A new study performed by a team of scientists led by Dmitry Titov from the Max Planck Institute for Solar System Research and based on images received from the European Space Agency's Venus Express spacecraft revealed the mysterious source of the light and dark bands seen on the planet's surface in ultraviolet light. Understanding their nature will provide more insight on the events and characteristics present at surface level.
Venus Express craft's instruments permit observing our closer-to-the-Sun neighbor in many different wavelengths, each being an indicator to some of its features. The ultraviolet images indicated the presence of a series of high-contrast atmospheric bands, which the scientists believe to be caused by the uneven distribution of some chemical in the cloudy atmosphere, absorbing the UV light. The source and nature of the chemical has not been uncovered, though.
Convection pushes material from the lower layers towards the top of the clouds, just like it happens with boiling water, at Venus' equator and tropics. The mid-latitude clouds were found to be colder and full of sulfuric acid, preventing the vertical layer mixing process that would provide UV-absorbing material from below, thus causing these regions to appear brighter. The clouds float some 72 km (45 miles) above the planetary surface in both regions.
"The sun heats the atmosphere at the equator and the atmosphere starts to boil or mix vertically," explained Titov for
Space. "It comes from the depths of the cloud. It's continuously brought to the top of the clouds by this convective activity." The thick blanket of clouds (20 km or 12 mi) only permits a tiny quantity of sunlight to enter, and traps it under it in a greenhouse effect that rises Venusian surface temperatures to about 465 Celsius (870 Fahrenheit).
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