Download 6.8 Part III The Solar System

SOL 6.8 / Earth/Space Systems Part 3
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The Solar System: The Planets
The planet closest to the sun is Mercury. Not much larger than Earth’s moon, Mercury
has a very thin atmosphere and extreme surface temperatures. Daytime highs can reach
425°C while nighttime temperatures plunge to -170°C. Mercury has no moons.
The second planet from the sun is Venus. Venus is similar to the Earth in size and has a
thick atmosphere of carbon dioxide. It is always cloudy on Venus. Due to the greenhouse
effect, Venus is the hottest planet in the solar system with temperatures reaching over
460°C. Like Mercury, Venus has no moons.
Earth, is one of the small, rocky planets in our solar system and is the third planet from
the sun. Scientific evidence indicates that the Earth is about 4.5 billion years old. It is
made up of active layers of rock and is covered by large areas of land called continents
and large bodies of liquid water called oceans. Frozen ice caps are located in its polar
regions. Earth also has a protective atmosphere composed of predominately nitrogen and
oxygen. This atmosphere, along with a natural magnetic field, helps to shield the Earth’s
surface from harmful solar radiation. With its oxygen-rich atmosphere and lifesupporting water, scientists believe that Earth is the only planet that is home to living
organisms. Earth has one moon.
Mars is the fourth planet from the sun and about half the diameter of Earth. Due to its
increased distance from the sun and its thin atmosphere, Mars is a very cold planet with
temperatures ranging from 37°C to -123°C. Mars has two very small moons.
© 2006
SOL 6.8 / Earth/Space Systems Part 3
Page 2
The Solar System: The Planets
(continued)
Jupiter is the fifth planet from the sun. Jupiter is the largest planet in the solar system
and is 300 times more massive than the Earth. Unlike the rocky inner planets, Jupiter is a
giant ball of liquid hydrogen and helium with a temperature of -153°C. It is one of the
four outer planets called gas giants. Four larger moons and a number of smaller moons
orbit it.
Saturn is the sixth planet from the sun. Saturn is another gas giant with temperatures
plunging below -185°C. It is slightly smaller than Jupiter and is mainly composed of
hydrogen and helium. Saturn has 5 large moons, a number of smaller moons, and a huge
system of rings encircling it. Saturn’s rings consist of chunks of ice and rock.
Uranus is the seventh planet from the sun. It is a gas giant made up mostly of hydrogen
and methane. Smaller than the other gas giants, Uranus is only four times the diameter of
Earth. It is two times farther from the sun than Saturn and temperatures on Uranus stay
around -214°C. It also has five large moons, a number of smaller moons, and ten thin
rings.
Neptune is the eighth planet from the sun and the last of the gas giants. It is composed of
hydrogen, helium, and methane and has a temperature of -225°C. Neptune is a little
smaller than Uranus and has more than ten moons in orbit around it. One of Neptune’s
moons, Triton, is the largest moon in the solar system.
© 2006
SOL 6.8 / Earth/Space Systems Part 3
Page 3
The Solar System: The Planets
(continued)
The solar system is so vast; it is difficult for us to imagine the great distances between the
planets and the sun. In order to visualize very small objects like atoms, or very large
objects like our solar system, we need to use models or scaled drawings. A scale is a
ratio between two distances. On a road map of your county, town, or city, the ratio or
scale might be: 1 centimeter = 5 kilometers. For us to create a scale map of something as
large as our solar system, 1 cm will have to equal millions of kilometers. The following
chart will help us understand the relative positions of the planets from the sun. Can you
use this chart to make a model or scaled drawing of our solar system?
Planets
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Scaled Distance (cm)
2
4
5
8
26
47
95
150
196
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Actual Distance (km)
58,000,000
108,000,000
150,000,000
228,000,000
778,000,000
1,427,000,000
2,869,000,000
4,505,000,000
5,890,000,000