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article imageRadar 'unclothes' planet Venus

By Robert Myles     Mar 10, 2015 in Science
Green Bank - As a planet, Venus, shrouded in thick clouds of carbon dioxide, doesn’t lend itself to visual observation. To lift the veil on Earth’s nearest planetary neighbor, spacecraft such as NASA’s Magellan probe use radar to penetrate Venus' clouds.
Recently, Earth-based telescopes have disrobed Venus of her modesty veil of clouds. Venus unclothed is shown to have many remarkable features including mountains, craters and volcanoes.
Conventional earthbound observation of Venus, which orbits the Sun at a distance roughly two-thirds that of Earth, is problematic due to Venus’ permanent cloud covering. But by combining the abilities of the National Science Foundation’s (NSF) Green Bank Telescope (GBT) and the NSF Arecibo Observatory’s powerful radar transmitter, astronomers were able to carry out a planetary survey from right here on Earth.
Located in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone, the 100-meter GBT is the world's largest fully steerable radio telescope. Its “quiet” location, where even wi-fi is banned, means that the highly sensitive telescope is isolated from unwanted radio interference, thus enabling it to perform some unique observations.
Radar signals transmitted from Arecibo passed through both Earth’s atmosphere and that of Venus. They pinged off Venus’ topographical features returning to earth to be picked up by the GBT, a process termed bistatic radar.
But this Venusian survey isn’t a one-off. Planetary scientists will examine the surface of Venus as it appears now but will also carry out further radar examinations to detect changes on the surface of Venus.
These changes might include evidence of active volcanoes or other geological processes. Revealing just how volcanically active Venus is today could give pointers to its geological past as well as subsurface conditions on the planet.
Commenting on this planetary survey of Venus, 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., said, “It’s 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.”
Mars, with its thin atmosphere and sub-zero temperatures, might appear inhospitable. But compared to Venus, Mars is relatively easy to explore with the aid of surface rovers. Such methods, using current technology, would be impossible on Venus where the average surface temperature is 462° Celsius. In addition, such is the weight of Venus’ atmosphere, made up almost entirely of carbon dioxide, pressing down on the planet that surface pressures are estimated to be the equivalent of those found at depths of 3000 feet in Earth’s oceans. The likes of Mars Curiosity Rover, if sent to Venus, would be contemporaneously roasted and crushed as soon as it hit the surface.
The Arecibo facility provided the first hi-res radar images of Venus as far back as 1988 with Arecibo and GBT combining to provide further images in 2012. In the intervening period, Lynn Carter of NASA’s Goddard Space Flight Center also provided further coverage of Venus in the early 2000s.
A paper discussing the comparison between the earlier and later observations has been accepted for publication in the journal Icarus, which focuses on research into the solar system.
More about Venus, Solar system, Planets, exploration of Venus, atmosphere of venus
 
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