(ESTD. BY GOVERNMENT OF TAMILNADU)


Mars


The planet Mars was named after the Roman god of war because of its angry red appearance. Early man thought that Mars was a distant, bloody battlefield. Iron oxide or rust in Mars' soil gives it a ruddy complexion. It is about half the diameter of Earth, and has a mass of approximately one tenth of the Earth's Mars orbits the Sun at an average distance of 22.8 crore kilometers. Mars is similar to Earth in many ways. Although it is much smaller in size, Mars has polar ice caps very similar to Earth's. The Martian year is 687 Earth days, but a Martian day is 24.6 hours. It is amazingly close to Earth's. The axis of rotation also tilted similar to the earth, and causes seasons on this red planet.

Mars has an atmosphere consisting of more than 95% carbon dioxide. Very little nitrogen, argon oxygen and water vapour are also present.

The distance between the Sun and Mars also continuously varies. Due to this, temperatures range from -125 degrees Celsius in the Martian winter to 22 degrees Celsius in the Martian summer. Polar ice caps shrink in size during the Martian spring and summer.

The orbit of Mars around the Sun is extremely elliptical. In their orbits around the Sun, Mars and the Earth come close to each other every 2 years and 50 days interval.

At those times the apparent size and brightness of Mars increase greatly. Also it will be observable throughout the night.

The distance from us also reduces to a mere 5.6 crore km compared to its farthest distance of 40 crore km. During such favourable periods in the year 1877 by observing the Mars with telescopes, Giovanni Schiaparelli in Italy and Percival Lowell in the United States mapped what they thought to be 'canals' constructed by Martians to bring water from the ice caps to irrigate fields.

Even in the twentieth century many people thought that a civilisation might exist on Mars. In 1965 the Mariner 4 spacecraft transmitted several close-up pictures of the planet. The images taken depicted a barren and rocky world, not capable of sustaining life.

The 'canals' that Percival Lowell thought were manmade, actually turned out to be a giant fracture zone that was 4800 kilometers across the Martian equator.

Now called Valles Marineris, the fracture zone is 200 kilometers wide and 7 km deep in places.

Another prominent feature on Mars is Tharsis: a huge bulge on the Martian surface that is about 4000 km across and 10 km high.

Hellas Planitia is a vast crater in the southern hemisphere over 6 km deep and 2000 km in diameter.

Valles Marineris was not created by running water. It was formed by the stretching and cracking of the crust associated with the creation of the Tharsis bulge.

There was, however, evidence that water did once flow there. In 1972 Mariner 9 sent astonishing pictures of channels that look like dried river beds. An excellent example is Valles Mangala. It has a lenghth of 350 kms and looks exactly like features on earth formed by sudden flood.

The Martian south polar ice cap was found to be half frozen carbon dioxide or dry ice, but the north polar icecap was found to be almost entirely water.

One of Mars' distinguishing features is Mount Olympus. Mount Olympus is an inactive volcano of 25 kilometers high and three times taller than Mount Everest. It is the highest volcano in the entire solar system.

In 1976 two American Viking spacecraft became the first craft to survive landing on mars. The Viking landers answered many questions about Mars. The landers conducted a great deal of experiments to ascertain whether there was life on Mars. The answer was 'probably no'.

A new spacecraft Mars Reconnaissance Orbiter was launched on 12th August 2005 to orbit Mars over a full martian year and gather data. The cruise to Mars will take about seven months and in March 2006 it will reach Mars.

In 2004 the Mars Expedition Rovers "Spirit" and "Opportunity" landed on Mars and sending back geologic data and many pictures; they are still operating after more than a year on Mars. Three rocks on the surface of planet Mars photographed by Spirit and Opportunity Rovers have been given Indian names - Kohinoor, Nalanda and Pongal Three Mars orbiters Mars Global Surveyor, Mars Odyssey, and Mars Express are also currently in operation.

Phobos and Deimos are two small moons in orbit around Mars. They are scarred with many craters and are very irregular in shape. Phobos is 27 kilometers long and Deimos 15 kilometers long. Phobos and Deimos are probably fragments of larger objects brocken apart in a collision.