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Thread: Water astrochemistry

  1. #1 Water astrochemistry 
    Time Lord
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    In space, water normally forms amorphous ice, which is stable apparently - e.g. planetary rings. So sublimation and solar wind does not erode it much? Or is an icy surface constantly losing water only to have much of that same water bond again?

    What about our crystalline (hex) ice, transported to space? Is it stable? Change to amorphous? On the surface or all through?


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  3. #2  
    Time Lord
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    Come on somebody help me here. :?


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  4. #3 Re: Water astrochemistry 
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by Pong
    In space, water normally forms amorphous ice, which is stable apparently - e.g. planetary rings. So sublimation and solar wind does not erode it much? Or is an icy surface constantly losing water only to have much of that same water bond again?
    This will depend entirely on context. What is the flux and frequency of radiation? What is the density of ice grains in the vicinity? What are the temperatures of those grains? etc
    Quote Originally Posted by Pong
    What about our crystalline (hex) ice, transported to space? Is it stable? Change to amorphous? On the surface or all through?
    I don't see, on the face of it, why the crystalline ice should become amorphous. The crystalline form is at a lower energy level and so should be more stable.
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  5. #4 Re: Water astrochemistry 
    Time Lord
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    Quote Originally Posted by Ophiolite
    What is the flux and frequency of radiation?
    I was wondering about conditions around 1AU, and 10 (Saturn) for comparison.
    Quote Originally Posted by Ophiolite
    What is the density of ice grains in the vicinity?
    In rings you mean? Rings vary widely, but here's a drawing recently published by the NASA-Cassini folks, to give you a sense:


    However some rings are dense/thick enough to block practically all light. Most rings include few particles larger than 1m, the bulk being 5cm or less.
    Quote Originally Posted by Ophiolite
    What are the temperatures of those grains? etc
    Rings, about 50 Kelvin. Though it'll change in the course of a "day".

    An artificial satellite at 1AU, we could say 260 degrees K, for starters - i.e. water just frozen aboard ISS and dropped out the airlock.

    Mercury may harbor polar ice, believe it or not. This is in pockets, where shade temperature less than 100K means ice could theoretically last billions of years - it just doesn't evaporate much.
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