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| Sunday, 24 August 2003 |
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Mars gets closest ever this week by Priyanka Koralagama, Lecturer, Planetarium. Mars will make its closest approach to Earth for almost 60,000 years at the end of August. On 27 August this year, they will pass at a distance of 55,760,000 km or 0.3727 AU (1 AU is the distance of the Earth from the Sun), closer than any time during the last 60,000 years. If that doesn't sound close, Mars was five times as distant just six months ago. But the distance between the two planets during these close encounters changes dramatically because Earth has an almost circular orbit while Mars has an elliptical one. (Mars swings far out and then back in towards the sun.) Throughout July, August and September, Mars will be easy to see with the naked eye. Each night it will rise earlier, until by late August it will be just above the horizon, south of east, soon after sunset. In August, you will be able to spot a bright, reddish object in the constellation Aquarius. For the next several days Mars should shine brighter than any other celestial body - save the sun, the moon and Venus. When close, through a good telescope, it is possible to see surface markings, polar ice caps and even thin clouds and frost. Compared to the other planets in our Solar System, Mars is the one most like Earth. Both planets have hard crusts (surfaces), both have dense cores (centers) and both are made up of the same kinds of material. What's more Mars even has four distinct seasons - just like Earth! However, here the similarity ends. Mars is just too cold and its atmosphere just too thin to support life. Or is it? Mariner 4 was the first spacecraft to obtain and transmit close range images of Mars. After its launch on November 28, 1964 and a journey of hundreds of millions of kilometres, Mariner 4 passed within 9,844 kilometres of Mars on July 14, 1965. Scientists didn't get their first close-up look at Mars until 1971 when the US spacecraft Mariner 9 orbited the planet. It sent back photos of an alien world with vast deserts, towering extinct volcanoes and gaping rift valleys - but no signs of life. Subsequent probes have provided tantalizing evidence that water once flowed freely on the surface. Right now, all the water appears to be tied up below the surface and in polar ice caps (also made up of frozen carbon dioxide). Four spacecraft are now headed for Mars. They were launched recently to take advantage of the close approach and are expected to arrive in the New Year to begin in ambitious exploration program. The probes are equipped with three Landers and two orbiters. |
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