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Four unmanned spacecrafts have landed on Mars to date. But there is no conclusive proof whether or not life exists on Mars. The Red Planet is still a source of fascination and fantasies, as it has been since the day it was discovered.

The Babylonians associated Mars (they saw it as a red star) with evil and considered it a bad omen. They called it Nirgal, after their god of pestilence and disease. But it was the Romans who gave it the name Mars (Greek Ares) after their blood red god of war.

Mars is the fourth planet from the sun and lies between Earth and Jupiter. It is the seventh largest planet, and its mass is approximately one tenth that of Earth. It is the only planet in the solar system, other than Earth, that has conditions that might have supported life at some point in its history. Mars seems to have had large amounts of surface water millions of years ago, but almost none exists today. There is a belief among scientists that this water may be frozen in the planet's large polar caps or beneath its surface. Although the atmosphere of Mars has some traces of oxygen, it is not enough to sustain living creatures. And the temperature on Mars rarely ever rises above 0 degrees centigrade, and on the average is as low as –55 degrees Celsius (-67 degrees Fahrenheit).

Mars revolves around the sun in an elliptical (oval-shaped) orbit. Its distance from the sun varies from about 154,800,000 miles (249,200,000 kilometers) at its farthest point, to about 128,400,000 miles (206,600,000 kilometers) at its closest point. Mars takes nearly twice the number of days to revolve around the sun, as does Earth, about 687 Earth-days. Thus, a Martian year would be of 687 Earth days. Its diameter of 4,223 miles (6,796 kilometers) is a little over half that of Earth. Just like Earth, Mars rotates on an imaginary axis, which is tilted. And it rotates in about 24 hours and 37 minutes, which is very close to the 23 hours and 56 minutes of Earth. The tilt of Mars’ axis causes seasons, which William Herschel concluded in 1799 while observing the changing color and size of the ice caps of Mars.

The surface of Mars contains large amounts of a brick-colored mineral called Limonite, found in deserts on Earth. Although most of Mars’ surface appears reddish, there are dark areas called maria (seas). A series of lines running between these dark areas were at one point mistaken to be waterways made by living creatures. Lowell glorified these canals and caused quite a stir in 1895. The Martian atmosphere contains mostly carbon dioxide and traces of oxygen and other gases. It is also believed that white clouds of water vapor, blue clouds of ice particles, and red clouds of dust give color to the Martian atmosphere. Dust storms of such huge proportions ravage the Martian surface and often prevent observation of the surface from Earth. The Italian astronomer Giovanni Schiaparelli observed a darkening of the surface along with the shrinking of the ice caps. He thought that the ice caps melted and the melt-water darkened the surface, but it was later learned that seasonal dust storms, not polar floodwater spreading toward the equator, change the appearance of the surface.

Mars is home to Olympus Mons, the largest mountain in the solar system: 24 km (78,000 ft.) high with a base more than 500 km in diameter. Tharsis is a huge bulge on the Martian surface that is about 4000 km across and 10 km high. Valles Marineris is the system of canyons 4000 km long and from 2 to 7 km deep, and Hellas Planitia is an impact crater in the southern hemisphere over 6 km deep and 2000 km in diameter.

The earth has one satellite, the moon. Mars on the other hand has two satellites, Phobos and Deimos. Small in size, Phobos with a diameter of 14 miles and Deimos 7 miles, they revolve very close to the surface of Mars. Both the satellites were discovered by Asaph Hall, the American astronomer.

A serious exploration of Mars began with the probes that flew past it. In 1964, the NASA probe Mariner 4 flew within 9,800 kilometers (6,100 miles) of Mars, but it only observed the heavily cratered southern hemisphere. Then came the orbiters, which circled Mars for long periods of time. In 1971, Mariner 9 entered orbit around Mars and in its year-long mission, provided most of the basic information that we have about Mars. Next came the landers Viking 1 and 2, taking thousands of images of the surface, making weather observations, and conducting chemical experiments on the soil. The Viking probes found many indications that water had flowed on Mars in the distant past. This intrigued NASA enough to come up with the Mars Observer, which launched in September 1992. It had the potential to gather more data than all previous Mars missions combined. But in August 1993, three days before Mars Observer was due to reach orbit, controllers on Earth lost contact with it. Then came the Mars Global Surveyor and the Mars Pathfinder. During nearly three months of operation, Pathfinder took about 16,000 pictures, including spectacular panoramas of the surrounding terrain. Observations by Pathfinder and Sojourner added further evidence to there once being water on the Martian surface.

The Surveyor orbiter made many useful observations although it was delayed due to technical problems. It beamed a picture of a canyon, named Nanedi Vallis, which appeared very clearly to have been cut by a river. Surveyor also confirmed that, unlike Earth, Mars does not have a global magnetic field. Instead, there are several weaker, localized magnetic fields, each aligned in a different direction. Two spacecraft, the Mars Climate Orbiter and the Mars Polar Lander, were launched in December 1998 and January 1999, respectively, and scheduled to arrive in late September and early December 1999. Both were lost.

To come are the Mars Surveyor 2001 mission, a third orbiter-lander pair likely to be launched in 2003, a mission in 2005 to bring Martian rock and soil to Earth for study, and the first manned interplanetary mission as early as 2010. The boldest visionaries believe that man will one day colonize Mars and transform Mars into an Earthlike planet by creating a breathable atmosphere, water to grow crops and sustain life, and a warmer climate (called terraforming). It is speculated that releasing enough carbon dioxide to complete the first stage of terraforming would take at least 100 Earth years. By then, the average temperature might be a more bearable minus 8 degrees Celsius (18 degrees Fahrenheit) and the atmosphere might be dense enough to allow people to work outdoors without space suits. The air would still not be breathable, however, so the next stage might involve introducing plants to produce oxygen.