The Stain - Page 18

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LWS


Posts: 3062

Reply: 341



PostPosted: August 17, 2011 2:18 PM 

Serpens;

I plead a defective memory and inadequate record keeping. As Hort points out above the images were from Sol 1217 sol 1223, i.e. 6 days difference rather than the 2 hours I'd mentioned above.

My mistake.

But my point is still a valid one, I think, even though the differences occurred over 6 days rather than 2 hours.

Winston

Barsoomer


Posts: 344

Reply: 342



PostPosted: August 17, 2011 3:51 PM 

The low entropy nature of the later image deserves an explanation. Since it all happened on a magnetic trap, it seems safe to assume that magnetic forces are involved. The dark "blobs" may be the fabled "dust aggregates" that have been mentioned in a MER paper.

It is tempting to surmise that these are related to the stain. Horton, is it possible to color the MI image from pancam images of the calibration target area taken around the same time?

I still feel that the growths and ebbs of the stain may be related to localized dampness in the areas traversed by Oppy. If this is so, then the stain history could potentially be used post facto as a surrogate rover "instrument" to measure the local variations in the humidity. This possibility might provide an incentive for the rover team to take some high resolution pancam images of the stain before the mission ends.

Serpens


Posts: xxx

Reply: 343



PostPosted: August 17, 2011 5:47 PM 

The change occurred during the dust storm. To me it looks like the effect of wind blowing roughly from top left top bottom right. Niote that the filter magnet is very low strength. No mystery here.

LWS


Posts: 3062

Reply: 344



PostPosted: August 17, 2011 7:58 PM 

Serpens;

Sorry, Its still a mystery to one of my, perhaps, inadequate brain power.

Why would the dust particles, thrown violently on the magnet, be concentrated primarily on the south eastern quadrant of the magnet? Why would most of those particles adopt an elongated anti-teardrop pattern re. your presumed wind flow? Why should they mimic fluid droplets only in that quadrant? If they were moving in the direction you posit should'nt there be a significant number of the elongated "drops" also populating the middle and the north western quadrant of the magnet as well?

Winston

Serpens


Posts: xxx

Reply: 345



PostPosted: August 18, 2011 12:12 AM 

Winston. Think about the force vectors. A wind providing force from the upper left will provide transport towards the lower right. The weak magnetic force of the filter magnet will try and attract the tiny particles which will be reasonably magnetic. Now to me it seems that the particles tended to clump in the initial image which would potentially indicate that the magnitude of the magnetic force varies across the face of the magnet, and I assume the lines are normal to the surface. (I don’t know enough about the magnet state the above as an absolute). If so then the particles could be expected to clump in the direction of the line of magnetic force, giving the magnetic particle structure a height. The higher the clump the greater the influence of the wind. If the wind force is sufficient it will topple and move the clump. At the end of the storm the magnetic particles had migrated, either completely off the magnet or to the right hand bottom. The ‘smears’ tend to indicate accumulations and toppling and reflect the position of particles when the wind generated force vector was removed. If the storm had lasted longer then the magnet could have ended up clear.

hortonheardawho


Posts: 3465

Reply: 346



PostPosted: August 18, 2011 8:36 AM 

The fields for the filter magnet are in Fig 3.27, page 69 of Numerical Modeling of Magnetic Capture of Martian Atmospheric Dust

This is a useful paper.

From the paper:

4.5 Summary

By way of conclusion to these theoretical considerations we observe that the drag force scales as the radius of the grain for grain diameters larger than the mean free path and as the radius squared for smaller grains, whereas body forces like gravity and magnetism scale as the volume of the grain, which is the radius cubed. This means that as the grains get smaller the drag force gets more and more important. For micron-sized dust grains the drag force is extremely important. Even quite large forces on dust grains lead only to relatively low terminal velocities and the stopping time for a grain is very short, which we have illustrated through specific examples.
For these small dust grains, therefore, their velocity is essentially always the sum of the local wind velocity and the terminal velocity of the grain; the terminal velocity being determined by the external force on the grain and the characteristic time of the grain. The motion of a grain is therefore determined by three influences: By the wind velocity field, which depends on geometry and Reynolds number of the specific situation; By the magnetic and gravitational forces, and thereby by the magnetic properties of the grain; and finally by the magnitude of the drag force as expressed by the characteristic time of the grain.

Hawkins


Posts: xxx

Reply: 347



PostPosted: August 18, 2011 8:58 AM 

why does NASA add more red to the color pics than is there in reality if you was standing there in person?

things that make ya go Hmmmmmm... Confused

what's up NASA, the Jig is Up on all your Crap!! Razz

I'm sure some of their employees sniff around this blog daily to see if we're buying the bridge they're selling! Wink

hortonheardawho


Posts: 3465

Reply: 348



PostPosted: August 20, 2011 9:37 PM 

sol 2691 ( Aug 20, 2011 ) infrared / visible saturated false color of the stain:

The mineralogy of the "stain" does not appear to be a simple, single material in this view.

I think it's time to visit some earlier full filter views of the stain at the Analyst's Notebook.

hortonheardawho


Posts: 3465

Reply: 349



PostPosted: August 27, 2011 4:22 PM 

sol 2694 ( Aug 23, 2011 ) backlit sundial stain and Cape York soil:

Wow. I don't have words for what I see. Totally unexpected. I will not comment until some of the regulars - especially the "rock guys" comment.

I recommend a download of the image and study using StereoPhoto Maker.

newboy


Posts: 1

Reply: 350



PostPosted: August 28, 2011 5:10 PM 

dx, 304: I agree, it's a good explanation.

So Hort, are you observing that the distinct white colour around both left facing corners is new? Can you see this in earlier images? Or is it because we finally have a new source of dust with a different composition? If so, we will start to see more of it.

hortonheardawho


Posts: 3465

Reply: 351



PostPosted: August 28, 2011 6:12 PM 

The distinct white areas in the corners are specular reflections from clean areas on the deck ( See this animation ). I have noted this before.

What I find astounding is the sharpness - and roundness - of the stain's boundary on top of the clean area.

WHY is the deck so clean under the stain?

And why the %*$( is no one on the MER team officially interested in this area?

Booo! Booo.

Barsoomer


Posts: 344

Reply: 352



PostPosted: September 1, 2011 11:38 PM 

A new look at the wider stain. Not sure what we are seeing now.

hortonheardawho


Posts: 3465

Reply: 353



PostPosted: September 3, 2011 8:35 AM 

sol 2625-2679 changes to the stain:

There also appears to be something "going on" near the center of the image.

dx


Posts: 1661

Reply: 354



PostPosted: September 4, 2011 8:53 AM 

newboy>>>

Good to see you return to comment, and thanks for taking the time to read my post 304.

Lately I have not thought much about this phenomena since Oppy can't get a real good close up shot of this corner of its deck. If it occurred we may be able to adjust our thinking on the matter.


horton>>>

I'm looking near and around the center and comparing with other pics-not sure what you are suggesting. For instance, those wires have always had dark tips to their ends.

yt
dx


hortonheardawho


Posts: 3465

Reply: 355



PostPosted: September 4, 2011 11:05 AM 

sol 1919-2679 ( Jun 17, 2009 - Aug 7, 2011 ) animation of the sundial stain:

Thought everyone would like a Martian year review of the changes. The second year will be quite interesting if there are any seasonal regularities.

dx


Posts: 1661

Reply: 356



PostPosted: September 4, 2011 1:02 PM 

fascinating horton, thank you.

yt
dx

hortonheardawho


Posts: 3465

Reply: 357



PostPosted: September 7, 2011 8:31 AM 

sol 2699-2708 stain changes:

Well. I didn't see that coming. Notice the stain is now behind the sundial near the deck edge.

glenn


Posts: xxx

Reply: 358



PostPosted: September 7, 2011 9:51 AM 

re: your 355, 44 frames over roughly 800 sols.

Can you by any chance identify the sols for each frame? I'd kinda like to calculate the diffusion speed, cm/week or whatever

Barsoomer


Posts: 344

Reply: 359



PostPosted: September 7, 2011 10:58 AM 

That is a dramatic change in just nine sols!

Note the central region that has just been vacated by the stain shows congealed reddish dust that has obviously been there all along while covered by the stain This shows conclusively--if any more proof were needed--that the stain is NOT a cleaning.

Barsoomer


Posts: 344

Reply: 360



PostPosted: September 7, 2011 11:56 AM 

The parts of the stain that didn't move appear to have been blocked by raised fittings on the deck.

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