The Hindu : A date with Mars

Online edition of India's National Newspaper
Monday, Jul 21, 2003

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National

A date with Mars

MUMBAI JULY 20. For the first time in recorded history, Mars will come closer to the Earth on August 28, raising expectations of a close encounter of a thrilling kind.

In a mutual dance of near-and-far-approaches that all planets indulge in, Mars and Earth come close to each other once every "opposition" — about once in two years — but not every opposition is the same with some closer than others.

Opposition happens for the superior planets, that is, for planets that have orbits outside the Earth's. At opposition, the superior planet would appear exactly opposite — 180 degree away from the position of the Sun — and is the closest to the Earth during that particular trip around the Sun.

Since planetary orbits are elliptical, some oppositions bring the planet closer to the Earth than others. This effect is the most pronounced on Mars. Oppositions when Mars is at aphelion (farthest distance from the Sun) keep the Earth and Mars much further apart than oppositions when Mars is at perihelion (closest to the Sun). Some oppositions are closer than the others; the coming one is the closest in the last 73,000 years with the distance between Earth-Mars being 55.8 million km. Mars will not get closer than this to the Earth until 2287 when the distance between the two will be 70,000 km.

The opposition can be seen from anywhere on the Earth, although better from lower latitudes — not too north and not too south of the Equator — gives better opportunities for viewing, as Mars will be seen higher up in the sky from lower latitudes. — UNI

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