April 1979
From The Space Library
NASA reported new data on Venus from the Pioneer mission and the radar at the Arecibo observatory in Puerto Rico. Radar had given best information on the surface of Venus, not visible through optical telescopes because of heavy cloud cover. Radar images covering an area 80 million square kilometers showed craters on Venus as large as 320 kilometers in diameter; like lunar craters, which they resembled, they apparently resulted from meteorite impacts.
A circular area 1,120 kilometers in diameter called Alpha, first noticed because of high radar reflectivity, consisted of many parallel ridges identifiable for great distances. This area had no Earth counterpart except extensive dune systems in the Arabian peninsula; Alpha showed a central dark object, possibly a volcano. Another radar feature known as Beta, with long rays of rough material extending out as far as 48 kilometers, also had a central dark area like a volcano crater. The radar also detected parallel ridges about 2,100 miles high, extending more than 960 kilometers across the surface of Venus, forming a structure exceeding the Grand Canyon in scale.
A report on Pioneer Venus orbiter and multiprobe mission findings included discovery of the largest canyon in the solar system, bigger than Mar's Vallis Marineris, previously thought largest. Lightning activity detected by USSR Venera spacecraft was continuous from altitudes of 32 kilometers down to 2 kilometers, with discharges as frequent as 25 per second. Pioneer's orbiter apparently saw this lightning also; experimenters Dr. Boris Ragent of ARC and Dr. Jacques Blamont of the University of Paris now theorized that a glow measured by Pioneer instruments was continuous indistinguishable lightning on Venus, rather than an occurrence on the spacecraft. The orbiter also found an 1,100-kilometer-wide hole containing few or no clouds in the North Pole cloud cover, suggesting a downflow of atmosphere there. (NASA Release 79-47; ARC Release 79-12)
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