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- Mars, named after the Roman god of war, has been
documented
since ancient times. Its reddish color has intrigued mankind
throughout
the ages, often shining as the third brightest object in the
night sky
after the Moon and Venus.
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- But, with the exception of a
few geographic features
detected by telescope and the discovery of two
small moons, relatively
little was known about the Red Planet prior to
the dawn of the "Space
Age."
-
- Four decades of robotic
international exploration of
Mars has yielded much information,
hopefully in preparation for a future
human expedition there.
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- Physical
Characteristics
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- Mars has an average diameter of 4,217 miles. This is
about half the size of Earth, and about twice the size of Earth's moon.
Despite its small size, Mars has approximately the same land area as
Earth,
primarily due to an absence of liquid water on its
surface.
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- The mass of Mars is about 10 percent that of Earth, and
its
gravity is about 38 percent as strong as our planet. The density of
martian land is 3.9 times greater than liquid water -- on Earth, land
density
is 5.5 times greater. Mars has no detectable magnetic
field.
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- Orbit
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- Mars is the fourth planet in the solar system, counting
outward from the sun. It is located between the Earth and Jupiter, and
is about 1.5 times farther away from the sun than Earth. The martian orbit
around the sun is elliptical and varies in distance from a maximum of
154.8
million miles to a minimum of 128.4 million miles.
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- It takes Mars 687
Earth-days to complete one revolution
around the sun. A martian day, or
period of rotation, is comparable to
24 hours, 37 minutes, 23 seconds
on Earth. The planet's poles are tilted
on an axis of 25 degrees,
which creates martian seasons similar to those
on Earth.
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- Environment
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- The martian atmosphere is
composed of 95.3 percent carbon
dioxide, 2.7 percent nitrogen and 1.6
percent argon. This would be sufficient
to suffocate a human in a
matter of minutes. The atmospheric pressure there
is about 1 percent
that of Earth's. Surface winds have been measured to
a maximum of 80
m.p.h. -- comparable to hurricane force on Earth.
-
- Dust storms occur frequently on
Mars. These can be local,
regional or can cover the entire planet. Dust
can reach as high as six
miles above the surface and settles very
slowly.
-
- Surface temperatures average -64 degrees Fahrenheit,
measured
from a minimum -199 degrees Fahrenheit during polar night to a
maximum
+80 degrees Fahrenheit at the martian equator.
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- Geography
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- The highest point on Mars is the Olympus Mons, a large
shield volcano about 16 miles high and 370 miles across. This surface
feature
covers about the same area as the state of Arizona. The martian
canyon
system of Valles Marineris is the largest and deepest in the
solar system.
It runs more than 2,500 miles and has plateaus that
extend upward from
the canyons to altitudes of three to six
miles.
-
- Martian "canals" were documented by astronomers
over
100 years ago, and were believed to have been constructed by living
creatures. These are believed to be large channels cut by ancient
rivers.
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- Moons
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- Mars has two moons, Phobos (Fear) and Deimos (Terror).
Each was named for a particular attribute assigned to sons of the Greek
god of war. Phobos has an average diameter of about ten miles and orbits
at a distance of 5,850 miles from Mars. Deimos has an average diameter
of about five miles, orbiting the Red Planet at a distance of 14,600
miles.
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