• The approximate volume of water on Earth is 1.338 Billion cu.km
  • Earth regularly intercepts a number of space objects as meteors
  • During the course of their descent through the atmosphere some burn totally to ash
  • Larger bodies may make it through the atmosphere burning off a part of their content which may remain part of the atmosphere, or make it to the surface.

    1. Does a meteor (subject to it's composition) add to, or deduct from the water volume on Earth?
    2. What is the approximate volume of water acquired/lost annually to such extra-terrestrial bodies by Earth?
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    $\begingroup$ This fits rather on Physics than on Space Exploration, perhaps. $\endgroup$ – gerrit Aug 17 '13 at 18:28
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    $\begingroup$ Hydrogen is lost naturally, and so is oxygen (but only 20 ton per day, which is no problem). $\endgroup$ – gerrit Aug 17 '13 at 18:30
  • $\begingroup$ The ET element made me think the question is be better suited here but I dread you may be right .. $\endgroup$ – Everyone Aug 17 '13 at 18:51
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    $\begingroup$ According to Emily Pope (University of Copenhagen): "Less than ¼ of its water budget over the last roughly 4 billion years.", but I'm not entirely sure this question is on-topic here. There are of course other sources and studies, but I'd believe those we have actual evidence here on the good old Earth first, personally. ;) $\endgroup$ – TildalWave Aug 17 '13 at 18:58
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    $\begingroup$ It is a question, which is, in one way or another, investigated with sounding rockets, experiments on the ISS and satellites. It is definitely atmospheric physics, but the atmosphere 'interacts' with space, so - it does fit in here, although not exclusively. (This would be a beautiful question for a geoscience.SE ...) $\endgroup$ – s-m-e Aug 17 '13 at 19:34

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