"To travel hopefully," said Robert Louis Stevenson, "is a better thing than to arrive." For the past week, you may have noticed, Weather Eye has travelled hopefully the length and breadth of the entire solar system in search of some brave new world that might be better than the one we live in. But from the evidence it is clear that such a world does not exist.
Mars is the planet whose climate most resembles ours, and yet it is lifeless, waterless and cold. Its average temperature is about 55C and the Martian thermometer rises above zero only on the very warmest Martian day. The skies, it must be said, are relatively free of cloud - except during the only weather event worth noting, when in late winter and early spring great dust storms develop to cover the entire planet. It might have been of Mars that William Cory wrote:
Your chilly stars
I can forgo,
This warm kind world is all I know.
Venus is even less inviting. The greenhouse effect has run amok on Venus, resulting in an average temperature of over 400C and making it, except for the sun itself, the hot spot of the solar system. In contrast to Mars, Venus has a very dense atmosphere; it exerts a massive pressure of 90,000 hPa (hectopascals) at the planet's surface, equivalent to the pressure more than half a mile below the surface of our seas. Venusians, if there were any, would live their lives in everlasting gloom, their planet covered by a flat featureless layer of thick cloud which allows in very little sunlight. And this cloud, alarmingly, consists of tiny droplets of sulphuric acid.
Nor do any of the other planets appear attractive to humanity. Mercury, as we saw yesterday, oscillates as it were, between the oven and the fridge. Jupiter, Saturn, Neptune and Uranus have no solid surface in the conventional sense; in each case, the outer layers of the planetary mass are fluid, and at their outer fringes they are bitterly cold, with temperatures between 150 and 220C. A visitor to these inhospitable worlds would sink deep into the insubstantial quagmires, and we would never hear of him or her again.
"Tout est pour le mieux, dans le meilleur des mondes possible," Voltaire once wrote. And when it comes to comparative celestial climatology, it seems that he might well be right. The weather conditions we experience here on Earth may not be always to our taste, but we have nonetheless the most amenable climate of our galaxy. Perhaps, in the end: "All is for the best, in the best of all possible worlds."