Mercury is the smallest planet in the solar system. It is the planet closest to the sun. This gives it the shortest and fastest orbit around the sun. The planet obtains its name from Mercury, the fleet-footed Roman messenger god. The planet has no satellites.

Mercury (photo: NASA).

Photo: Mercury is the smallest planet and closest to the sun (NASA).

Facts About Mercury

Distance from the sun: 69.8 million kilometers (aphelion), 46 million kilometers (perihelion).

Size:  radius of 2.4 thousand kilometers.

Mass:  5% that of earth.

Gravity:  38% that of earth.

Satellites: none.

Rotation:  58.6 days (length of a day).

Revolution:  87.9 days (time to orbit the sun).

Surface Temperatures: 80-700 °K

Surface of Mercury

The surface of the planet is covered with impact craters and large plains. The craters were caused by the impact of meteors on the planet’s surface. As a result, the surface of the planet resembles the Earth’s moon. The largest of these craters is the Caloris Basin which is over 1500 kilometers in diameter.

The planet has very little atmosphere. During the day, temperatures may rise to 450° Celsius. At night, temperatures drop to as low as -170°Celsius. Despite the high temperatures during the day, the polar regions are thought to have water in the form of ice.

Mercury is still geologically active. The planet’s core is cooling and shrinking. This causes the warping of the planet’s surface. The warping results in the formation of large scarps. A scarp is a very steep bank or slope.

Vocabulary Building

The following is a recommended list of words and their definitions for students.

core: the central part of a planet.

scarp: a very steep bank or slope.

surface: the outer or uppermost layer of an object, such as the surface of the planet.

Improving Your Reading and Thinking Skills

Think for a few moments. Try to recall the major ideas in this article. Try to answer the following questions to improve your reading comprehension.

•  Where is Mercury located in the solar system?

•  Describe the changes surface temperatures of the planet from day to night.

•  Why is the planet still geologically active?.



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13 comments on "Mercury: Small but Really Hot Stuff"

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Webster Gabiana

Ang mga planeta at mayroon silang kahit ibat-ibang mga tempreatura.

Webster Gabiana

The temperature to day is that it rise about 450 Celsius. At the night the temperature drops low as 170 Celsius.


mercury is the smallest planet in the solar system

Webster Gabiana

Mercury at matatangupan sa unang planeta sa solar system.

Webster Gabiana

Mercury is located in the frist planet on the solar system.