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Mars as depicted in Danny Phantom. Comet Encke is in the foreground. The Valles Marineris is faintly visible.

Mars is the fourth planet from the Sun, orbiting it at a distance of 228 million kilometers. Mars is 78.3 million times further away from Earth. It is sometimes called the 'Red Planet' because of its red soil. The soil on Mars is red because it contains iron oxide (rust). It has two moons, called Phobos and Deimos. Phobos is 22 kilometers in diameter while Deimos is 5 kilometers wide. A year on Mars is 687 days long; a day on Mars is 24,5 hours long.


Mars was named after the Roman god of war. The two moons of Mars, Phobos and Deimos, are named after the sons of Ares, the Icons-flag-gr.png Greek god of war. In eastern Asian cultures, Mars was referred to as the "fire star" (火星 kasei), due to its red coloration.[1]

Physical Properties

Mars is 6,779 kilometers in diameter and is half the diameter of the Earth, having a surface area only slightly less than the total area of Earth's dry land.[2] The thin air on Mars makes it a dangerous place for humans, as it is mostly poisonous carbon dioxide. Recently, scientists found lots of frozen water (scientists say water ice) just under the surface of Mars. This means astronauts who may visit Mars in the future will have plenty of water - enough to fill Lake Michigan twice. Mars has a smaller density than Earth, having around 15% of Earth's volume and 11% of the Earth's mass, resulting in Mars's gravity level being about 38% of Earth's surface gravity. The red-orange appearance of Mars's crust is caused by iron(III) oxide, or rust.[3] Occasionally, the surface of Mars can look like butterscotch;[4] but other common surface colors can include golden, brown, tan, and even greenish, depending on the minerals present.[4] The soil on Mars has been found to contain Boron, an element essential for the presence of life.

Comparison: Earth and Mars
Animation (00:40) showing major features of Mars
Video (01:28) showing how three NASA orbiters mapped the gravity field of Mars


Olympus Mons may be the second largest volcano in our solar system. It is three times taller than Mt. Everest (the tallest mountain on Earth) at 22 kilometers high and as big as the state of New Mexico. Olympus Mons is just one of four volcanoes that line up Mars's equator; they were originally active when the planet was still forming; they are no longer since Mars has since cooled down. Valles Marineris is a grand canyon that is longer than the Icons-flag-us.png United States of America is as wide. There are also lots of interesting meteor craters and rocks. Sunsets on Mars are also blue in color.

About 100 years ago, Icons-flag-it.png Italian astronomer Giovanni Schiaparelli studied Mars through his telescope; he thought he captured many straight, dark lines on the planet's surface which he named the Canali (Italian for channel), but some mistook it for canals. People who heard about the supposed "canals" thought of them as waterways dug by its inhabitants. However, the Viking 1 spacecraft, the first spacecraft to visit Mars which was only around a meter wide and launched on July 20, 1976, found no canals on Mars's surface.

Extents of north (left) and south (right) polar CO2 ice during the course of a martian year.

NASA's Hubble Space Telescope took three images of the planet's North Pole over the course of a Martian year. In winter, the ice cap on the pole had grew noticeably large. At summer, the ice cap had almost disappeared. Color changes are the result of dust storms exposing or burying minerals on the surface. Chasma Australe, a major valley, cuts across the layered deposits in the South polar cap. On the 90 degrees E side, the deposits rest on a major basin, called Prometheus.[5] The ice caps are composed mainly of water, just like those on Earth, but also of carbon dioxide (CO2). They have an average thickness of 0.9 kilometers and cover an area 1.5 times larger than the state of Texas. The Martian caps have less ice than on Earth's ice caps - only around 4% of the Antarctic ice sheet.

Mars, shown with its two moons, Phobos and Deimos.

An instrument called MOLA (Mars Orbiter Laser Altimeter) aboard the Mars Global Surveyor sent laser pulses toward the planet and measures the time it takes for them to bounce back. Scientists have analysed these measurements to make 3D maps and graphs of Mars's north pole in 1998. The ice cap has canyons that are more than 3000 feet deep and are formed by water erosion. This is proof that scientists believe an ocean could have existed on Mars, with a volume 10 times larger than the water in the current ice caps.


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  4. 4.0 4.1 NASA – Mars in a Minute: Is Mars Really Red? (Transcript)
  5. ISBN 978-0-521-87201-0