On the Road Again - volume 4 - Page 6

There is pretty clear movement of some particles both in and around the rat hole including small bits of the grind head 'rim wall'. Physical movement requires the application of force and in this case the only influences available would seem to be wind, vibration from the MI contact sensor on adjusting the MI focus and gravity. Probably a combination of all of the above. These particles are very small and appear also to be quite 'fluffy' so it would not take much to move them a bit.

I am not sure how long elapsed between the grind and the first image, but given the short time between the images in Hortonheardawho’s animation I don’t see that there could be any cooling or moisture related changes particularly given the environment.

Here is the image (a GIF animation) I referred to above

http://www.smugmug.com/photos/153425717_6BC8M-X3.gif

Winston

The only change by the rover between the exposures was a tiny movement of the IDD to create a slight offset in the MI.

But there were much larger changes in the position of the MI that resulted in NO change in the SOD distribution before and after the mass change.

So why did the SOD suddenly leap around - and then stop?

OK, here goes my guess about what's going on:

I think the changes observed were caused by a sudden large change in the magnetic and electrical field associated with one of the positioning motors on the IDD. Perhaps one ( or more ) have broken wires in the core that briefly cause a spike in the surrounding E/M fields.

I have speculated for some time that the organization of the SOD was largely magnetic or electrostatic and now believe that the sudden rearrangement of SOD particles is the result of changes to the electromagnetic environment of the SOD.

This ties in with the observation that the RAT dust is defying gravity and common sense by hanging onto a vertical face of Marquette in spite of the vigorous forces created by the RAT operation ( thermal, mechanical, electrical forces both static and dynamic caused by the RAT motors )

This does not answer the question of exactly what SOD is but perhaps provides a clue.

Hi Barsoomer and Serpens

Your explanations for the movement are quite logical and probably are correct. Wind and Rover movements are the most likely cause for any movement of small objects in the Rat "holes". However, would wind be likely to move numerous small objects roughly the same distance both inside the rat holes and outside it? Would small objects throughout the rat hole be moved? would the raised sides of the rat hole create a situation where a particular segment of the wall would be sheltered from the wind mediated movement of particles?

I would tend to think that rover movement or MI movement might be a more likely explanation and we have seen several examples of fairly large objects displaced by rover movement in MIs. This usually took place after the rat was used to dust surfaces or the focus thingie was used and disturbed loose particles. However, in this case, How much Rover movement is likely if the MI is set up to take images at set intervals and there is no ratting or dusting during that period?

I don't think we know all there is to know about moisture and its influence on the SODs at meridiani. I've suggested before that perhaps there should be an imaging of undisturbed RAT holes over a period of time (minutes, days, etc.) to investigate if there are any surface changes to undisturbed surfaces that had been previously disturbed by the Rat. If there are none, Fine. If they are, note them and see where they lead. AS far as I know there were no further imagings of undisturbed surfaces of ratted rocks. Perhaps this might be an opportunity to take some further images and see what happens.

Looking at Hort's gif I have the impression that, even though the general direction of movement appears to be almost unidirectional, there appears to be some sort of "upswelling" of the matrix with some small objects sinking into the matrix or rising from the matrix. This is probably not real. But could it bear some investigation?

Winston

I wonder if static electricity is involved. After all, you are grinding a crystalline-mineraled rock in a very dry environment. A static charge would tend to fluff the dist up by repulsion. As the charge leaked away (remember the old gold leaf electroscope experiment where radiation can dissipate a charge?) the dust unfluffs.

Just a thought...

--Bill

Hort

I like your E/M field explanation. Its elegant and fits the likely situation with the rover and some observations on the alignment of the SODs. I did not see your 102 before I posted my 103 or I would have amended it a bit.

Winston

Yet again a comment disappeared into the aether.

To repeat, I am not sold on the the rover induced electrical/magnetic field as the motive force. The working distance for the MI is is 63 mm from the front of the lens barrel to the trarget and the motors etc are probably shielded to a degree. But Bill Harris' dry grind induced electrostatic charge is a good prospect.

Again, it is important to note the suddenness of the change. The event was not a steady anything.

The first MI in the sequence was almost an hour before the event. The RAT grind was most likely days earlier.

If you remember, I was concerned about the very long time the RAT sat on Peck Bay without anything appearing to happen. My best guess now is that the grind was done before Christmas, everybody cheered "yay" - and went home for the holidays.

So perhaps 10,000 minutes occurred between the grind and the 1 minute window during which the event occurred.

The MI sequence was about 70 minutes long and no other large changes occurred during that time.

IF this was a wind event strong enough to move some of the rather "large" grains, then I would expect a corresponding strong "cleaning event".

From the Opportunity updates:

sol watt-hours tau dust factor

2079 360 0,508 0.529
2090 359 0.498 0.529
2096 354 0.462 0.528
2103 336 0.490 0.520
2110 315 0.509 0.509
2117 320 0.438 0.519

On sol 2117 there was a small increase in the watt hours from sol 2110 - but this is complicated by a decrease in tau ( clearer air ).

My guess is the dust factor is a derived number from a rover model with the tau and watt-hours as input, so the drop in the dust factor on 2110 is an indicator of a "cleaning event".

But, oddly, the dust factor is back almost as high on sol 2117 as on sol 2103. So I'm not sure what's going on.

I wonder about the precision of the tau number. Can the average tau during the entire day actually be calculated to 4 places from a single measurment of the image of the sun once a day? ( Remember, the atmosphere is a dynamic sort of thing with clouds and dust and stuff )

BUT NASA will argue that the numbers are the best science has to offer, so the best scientific guess is that there was a minor "cleaning event" on sol 2110 between 13:05:12 and 13:06:34.

Accepting that the motice force was in fact a wind gust, we are still left with question of why the particles moved by the wind moved the way they did and did not in fact fall downwards once loosened.

The conclusion is the binding forces between the SOD must be stronger than the gravitational forces acting on them. They are in fact "sticky".

I will spend a little time today looking at how well the shapes of moving SOD is conserved.

The RAT would create heat during the brushing, once complete the rock would cool rapidly and surely some condensation would have occured. Wind gusts are often in the form of a vortex and Oppy could create further turbulance as it passed over it having an effect on the shape of the Vortex.
I get the impression things can be a bit damp at dawn as there is possibly a dew every day.

My take, FWIW?

It was probably a gust of wind, given the timing and the nature of the event. We've seen dust bunnies move with the wind before. Even though I mentioned static electricity, I was thinking more as a factor for the general cohesiveness of the dust-- the charge has had plenty of time before the event to dissipate. Being a silicate rock in a dry environment it could retain the charge for a long time since it is effectively not grounded.

In a way, a rolling rover is a great vandegraff generator...

--Bill

sol 2122 ( Jan 12, 2010 ) L0 3x1 in the next drive direction:

with a link to the R12 4x1 detail.

Oppy is back on the road, heading for "fresh crater"?

Well, there were in fact morning clouds on sol 2110 and 2111.

Unfortunately, I have no access to the camera pointing information so I can't confirm that the wind direction was towards Peck Bay.

Yeah, "the event" was probably a gust of wind in an otherwise placid zephyr of 10 km /hr or so.

The piece of outcrop or debris on the right side looks more eroded than usual. Also, the marks on the soil nearby may indicate either a localized wind pattern or scrape marks from sliding debris.

Definitely an atypical Meridiani outcrop.
Don't suppose they have time for a closer look.

I've noticed a few of these atypical outcrops (raggedy-edged, not planed down flush and smooth) at this site. Wonder if they could be related to ejecta from Fresh crater? We'll see as we approach that feature.

Also the ripples seem to be getting deeper. Maybe this signals a major change in the terrain-- Meridiani has been monotonously consistent since leaving Victoria.

--Bill

Those mini dunes suggest softer sand to me, careful Oppy keep out of the basin areas underneath the ridges.

From the Weather Department.

It was a breeze and nothing more.

Fred

Here is a link to a route map for Sol 2054 (close to where we stopped at Marquette). She'll head South-Southeast along the bedrock exposures to avoid the deeper sand, then due South in the inter-ripples to Fresh crater. I'd expect her to make good time on the bedrock.

Craters are like roadcuts, they give you an idea of what subsurface conditions are.

http://www.unmannedspaceflight.com/index.php?act=attach&type=post&id=19497

--Bill

The sol 2122 ( Jan 12, 2010 ) position is about 13 meters from Marquette. The "atypical Meridiani outcrop" is about 3.8 meters distant.

I will update and post my map after today's drive images are posted around 3:40 PM EST.

There wasn't even a planned pancam image of the atypical outrop or a look back at Marquette. There is only an L1 "ripples" sequence.

Perhaps today's drive was a "bump" to study "atypical outceop"???

"Fresh crater" is now about 330 meters distant - 5 typical drives. Maybe Oppy will be there for the weekend after next "science stop"?

Seems to be quite a lot of ragged-looking outcrop around here. Could there be gas emissions from the subsurface that are disturbing the outcrop?