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7.9A: Characteristics of the Solar System
Earth and Space
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Name: ____________________________________
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Life on Earth
Lexile 1060L
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Earth is the third planet from the
Sun. It is the only planet in the solar
system to have just the right
conditions for life as we know it to
exist. The conditions such as the
distance from the Sun, the presence
of an atmosphere and magnetic
field, and the existence of water
make Earth a one-of-a-kind planet.
Located 93 million miles away from
the Sun, Earth is in the ideal place in
the solar system to have perfect
temperatures to support life. If Earth were any closer to the Sun, the temperatures
would rise. The same would be true if Earth were positioned too far away from the
Sun. Average temperatures would be too cold to support life as we know it on
Earth.
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Another unique condition that allows life to thrive on Earth is the presence and
composition of the atmosphere. In order for a planet to have an atmosphere, there
has to be a gravitational force strong enough to hold it there. Not all planets in
the solar system have atmospheres, especially one that can support life. The
atmosphere, all of the air and gases that surround Earth, rises 600 kilometers
above Earth into space. This mixture of air and gas is composed of 78% nitrogen,
21% oxygen, and 1% argon and carbon dioxide. The presence of these gases in
these amounts not only helps to keep the temperature stable and cool, but it
also provides us with the oxygen that most life forms need.
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Rice University – All Rights Reserved
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Reading Science!
7.9A: Characteristics of the Solar System
Earth and Space
4 Extending just outside of the atmosphere is another interesting feature
that allows life to survive on Earth: its magnetic field. Earth’s magnetic
field can be thought of as a giant protective bubble that shields Earth
from harmful solar particles that stream from the Sun. Life would not be
possible without this protection.
5 The fourth and last characteristic that allows life to exist on Earth is the
presence of water. Water is a necessity for all living things. Earth is the
only planet in the solar system that possesses liquid water. In fact, three
fourths of Earth is covered in water. Just like the atmosphere helps keep
the temperatures on Earth stable, so do the oceans. Here water can exist
in all three states of matter; it can be a solid in the form of ice, a liquid in
the form of water, or a gas in the form of water vapor.
6 With the combinations of the location of Earth, the presence of an
atmosphere and magnetic field, and the availability of liquid water,
conditions for life are exactly perfect. Earth is the most interesting and
unique planet in the solar system.
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Rice University – All Rights Reserved
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B
C
D
© 2011
Earth and Space
What would happen if Earth was
located farther away from the Sun
than 93 million miles?
A
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7.9A: Characteristics of the Solar System
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The conditions on Earth would
be suitable for life because the
temperatures would not
change.
The conditions on Earth would
be too cold to support life as we
know it on Earth.
The conditions on Earth would
be exactly the same.
Earth’s magnetic field is important to
the survival of life. Why?
A
The magnetic field shields Earth
from harmful particles that
stream from the Sun.
B
The magnetic field is a bubble
around Earth.
C
The magnetic field holds in all
the oxygen, nitrogen, argon,
and carbon dioxide.
D
The magnetic field is only
imaginary and it is not really
doing anything for the survival
of life on Earth.
The conditions on Earth would
not be suitable for life because
the temperatures would be too
high.
The atmosphere is composed of what
elements?
A
78% oxygen, 21% nitrogen, and
1% argon and carbon dioxide
B
78% nitrogen, 21% carbon
dioxide, and 1% oxygen and
argon
C
78% argon, 21% oxygen, and 1%
nitrogen and carbon dioxide
D
78% nitrogen, 21% oxygen, and
1% argon and carbon dioxide
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Something interesting about water
on Earth is that it can exist in all
three states of matter. What are
these forms?
A
Ice, rain, and water
B
Ice, water, and water vapor
C
Ice, oxygen, and hydrogen
D
Water vapor, carbon dioxide,
and ice
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© 2011
7.9A: Characteristics of the Solar System
Earth and Space
What favorable characteristics does
the atmosphere provide that enable
life to thrive on Earth?
A
The atmosphere contains
oxygen and it helps keep
temperatures stable.
B
The atmosphere is held in place
by gravity and rises 600
kilometers above Earth into
space.
C
The atmosphere is held in place
by gravity and has a
magnetosphere.
D
The atmosphere allows for the
existence of water in all three
states of matter.
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