GCSE Astronomy

Mars 2003

(as written in early 2003)

In 2003, Mars will approach closer to Earth than it has done for 60,000 years - on the night of August 26/27, to be precise. I haven’t personally seen any advance TV schedules, but the magazine Sky and Telescope are of the belief that once the broadcast industry wakes up to this fact, we will be treated to replays of films like War of the Worlds - the book, of course, being penned by HG Wells who started off his working life in a shop in Kings Road, Southsea (on the corner of St. Pauls Road, I believe).

Talking in numbers, the Earth lies about 150 million kilometers from the Sun, while Mars is about half that distance again. So very roughly speaking, you would expect Mars to get as close as about 75 million kilometers to Earth. However due to the elliptic nature of planetary orbits, the closest approach is usually in the region of 56 million to 58 million kilometers (which occurs every 15-17 years). In 2003, it will be 55.76 million kilometers

To be perfectly honest, the event is likely to suffer from quite a bit of hype. Mars can be described as a ‘telescopic challenge’ - normally, most amateur telescopes are able to pick up only limited detail of the Martian surface and this close approach will not improve matters too much. Many ‘lay’ people interested in viewing the planet through such a device could well feel disappointed, but one thing is certain - the planet will be very prominent in the sky, about as bright as a planet is capable of becoming. For comparison, the bright star you can see almost overhead in Summer is Vega - at the end of August, Mars will be 15 times brighter than Vega (and have a magnitude of -2.9).

In early July, it is rising after midnight and is low down for those of us in Britain, but by the end of August it will be a bit higher up and should be visible around nightfall, reaching its most prominent position about midnight. It will be the brightest object in the sky, with the obvious red features from which it receives its nickname.

This time around, the planet will be tilted towards us in such a way that its Southern Hemisphere will will be tipped towards us. For those who have the patience to view it over longer periods through a telescope during July and August, you should be able to see the southern polar cap shrinking perceptibly, with the onset of the Martian spring in the South.

Up until now, scientists have believed that these polar caps are predominantly carbon dioxide (dry ice), but this year NASA has been publicizing results implying that the upper dry ice layer is thinner than previously thought and that the caps are, in fact, largely frozen water. If true, this will require a major overhaul of martian and planetary theories.

During July and August, the planet will be in the constellation of Aquarius. During the close approach at the end of August, it will appear to ‘backtrack’ in the sky, a characteristic which gives the planets their name (from the Greek for ‘wanderer’). In other words, in contrast with the Sun which tracks a steady ‘one-way’ course throught the zodiac, or background constellations, the planets will, every so often, appear to reverse direction for a few days, before resuming their original direction again.

For the rest of the year the planet will be getting higher in the sky and rising earlier and earlier, although also getting dimmer and dimmer. Nevertheless, you should still be hearing more of the planet, by virtue of at least three spacecraft currently making their way there. The best-known in Britain is Mars Express, carrying the British Beagle 2 probe. Mars Express is the first fully-European mission to a planet and, if all goes well and to plan, Beagle 2 will land on Mars at 0254 Greenwich Mean Time on December 25, possibly bringing back memories to some of Christmas 1968 and man’s first orbit of the Moon in Apollo 8.

Incidentally, this year’s record will beaten on 28. August 2287, when the two planets will be separated by a distance of only 55.69 million kilometers.