Lead sulfide — also called galena — a mineral often found in the world and, as it turned out now, and on other planets in the solar system. Recent thermodynamic calculations made by researchers from the University of Washington, gave convincing evidence "of snow heavy metal," which covers the Venusian hill consists of sulphides of lead and bismuth. They denied a pre-existing hypothesis that the snow can be composed of tellurium. And that's good — snow of lead sulfide will help date the surface of Venus in the isotopes of lead, if any expedition will bring a sample of the soil.
The researchers calculated the equilibrium compositions for 20 trace metals in the lower atmosphere of Venus, looking for anything that can condense at a height of 2.6 kilometers. The best candidates were sulphides of lead and bismuth.
Metallic snow on Venus was discovered in 1995 in the analysis of data collected by the expedition of "Magellan" in 1989. Then the scientists showed that it was a snow depth of only a few millimeters could give bright spots on the obtained using radar maps. The hypothesis of a metal snow caught on in the scientific community, but its chemical composition was unknown (speculated about the possible 98 metallic compounds).
American scientists have argued as follows: these compounds were to be released into the atmosphere by volcanoes. Discarded volcanoes substances should remain in a gaseous state until they reach a sufficiently high atmospheric layers (where the temperature is low enough) to begin to condense. Because the temperature decreases with increasing altitude, given the altitude remains snow conceivable wherein these agents begin to condense.
The group made a list of all the possible connections and based on knowledge of the chemical thermodynamics narrowed the "list of suspects." So was expelled tellurium — researchers have shown that even when volcanoes spew this stuff into the atmosphere, it can not condense to us, and will react with sulfur dioxide, which has turned into a sulfide tellurium. Lead and bismuth sulfides gave themselves dielectric constant. Most of the erupting volcano rock is low — no more than 4, and the surface of Venus highlands is much higher — about a hundred. This value may be a semiconductor or a conductor, and from the list of substances suspected only sulfides of lead and bismuth have the desired value.
Battery News, 13-02-2004 9:39