Water plumes over Europa |
Water plumes over Europa |
Dec 12 2013, 04:55 PM
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Member Group: Members Posts: 401 Joined: 5-January 07 From: Manchester England Member No.: 1563 |
This seems like the relevant place to post this (could be wrong): Water plumes from Europa? Apologies if it's already been up. The link to the Science article at the bottom doesn't work for me, does anyone have a working link to the original? Cheers.
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Dec 16 2013, 10:46 PM
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Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
I kinda said this earlier, but it it possible that the radiation environment dissociates plumes into atomic constituents almost immediately (well, at least in too short a time frame to catch the molecular effluent in action using the imaging systems that have been close enough in the Jovian system to date)?
Given the apparent volume of the ground-based plume image & even if the activity is highly sporadic it sure seems like we should have seen something visible long before. Io vents mostly sulfur compounds; lots heavier than hydrogen & oxygen, and with colorful allotropic states to boot. Not asserting this as a theory, just throwin' it out there for consideration. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Dec 17 2013, 11:44 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
I'm curious as to what would be the half-life of an H2O molecule in a plume over Europa, given the dissociation that radiation can cause.
This paper: http://people.virginia.edu/~rej/papers09/Paranicas4003.pdf Derives for the surface, an "average integrated column production rate of H2O2 in icy regions" of ~5 × 10^10 H2O2/cm^2/s. The recent report is of 7 tonnes of H2O per second, which spends about 1200 seconds between ejection and falling back onto the surface. That means 2x10^29 molecules of water being ejected per second, so at any time there should be about 3x10^32 molecules of water in the plume. The plume has an area of about 2x10^25 cm^2, so radiation hitting that area of surface would radiolyse about 1e^36 molecules of water per second, quite a bit more than what is in the plume. But the final factor to take into account is how much of the radiation would actually hit any molecules in the plume, which would seem to be a slim minority since it's mainly empty space, whereas all charged particles hitting the surface will hit some molecule very soon. Given 3x10^-10 for the span of a water molecule, the plume has a total cross section of about 2.5x10^13 m^2, which means it's only about 10^-8 of the plume, so the radiolysis rate should be more like 1x10-28 molecules per second. The plume has 30,000 times that number of molecules in the air for 1200 seconds, so it looks like the amount radiolysed should be several percent, but less than half. And, as I noted earlier, the effect would be proportionately less closer to the plume's origin. This sort of computation merits peer review if anyone's interested. |
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