Venus, the evening/morning star, is the second planet from the sun, between earth and Mercury, and the third brightest object in the sky after the sun and moon. Seen through a telescope Venus appears to go through phases like the moon over a period of several months. It orbits about 63 million miles (109 million kilometers) from the sun and is tipped over almost 180 degrees and rotates very slowly. A 'day' on Venus lasts longer than its 225 earth-day 'year'. (All images courtesy NASA/JPL and Wikipedia)
Even through the most powerful telescope, Venus in visible light shows only cloud tops. Those clouds are composed in large parts of sulfur and and carbon dioxide. The atmosphere is 93 times denser than earth's producing the most powerful greenhouse effect known for any planet.
Above, Venus revealed: surface features as seen through the radar eyes of Magellan. Surface temperature is about 860 °F (420 °C) and the ground is composed of bare rock. The geology is poorly understood due to the difficulty of landing on the surface. But the surface appears to be about 500 million-years old everywhere suggesting the planet was resurfaced half a billion years ago. Large volcanoes, collapsed domes, rifts, and lava plains dominate the landscape making Venus a real life version of hell.
Above, a radar reconstruction of a volcanic feature on Venus. Although no active volcanoes have been observed, there is indirect evidence that some episodic activity is ongoing. On the upper slopes of peaks of dormant volcanoes, a bright shiny substance 'snows' out. One possibility is the element Tellurium; on Venus it's so hot it snows metal.
One of a handful of images taken from the surface by Venera 13. The horizon is in the upper left corner and parts of the spacecraft can be seen near the bottom right. That the instrument package landed safely and lasted about an hour before being fried is a tribute to the Russian designers.
Billions of years ago, lovely Venus was true to her mythological name, hospitable, inviting, and probably much more like earth. Evidence suggests she had warm liquid oceans and everything else a heat loving anaerobic microbe could want. But proximity to the sun and relentless solar heating evaporated more and more water. Water vapor is a potent heat trapping gas. The temperature rose further evaporating more water, the process fed back, viciously, and eventually the oceans boiled off completely cloaking the planet in thick steam. High in the atmosphere, under the influence of harsh solar UV, hydrogen atoms escaped their watery embrace with oxygen and bled into space. The oxygen combined with left over nitrogen to form clouds of acid. Nearer the now broiling surface, carbon was baked out of the rock and combined with oxygen to form CO2, trapping even more heat.
Needless to say, under these conditions it will be a very long time before humans visit the surface of this red-hot world, if ever. Even landers or rovers, like the Mars Vikings or the intrepid Spirit and Opportunity still going strong, are out of the questions unless new materials can be developed that can withstand the heat of a kiln and the enormous pressure.
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