For the week including February 4, 2011
THE MORNING STAR
Before dawn, the constellation of Scorpius, the Scorpion, stands just above the southern horizon. This constellation is easy to spot because of the stream of stars forming the Scorpion’s tail and the bright orange-red star, Antares which marks the Scorpion’s heart. These days, the Scorpion is even easier to find because of the brilliant star nearby. This star is so luminous that its appearance in the sky always generates mail from people asking me about its identity. Actually this “star” is the planet Venus. It’s the second-closest planet to the Sun and the brightest object in our sky after the Sun and Moon. Because of this brightness, Venus has had a lot of attention paid to it for thousands of years. But early efforts to explore Venus using telescopes were frustrated by the discovery of a thick layer of clouds that hid any details of the planet’s surface. Perhaps because it’s named for the Roman goddess of love, Venus has had the most romantic notions attached to it. Venus’ proximity to the Sun and its heavy cloud cover attracted images of a warm, rainy planet conducive to life. One inspired idea was that Venus might be some lush tropical paradise similar to the rain forests found on Earth. More than one writer has conjectured that Venus harbored dinosaurs living in jungles bordered by immense oceans teeming with fish. Some folks exuberantly declaimed that Venus was actually the site of the long-lost Garden of Eden.
NASA’s Magellan space mission to Venus eventually showed a very different picture.
The Venusian clouds have a little water, but they also turned out to be filled with sulfuric acid, so notions of a Gene Kelly splashing through Venusian rain puddles aren’t so entertaining. Venus is warm like everyone expected, but the thick, reflective atmosphere (a hundred times thicker than Earth’s) acts like a big pressure cooker, raising temperatures to over 800 degrees -- hot enough to melt lead. Needless to say, there are no jungles on Venus, just wide, dry plains, canyons, and some highlands. The only changes in the Venusian terrain seem to come about from volcanic activity. The photograph at lower left shows a series of flattened-domed “pancake” volcanoes created by a slow seepage of lava welling up from the planet’s interior. At middle left, windblown debris streams from a volcano’s caldera. Venus’ landscape also shows tremendous craters caused by the impact of meteors large enough to make it through the thick atmosphere. It seems that we’ll just have to keep the Earth as this solar system’s garden spot.
As shown in the Mariner 10 photograph at upper left, Venus has phases like our Moon, a feature that is easily picked out with a small telescope. Unlike most of the other planets in our solar system Venus has no moons, a fact that was in dispute for a couple of centuries. Beginning in the late 1600s and extending through the 1880s various prominent astronomers reported seeing a strange moon orbiting the planet. But the efforts of the scientific community failed to confirm the existence of Neith, Venus’ hide-and-seek companion. The mystery was finally solved when later observations showed that Neith’s discoverers had actually sighted distant background stars and were fooled into believing they were seeing a Venusian moon.
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