Phoenix science results, Beginning with December 2008 AGU meeting |
Phoenix science results, Beginning with December 2008 AGU meeting |
Dec 15 2008, 09:22 PM
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#1
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I figured it was time for a new thread, since we finally seem to be getting some science results out of Phoenix. The press release should be out shortly.
First numerical result I've heard was given by Peter Smith at today's press briefing at AGU: TEGA found that the soil is composed of 5% calcium carbonate, which is a significant result. Hopefully more will hit the Web soon -- post here when the links go up! --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Feb 18 2009, 05:48 PM
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#2
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Senior Member Group: Members Posts: 4250 Joined: 17-January 05 Member No.: 152 |
There's an article on New Scientist about this:
http://www.newscientist.com/article/dn16620 In that article there's a link to this conference abstract: http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1440.pdf |
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Feb 21 2009, 09:44 AM
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#3
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Member Group: Members Posts: 237 Joined: 22-December 07 From: Alice Springs, N.T. Australia Member No.: 3989 |
conference abstract: Very interesting abstract. I'm hanging out to hear the full exposition at the conference. This is an important topic with wide implications. Well, they say they have a smoking gun, and let's hope it doesn't turn out to be the smoky sublimation from an ice pistol (sorry I couldn't resist!). This is basically the story of the photos of two spheroids on the legs of Phoenix. From these photos it looks like a smaller spheroid could have merged with a larger one just below it. For a really good enhanced photo - by HortonHeardAWho - of Phoenix leg and spheroids go to http://www.flickr.com/photos/hortonheardaw...392520/sizes/o/ From my amateur level of understanding the key underpinning general points are that: - a. The index of refraction of liquid water is larger than that of water ice. [Thus - in these photos - a darker spheroid is likely to be liquid.] b. If the spheroids were made up of supersaturated aqueous solutions they would grow due to attracting atmospheric water vapour hygroscopically (deliquescence). c. If they were made up of ice, they would sublimate and so would shrink. [Counter argument: Alternative explanation for growth - water vapour from ice below Phoenix could have sublimated and recondensed on ice spheroids on the relatively cold (in shadow) legs faster than the spheroids were sublimating]. However, the spheroids are highly like to be liquid as: - 1. The fact that shapes observed were spheroidal suggests the presence of the liquid phase. (They could have gone through a number of freeze/thaw cycles). 2. The small upper spheroid darkened between photos. This suggests it changed phase from ice to liquid. 3. The spheroids look as if they joined between photos with the upper spheroid reduced in size afterwards (actual joining not observed). Thus they moved. Therefore they were liquid. [Counter argument - changing light between photos only gives the illusion of movement.] 4. Growth is suppressed in the smaller upper spheroid left behind.......suggesting that when it moved most of its salts were carried with it. [Implication - as a less concentrated solution it froze. This runs against the counter argument in a. above which indicates it should have grown]. Any experts out there, please feel free to correct me! |
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Feb 21 2009, 01:19 PM
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#4
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
4. Growth is suppressed in the smaller upper spheroid left behind.......suggesting that when it moved most of its salts were carried with it. The growth rate suppression is the part I don't quite get. In the scenario where the two spheroids merged, as the two spheroids joined, the capillary action should have sucked the bulk of the initial upper drop into the lower drop. The uppermost part of the drop would have clung (hanging on for dear life) to the surface of the strut. The initial upper drop salt concentration should have been uniform across the drop. So when it got ripped apart, the salt concentration in the remaining part of the upper drop should have been the exact same as the part of the upper drop that joined the lower drop. I *think* that assuming an equilibrium, the salt concentrations of all the drops should all be the same. So the size of the drop should only be dependent on the amount of initial salt that nucleated the deliquesence. So after the merge/ripping apart, the small remaining upper drop will have a smaller absolute quantity of salt than the big lower merged drop. (The concentration of the two drops should be the same). If at the time of merge/ripping apart all the drops were close to the maximal final concentration, then the growth rates for all the drops would be pretty small. So after the merge, did all the drops grow faster than the remainder upper drop? Or were all the growth rates similar (if at all, the merge could have happened close to maximal drop size) -Mike [EDIT: Using the images in the abstract, it looks most of the neighbor drops increased ca. 10% from Sol 31 to Sol 44, but the remainder drop didn't appear to increase. I'm baffled.] -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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