Page 18 - (DK) Eyewitness - Mars
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Mantle of
silicate rock Mars in the Solar System
The heart of our Solar System is the Sun, a star also known as
“Sol.” The fiery Sun is the greatest body in the Solar System, 110
times larger than Earth, 200 times larger than Mars. The gravity, or
attraction-power, of the Sun controls the movements of nine major
Rock crust Small, probably
solid iron core planets—the term for bodies that orbit around a star. There are also
COMPOSITION OF MARS thousands of smaller bodies in the Solar System, all orbiting the
Like Earth, Mars is covered by an Sun. These include asteroids, comets, and meteoroids. In order, the
outer crust. Mars may have
frozen water-ice below the crust’s four planets nearest the Sun, the “inner planets,” are Mercury, Venus,
surface. Next is the solid, rock-
hard mantle, composed of Earth, and Mars. Next comes the Asteroid Belt, a great ring of small
silicate. The core of the planet is “planetoids” of varying sizes. The fifth planet is Jupiter, the largest,
made of an iron-rich material
that is denser than the mantle. followed by Saturn, second largest, then come Uranus, Neptune, and
Pluto, the smallest planet.
Mars is rocky
and cratered
Vital Statistics
Light areas are
covered with dust
Diameter 4,220 miles (6,794 km)
Average distance from sun 141.6 million miles (227.9 million km)
Dark areas could Orbital speed around Sun 15 miles/sec (24.1 km/sec)
be exposed rock
Sunrise to sunrise 24 hours, 39 minutes (a solar day)
Mass (Earth = 1) 0.11
Volume (Earth = 1) 0.15
Average density (water = 1) 3.93
Surface gravity (Earth = 1) 0.38
Average surface temperature -81.4°F (-63°C)
Number of moons 2
Axis tilts from the Orbits Sun
vertical by 25.2° in 687 days
Spins on its axis
once every 24
hours and 39 minutes
AXIS AND ROTATION
Mars spins on an axis tilted about 25 degrees,
rotating counterclockwise. One rotation is a
Martian day, called a “sol.” One sol is 24 hours
and 39 minutes. A Martian year has 669 sols.
“FOURTH ROCK” FROM THE SUN
The four worlds nearest the Sun are termed
“terrestrial” planets because they resemble
Earth. Mars is one and a half times farther than
the Earth from the Sun. Though much colder and
drier, and lacking breathable oxygen, Mars is the
planet most like Earth.
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