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THE TERRESTRIAL PLANETS

The terrestrial planets are similar in composition, but due to their respective orbits vary great in atmosphere and temperature. They also vary in size, although Earth and Venus are very close in size.

For more information on the terrestrial planets follow the links to the right.

QUICK FACTS
Mercury's diameter is 3,025 miles.

The diameter of Venus is 7,502 miles.

Earth's diameter is 7,909 miles.
The diameter of Mars is 4,212 miles.

Mercury consists of virtually no atmosphere.
The atmospheric pressure of Venus is 97 times that of Earth.

Earth's atmosphere is 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases.

Mars' atmosphere is primarily carbon dioxide (thin).

Mercury's temperature is 950° F, sunlit side; 210° F, dark side.

Venus' surface temperature is 900° F.

Earth's temperature ranges are hospitable to life.

The surface temperature on Mars ranges from about -120° F at night to -20° F in the afternoon.

Information and Images Courtesy NASA

WHAT ARE THE TERRESTRIAL PLANETS?

The four planets closest to the Sun—Mercury, Venus, Earth, and Mars—are called the terrestrial planets because they have solid rocky surfaces. Generally speaking they are small, rocky bodies (lots or materials made of the elements silicon, oxygen, aluminum, magnesium, sulfur and iron) with thin atmospheres.

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Mercury is only about one-third the size of the Earth. It is smaller than any other planet except Pluto. Mercury is very close to the Sun and has no substantial atmosphere. These factors contribute to the fact that the surface of Mercury has the greatest temperature range of any planet or natural satellite in our solar system.

Venus and Earth are similar in size, composition, and mass. They differ in that Venus does not have oceans or human life, and its temperature during the day reaches 484 degrees Celsius. The daytime temperature is so hot it could melt lead. The dense atmosphere is composed of carbon dioxide and sulfuric acid which acts as a greenhouse and traps the heat.

The amazing gaseous atmosphere of planet Earth is responsible for making life possible on this, the third planet from the Sun. Our atmosphere contains water vapor which helps to moderate our daily temperatures. Our atmosphere contains 21% oxygen, which is necessary for us to breathe, 78% nitrogen, and .9% argon.

Because the distance between the Sun and Mars varies, temperatures range from -125 degrees Celsius in the Martian winter to 22 degrees Celsius in the Martian summer. At the Martian poles are polar ice caps which shrink in size during the Martian spring and summer.