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Tracing Venus' watery past.

A new analysis of the chemical processes that deplete deuterium and hydrogen in Venus' atmosphere hints that Venus might once have had an ocean as deep as 10 meters--more than double previous estimates based on atmospheric chemistry.

Mark Gurwell and Y.L. Yung of the California Institute of Technology in Pasadena base their study on the relative efficiencies with which molecular oxygen and related oxygen products can knock hydrogen and its isotope, deuterium, out of the atmosphere. They calculate that it is far easier to deplete deuterium, relative to hydrogen, than previously estimated.

That finding alone does not alter current thinking about an ancient ocean on Venus. But researchers also know that the ratio of deuterium to hydrogen on Venus hasn't stayed the same throughout history, although on Earth the ratio has remained relatively constant. The Venusian ration, now about 100 times the ration on Earth, apparently equaled the terrestrial value billions of years ago. So if much more deuterium exited the Venusian atmosphere over that time than had been believed--as the new calculations indicate--then a larger amount of hydrogen must also have escaped. To put it another way, Venus may once have had a greater reservooir of hydrogen than scientists had estimated. Since the concentration of hydrogen typically indicates the presence of water, the new calculations suggest that Venus might have had a substantially larger ocean than researchers had speculated, Gurwell says.

He cautions, however, that a higher concentration of hydrogen over the the lifetime of Venus may not mean that the planet contained a huge amount of hydrogen at any one time.
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Title Annotation:Astronomy
Author:Cowen, Ron
Publication:Science News
Article Type:Brief Article
Date:Nov 23, 1991
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