Venus - Receding Visions
Last time we talked about the mythology of the innermost planet in the solar System - Mercury. Today we take a step outwards and encounter Venus. There is a classic mythology of the Roman Venus or her equivalent the Greek goddess of love Aphrodite. Most of us have or will learn these stories in school. However there is another mythology of Venus much more recent which is fading under the onslaught of scientific knowledge. Having been brought up on these stories, I find that the ferociously hot, absolutely dry and barren world of reality is a poor substitute. I speak of course of the "Venus of Dreams" - the dreams of those like Edgar Rice Borroughs, Robert Heinlein and Pamela Sargent.No planet comes closer to the Earth than Venus, not even Mars. Yet no planet was more shrouded in mystery because we could never see anything but an unbroken layer of clouds. Like all unknown lands this Venera Incognito spawned countless myths of her own. I remember the "Big Rain" where a stranded man desperately struggles across swamps trying to find his personal refuge, a way station with its precious Sun Room where at least the illusion of a Sun could drive away the endless gloom of rain. He finally reaches his goal to find it destroyed and the reality of the endless rain pouring through the dome where the ersatz Sun should have been gleaming.Often Venus was imagined with Jurassic or Cretaceous swamps filled dinosaurs little different from the giants that roamed Earth more than 65 million years ago. In some tales, weird swamp trolls impeded intrepid explorers. Countless stories from five page shorts to thousand page trilogies described attempt to turn this "younger planet" into a new Earth. Everyone of these stories seemed plausible because Venus was certainly cloudy and where there are heavy clouds what else could there be but rain? Well today we know that other substances make clouds as well such as boiling hot sulfuric acid but still the stories die hard.As a kid I grew up knowing that the sun-ward side of Mercury was the hottest place outside of the Sun in the solar system. Venus was probably a hot tropical rain forest. Mars was a dying world, now too cold to maintain life let alone civilization. The gas giants were simply cold balls of gas. Saturn was the ringed planet Even in college, the accepted view of the solar system was not very different. But by the time my children were ready for these tales, it was obvious that it was time to assign them to that dust bins where faded myths are discarded.Mercury had no permanent sun-ward side. Venus had a run away greenhouse effect which made its surface hotter than molten lead or tin. Jupiter turned out to actually emit twice as much infrared radiation as the total sunlight that feel on it. Jupiter's inner regions were far from cold reaching temperatures in the tens of thousands of degrees. Mars had no great canals. The lines seen by countless observers turned out to be artifacts of the human eye while looking at low contrast small images. Saturn's rings remained, but we discovered that all the gas giant's had rings of some sort.The earliest signs that all these stories would disappear came from new generations of instruments attached to optical and radio frequency telescopes. Spectrograph noted little or no water but sulfuric acid and carbon dioxide in the atmosphere of Venus. Thermocouples aimed at the night side of the planet indicated a very high temperature. The great radio telescope at Aracibo Puerto Rico began to map the surface of the planet with interplanetary radar signals. Not only was Venus far hotter than through before, but now it was obvious that it turned very slowly. Its "day" was longer than its year. Finally conclusive evidence came with space probes. Yet even here the first probes underestimated how nasty Venus really was. The first Venera probe was destroyed by heat and an atmosphere 90 times as dense as our own.So long, the fanciful Venus and greetings to the cautionary Venus. Run away green house conditions trapped heat far beyond what you would expect. If Earth was in Venus' orbit but otherwise unchanged, it would have a temperature below the boiling point of water although steamy hot by our standards. If we ever let our green house gasses become even partially as thick as Venus then this planet will be livable only by bacteria.