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Mars

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The planet Mars is the last terrestrial planet and the fourth planet of our solar system. He is the most likely target for a manned space mission. Already the first ancient civilizations were fascinated by him and honoured Mars as a god (for Romans/Greeks were he the god of war).

As a result of iron oxide (rust) the planet Mars has a reddish colour and therefore he earned the name the Red Planet, furthermore he is the only planet in our solar system with two moons.

Meanwhile over 30 space probes was send to him, but not all were successful, especially the Soviet/Russian space agency had a lot of problems with their missions. The first fly by at Mars succeeded the American spacecraft Mariner 4 on July 1965. The first mission with soil contact was the Soviet spacecraft Mars 2, but it didn't send reusable Data's because the spacecraft was destroyed by landing.

At the moment are an armada of spacecrafts in an orbit (the European Mars Express and the American space probes Mars Odyssey and Mars Reconnaissance Orbiter) and two Rovers (Spirit and Opportunity) on the surface.

Surface

Mars has only a quarter the surface area of the Earth and only one-tenth the mass, though its surface area is approximately equal to that of the Earth's dry land.

It is probably that Mars was once very similar to the earth and only due to the small force of gravity lost his water and thick atmosphere. However, the thermal emission spectrometer on Global Surveyor found no detectable carbonate signature in surface materials at scales ranging from three to 10 kilometers (two to six miles) during its six-year Mars mapping mission. Therefore, some scientists have their doubts that the Mars was similar to the earth.

In contrast to that, the Rovers found traces of ancient water, but the quantity is not clear. And also the Mars orbiters (especially the Mars Odyssey and later the Mars Express spacecraft) found "dirty ice" in the underground on the north and south pole of the planet. Although the visible polar caps consist of frozen carbon dioxide (dry ice).

Since Mars was volcanically in the past more active in the north than in the south, traces of meteorite impacts are mainly in the south. For example the Lowell Crater, which was designated after the American astronomer Percival Lowell. On the other hand in the north are the biggest volcanoes of our solar system with biggest Vulcan Olympus Mons.

Periodically, great dust storms engulf the entire planet. The effects of these storms are dramatic, including giant dunes, wind streaks, and wind-carved features.

An other characteristic feature of Mars is the greatest canyon of our solar system, the Mariner Valley.

Orbit

A solar day (or sol) on Mars is very close to Earth's day: 24 hours, 39 minutes, and 35.244 seconds, but a year on Mars is nearly twice as long as on earth. Mars is moving on a ellipticity orbit around the sun and has a eccentricity of 0.0935 and a inclination of 1.85 deg.

Atmosphere

Mars' atmosphere is thin: the atmospheric pressure on the surface is only 750 pascals, about 0.75% of the average on Earth. However, the scale height of the atmosphere is about 11 km, somewhat higher than Earth's 6 km. The atmosphere on Mars is 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water.

The mystery of the methane

The European Mars Express probe detected 2004 with its Planetary Fourier Spectrometer (PFS) the volatile gas methane and this was a surprise that the scientists not expected. Because methane is only for 300 years stable in the Mars atmosphere and therefore somewhat must generate it. Either there is life on Mars or still a volcanic activity. [1]

Moons

Asaph Hall was an American astronomer and supported by his wife for searching after Mars moons and in August 1877 he discovered Deimos and six nights later Phobos.

Ninety-four years later, NASA's Mariner 9 spacecraft got a much better look at the two moons from its orbit around Mars. The dominant feature on Phobos, it found, was a crater 10 km (6 miles) wide - nearly half the width of the moon itself. It was given Angelina's maiden name: Stickney.

Mars' moons are among the smallest in the solar system. Phobos is a bit larger than Deimos, and orbits only 6,000 km (3,700 miles) above the Martian surface. No known moon orbits closer to its planet. It whips around Mars three times a day, while the more distant Deimos takes 30 hours for each orbit. Phobos is gradually spiraling inward, drawing about 1.8 meters closer to the planet each century. Within 50 million years, it will either crash into Mars or break up and form a ring around the planet.

[1] http://www.esa.int/esaCP/SEMB9OE3GXF_index_0.html

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