A DATE WITH MARS
Dr. N. Rathnasree *
Would you like to
really befriend Mars - the planet of war? There is no time like
the present. On August 28, 2003 Mars is going to be closer to
Earth than it had ever been in recorded history! A close encounter
of a thrilling kind, no doubt indeed.
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 - some
are 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 degrees away from the position of the Sun, in the sky, and
is the closest to Earth, in physical distance, during that particular
trip around the Sun. Planetary orbits are elliptical rather
than circular. Therefore, some oppositions bring the planet closer
to 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 - and the coming one - the closest
since the last 73,000 years - with the Earth-Mars distance being
about 55.8 million kilometers! One must not miss
the opportunity of viewing this planet and learning more about
it at this time - Mars will not get closer than this to Earth
until the year 2287 when it will be 70,000 km closer to it. And,
this is a treat for all Earth observers - this can be seen from
anywhere on Earth, although 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.
Usually Mars is a
poor lookout for telescope viewers as it presents a small disk
for view. But oppositions usually give a better look at Mars.
Amateur astronomers the world over, wait for favourable Mars oppositions
to painstakingly view this planet.
What is one expected
to see at this time - different from other non-favourable occasions
of Mars viewing? One usually looks out for subtle surface markings
and polar ice caps while viewing Mars. These should become very
prominent at this time, provided there is no dust cloud obscuring
the view. Mars changes in apparent diameter dramatically - from
conjunction, when it appears close to the Sun in the sky, to opposition.
Compared to that
dramatic change - the change in its apparent diameter may not
be so dramatic from opposition to opposition. So, one should not
look for dramatic changes in its appearance compared to some of
its favourable oppositions in the recent past – it would not be
very different from the views of 1956 or 1988. But, still, a record
is a record - Mars will be closer to us this time than any of
these favourable oppositions in recent history. The last time
it had been this close was in 57,538 BC!
A simulated image
of Mars - showing the hemisphere visible from Earth, during the
August 28, 2003 opposition is shown in the accampanying illustrations.
Of course, the views through ordinary amateur telescopes would
be much less dramatic - be aware of that! Kalidasa,
in his Malvikaagnimitram, refers to the retrograde motion
of Mars. At the end of the third act of this play king Agnimitra
talks to his wife, Iravati. She expresses some misunderstandings
over his fascination for Malvika. The queen sweeps away from him
after some arguments and Agnimitra’s friend and courtier, Gautama,
advises him to make haste and move away from the place before
Iravati retraced her steps like the planet Mars in retrograde
.
A forced simile,
in the context of the play, perhaps, but testifying to Kalidasa’s
interest in the skies and to the fact of retrograde motions of
planets having been minutely observed and recorded in his times.
Mars has fascinated
us from the beginning of history. A historic occasion is ahead
of us. Let us keep our date with Mars! During July, we can see
it after midnight in the southeastern direction. Closer to the
opposition, it will be rising earlier in the evenings as a bright
object in the southeastern skies.
*
Director, Nehru Planetarium, New Delhi
