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 Jörn 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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