The Stain - Page 13

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Barsoomer


Posts: 344

Reply: 241



PostPosted: April 17, 2011 10:51 PM 

The possibility that the stain is an aggregate of the dark more magnetic dust is an interesting one.

However, how does this fit with our past observations of the stain? We have seen that while Oppy was parked at Santa Maria, the stain started fading away, but as soon as we hit the road again, the stain came "back with a vengeance." It does seem that the advances of the stain have some connection with the rover drives.

One would think that vibration would tend to break up aggregates. I guess it is possible though that it might promote them. Maybe that corner of the sundial platform is loose in such that a way that it vibrates at just the right resonant frequency to sort the dark more magnetic dust from the lighter reddish dust and help it form aggregates. Once a partial aggregate has formed, that might form a "seed" that catalyzes the formation of aggregate in the adjacent material. Just brainstorming here. It also seems to me that the stain only began after Oppy started driving backwards, but I need to check on that.

Another effect of vibration is that it can cause liquefaction of poorly consolidated soil or sand. There is an article in today's SF Chronicle about that.

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/04/17/MNJ01ID42Q.DTL

"When a severe earthquake shakes the sand of any filled-in land close to water, the water---even many feet down---rises into the spaces between each individual grain of sand."

Perhaps some water or ice is trapped in the narrow gap under the sundial platform and is drawn out by the vibration of the drives.

Ben


Posts: 2270

Reply: 242



PostPosted: April 18, 2011 1:44 PM 

OT but it relates to vibration...
In 1968 I was seconded to the USBM to develop improved gold placer sampling devices over the old churn drill method.

Shell oil had been developing a vibratory drill for shot hole drilling which was powered by an air-coolled Corvair engine.
The result was, we were able to penetrate loose sand and gravel quickly but liquefaction caused the gold particles to migrate downward with the head of the drill
thereby destroying the accuracy of the samples. Laughing

Barsoomer


Posts: 344

Reply: 243



PostPosted: April 24, 2011 2:25 AM 

Horton, did you get any results from the comparison of the spectral signature of the stain to that of the dark magnetic dust?

hortonheardawho


Posts: 3465

Reply: 244



PostPosted: April 24, 2011 8:27 AM 

Barsoomer, I wrote the author of the paper you cited in reply 232 and received the following reply:

...
As it turns out, we have been asked about this before, and Jim Bell (Pancam leader at Cornell) thinks that they are actually "micro-cleaned" regions of the deck caused by wind swirls created by wind going around the deck topography. He says, "We've seen little splotches and streaks in that region (and elsewhere on the deck) for hundreds and hundreds of sols, in fact. The shapes come and go, sometimes sharp, sometimes fuzzy. Their color is distinctly "deck like"--that is, slightly blueish, allowing these little micro-cleaned regions to be distinguished from shadows (which are slightly reddish). I would guess that the details of their morphology are likely dependent on the strength and orientation of the last big wind gust."
...

Alicia also explained in detail how the R* reflectance spectra from the PDF IOF data was calculated.

I was so discouraged by her answer that I didn't do my own spectra.

It seems that no matter what evidence is presented the "team" will simply say it's just a clean deck ( and clean solar cell? - and unclean bright contacts?? ) - and they - being the all knowing scientists - will be deemed "right" by the masses.

Ah well, it's not important. It's time to feed the cat. But wait. I am not owned by a cat - so I can wash the bowl.

Barsoomer


Posts: 344

Reply: 245



PostPosted: April 24, 2011 2:02 PM 

"There are none so blind as those who will not see."

Barsoomer


Posts: 344

Reply: 246



PostPosted: April 24, 2011 2:10 PM 

The daily energy yield from the solar cells has been hovering around 400 WH and slowly dropping. It doesn't seem as if we have had a significant cleaning event for months. I suspect that we are in somewhat of a sheltered area protected by the "wind shadow" of the rim of Endeavour.

Yet the stain has had a significant re-emergence since we left Santa Maria. It's unlikely this is due to wind.

Kye Goodwin


Posts: 1166

Reply: 247



PostPosted: April 24, 2011 2:40 PM 

Horton, Re your 244, Thanks much for corresponding with Jim and Alicia, and Thanks Jim and Alicia.

I have difficulty with the wind gust theory. It does not match the changes to the stain over time, in the sense that the changes are concentrated in a small area. They are contiguous. The stain appears and disappears but covers a larger and larger area over time. Is the aerodynamic environment in that part of deck special enough to explain repeated incremental changes? The wind direction is not constant. The orientation of the rover has changed repeatedly since the stain appeared. It is hard for me to believe that this small area of deck has a sufficiently unusual effect on wind to make things happen there over and over despite changes to the wind direction across the deck.

Psych Author Profile Page



Posts: no

Reply: 248



PostPosted: April 24, 2011 11:13 PM 

Yes, thanks for that correspondence Horton. Seems the question isn't so much what it is but what may be the actual mechanism causing removal in that specific area. Time to model the deck and stick it in a wind tunnel.

Kye Goodwin


Posts: 1166

Reply: 249



PostPosted: April 25, 2011 1:59 AM 

At least 4 times areas outside the stain but on the border of the stain darkened, becoming indistinguishable from the stain. The areas that darkened were not random or even discontinuous with each other. There has to be a good reason why these areas in particular were affected one after another. Imagining that 5 wind gusts cleared 5 contiguous small areas just doesn't intuitively cut it for me. If the area affected by the stain were in a narrow corridor between obstacles that clearly forced a special wind environment, then I could maybe find this explanation plausible. As it is I can't accept that the unexceptional deck topography combined with a variable wind direction could carry enough information to accurately select 5 adjacent small areas for cleaning.

Serpens


Posts: xxx

Reply: 250



PostPosted: April 25, 2011 4:46 AM 

Oh for goodness sake. Cleaning phenomona or dust deposition - whatever, this is not as some would have us believe a magical living organism. It is a mechanocal arttifact influenced by rover orientation to the wind direction. Crying or Very Sad

Kye Goodwin


Posts: 1166

Reply: 251



PostPosted: April 25, 2011 9:48 AM 

Serpens, re your 250, So if it isn't just wind, then it has to be "magical"? I think it is very reasonable given the history of the stain to suggest that the darkened area of deck somehow helped to induce the darkening of adjacent areas of deck.

Barsoomer


Posts: 344

Reply: 252



PostPosted: April 25, 2011 11:18 AM 

Some other facts relating to the stain.

1. The previous other stain, noted I think by Psych, also adjacent to a bolted-down plate on the deck.

2. Spirit has apparently never shown any signs of a similar stain.

Bonus image:

http://remote-sensing.net/images/ssignatures.png

hortonheardawho


Posts: 3465

Reply: 253



PostPosted: April 27, 2011 7:00 PM 

sol 2546-2569 ( Mar 24-Apr 16, 2011 ) L267 X2 regT unsharp2 animation of changes to the stain:

Notice that - again - the stain has covered a solar cell contact.

THIS IS NOT A DECK CLEANING!

Excuse the shouting but I am so very discouraged by the "science guys" view of this stupidly simple feature.

MPJ


Posts: 250

Reply: 254



PostPosted: April 28, 2011 5:00 AM 

I guess there are no means of resolving the true nature of this feature - the rover just cant get a sample to measure or at least check more detailed. I fear this will remain a mystery while the deck cleansing explanation is satisfying enough to avoid nasty questions Confused

btw: i dont think its just some odd cleaning as well

Barsoomer


Posts: 344

Reply: 255



PostPosted: April 28, 2011 11:03 AM 

I think it's obvious that it is not a cleaning; I don't know why that myth persists.

If the MER team really wanted to study this, they could at least take the highest resolution pancam images of the whole stain area. In fact, they could do a super-resolution series of images.

It might even be possible to get a sample that could be studied by the IDD, once they get to an area where there is some relief. The idea would be to try to scrape off a piece of the stain onto an overhanging rock, then turn around and examine the scrapings.

Fred


Posts: 73

Reply: 256



PostPosted: April 28, 2011 11:44 AM 


Why does it like that spot?

hortonheardawho


Posts: 3465

Reply: 257



PostPosted: April 28, 2011 12:03 PM 

sol 2561-2579 ( Apr 8-26, 2011 ) animation of changes to the stain:

Notice that, once again, a spot near the corner of the sundial once covered by the stain is now blue-grey ( perhaps an actual clean area of the deck? )

Ben


Posts: 2270

Reply: 258



PostPosted: April 28, 2011 1:15 PM 

OK Fred, is that small clean? area in Hort's 257 the most likely for wind to clean first ??

Barsoomer


Posts: 344

Reply: 259



PostPosted: April 28, 2011 1:52 PM 

> perhaps an actual clean area of the deck?

I don't think so. It doesn't look smooth enough.

I think what we are seeing is wetting and drying, however unlikely that might seem. It is the simplest explanation.

Psych Author Profile Page



Posts: no

Reply: 260



PostPosted: April 29, 2011 6:24 PM 

ALthough they say the stain is mostly blue as per as clean deck and in relation to my observations the the stain is DARK in every filter but the Blue and UV where it appears to get lighter, translating to passage of blue light through the blue filters. That tells me it is blueish. there are some early frames of the deck in the L6 filter the show the deck dark : and light, which , makes me wonderif I really understand what the filters are showing us.

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