Ceres Geology |
Ceres Geology |
Jan 22 2014, 06:14 PM
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#1
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Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
Paper out tomorrow: http://www.bbc.co.uk/news/science-environment-25849871
Very exciting that we will visit this world soon! |
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Jan 22 2014, 06:22 PM
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#2
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
Comet Piazzi ?
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Jan 22 2014, 06:32 PM
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#3
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
paper just out in Nature: Localized sources of water vapour on the dwarf planet (1) Ceres
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Jan 22 2014, 07:45 PM
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#4
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Member Group: Members Posts: 495 Joined: 12-February 12 Member No.: 6336 |
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. |
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Jan 22 2014, 07:47 PM
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#5
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
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Jan 22 2014, 07:54 PM
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#6
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Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
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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Jan 22 2014, 08:01 PM
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#7
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
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.
-------------------- 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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Jan 22 2014, 08:14 PM
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#8
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Member Group: Members Posts: 715 Joined: 22-April 05 Member No.: 351 |
Could we get FedEx to deliver a mass spectrometer to Dawn post haste?
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Jan 23 2014, 11:49 AM
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#9
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
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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Jan 23 2014, 01:59 PM
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#10
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Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
Nprev, the ESA article states:
QUOTE Almost all of the water vapour was seen to be coming from just two spots on the surface. Super interesting! Andy |
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Jan 23 2014, 02:35 PM
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#11
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
I stand corrected, yet skeptical. Always happy to be proved wrong, of course.
-------------------- 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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Jan 23 2014, 03:53 PM
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#12
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Member Group: Members Posts: 401 Joined: 5-January 07 From: Manchester England Member No.: 1563 |
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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Jan 25 2014, 12:32 PM
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#13
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Junior Member Group: Members Posts: 30 Joined: 3-October 07 From: Fátima - Portugal Member No.: 3927 |
... 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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Jan 25 2014, 01:47 PM
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#14
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Member Group: Members Posts: 159 Joined: 4-March 06 Member No.: 694 |
According to the Wikipedia page, Ceres has an axial tilt of about 3 degrees, similar to Jupiter and Venus.
-------------------- I call heaven and earth to witness against you this day, that I have set before thee life and death, the blessing and the curse; therefore choose life, that thou mayest live, thou and thy seed.
- Opening line from episode 13 of "Cosmos" |
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Jan 25 2014, 11:34 PM
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#15
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Member Group: Members Posts: 102 Joined: 8-August 12 Member No.: 6511 |
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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