Weather wise

NEXT TIME you look out of the window, see the rain pelting down and decide to stay in bed for the day, think how much worse it could be if you were unlucky enough to live anywhere else except on our own dear planet. For, however beastly the weather gets here, there is nothing Earth can throw at us which compares in nastiness with the conditions found on the other planets. In fact, there is nowhere else in our solar system where you could lay out a sheet and have a pleasant afternoon picnic without being boiled, frozen, evaporated, crushed or suffocated.

Our nearest planetary neighbour, Venus, has the most appalling weather. The surface glows a dull 400C red, the result of a runaway greenhouse effect. The air, more or less pure carbon dioxide, is so soupy that a (well insulated) human being could easily fly with the aid of strapped- on wings.

People used to think Mars was criss-crossed by canals, but any canal- builders on the Red Planet would need to be hardy souls. The Pathfinder lander which arrived on the Martian surface last summer beamed back details of pressure, temperature and wind speed. Mars is cold. The maximum temperature recorded was around -7C, the minimum a perishing -78C.

And visitors would need to pack more than a set of long johns. The surface pressure, around 6.5 millibars, is less than 1 per cent of that on the Earth. Water at these pressures simply boils into vapour, and, as our bodies are mostly made of water, an unpressurised astronaut would die in agony as his blood foamed in his veins.

As for Jupiter and Saturn, these planets are composed almost entirely of hydrogen and methane gas - they are almost made of weather. Jupiter's speciality is hurricanes, with wind speeds of 600mph and more. Some of these storms, like that which shows as the Great Red Spot, are as big as the Earth and last for centuries.

Most of the moons in the solar system are too small to have atmospheres, and hence have no weather. But Titan, the largest moon of Saturn, has a thick cloudy atmosphere, thicker in fact, than that of the Earth. Surface pressures are a survivable 1,500 millibars, but the temperature is a rather less pleasant -170C. You would need oxygen tanks too, as the air near the surface is almost pure molecular nitrogen. Titan might be the only place in the solar system other than the Earth which experiences rain, though on Titan the rain would consist of liquified ethane, perhaps falling into ethane oceans and rivers.

The outer planets, Uranus, Neptune and Pluto, are all extremely cold, orbiting billions of kilometres from the Sun. Pluto is a frozen airless world, blue Neptune and green Uranus are gas giants like Jupiter and Saturn, with howling methane hurricanes and unimaginable pressures deep below the visible cloud tops. Like everywhere except our own blue haven, the long-range forecast for these planets is uninhabitable.