Stormy Weather on Earth's Twister Sister

December 04, 2008

This past week even casual sky watchers couldn't help but notice a pair of bright stars in the west at sunset. The brighter of the two is Venus, glistening like a diamond in the sky (without Lucy?). Fellow Discovery Channel blogger Alan Dyer has nicely covered this beautiful conjunction of Venus and Jupiter.

In visible light, telescopic views of Venus show a bland and featureless cloud-shrouded planet. The Roman Goddess of Beauty is, well, coy. This teased early Venus watchers into thinking the clouds covered a tropical world, or a world of carbonated soda pop oceans, or a world of oceans of oil.

But the European Space Agency’s Venus Express orbiter is revealing that Venus’ beauty is only skin-deep. The explorer’s penetrating infrared and ultraviolet vision is uncovering what looks like a witch's cauldron of bubbling turbulent gases and swirling cloud vortexes. Its atmosphere is totally alien because it is not driven by the thermal interplay of oceans and continents. the atmosphere only blankets continuous volcanism on the surface which belches sulfur into the skies.

Ultraviolet light from the sun reflects off the cloud tops. The infrared light comes from heat radiating from the lower atmosphere (at about 400 degrees Fahrenheit). The lower atmosphere has a deep layer-cake structure of noxious sulfuric acid cloud and haze layers. The IR shines through the sulfuric acid clouds, which appear much darker than the bright gaps between clouds. Near the equator, the clouds appear fluffy and blocky. Farther north, they are stretched out into east-west filaments by winds estimated at more than 150 miles per hour.

Not surprisingly, UV images show that equatorial clouds are hot and undergoing violent convection, like bubbling oatmeal on the stove. The convection cells dredge up unknown darker material from deep within the planet. This mysterious chemistry absorbs UV light; creating a visual contrast the helps map out atmospheric flows. At higher latitudes a ring of cold air, dubbed the ‘cold collar’, appears as a bright band.

Most ominous of all is a monstrous hurricane-like feature at the south pole that is half the size of the continental United States. This Jupiter Red Spot wannabe completes a rotation around the pole every 2.5 days.

To me such a view of a neighboring Earth-sized and totally alien planet is amazing. But it also looks gloomy and foreboding, like an approaching thunderstorm. Venus’ atmospheric circulation may be the archetype of many such bone-dry terrestrial worlds orbiting other stars.

I previously blogged about a farfetched scheme to build floating cities on Venus. After seeing these picture it's hard to imagine creating an off-world paradise on such a hellish looking place.