Instruments aboard the Venus Express spacecraft have obtained the first large-area temperature map of the southern hemisphere of Venus' searing surface.
By identifying hot spots on this inhospitable planet, the new data--obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)--could spot active volcanism.
VIRTIS looked through the thick carbon dioxide curtain surrounding Venus and detected the heat directly emitted by the hot rocks on the ground. The instrument made use of the so-called infrared spectral "windows" present in the Venusian atmosphere. Through these windows thermal radiation at specific wavelengths can leak from the deepest atmospheric layers, pass through the dense cloud curtain, and then escape to space, where it can be detected.
On Venus there are no day and night variations of the surface temperature. The heat is globally trapped under a thick carbon-dioxide atmosphere, with pressure 90 times higher than on Earth. Instead, the main temperature variation is due to topography.
Just like on Earth, mountain tops are cooler, whereas the lowlands are warmer. The only difference is that on Venus cold means 837 degrees Fahrenheit (447 degrees Celsius), while warm means 891 degrees Fahrenheit (477 degrees Celsius). Such high temperatures are caused by the strongest greenhouse effect found in the Solar System.
The VIRTIS results represent a major step forward in our attempt to identify specific features on the surface of Venus, said J?rn Helbert from the German Aerospace Center's (DLR) Institute of Planetary Research in Berlin, Germany. "By peeling off the atmospheric layers from the VIRTIS data, we can finally measure the surface temperature."
The researchers hope to identify volcanoes on the surface of Venus. In the Solar System, besides Earth, active volcanoes have been observed only on Io, a satellite of Jupiter, on Neptune's satellite Triton, and on Saturn's moon Enceladus. Venus is the most likely planet to host other active volcanoes.
The findings were presented today at the annual fall meeting of the American Geophysical Union in San Francisco.
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