The Stain - Page 12

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Posts: 3465

Reply: 221

PostPosted: April 12, 2011 5:54 PM 

sol 2559-2560-2563 ( Apr 6-7-10, 2011 ) animation of changes to the stain:

It's getting bigger again.

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Reply: 222

PostPosted: April 12, 2011 7:58 PM 

Back with a vengeance.


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PostPosted: April 13, 2011 3:25 PM 

The repeated emergence of the stain from behind the sundial platform IMHO makes it very likely that the stain material is being replenished somehow.

The only mundane explanation I can think of is that dark dust suspended in the atmosphere is accumulating on the part of the sundial platform that is facing in the direction of motion for the backward drives, the "windshield" so to speak. Note that the platform has been bolted onto the deck in a somewhat skewed orientation where the stain side is further from the end of the deck than the other side. Thus, any accumulation of dust on that vertical face would tend to be forced to that side by either the wind or any jerk that occurs when the rover lurches into motion.


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PostPosted: April 13, 2011 6:15 PM 

Barsoomer; Good call Smile


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Reply: 225

PostPosted: April 14, 2011 8:25 AM 

sol 2561 ( Apr 8, 2011 ) 3D infrared / visible false color of sundial stain:

The stain is not atmospheric dust. Period. Full Stop. Get over it.

Notice that the dust is bright in the intfrared and red in the visible. The stain is neither.

The stain is not the black paint on the gnomon.

Notice that the gnomon paint is black in the infrared and blue in the visible.

The stain is not.

Here is a table of measured values for the stain and the gnomon paint:

Area Infrared Visible

gnomon 25 12 4 54 99 101
stain 130 100 85 121 108 109

And there is the fact that the dust on the deck does not change when the stain changes.



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Reply: 226

PostPosted: April 14, 2011 8:58 AM 

Well to me it looks like the dark dust is now being blown back towards the sundial. We just came out of the depression (paleo crater?) that Santa Maria was formed in so the environnment has changed yet again.


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PostPosted: April 14, 2011 11:29 AM 

Hort; The stain is not the dust you show ,but a dark ,heavier, component of constantly,winnowed dust that is trapped at this location and migrates around as the rover jostles along over the uneven terrain.
They could be magnetite, immenite, olivine, or other minerals.



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PostPosted: April 14, 2011 11:41 AM 

The shape of the stain and the animation clearly shows that the "new" stain pattern is emerging from the sundial area, not being blown back towards it.

Yes, the spectral response of the stain is clearly different from the reddish dust all over the rover deck. My thought was that the reddish dust is falling dust that consists of larger particles whereas the dust captured by the forward motion of the rover is suspended dust made up of smaller particles. Thus, different populations of dust that might have different properties.

But I do think this idea strains credibility especially since the rover speed is so low. It was the only thing I could come up with. It does seem the stain material is being replenished. Maybe some more exotic explanation for this is needed.

Kye Goodwin

Posts: 1166

Reply: 229

PostPosted: April 14, 2011 6:06 PM 

Maybe this is a "stain" in it's natural habitat (first image - center right, second image - top center) :

These little dark "flows" on sand slopes appear in images from several craters at Meridiani. In the second image a dark area, much like the "stain" and the little dark streak in the background, emerges" from under a solar panel hinge flange (right of center)


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Reply: 230

PostPosted: April 14, 2011 8:13 PM 

What, other than very dry dust can move around on the observed surface without leaving some trace of its prior position??


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Reply: 231

PostPosted: April 14, 2011 10:27 PM 

A covering that fades away in one location and grows in another location. In that case, the covering would only appear to move.

Or large particles that have very little contact with the underlying surface and just hop around.

By dryness, I assume you really mean lack of adhesion? Any substance with strong cohesive forces but weak adhesive forces would fit the bill.


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Reply: 232

PostPosted: April 15, 2011 11:26 AM

"Pancam and Microscopic Imager observations of dust on the Spirit Rover: Cleaning events, spectral properties, and aggregates"

Alicia F. Vaughan1, Jeffrey R. Johnson1, Kenneth E. Herkenhoff1, Robert Sullivan, Geoffrey A. Landis, Walter Goetz and Morten B. Madsen

The above paper analyzes different populations of dust and sand on Spirit. It discusses dust particles of size

If the far side of the sundial platform was able to trap and concentrate saltating sand, then this would be a different population from the airfall dust (not dust all, but sand), and it would be understandable if it had different reflectance and mobility properties. Whether these would correspond to the stain's properties, I don't know.

Kye Goodwin

Posts: 1166

Reply: 233

PostPosted: April 15, 2011 12:23 PM 

Considering the entire history of the stain, it seems to have appeared and grown larger, but at the same time parts of the affected area have been hidden and unhidden, maybe by the regular dust that comes and goes on all surfaces. At times the area right next to the sundial where the stain first appeared has not shown the stain, but it has always reappeared in that same area (see Hort's reply 225). The shape of the stain in the original location is much the same now as it was the first time, and it still has sharp boundaries. Too much coincidence is required to imagine the stain returning by chance to where it had been before. There has to be some influence continually present in that area even when the stain is not seen. Perhaps the stain creates a place where deposited dust has a different fate than in the surrounding areas, becoming transparent with time, or re-lofting more easily.


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Reply: 234

PostPosted: April 15, 2011 12:30 PM 

Thanks Barsoomer for posting the link to the dust paper.

The most interesting part of the paper was the belief that the larger particles on the Spirit deck most likely did not get there by saltation but rather by falling from the air after magnetic clumping.

The fact that the most magnetic dust is a darker mix of magnetite and "something else" suggests that perhaps the sundial stain is a very large magnetite dust aggregate ( plus something else? ) that "just happened" to fall behind the sundial in Victoria as the rover was churning away in dark soil.

BUT the high wind speeds ( > 20 m /sec ) required to move a large clump of magnetic dust from behind the sundial would constitute a "cleaning event" that would disturb the "bright" ( less magnetic ) dust even more. I don't believe that the movement of the stain is correlated with any "cleaning events". ( Perhaps a table of sol vs power levels would be useful. )

Perhaps the authors of this paper will do a pancam spectra study of the stain and see if it matches the dark dust on the filter magnet.

Saaay, that's something we can do now with the original data...


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Reply: 235

PostPosted: April 15, 2011 11:26 PM 


Interesting yet 'meh' read from your link. Speculative at best.

And this 'dust' paper won't amount to a hill of beans when Curiosity hits the scene. He ain't go no panels!


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Reply: 236

PostPosted: April 16, 2011 9:13 AM 

Too bad they did not put a weather vane finial on top of that gnomen and an anemometer...

Kye Goodwin

Posts: 1166

Reply: 237

PostPosted: April 16, 2011 1:30 PM 

Barsoomer, Thanks for posting this dust paper:

It includes many collected observations from Spirit of the magnet experiments and the dust on the solar panels from pancam and MI images and coordinates these with the cleaning events and the dust storm. Two tentative conclusions:

Dust aggregates, as opposed to dust or sand, might be a significant component of the material being moved by the wind. These might form in the air and eventually fall out as they get larger, maybe saltating before coming to rest. Large dust aggregates formed in place on the solar panels and magnets.

There are two components to the dust: a brighter, redder, more weakly magnetic component and a darker more strongly magnetic component. These were separated by wind as the cleaning events removed more of the brighter component from the magnets leaving the dark component behind.


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PostPosted: April 16, 2011 3:53 PM 

sol 2561-2568 ( Apr 8-15, 2011 ) changes to the stain:


Posts: xxx

Reply: 239

PostPosted: April 17, 2011 6:20 PM 

Sure looks like the material is blowing back towards the sundial this time.


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Reply: 240

PostPosted: April 17, 2011 7:22 PM 

Serpens, I don't think so.

In particular, the reply 221 animation demonstrates that the motion of the stain is away from the sundial - and the patch of darkness furtherest from the sundial ( presumably your source of the stain blowing back towards the sundial ) has not changed at all.


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