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The planet Mars

Known since ancient times when it was associated with the greek and roman gods of war, the planet mars is the fourth planet from the sun. Orbiting at a distance of between 128,412.000 and 154,861,000 miles, it had it's closest approach to earth (at 42 million miles) on wednesday 13th june 2001. This sort of close approach occurs every 779.74 days, when mars, the earth and the sun all line up. The previous closest occured over 12 years earlier. The closest approach for 60,000 years occured on 27th August 2003.

The planet mars has fascinated observers for centuries. This has been very significant throughout history, with Tycho Brahe making incredibly precise observations, the analysis of which resulted in Johannes Kepler discovering his first two laws of planetary motion in 1609.

In 1666, D Cassini used further observations to discover the rotation of mars, which we now know rotates every 24 hours and 37 minutes 22.7 seconds. Mars was described by William Herschel as "the planet that most greatly resembles the earth" in 1783, after he saw melting of the polar ice caps, and Wilhelm Beer and Johann Heinrich von Madler managed to produce the first map of mars in 1840, based on observations made between 1830 and 1839.

Interest in mars increased considerably in 1867 when the italian astronomer Schiaparelli discovered "canali" (which means lines) on mars. This was miss-translated as "canals", which were hypothesised to have been artificial, and resulted in a large number of science fiction stories about martians. The most well know of these was "the war of the worlds" by Herbert George Wells.

Mars had further surprises for us in 1877, when Asaph Hall discovered from the US Naval Observatry in Foggy Bottom that it had two satellites (later named Phobos and Deimos). These were later discovered to most likely be captured asteroids.

By 1909 Antoniadi had managed to disprove the geometric nature of these "canals", by taking further observations with better equipment. At the same time, Tichov used colour filters to study the surface of mars looking for vegetation.

In 1922 Pettit and Nicholson were making the first measurements of the temperature variation on mars. By the 1930's, there was a set of scientists who thought that mars might be inhabited, and so a call went out for radio silence for a few minutes, so that scientists could listen for faint radio signals from mars. It was shortly after this that Orsen Wells and the mercury theater did the famous dramatisation of war of the worlds, and that is why it was so effective.

The Mariner 4 probe discovered craters on mars, in 1965. It also managed to measure the atmospheric pressure.

Pictures of the surface of Phobos and Deimos were obtained by Mariner 9 in 1971 and 1972. This probe took a total of 7329 photographs from orbit.

It was during the maping of mars that Olympus mons (the largest volcano in the solar system) and the valles marineris (a set of canyons that dwarf the grand canyon) were properly imaged.

Later, in 1974, the soviet "mars 6" probe made a direct measurement of the atmosphere of mars. In 1976, the Viking Probes landed on mars, and surprised us again, as the sky was found to be pink, and the soil was found to contain a large amount of a highly reactive iron compound which will make manned exploration much more difficult than was previously suspected.

In the late 1990's, "mars pathfinder" landed on the planet, proving certain technologies that make exploration easier. This contained the "Sojourner" robot, which produced lots of pictures of mars that lots of people spent lots of time looking at.

Recently, "mars global surveyor" found that there was a large difference between the north and south poles, with the crust being significantly thinner at one pole than at the other.

In 2004 one of nasa's probes located the site of a salty sea, and someone else spotted methane in the atmosphere of mars, which only lasts for around 300 years, and thus must be being generated regularly.

For the future, people like the mars society, and Robert Zubrin, are advocation for manned missions to mars, and in the case of Zubrin, actually doing the research that forms the basis for any future manned mission. Some of this research is set out in zubrin's book, The case for mars.

For a detailed summary of the planned mission, see the write-up of Mars Direct at Pescu.

See also Zyra's Mars review.

Mars is also known as the red planet because of the iron based dust making it look rusty.