Exploring The Planets: Mars

Mars is the fourth planet from the sun and the second-smallest planet in our solar system. It appears bright and reddish in thenight sky. Photo from: NASA/JPL/MSSS.

Mars is the fourth planet from the sun and Earth’s outer neighbor. This planet travels aroundthe sun from an average distance of about 142 million miles. It has two small, rocky moons,Phobos and Deimos.Easily visible from Earth with the naked eye, Mars has intrigued stargazers since ancienttimes. It often appears quite bright and reddish in the night sky. Babylonians mentioned Marsin records from about 3,000 years ago, associating the blood-red planet with their god ofdeath and disease. The name Mars is that of the ancient Roman god of war.For centuries, people have wondered whether there is life on Mars. Studies have shown thatthere are no obvious signs of life on the planet. However, scientists are still trying to find out ifvery tiny, simple life-forms may have ever existed on Mars.

By Encyclopaedia Britannica, adapted by Newsela staff on 08.25.17 Word Count 688 Level MAX

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Physical Features

The orbit of Mars lies between Earth’s orbit and the main asteroid belt. Jupiter, which liesbeyond the belt, is its very distant outer planetary neighbor. Mars is the outermost of the fourinner planets of the solar system, which are Mercury, Venus, Earth and Mars. The innerplanets are also called the terrestrial, or Earth-like, planets. All four are dense, rocky worldswith solid surfaces and few or no moons.

Mars is the second-smallest planet in the solar system, after Mercury. Its diameter, or distancethrough its center, is about 4,224 miles, which is about half the size of Earth’s diameter. Marshas layers like Earth’s. These layers consist of a metal core, a thick, rocky middle and a crust.The surface of Mars consists of rock and dust, and many large dust storms sweep across it.Parts of the planet have many pits called craters. The landscape includes plains, deep valleysand high mountains.The atmosphere, or layer of gases, surrounding Mars is thin. It does not trap heat well. Thetemperature at the surface of Mars is about −28 degrees Fahrenheit in the afternoon, but itcools to about −118 degrees Fahrenheit before dawn.

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Water is rare in the solar system, except on Earth. Water exists on Mars as ice caps at itsnorth and south poles, and as patches of ice beneath its surface. Small amounts of water arealso found as a gas in the air. Some evidence suggests that in the past Mars had some liquidwater on its surface. For example, Mars has hundreds of channels that look like dried-upriverbeds. Some scientists think Mars was once a warm planet with large seas.

Orbit And Spin

Like all planets, Mars has two types of motion: orbit and spin. Mars orbits, or travels around,the sun. It completes one orbit every 687 Earth days. In other words, a year on Mars lasts 687Earth days. Mars spins about its center at nearly the same rate as Earth does. Mars takes about 24.6hours to complete one rotation, so a Mars day lasts about as long as an Earth day.

Observations And Exploration

Since 1964, many unmanned spacecraft have collected information about Mars. The UnitedStates and the Soviet Union each sent several spacecraft to Mars from the 1960s to the1980s. Some of them flew past Mars or orbited around it. Other spacecraft, including the U.S.Viking crafts, successfully landed on Mars.

Since the 1990s, the United States and Europe have sent several spacecraft to orbit theplanet. They include the U.S. Mars Global Surveyor and Odyssey and Europe’s Mars Express.

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The U.S. spacecraft Pathfinder landed on Mars in the 1990s. It released a robot called a roveron the surface. The United States sent two more rovers, called Spirit and Opportunity, to theplanet in 2003. In 2012, a fourth rover, called Curiosity, landed on Mars as well. The roversmoved around on the surface and performed experiments there.

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Exploring The Planets: MarsPhysical FeaturesOrbit And SpinObservations And Exploration