Radio jolts indicate Venusian bolts.Lightning often flashes across the sky on Earth, and spacecraft have photographed "superbolts" on Jupiter. Uranus, Saturn and Neptune also appear to harbor the telltale crackle crackle /crack·le/ (krak´'l) rale. of electrical storms electrical storm Cardiology A cardiac event defined as multiple recurrent episodes of ventricular fibrillation, or hemodynamically destabilizing ventricular tachycardia, with a very poor prognosis; ES is most common in older men with CAD, often in a background of , but for years researchers have debated whether Venus experiences such jolts. Data from the orbiting U.S. Pioneer-Venus spacecraft and a series of Soviet craft that landed on the planet remain suggestive but inconclusive. Now, a series of radio bursts detected by the Galileo craft as it swung around Venus last year appear to confirm the existence of lightning on the planet.
A special antenna, designed to detect radio signals from Jupiter when Galileo reaches the giant planet in 1995, took center stage in the Venusian discovery. The antenna's ability to detect higher frequency radio signals than previous craft enabled Galileo scientists to search for characteristic radio burst associated with lightning.
Lightning also produces lower frequency radio waves Radio waves
Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second. . But such signals -- like those from a radio station -- would bounce back from Venus' ionosphere ionosphere (īŏn`əsfēr), series of concentric ionized layers forming part of the upper atmosphere of the earth from around 30 to 50 mi (50 to 80 km) to 250 to 370 mi (400 to 600 km) where it merges with the magnetosphere, the region rather than pass through it. Thus, most of the waves would remain trapped inside Venus' lower atmosphere and could not reach Galileo, notes Donald A. Gurnett of the University of Iowa Not to be confused with Iowa State University.
The first faculty offered instruction at the University in March 1855 to students in the Old Mechanics Building, situated where Seashore Hall is now. In September 1855, the student body numbered 124, of which, 41 were women. in Iowa City Iowa City, city (1990 pop. 59,738), seat of Johnson co., E Iowa, on both sides of the Iowa River; founded 1839 as the capital of Iowa Territory, inc. 1853. Among its manufactures are foam rubber, animal feed, paper, and food products. The city is the seat of the Univ. . He and his colleagues, who built the antenna, detail their findings in the Oct. 4 SCIENCE.
During a survey that lasted just under an hour an Feb. 10, 1990, the antenna detected nine bursts as it pointed toward the night side of Venus. Although the intensity of the bursts -- transmitted to Earth last December -- only slightly exceeded noise levels in the instrument, Gurnett's team says lightning seems the most likely cause of the signals. The antenna found no such bursts during hour-long control studies conducted in flight before and after the Venus Flyby fly·by also fly-by
n. pl. fly·bys
A flight passing close to a specified target or position, especially a maneuver in which a spacecraft or satellite passes sufficiently close to a body to make detailed observations without , they note.
"The findings do indeed indicate that there is lightning on Venus," says William J. Borucki of NASA's Ames Research Center in Mountain View, Calif. "But that doesn't answer the fundamental question: What causes it?"
Some researchers speculate that if Venus still experiences volcanic acitivity, dust particles produced by the flow of molten rock would rub against each other, taking on electric charge and providing the raw material for lightning. But Borucki asserts that this explanation would require an unrealistically high level of volcanism volcanism
Any of various processes and phenomena associated with the surface discharge of molten rock or hot water and steam, including volcanoes, geysers, and fumaroles. , sinc ethe Venusian lightning may occur as frequently as 100 times a second. Instead, he favors the idea that sunlight on the planet's day side creates updrafts of dust or other particles, which form the basis for lightning. That scenario, he says, could explain why most attempts to photograph lightning flashes on Venus' night side have failed.