Mike Burden, age 12, of Santa Maria, California, for his question:
Does it rain on other planets?
For ages, even the wisest men thought that ours was the one and only world in all creation. Then it was proved that the earth is just one of nine planets of the Solar System. And modern science has found other solar systems. The planets in the universe may well outnumber the stars.
Mankind is a born star gazer. For ages men used only their eyes to chart the moving stars. Then they invented instruments and clever mathematical tricks to figure out things they could not see. They used the eye of the telescope to see farther and still farther into the universe. Not so long ago, the radio telescope was invented. It gathers sounds from beyond the range of a telescope. Meantime, more and still'. more clever detective skills were invented to figure out the nature of the heavenly bodies indirectly.
For perhaps a century, astronomers have suspected that other starry suns besides our own are orbited by planets. In the last few years, they have proved that one or two nearby stars do indeed have planets. This exciting discovery was a challenge to the math experts. They set about figuring how many stars are likely to have planetary solar systems. And the latest estimates suggest that there are millions and perhaps billions of them. It seems likely that there are billions of planets in our Galaxy alone, without even trying to count those in the millions of other galaxies in the cosmos.
In any case, an up to date young space ager can be pretty sure that the number of planets in the universe is too big to count. In this astronomical number, there must be other planets almost, if not exactly, like our own. Any world that has an atmosphere like ours and gets the same amount of heat and light from its sun is bound to have rain, just as we do. So far, not a single one has been discovered but almost without a doubt, way out in space there are many earth type worlds showered with earth type rain.
No other planet in our Solar System has our kind of rainy weather. Mercury has little or no atmosphere besides, one side is too hot and the other too cold for rain. The dense air of Venus seems to have little water vapor and rain, if any, would turn to steam. The thin air of Mars is not likely to have enough vapor to shower rain on the arid ground. The other planets are so cold that any trace of liquid rain would be frozen. Their main gases are methane and ammonia that freeze at lower temperatures. These substances may or may not form cloudy droplets of liquid. But if showers fall, they would not be showers of the watery raindrops that fall upon our own rich, green earth.
Our teeming plants and animals are always thirsty and a continuous cycle of water is needed to keep them thriving. The earth is blessed with a blanket of life giving gases. Its beaming sun is just right in the distance away to soak up moisture from its watery oceans and fill the atmosphere with misty rain clouds. Ours is the only planet in the Solar System with these conditions. So, to find another world with earth type showers, we shall have to go searching far, far out into space.