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Ceres Geology
remcook
post Jan 22 2014, 06:14 PM
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Paper out tomorrow: http://www.bbc.co.uk/news/science-environment-25849871
Very exciting that we will visit this world soon! smile.gif
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alan
post Jan 22 2014, 06:22 PM
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Comet Piazzi ?
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Paolo
post Jan 22 2014, 06:32 PM
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paper just out in Nature: Localized sources of water vapour on the dwarf planet (1) Ceres
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TheAnt
post Jan 22 2014, 07:45 PM
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Thank you for the heads up.

Hydroxyl. OH have previously been found to make up the main part of Ceres extremely rarefied atmosphere.
So finding water vapour is not completely unexpected, it might be the source of the hydroxyl after water molecules have been dissociated by UV-radiation from the Sun.
BBC stated 6 kg per second, and the diagram of the paper suggest it only happens when Ceres is in certain parts of its orbit. So I place my bet that its a slow sublimation, even though -35 C as the warmest summer day isn't exactly balmy. smile.gif
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Holder of the Tw...
post Jan 22 2014, 07:47 PM
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QUOTE (alan @ Jan 22 2014, 12:22 PM) *
Comet Piazzi ?

Neh, don't think so. Mars loses plenty of water vapor to space, too.
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Explorer1
post Jan 22 2014, 07:54 PM
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Will anything be detectable from the camera at high phase angles, like Cassini and the Enceladean plumes, or will they have to rely on GRaND and VIR? A few kilos a second isn't that much...
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nprev
post Jan 22 2014, 08:01 PM
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Dunno if there will be anything visibly detectable at all; kinda doubt it. 6 kg/sec outflow isn't very much, not much more than an average bathtub faucet flow. If that's a global rate rather than highly localized it's damn near gotta be just sublimation.


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vjkane
post Jan 22 2014, 08:14 PM
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Could we get FedEx to deliver a mass spectrometer to Dawn post haste? smile.gif


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machi
post Jan 23 2014, 11:49 AM
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6 kg/s sounds uninteresting but it's 518 tons per day. I don't know exact numbers for Enceladus but I saw somewhere number 200 - 250 kg/s.
So maybe with luck, Dawn will be capable of detecting Cerean atmosphere with his camera or VIR spectrometer.


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AndyG
post Jan 23 2014, 01:59 PM
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Nprev, the ESA article states:

QUOTE
Almost all of the water vapour was seen to be coming from just two spots on the surface.


smile.gif

Super interesting!

Andy
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nprev
post Jan 23 2014, 02:35 PM
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I stand corrected, yet skeptical. Always happy to be proved wrong, of course. smile.gif


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marsbug
post Jan 23 2014, 03:53 PM
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Visibility will depend on the exact nature of the sources to some extent, won't it? I mean that a diffuse source will be much less visible than a concetrated, point-like one?
While this isn't exactly a discovery on par with finding a duplicate Earth hiding behind the Moon, this is a nice little appetite whetter for Ceres. And it does confirm that there is probably a fair bit of water ice there.


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Cruzeiro do Sul
post Jan 25 2014, 12:32 PM
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QUOTE (TheAnt @ Jan 22 2014, 08:45 PM) *
... and the diagram of the paper suggest it only happens when Ceres is in certain parts of its orbit.

As the Ceres orbit has an eccentricity of 0,080 and an orbital period of 4,6 years, is it possible that Dawn spacecraft will be able to stay in Ceres orbit until its perihelion and so, to tentatively observe the surface spots from where this water vapour is originated?
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angel1801
post Jan 25 2014, 01:47 PM
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According to the Wikipedia page, Ceres has an axial tilt of about 3 degrees, similar to Jupiter and Venus.


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Doug M.
post Jan 25 2014, 11:34 PM
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QUOTE (Cruzeiro do Sul @ Jan 25 2014, 02:32 PM) *
As the Ceres orbit has an eccentricity of 0,080 and an orbital period of 4,6 years, is it possible that Dawn spacecraft will be able to stay in Ceres orbit until its perihelion and so, to tentatively observe the surface spots from where this water vapour is originated?


Ceres' last perihelion was September 2013, just four months ago. Aphelion will be at the end of 2015 and the next perihelion in April 2018.

Dawn will arrive there in late March 2015 and (IIUC) currently has a nominal one-year mission. So it will certainly be there through aphelion. It would have to hang around another two years for perihelion. I don't see anything that would prohibit this, though some orbital manipulation may be required -- lower orbits burn fuel faster, as the spacecraft has to make more adjustments.

If the water vapor production really is driven by sublimation -- a reasonable assumption, but who knows -- then we'd expect it to be peaking in the months after perihelion when Ceres' surface is warmest, i.e. right around now. So in that sense Dawn would be arriving at exactly the wrong time. But we really don't know. We'll start getting respectable imaging of Ceres' surface a couple of months before Dawn arrives, i.e. January 2015. So... we wait.


Doug M.
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