Thursday, July 30, 2009

Forecast for Venus: “Hot, Overcast, and Dense”

Venus’s thick atmosphere and its proximity to the sun are a cruel combination. The planet absorbs more of the sun’s energy (being closer to the sun than the earth) and because of its heavy cloud cover, is unable to radiate away much of the heat. Even before astronomers saw pictures of the planet’s surface, they knew that it would not be a welcoming place.
Until the advent of radar imaging aboard space probes such as Pioneer Venus (in the late 1970s) and Magellan (in the mid-1990s), the surface of Venus was a shrouded mystery. Optical photons bounce off the upper clouds of the planet, and all we can see with even the best optical telescopes is the planet’s swirling upper atmosphere. Modern radio imaging techniques (which involve bouncing radio signals off the surface) have revealed a Venusian surface of rolling plains punctuated by a pair of raised land masses that resemble the earth’s continents. Venus has no coastlines, all of it’s surface water having long ago evaporated in the ghastly heat. These land masses, called Ishtar Terra and Aphrodite Terra, are plateaus in a harsh waterless world.
The Venusian landscape sports some low mountains and volcanoes. Volcanic activity on the surface has produced calderas (volcanic craters) andcoronae, which are vast, rough, circular areas created by titanic volcanic upwellings of the mantle.
Venus is surely lifeless biologically, but geologically it is very active. Volcanic activity is ongoing, and many astronomers believe that the significant, but fluctuating, level of sulfur dioxide above the Venusian cloud cover is the result of volcanic eruptions. Probes sent to Venus thus far have not detected a magnetosphere; however, astronomers still believe that the planet has an iron-rich core. Scientists reason that the core of Venus might simply rotate too slowly to generate a detectable magnetic field.

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