Wikijunior:Solar System/Mars

Mars Facts: Mars is the fourth planet from the Sun. It is called a terrestrial planet because its outer layers are made of rocky material like the Earth.
 * Mars is red because of rust in the surface rocks
 * A volcano on Mars called Olympus Mons is the highest mountain in our Solar System.
 * Mars has polar ice caps that look like the ones on ../Earth/.
 * Mars has ancient river beds where scientists think liquid water flowed millions or billions of years ago.
 * The Tooting crater on Mars was named after a suburb in London because the discoverer "thought [his] mum and brother would get a kick out of having their home town paired with a land form on Mars".

How big is the planet?
Mars is the second smallest of the eight major planets in the Solar System. Only Mercury is smaller. It is nearly 7,000 kilometres (km) wide; just over half the width of the Earth. Its volume is about 15% of the Earth. Since a lot of the Earth is covered by water, the total surface area of the Mars is nearly as large as all of the land on the Earth. It is possible that its size may eventually permit human colonies.

What is its surface like?


The surface of Mars is a lot like a desert on Earth; it is very dry and dusty, but it is also very cold. There are a lot of loose rocks and dunes of fine sand. Crater impacts mark the surface, but these are not as common as on the Moon. One of the craters is the huge Hellas Planitia. It is about half the size of the continental United States. The southern half of the planet has more craters than in the north. The south is also higher in elevation.

There is an area on Mars called the Tharsis Bulge, which has four huge volcanoes. These volcanoes have not erupted for millions of years. The largest volcano is called Olympus Mons. It is 27 km tall, making it the highest mountain in the Solar System; more than three times higher than Mount Everest on Earth. It is 625 km across and takes up an area as big as the US state of Arizona. Mars also has a huge canyon called the Valles Marineris. It is much bigger than the Grand Canyon on Earth. It is 4000 km long, up to 7 km deep and up to 200 km wide. Scientists think that when the Tharsis Bulge was created, the surface of Mars cracked to form the Valles Marineris.

Like the Earth, Mars has ice caps at its poles. However, they are made from frozen carbon dioxide as well as ice. During the Martian winter at each pole, the cap grows as carbon dioxide from the atmosphere freezes. The cap shrinks again during the Martian summer. As on Earth, when it is winter at one pole it is summer at the other.

In some places, there are dry channels that look like they were made by running water. So, a long time ago Mars may have had lakes and streams made of water. Now all of the water is frozen into ice under the surface.

There is an atmosphere on Mars, but it is very thin. There is also much more carbon dioxide in it than oxygen. (Oxygen is the gas we need when we breathe in; carbon dioxide the gas we get rid of when we breathe out.) So, we would need spacesuits to visit Mars. The atmosphere helps protect the surface from smaller meteorites.

When Mars comes closest to the Sun, the atmosphere can stir up storms of dust. Some of these storms are gigantic; they can cover the entire planet in clouds of dust. Dust storms on Mars can last for hundreds of days, with wind speeds of up to 200 kilometres per hour. Huge storms like these have been seen from the Earth through telescopes.

How long is a day and year on this planet?
One day on Mars is only 39 minutes and 35 seconds longer than a day on Earth (1.026 Earth days). A year on Mars is almost two Earth years long (687 Earth days).

Much like the Earth, the axis of rotation of Mars is tilted at an angle. This tilt causes seasons on Mars as it travels around the Sun. Summer occurs on the half of the planet that is tilted toward the Sun, and winter on the other half. After half a Martian year has passed, the seasons are reversed. But these seasons are about twice as long as on Earth.

What is it made of?


The outer, rocky surface of Mars is called the crust. Most of the crust is made from basalt, a type of rock made when lava grows cold.

Like the Earth, Mars has a thick layer of rock below the crust called the mantle. The mantle is much hotter than the crust, and the mantle rock is partly molten. But the crust on Mars has grown thick, so the lava from the mantle no longer reaches the surface. There are volcanoes on Mars, but they are no longer active.

At the center of Mars is a core made of the metals iron and nickel. If Mars were the same size as the Earth, the core of Mars would be smaller than the Earth's core. So a larger amount of Mars is made out of rock. Because rock is lighter than the metals in the core, Mars has a lower density than the Earth.

How heavy would I be on Mars?


If you were on Mars, you would be lighter, as Mars' gravity only has a force about two fifths as strong as the that of Earth's. You could lift objects that weigh almost three times as much compared to similar objects here on the Earth. You could jump up almost three times higher, and it would take much longer to fall to the ground from the same height.

Even though it looks as though you would be like a comic-book hero on Mars, there are some things you couldn't do. Although a big rock would weigh less and you could pick it up, it would still have the same mass. If you tried to catch it, it would knock you over, and if it landed on you it would crush you. A car on the surface of Mars would need the same amount of power to speed up, although going uphill would be less of a problem. It may, however, need more room to stop. Because of the reduced gravity a vehicle would not "grip" the ground on Mars as strongly, but the constant mass would keep the vehicle moving just as strongly, making it easy to go into a skid.

Who was it named after?
In Roman mythology, Mars was the god of war and agriculture. The planet Mars was named this because the planet looks red like blood, from rust in its surface rocks.

Who discovered Mars?
Nobody knows, but the earliest records we know of were by Ancient Egyptians, more than 4000 years ago, noting Mars' movement. On one pharaoh's tomb, named Seti I, Mars is drawn on the ceiling. The Babylonians (in the Middle East), Chinese, and Greeks also studied Mars more than 3000 years ago. The Greeks learned about Mars from the Babylonians, and since the Babylonians called it their god of war, named Nergal, the Greeks called it their own god of war, Ares. Exploration of Mars was first attempted in 1960, with Mars 1. It failed, along with several other missions by the Soviet Union in the 1960s. The first successful mission to Mars was in 1964, by Mariner 4, by the U.S. Most of the other Mariner missions to Mars were successful. The last Mariner mission to Mars, Mariner 9, got there in the midst of a dust storm, and orbited the planet for several months before it could get a good look at the surface. So far, all these missions were flybys or orbiters. The first spacecraft to land on Mars was Viking 1 in 1976. Viking 2 landed 19 days later. Together, they took many good pictures of Mars' surface. Next Topic: Asteroid belt