Download Meteors and Meteorites

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 680.
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 meteorss. 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.
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?
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.
3. What causes meteors?
This piece of iron is part
of a huge meteorite. The
energy of the impact
melted the metal and
changed its shape.
VOCABULARY
When it is still in space, a
meteorite is called a
meteoroid.
• meteoroid: in space
• meteor: streak of light
in atmosphere
• meteorite: on Earth’s
surface
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 19: Our Solar System 681