontal lane to the left is Sinus Meridani. One of NASA's Mars
Exploration Rovers, named "Opportunity," will land at
the western end of this region in January 2004.
The picture shows that it is a relatively warm summer on Mars, as
evident in the lack of water-ice clouds at mid-latitude, and the
receding southern polar cap. Ice on the rugged topography gives a
somewhat ragged, scalloped look. Up north, at the top of the disk
where it is Martian winter, a frigid polar hood of clouds covers
the northern polar cap and surrounding region.
Even in the relatively balmy Southern Hemisphere, daytime highs
are just above freezing in the Hellas impact basin, the circular
feature near the image center. Hellas is nearly 5 miles deep (8
km). Hellas is like Death Valley – except that Mars is much
drier than even Death Valley. Having a diameter of 1,100 miles
(1,760 km), Hellas was formed when an asteroid slammed into Mars
billions of years ago. Many summer dust storms originate in this
basin, though it is remarkably clear of dust in this Hubble
image.
Mars and Earth have 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 will be much closer during this year's close
approach, the planet appears 23 percent bigger in the sky.
This photograph is a color composite generated from observations
taken with blue, green, and red filters. The resolution is 8
miles (12 km) per pixel.