Venera Images, VENERA 13 fully calibrated image |
Venera Images, VENERA 13 fully calibrated image |
Sep 14 2005, 09:26 PM
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Senior Member Group: Members Posts: 1089 Joined: 19-February 05 From: Close to Meudon Observatory in France Member No.: 172 |
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Guest_BruceMoomaw_* |
Oct 9 2005, 05:58 AM
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Guests |
QUOTE (tedstryk @ Oct 5 2005, 09:13 PM) There is no sulfuric acid rain on the surface of Venus. There has been speculation that it exists in the upper levels of the atmosphere. But in none of those models does it come anywhere near the surface before evaporating. It's more than "speculation"; it's been known fact for three decades. Venus' clouds are a mist of sulfuric acid, produced by the fact that the traces of sulfur dioxide dumped into its air by its still-actve volcanoes rise high into the atmosphere and are converted by solar UV into sulfur trioxide, which in turn reacts very readily with the remaining tracres of water vapor to form an H2SO4 cloud layer at the 64 to 46 km level. (This is the same process that created such large amounts of H2SO4 on early Mars, which as we now know has had a radical effect on its surface mineralogy.) But: (1) As one might expect, given the tiny trace amounts of the gases out of which they form, Venus' clouds are actually very rarified -- you could see through them for kilometers with little blurring. They are opaque to visible light as seen from above (or below) simply because the layer is so spatially thick (as is also the case with Titan's organic smog). (2) Pioneer 13's biggest entry probe carried a cloud particle-size spectrometer which worked fine -- but detected not a single, solitary particle in Venus' air from 30 km altitude down to the surface. (3) There are obviously other substances mixed in with the H2SO4 in Venus' clouds, whose identifies we do not know well, and which are subjects of major scientific interest. In particular, there's the stuff that makes so many regions of Venus' clouds look dark in UV photos -- we actually still do not know what this UV absorber is, although the favored theories revolve around its being one of several sulfur compounds. Then there's the possible detection by several of the Soviet landers of small amounts of other elements (Cl, P, and I think Fe) in the clouds, although given the accuracy of Soviet science instruments this is open to question. Finally, that same cloud particle-size spectrometer on Pioneer 13 located what seems to be a small separate population of cloud particles which are considerably larger than the other liquid acid droplets -- and may possibly be nonspherical solid crystals of something. |
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