Download Meteors and Meteorites

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MAZER
Page 439
Most comets are too faint to be noticed easily from Earth. Many
years can go by between appearances of bright comets, such as the one
in the photograph on page 438.
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What makes a comet visible?
Meteors and Meteorites
Earth collides constantly with particles in space. Earth orbits
the Sun at about 100,000 kilometers per hour (70,000 mi/h),
so these particles enter Earth’s thin upper atmosphere at very
high speeds. The particles and the air around them become
hot enough to glow, producing brief streaks of light called
meteors . You may be able to see a few meteors per hour on a
clear, dark night. Several times during the year, Earth passes
through a stream of orbiting particles left by a comet. In the
resulting meteor shower, you can see many meteors per hour.
A meteor produced by a particle from a comet may last
less than a second. Bits of rock or metal from asteroids may
produce brighter, longer-lasting meteors. Rarely, a very bright
meteor, called a fireball, lights up the sky for several seconds.
An object with greater mass, perhaps 10 grams or more,
may not be destroyed by Earth’s atmosphere. A meteorite is
a space object that reaches Earth’s surface. The outside of a meteorite
is usually smooth from melting, but the inside may still be frozen. Most
meteorites come from the asteroid belt, but a few are rocky fragments
that have been blasted into space from the Moon and Mars.
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This piece of iron is part
of a huge meteorite. The
energy of the impact
melted the metal and
changed its shape.
What is the difference between a meteor and a meteorite?
KEY CONCEPTS
CRITICAL THINKING
1. How are Pluto and most
moons of the gas giant
planets similar? (8.4.e)
4. Apply Of the four types of
processes that shape terrestrial
worlds, which also shape the
surfaces of moons of
giant planets?
2. List two differences between
asteroids and comets. (8.4.e)
3. What causes meteors? (8.4.e)
CHALLENGE
6. Predict What do you think
Pluto would look like if its orbit
brought it close to the Sun?
5. Compare and Contrast
How is a comet different
from a meteor?
Chapter 13: Our Solar System 439
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