Destination Mars
Mars. The Red Planet. If interplanetary travel is your cup of tea,
Mars is probably your best bet. Venus is closer, but its blistering
surface temperature and crushing atmospheric pressure make it a poor
prospect for tourism.
A Distant Desert
Though it is generally colder than most
places on Earth, Mars offers a desert experience, punctuated by
majestic mountains, many of them of volcanic origin, and dramatic
valleys that make the Grand Canyon look like a humble ditch.
The distance between Mars and Earth varies as these two neighbors
orbit the Sun. They can be as distant as 400 million kilometers (250
million miles) or as close as 57 million kilometers (35 million miles).
Even at its closest, though, no one would
say Mars is a stone's throw away. Your trip to Mars, following an
elliptical orbit and traveling at an average cruising speed of 80,000
kilometers per hour (50,000 miles per hour), should take between 7 and
10 months.
The Canyonlands
The best word to describe the Martian
landscape is "awesome." The valleys are deeper and the mountains are
higher than anything you'll find on Earth. The Mariner Valleys (Valles Marineris) cut a 4,000 kilometer (2,500 mile) long scar just south of the Martian equator.
Named after Mariner 4, the American spacecraft that was the first to
take close up pictures of Mars when it flew by in 1965, the Mariner
Valleys are really a system of canyons almost ten times longer than the
Grand Canyon and twice as deep. These canyonlands are works in
progress, holding the history of the planet within their steep walls.
The huge rift probably started out as a long crack in the surface as
forces within the planet's interior stretched the Martian crust. Fierce
winds carrying dust and sand
have carved out the valleys over billions of years, and rockslides have
shifted the landscape, filling in some places and leaving sharp cliffs
in others.
In Search of Water
Giovanni Schiaparelli, a nineteenth-century
Italian astronomer who studied Mars through a telescope, interpreted
dark areas of the planet as seas. He called them maria, the plural form of mare,
the Latin word for "sea." But don't expect to find bodies of water of
any size on the planet today. Although scientists have evidence there
was once liquid water on Mars, not a drop can be found on the surface
now. The atmosphere is too thin to permit surface water to exist in a
liquid state.
The Viking spacecraft observed many features on Mars that look like
dry riverbeds, with meandering banks. There are also "islands" shaped
like tear drops, perhaps formed by giant floods long ago on Mars.
Windy Weather
Although it is frequently overcast on Mars,
the clouds do not hold much water. One type of gloomy weather can last
for weeks during the summer and fall. That's when cyclones sweep out
from the poles, churning up the fine rust-colored dust on the surface
and producing yellowish clouds that sometimes cover the entire planet.
At other times, wispy white morning clouds drift over the landscape,
then disappear as the day grows warmer. This "Martian mist" consists of
crystals of frozen carbon dioxide, otherwise known as "dry ice."
From Pole to Pole
A trip to the poles should be on any
visitor's list. As on Earth, the warmest temperatures in the northern
hemisphere occur during the summer months, when the north pole tilts
toward the sun. During those months, it is winter in the southern
hemisphere. The biggest seasonal change takes place at the poles, where
the vast ice caps shrink and expand with the passage of months. There's
another reason to go in summer, though. You might see the water ice
uncovered as the layer of dry ice
above it evaporates.
If it is true that Mars was once a warmer place, this water ice may
be the remnant of a time, perhaps as long as 4 billion years ago, when
Mars was a watery planet and living things may have thrived.
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