Police prepared for spate of UFO sightings as Mars approaches

Police forces prepared for an increase in UFO sightings yesterday, although the cause was not so much "Mars attacks!", as Mars approaches.

Police forces prepared for an increase in UFO sightings yesterday, although the cause was not so much "Mars attacks!", as Mars approaches.

Our closest planetary neighbour came close enough to Earth last night for its polar ice caps to be visible through a small telescope ­ its nearest approach in 13 years.

The planet was just 42 million miles away and forces were expecting that some worried callers might think the bright red disc, which would appear to hover unwavering above the tops of houses, could trigger anxious reports of UFOs. That has been the pattern in previous approaches ­ known as "opposition", when Mars and the Earth are lined up in their orbit around the Sun.

Robin Scagell, the vice- president of the Society for Popular Astronomy, said: "If you're driving in a car and see Mars above the tree tops, it can appear to be following you. People then think they've seen a UFO."

Opposition occurs roughly every two years, though the elliptical orbits of the planets mean that the distance of approach varies slightly. This year's is the closest since 1988, when the two planets were 36.6 million miles apart. At their furthest, the planets are 250 million miles apart, on opposite sides of the Sun. Mars appeared quite low on the horizon between the constellations of Scorpius and Sagittarius, near the bright star Antares.

Robert Naeye, an American and editor of Mercury magazine, published by the Astronomical Society of the Pacific, said: "Telescope observers under favourable viewing conditions will easily see Mars's famous dark markings, one or both polar caps, and on occasion, clouds. The southern polar cap will be more prominent during this year's opposition because winter is just ending in Mars's southern hemisphere. Telescope users can also use colour filters to bring out additional details in the planet's surface and atmosphere." A magnification of 40 or 50 would have been enough to reveal the planet's main features. The planet appears red because of its rusty dust, caused by large amounts of iron in its soil. Technically, Mars will be at its closest to Earth, a distance of 41.8 million miles, a few days after opposition on 21 June.

There will be an even more spectacular view of Mars in August 2003. The planet will then be just 34.8 million miles from the Earth ­ closer than it has been for about 6,000 years.

The closeness of the approach will not affect the timing of plans for either robot or crewed missions to Mars. The European Mars Express mission is due to be launched in 2003, and will carry the mainly British Beagle II probe, which will land on the planet to search for signs of life beneath the soil. It will follow up the intriguing ­ but ultimately negative ­ results from the 1997 Mars Pathfinder mission, which had its own six-wheeled "Mars rover" vehicle to examine rocks.

Plans for a crewed mission to Mars are still indefinite, with the American space agency Nasa unwilling to commit the billions of dollars that would be needed to send a team to the planet. The journey would take roughly two years each way, and there is intense debate on the physical and psychological effects of being cooped up inside a spacecraft for such long periods.

The timing of the take-off also requires favourable planetary alignment, but would not occur during opposition because that would actually lengthen the journey required.

Calculations suggest that the best time to launch a mission would be in January 2014, when the planets' alignments would increase the chances of being able to return to Earth in case of an accident like that suffered by the Apollo 13 spacecraft on its journey to the Moon in 1970. The safest return trip ­ if a Mars landing had to be aborted ­ would then actually be via the planet Venus, by swinging around it and back towards the Earth.