Mohawk Valley Astronomical Society

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Electric Fire

by Perry Pezzolanella

Venus is the planet next door and yet there is still so much to learn and understand about her. The problems are primarily the clouds that completely hide the surface from view and the hostile surface conditions. The clouds are composed of carbon dioxide laced with sulfuric acid and the heavy carbon dioxide atmosphere reinforces the intense greenhouse effect. The average surface temperature is 870 F and the atmospheric pressure is 92 times Earth's. The hardiest spacecraft have survived no longer than two hours on the surface, hardly allowing enough time to confidently answer two burning questions about Venus: are there active volcanoes and is there lightning?

The Magellan orbiter was a highly successful mission launched by NASA on May 4, 1989. It arrived in orbit around Venus on August 10, 1990 and remained in orbit until its fiery demise into Venus' thick atmosphere on October 12, 1994. The thick clouds hinder the use of a regular optical camera so Magellan used radar to determine the elevation and texture of the surface. The main goal was to map 98% of Venus at a resolution of only a few hundred feet, which finally revealed its landforms. There was a stunning discovery that the surface of Venus is quite young, hardly 500 million years old. There are very few craters, which indicates that the surface is young, but the biggest proof was the discovery of volcanoes everywhere. Thousands of volcanoes pepper the surface of Venus with towering giants, smaller pancake domes, and fields containing clusters of small volcanoes and cinder cones. Solidified lava flows are everywhere with evidence of a huge global lava flood and thin channels, some about 4000 miles long carved by thin running lava.

The number of volcanoes and the severity of the eruptions almost certainly altered the climate causing the inferno of today because the carbon dioxide belched by the volcanoes had nowhere to go so it remained in the atmosphere creating a runaway greenhouse effect. It is possible that Venus was even hotter at the height of its volcanic eruptions, possibly as hot as 1200 F, and is only now cooling off. At such high temperatures the clouds would have cleared and the red hot surface glowing with lava would have easily been seen from Earth. As Venus cooled below 1000 F the clouds returned, which hid the surface from view once again.

The question is whether Venus is still volcanically active today. There is some proof that it still is. The Pioneer Venus Orbiter arrived in 1978 to find unusually high levels of sulfur dioxide in the atmosphere, which is a common gas from volcanoes. The amount of sulfur dioxide dropped steadily during the 1980's and eventually leveled off, hinting at a possible eruption around 1977-78. Venus Express has been orbiting Venus since 2006 and has shown large changes in the amount of sulfur dioxide. Venus has over a million times as much sulfur dioxide generated by volcanic activity as Earth. Most of this gas is located deep beneath the upper cloud deck since sunlight readily destroys this gas. Detecting the gas above the clouds means something has to supply it fresh from below.

Venus Express can map the amount of heat radiating from the surface, even at night, even though the average surface temperature is a blistering 870 F. There are hotter spots. A few very small spots are as hot as 1300 F and could be active volcanic vents or fumaroles. One of the mountain peaks is anonymously warm indicating that it erupted not long ago and may still be active today. There was a big surge in sulfur dioxide when Venus Express arrived followed by a sharp decrease of about ten times. A volcano could blast sulfur dioxide high into the atmosphere, but there could also be poorly understood wind patterns that churn up sulfur dioxide from lower levels. Because the clouds whip around Venus in hardly four days, it is difficult to pinpoint the origin of the gas. It is also possible that several active volcanoes in a cluster on one part of Venus could cause the observed increase in sulfur dioxide instead of one huge blast.

Another Venus mystery that was finally solved is whether there is lightning. The Pioneer Venus Orbiter and the Venera landers detected electrical signatures clustered around several mountains that later turned out to be volcanoes. Eruptive ash plumes on Earth generate a tremendous amount of static electricity, which results in nearly non-stop lightning. This led to the assumption that Venus has active volcanoes. Then there was a long period of no lightning detected and it was questioned whether lightning had really been observed. Venus Express finally settled the question a few years ago when it detected lightning on the late afternoon side of Venus near the equator where solar heating is most intense. The atmosphere is very dry and windy, so it does not take much convection to build up the charges to generate lightning. Lightning on Venus is different because it is generated in clouds containing sulfuric acid instead of water. The clouds circle Venus around 30 miles above the surface, so the lightning remains in the clouds since the surface is too far below. It is possible that lightning could strike the surface from the low ash clouds, which further adds to the frightening and deadly gloom of this inferno world. The discovery of lightning is crucial because lightning is capable of breaking apart molecules and recombining them into different and often complex compounds, which are important for the creation of life. Although life does not seem possible on Venus, there is a zone in the atmosphere where temperature and pressure are nearly earth-like.

Venus is about as hostile as it can possibly be for a world so earth-like in size and composition. The image of a volcanic landscape with red-hot flowing lava, immersed in searing 900 F heat, crushing carbon dioxide atmosphere 92 times heavier than Earth, sulfuric acid mist, and bathed in an eerie, orange light punctuated by lightning flashing in the volcanic plumes and in the clouds high above stirs the imagination of how deadly a world can be, and Venus is the reality.