A projection of the radar data of Venus collected in 2012. Striking surface features -- like mountains and ridges -- are easily seen. The black diagonal band at the center represents areas too close to the Doppler “equator” to obtain well-resolved image data. Credit: B. Campbell, Smithsonian, et al., NRAO/AUI/NSF, Arecibo
From earthbound optical telescopes, the surface of Venus is shrouded
beneath thick clouds made mostly of carbon dioxide. To penetrate this
veil, probes like NASA’s Magellan spacecraft use radar to reveal
remarkable features of this planet, like mountains, craters, and
volcanoes.
Recently, by combining the highly sensitive receiving
capabilities of the National Science Foundation’s (NSF) Green Bank
Telescope (GBT) and the powerful radar transmitter at the NSF’s Arecibo
Observatory, astronomers were able to make remarkably detailed images of
the surface of this planet without ever leaving Earth.
The
radar signals from Arecibo passed through both our planet’s atmosphere
and the atmosphere of Venus, where they hit the surface and bounced back
to be received by the GBT in a process known as bistatic radar.
This
capability is essential to study not only the surface as it appears
now, but also to monitor it for changes. By comparing images taken at
different periods in time, scientists hope to eventually detect signs of
active volcanism or other dynamic geologic processes that could reveal
clues to Venus's geologic history and subsurface conditions.
High-resolution
radar images of Venus were first obtained by Arecibo in 1988 and most
recently by Arecibo and GBT in 2012, with additional coverage in the
early 2000s by Lynn Carter of NASA's Goddard Spaceflight Center in
Greenbelt, Md. The first of those observations was an early science
commissioning experiment for the GBT.
“It is painstaking to
compare radar images to search for evidence of change, but the work is
ongoing. In the meantime, combining images from this and an earlier
observing period is yielding a wealth of insight about other processes
that alter the surface of Venus,” said Bruce Campbell, Senior Scientist
with the Center for Earth and Planetary Studies at the Smithsonian’s
National Air and Space Museum in Washington, D.C. A paper discussing the
comparison between these two observations was accepted for publication
in the journal Icarus.
The 100-meter Green Bank
Telescope is the world's largest fully steerable radio telescope. Its
location in the National Radio Quiet Zone and the West Virginia Radio
Astronomy Zone protects the incredibly sensitive telescope from unwanted
radio interference, enabling it to perform unique observations.
The
National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
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Contact: Charles Blue
NRAO Public Information Officer
(434) 296-0314; cblue@nrao.edu
