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The red planet Mars has inspired
wild flights of imagination over the centuries, as well
as intense scientific interest. Whether fancied to be
the source of hostile invaders of Earth, the home of
a dying civilization, or a rough-and-tumble mining colony
of the future, Mars provides fertile ground for science
fiction writers, based on seeds planted by centuries
of scientific observations.
We know that Mars
is a small rocky body once thought to be very Earth-like.
Like the other "terrestrial" planets - Mercury,
Venus, and Earth
- its surface has been changed by volcanism, impacts
from other bodies, movements of its crust, and atmospheric
effects such as dust storms. It has polar ice caps that
grow and recede with the change of seasons; areas of
layered soils near the Martian poles suggest that the
planet's climate has changed more than once, perhaps
caused by a regular change in the planet's orbit. Martian
tectonism - the formation and change of a planet's crust
- differs from Earth's. Where Earth tectonics involve
sliding plates that grind against each other or spread
apart in the seafloors, Martian tectonics seem to be
vertical, with hot lava pushing upwards through the
crust to the surface. Periodically, great dust storms
engulf the entire planet. The effects of these storms
are dramatic, including giant dunes, wind streaks, and
wind-carved features.
Scientists believe that 3.5 billion years
ago, Mars experienced the largest known floods in the
solar system. This water may even have pooled into lakes
or shallow oceans. But where did the ancient flood water
come from, how long did it last, and where did it go?
In May 2002, scientists announced the
discovery of a key piece in the puzzle: the Mars Odyssey
spacecraft had detected larged quantities of water ice
close to the surface - enough to fill Lake Michigan
twice over. The ice is mixed into the soil only a meter
(about 3 feet) below the surface of a wide area near
the Martian south pole.
Many questions remain. At present, Mars
is too cold and its atmosphere is too thin to allow
liquid water to exist at the surface for long. More
water exists frozen in the polar ice caps, and enough
water exists to form ice clouds, but the quantity of
water required to carve Mars' great channels and flood
plains is not evident on - or near - the surface today.
Images from NASA's Mars Global Surveyor spacecraft suggest
that underground reserves of water may break through
the surface as springs. The answers may lie deep beneath
Mars' red soil.
Unraveling the story of water on Mars
is important to unlocking its past climate history,
which will help us understand the evolution of all planets,
including our own. Water is also believed to be a central
ingredient for the initiation of life; the evidence
of past or present water on Mars is expected to hold
clues about past or present life on Mars, as well as
the potential for life elsewhere in the universe. And,
before humans can safely go to Mars, we need to know
much more about the planet's environment, including
the availability of resources such as water.
Mars has some remarkable geological characteristics,
including the largest volcanic mountain in the solar
system, Olympus Mons (27 km high and 600 km across);
volcanoes in the northern Tharsis region that are so
huge they deform the planet's roundness; and a gigantic
equatorial rift valley, the Valles Marineris. This canyon
system stretches a distance equivalent to the distance
from New York to Los Angeles; Arizona's Grand Canyon
could easily fit into one of the side canyons of this
great chasm.
Mars also has two small moons, Phobos
and Deimos. Although no one knows how they formed, they
may be asteroids snared
by Mars' gravity.
Related Links
More on Mars:
Education and Activities
Images, Movies and Animation
Source: NASA
Last Updated : 08.20.2003
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Distance from the Sun:
(Semimajor axis of orbit)
227,936,640 km
1.52366231 A.U.
Radius:
3,397 km
(0.5326 of Earth's radius)
Volume:
0.149 (Earth = 1)
Mass:
0.64191 x 1027 g
Density:
3.94 gm/cm3
Surface Gravity:
371 cm/s2
Escape Velocity:
5.02 km/s
Sidereal Rotation Period:
1.02595675 days
Sidereal Orbit Period:
1.8808476 sidereal years
Mean Orbit Velocity:
24.1309 km/s
Orbit Eccentricity:
0.09341233
Orbit Inclination:
1.85061 degrees
Equatorial Inclination:
25.19 degrees
Mean Surface Temperature:
186 to 268 K
Major Atmospheric Constituents:
CO2, N2, Ar
Natural Satellites:
1. Phobos
2. Deimos
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