A Discussion on Dust on Opportunity's Solar Panels

How exactly does an image or two of sand dunes answer the question I originally asked?

which was....

Please can someone explain to me, in a simple way, how the solar panels are not absolutely covered in dust?

Regardless of the filter used to take the picture, there should still be some visible dust after 5.5+ years without being cleaned at all. Even in a Martian thin atmosphere the dust is being blown about and continues "to turn the landscape red". I place this in quotes because this is what I have seen in the images and this is how the red cast is explained. The screw/rivet heads are still visible which must be raised a few millimetres from the surrounding area..

Do we honestly think that 'cleaning events' will bring the rovers solar panels back to this condition after 5.5 years in a dusty thin atmosphere. Is it a reasonable thing to say that 'cleaning events' have removed the dust from the solar panels when the wind is weak in the first place and the dust blown about is miniscule particles 3-20 micrometres in size? There is no buildup around the parts which are raised above the surface of the panels.

I would have expected to see a load of dust on these panels after so long "on the road".

Originally posted by qmantoo
How exactly does an image or two of sand dunes answer the question I originally asked?

which was....

Please can someone explain to me, in a simple way, how the solar panels are not absolutely covered in dust?

Regardless of the filter used to take the picture, there should still be some visible dust after 5.5+ years without being cleaned at all. Even in a Martian thin atmosphere the dust is being blown about and continues "to turn the landscape red". I place this in quotes because this is what I have seen in the images and this is how the red cast is explained. The screw/rivet heads are still visible which must be raised a few millimetres from the surrounding area..

Do we honestly think that 'cleaning events' will bring the rovers solar panels back to this condition after 5.5 years in a dusty thin atmosphere. Is it a reasonable thing to say that 'cleaning events' have removed the dust from the solar panels when the wind is weak in the first place and the dust blown about is miniscule particles 3-20 micrometres in size? There is no buildup around the parts which are raised above the surface of the panels.

I would have expected to see a load of dust on these panels after so long "on the road".

There is no dust because they travel along flat Martian roads laid down by the friendly local population so that the rovers never have to negotiate the slightest bump or incline in there journey around the surface.

They also take them indoors if the wind starts up so none of the dust gets blown on to them ,I mean if the wind is strong enough to do that it could never be strong enough to blow it off again could it

Originally posted by qmantoo
How exactly does an image or two of sand dunes answer the question I originally asked?

which was....

Please can someone explain to me, in a simple way, how the solar panels are not absolutely covered in dust?

Regardless of the filter used to take the picture, there should still be some visible dust after 5.5+ years without being cleaned at all. Even in a Martian thin atmosphere the dust is being blown about and continues "to turn the landscape red". I place this in quotes because this is what I have seen in the images and this is how the red cast is explained. The screw/rivet heads are still visible which must be raised a few millimetres from the surrounding area..

Do we honestly think that 'cleaning events' will bring the rovers solar panels back to this condition after 5.5 years in a dusty thin atmosphere. Is it a reasonable thing to say that 'cleaning events' have removed the dust from the solar panels when the wind is weak in the first place and the dust blown about is miniscule particles 3-20 micrometres in size? There is no buildup around the parts which are raised above the surface of the panels.

I would have expected to see a load of dust on these panels after so long "on the road".

There is visible dust.

Opportunity's panel on Sol 1:



Source

Opportunity's panel on Sol 2137 (from your OP):



The 2nd picture shows a very dusty panel.

Black and White, or Grey Scale images can be hard to show the dust, so let us look at some colored in images:

Opportunity panorama Sol 1:



Source

Opportunity panorama Sol 3137:



Source

Quite dusty compared to it's first day there.

I think one of the things you are asking is: why isn't the dust piled up on it? Like sand dunes, or in large amounts?

First, unlike geological features on Mars, the rovers are moving. They may move slow, but they are still moving, and not over very something as smooth as a newly paved road. Any vibrations, slight jolts, etc, are going to knock some of that dust around.

Second, as been explained to you, the winds can move the dust, and if placed at the right angle, move the dust off, so it doesn't have a chance to pile up greatly.

Third: exactly what makes you think that even after 5 years on Mars, that dust would completely cover something up every single time?
There are a lot of factors involved: how much dust is suspended in the air in that area, winds, dust storms, rover movement, rover pitch (angle that it's panels may be at).

During the spring here where I live, the air get very thick with pollen, so thick that it can leave layers of fine yellow "dust" over everything. Now we do have a thicker atmosphere, stronger winds (because of the higher air pressure) and of course rain to wash it away.
Even with all that, I have seen parked cars on days when there is no wind and rain, where some of them are completely covered with yellow pollen, yet at my sister's house located miles away, her 2nd broken down car is no where near as covered as other vehicles I've seen. All because of how much of that pollen was in the air in the different areas. That alone made a big difference.

Opportunity hardly looks "new" at all in Sol 2137 and certainly not by Sol 3137. I also am not sure why you think dust should be so piled up on them worst than it already is.

Can you explain why you think this? Why it should be piled up on something that is moving around with vibrations, jolts, shifts in angles? Remember, the dust has the same consistancy as flour.

That means you could try replicating it here. Get a remote control car, some flower, and a very calm day. Tape some cardboard on it horizontially to represent the rover's solar panels. Sprink the flour on it, then drive it around, get it to go up and over things. Sprinkle more flour and repeat and record your results

Wind blows dust on to the panels. Wind blows dust off of the panels.

Why is that so difficult to understand?

Wind blows dust on to the panels. Wind blows dust off of the panels.
Why is that so difficult to understand?

Firstly because the model NASA generated before the mission predicted a cumulative buildup, but they admitted their model was wrong because there are times when the wind causes a 'cleaning event' as shown on this and other threads. Secondly I would have expected over more than 5 years of being in this dusty environment and in spite of the 'cleaning events' that dust would have built up in the areas where it first fell but which is difficult to dislodge. These areas are between pipes, behind pieces of equipment, similar to the lee areas behind rocks on Earth where the wind does not often go.

It is one thing to deposit dust as a blanket, but another thing entirely to blow it clean away from all the small nooks and crannies on the rover. Thats why it is so difficult to understand.

First, unlike geological features on Mars, the rovers are moving. They may move slow, but they are still moving, and not over very something as smooth as a newly paved road. Any vibrations, slight jolts, etc, are going to knock some of that dust around.

Of course it will knock some dust around, but not in all areas which are sheltered. As I am sure you know, the rovers are/were moving very very slowly indeed. More like tortoise speed.

Second, as been explained to you, the winds can move the dust, and if placed at the right angle, move the dust off, so it doesn't have a chance to pile up greatly.

and has been explained to you, the number of 'cleaning events' are not going to remove dust from out of reach places, but a blanket deposit WILL reach these places. Just like dust which gets into my cupboards does not get blown out with a 'cleaning event' to leave it dust free. I wish it did.

Third: exactly what makes you think that even after 5 years on Mars, that dust would completely cover something up every single time?
There are a lot of factors involved: how much dust is suspended in the air in that area, winds, dust storms, rover movement, rover pitch (angle that it's panels may be at).

It really does not have to cover something every single time, but enough will be left - even after the 'cleaning events' to show it in "in between places" between equipment etc.

Why are you so adamant that the rovers are different to other rocks and ground which are also in the same environment? Very very slow movement will not be the one thing which knocks the dust out of the hard-to-reach places. Even if the panels were perfectly smooth, I do not think you would get a clean sweep like we are seeing.

reply to post by qmantoo



Mmmmmm. You have this discussion going on in two threads. Maybe I should concentrate my answers here? I just spent a lot of time replying in the other thread.

I would not compare the rovers with the rocks. Rocks have been there a long time, much longer than the rovers. The rovers are moving, rocks are not (or at least not anywhere as much as I'm sure any quakes or impacts will move them). Rocks have a lot more rough shapes to them and all sorts of nook and crannies for dust to get stuck in, where as the solar panels on the rovers are much more flat and certainly much more exposed.

And because they are flat and exposed like that, wind on Mars can reach it's entire surface, especially if the wind changes direction, or the rover turns and the wind is now blowing from a different angle.

The dust looks to me like it has gotten all over the rovers pretty well after 5 years, and I'm surprised that Opportunity can even still function to tell you the truth:

The dust looks to me like it has gotten all over the rovers pretty well after 5 years, and I'm surprised that Opportunity can even still function to tell you the truth:

Ahh, but the "cleaning events" are so thorough that it sweeps all the dust away, every little speck from every little nook and cranny. I bet NASA are so pleased.

In the early days, NASA showed us Mars as a very red and dusty place, but recently there must have been fewer dust storms.

They always say that these are false colour images anyway due to all the images being taken as B & W through different filters. So, technically, these are coloured B & W images using the filters to interpret the colours. Often they are as-we-would-see-it I believe they say. This one looks extremely dusty coloured, must have been taken after a dust storm and before a good cleaning.

I think we had better agree to disagree on this dust issue.

The fundemental problem I have is this image which has had false colour applied to it (my false colour, I have applied) and as you can see it is very dusty with all that red dust everywhere. If there was any sky in that image, then that would be very dusty too.

Originally posted by qmantoo

The dust looks to me like it has gotten all over the rovers pretty well after 5 years, and I'm surprised that Opportunity can even still function to tell you the truth:

Ahh, but the "cleaning events" are so thorough that it sweeps all the dust away, every little speck from every little nook and cranny. I bet NASA are so pleased.

In the early days, NASA showed us Mars as a very red and dusty place, but recently there must have been fewer dust storms.

They always say that these are false colour images anyway due to all the images being taken as B & W through different filters. So, technically, these are coloured B & W images using the filters to interpret the colours. Often they are as-we-would-see-it I believe they say. This one looks extremely dusty coloured, must have been taken after a dust storm and before a good cleaning.

I think we had better agree to disagree on this dust issue.

Well hang on before we agree to disagree.

I don't even know what it is you think is going on.

You've asked how the dust can get there, and how it can be removed. We've explained how the winds on Mars can do these cleaning events. You asked how if the atmosphere is so thin, how it can move the dust around, and we showed you how small the dust particles are compared to other mater in the soil (larger grains of sand, pebbles, the blue berries, etc).
You asked why the dust isn't piled up against the rocks, and we showed you pictures where it is. You asked why the blue berries do not get piled up by the wind, and I showed you how it's because they are 5,000 times larger than the dust that does get moved around.

You've asked a lot of really good questions (they are good ones), and many of us have tried our best to answer them as best as we can.

But you are saying that you don't agree with what we are telling you and should agree to disagree.

Okay, I can do that. But at the very least, after spending a lot of time posting answers to your questions, I for one, would like to know what it is that you think is going on.

Obviously you have a different idea and opinion about all this. But I'm not really sure what it is you think is going on. It would be nice to at least know what the other half of the disagreement is....before I agree to disagree with it.

whew....way too many "agrees" and "disagrees" in that last one. And it's late for me, after midnight, so I'm off to bed and will check back in the morning. I hope not to be disappointed that you didn't explain what you think is going on.
Or if you have, and I've forgotten it in my old age, please at least post a link.

You've asked how the dust can get there, and how it can be removed. We've explained how the winds on Mars can do these cleaning events. You asked how if the atmosphere is so thin, how it can move the dust around, and we showed you how small the dust particles are compared to other mater in the soil (larger grains of sand, pebbles, the blue berries, etc).
You asked why the dust isn't piled up against the rocks, and we showed you pictures where it is. You asked why the blue berries do not get piled up by the wind, and I showed you how it's because they are 5,000 times larger than the dust that does get moved around.

1) minute dust particles are carried by the wind. Larger sand grains are moved(but not suspended) to form sand dunes.

2) Rovers solar panels get dusty from the suspended dust particles since the solar panels are too high for the heavier sand grains to be lifted above the ground by the weak wind.

3) Small dust particles get blown out from around and between larger rocks and blueberries to be lofted into the air and carried with the wind to be deposited elsewhere. Nothing larger than 30 micrometres gets moved. Nothing larger than 6 micrometres gets suspended.

4) Jeep3r posted evidence that erosion is almost non-existant

5) No, you have not shown rock erosion, all you have shown is sand dune movement. No, you have not shown dust buildup behind rocks, you have shown sand dunes in front of the camera.

6) No, you have not explained how the dust gets magically moved from lee areas on the rover after it has been deposited there after being in suspension. You have not shown me places on the rover where 5 years worth of sand storms and wind has settled the dust into piles near/behind the rover pipes/equipment. All you have both said is that the rovers movement alters the angle and the wind manages to blow it all away again.

7) The point of my false colour image was that anyone can produce a false colour image to a prove dusty environment or sky.

8) What makes the dust devils white like smoke or cloud? How come they can produce tracks behind them which can be seen from space in the images? Yet strangely, the do not blow other stuff around.
From here (dust particles are dusty red NOT white) my bolding.

On Mars, there is too little water vapor in the atmosphere to contribute significantly to atmospheric convection on local scales. The cloud that we see in this image is produced by dust particles, not raindrops. The astounding heights of Martian dust devils are made possible because mass of an atmospheric column on Mars is less than 1 percent than that of a column on Earth. Transfer of heat from the surface into this less dense atmosphere can produce more vigorous convection, which will penetrate higher into the Martian atmosphere than its counterparts do on Earth.

Now, what would happen if you were caught in its path? Because the density of Mars' atmosphere is so low, even a high velocity dust devil is unlikely to knock you over. However, you might be blasted by any sand or dust particles carried along by the dust devil, which might scratch the visor of your space suit quickly if you were caught outside by this monster!

This vortex left behind a bright track as its winds disturbed the dust-covered surface, tracing the path of the dust devil from the northwest towards the southeast.

==============================================
The main point now seems to be this:
All this does not explain why NASA would say that the sand grains blown in the wind would scratch your sun visor at least 1 metre off the ground. Does not sound as if it takes eons to start eroding something if the visor material is going to be scratched by sand grains?

See that? Thats why we can agree to disagree because no-one has explained how NASA can argue both sides of the discussion in different articles.

reply to post by qmantoo


From the jeep3r post

The abundance of erosional features such as an exhumed former soil horizon, sculpted wind tails, ripplelike and other lag deposits, and ventifacts (fluted and grooved rocks) all suggest the site has undergone net deflation or loss of 3–7 cm of material (...)

Most ventifacts probably formed soon after the catastrophic flood, which likely introduced a large, fresh supply of sand-size particles distributed across the rocky plain.

VENTIFACTS how are they formed well qmantoo



Well what do you know WIND BLOWN SAND & GRIT!!!!

Well what do you know WIND BLOWN SAND & GRIT!!!!

Great, so now what happens and what or who do we believe?

I cannot see any Youtube videos because the Great Firewall blocks all social sites here. No big deal though I can easily live without them. :-)

Originally posted by qmantoo

Well what do you know WIND BLOWN SAND & GRIT!!!!

Great, so now what happens and what or who do we believe?

I cannot see any Youtube videos because the Great Firewall blocks all social sites here. No big deal though I can easily live without them. :-)

That's easy the winds on Mars can blow sand/grit if small enough on and off the solar panels and it can cause ventifacts like here on Earth but will take longer to do it due to velocity and size.

You're right that it's the sand that piles up, not the dust. The dust is just too fine and too easily moved by the wind to do that. Instead, it coats the surfaces with a fine layer, which can be removed by the wind. Many rocks in rover images are dust-free.

I am quite sure that even the finest dust carried by the wind causes erosion. Martian rocks had billions of years to be eroded, bit by bit.

P.S. just came across this Wiki article for a particular Martian ventifact: en.wikipedia.org...

The Jake rock is a ventifact with a volcanic fabric. Its pyramidal shape was formed by eolian drifted grains of sand. The little cavities on its surface were formed by the blast-effect, which is caused by different flow dynamics at the micro-relief. On the surface one could see the marks of the main wind direction, by which Jake was formed.

Many rocks in rover images are dust-free.

It is totally strange how everyone has been arguing for nothing being blown about, only the smallest of the small dust, and now suddenly you are so so happy that you have found an article to say that there is sand and grit blown about.

There is still the matter of NASA promoting both ideas in articles. Had you forgotten? Perhaps we should believe the one which suits us at the time. Just like NASA in fact.

Originally posted by qmantoo

Many rocks in rover images are dust-free.

It is totally strange how everyone has been arguing for nothing being blown about, only the smallest of the small dust, and now suddenly you are so so happy that you have found an article to say that there is sand and grit blown about.

There is still the matter of NASA promoting both ideas in articles. Had you forgotten? Perhaps we should believe the one which suits us at the time. Just like NASA in fact.

PLEASE show side by side what 2 ideas you are complaining about. MAYBE it's the terms used used after all what size is sand/dust/grit.

Okay, first let us talk about Erosion.

The process of eroding rocks can be done in many ways. Water, Wind, Gravity, Temperature. Depending on the situation, you can either see the erosion happening quickly, or it can take eons.

Take my rock tumbler as a way to erode a rock quickly. I take rocks that are very rough around their edges and faces, and place them in a container with water and grit. The grit I normally start off with is very course and large. The tumbler rotates the container constantly with the rocks banging together, and with the course grit water flowing all around those rocks constantly for a week.

They start out looking like this:


And after 1 week of course grit, 1 week of medium grit, and then one week of fine grit, they end up looking like:


So we can see the erosion happening, but only because the rocks were put through a very accelerated process for it. The tumbler moving the rocks around constantly, with a constant flow of water and grit.

The final tumbling of the rocks with the fine grit and Aluminum Oxide, the consistency which is like flour, and the result is this:


Now we can get rocks like this eroded smooth by nature, simply by going to any river. Small stones that are smoothed and rounded like this are commonly called River Rocks, and become this way due to the silt in the river water passing over them.

It takes the river rocks a very long time to look like this because the silt levels in the river are not constant and the currents of the river changes, which changes the flow going by the rock, or even the moving of the rock. It might even take thousands of years for it to happen.

In both cases the motion of the rock, and the water help accelerate the process of erosion, but it's the particles in the water that are doing the eroding in this way.

Wind eroding rock is actually the same thing: wind carrying particles against the surface of the rock erode it. And just like the river, the amount of erosion depends on particle size and how much wind is blowing against the rock. The process can take millions, tens of millions, hundreds of millions of years.....or even longer.

You are not going to be able to witness the process actually change the rock. Not unless you live for millions of years. All you are going to be able to see is the result of that process.

Ever use a bead or sand blaster? I have to clean metal casings used to house the electronics used to get cable to people's houses that are on telephone poles. The blasters use particles that are much bigger than the martian dust, at air pressure much greater than the martian atmosphere. But the results are the same. The only difference is: how long it takes.
I can see the erosion happening almost instantly with a blaster. The rock on Mars will take longer than humans have existed.

So no, you will not actually SEE the erosion in action with rocks on Mars. The process is much too slow. Rocks, some of them 4 billion years old. You are only going to see the results of that process.

Soil erosion is different on the other hand. Soil is loose and made up of much smaller particles.

Using a garden hose, the flow of water can move soil around, basically "eroding" a channel in the dirt.

Wind can move loose soil particle around, and you can actually see the process happening, only because the soil is made up of much smaller loose particles.

Okay, that's just the Erosion. Other posts for your other points.

Dust Devils are not the same thing as just wind.

Wind is air moving due to thermal currents and pressure gradients.

Dust Devils are a well formed whirl wind like a tornado, only not as strong as an actual tornado.

Wind can be a gentle breeze to small gusts that blow dead leaves around. Or the wind can gust strong enough to break tree branches or even knock over trees. Hurricane force winds are strong enough and sustained long enough to cause major structure damage.

But a tornado. A tornado can pick up a whole house and carry it away. It can fling train locomotives miles away from the tracks it was on.

I've actually had a EF2 tornado pass by my house here.....while I was in it. Not fun. The entire house was moving and the noise was deafening.

Dust Devils are not anywhere near as strong as a tornado. But they are a organized whirl wind which consistently shows us that even a Dust Devil can move things around, even at lower speeds than a strong gust of wind.

Strong enough to clean the surfaces of Spirit and Opportunity......even the areas that you think the dust should have piled up:

Mission members monitoring the Spirit rover on Mars reported on March 12, 2005, that a lucky encounter with a dust devil had cleaned the solar panels of that robot. Power levels dramatically increased and daily science work was anticipated to be expanded.[18] A similar phenomenon (solar panels mysteriously cleaned of accumulated dust) had previously been observed with the Opportunity rover, and dust devils had also been suspected as the cause.[19]

Source

As for it looking white:

I'm not 100% sure as the the why, all though I seem to remember reading something about how the dust looks laying on the ground as compared to moving in the air, such as dust storms.

------------------------

"To be Sand Blasted or Not Sand Blasted."

You will note in the article that you quoted they used a word when talking about what would happen to a astronaut caught in a dust devil:

"might'

That's a important word. They don't know for sure. We do know that Spirit and Opportunity encountered martian dust devils and all that happened to them was they received a very good cleaning (answering your question as to how the wind could clean even the hardest to get places on them).

Even NASA is allowed to speculate, just like any of us on here. They were thinking that is what might happen to someone on Mars, yet didn't happen to the rovers.

It's quite possible that the encounters the rovers had were much more gentle in nature than others that can occur.

A EF1 tornado is no where near as powerful as a EF5 (known as "The Finger Of God"). A EF1 can pass right over houses and only very minor damage happens.
Where as a EF5 will scour the earth like a gigantic bulldozer.

Keep in mind too, Dust Devils happen here and there, but not everywhere all the time. Just like here on the Earth. A tornado can cut a destructive swath in it's path, but things outside it are not touched.

A dust devil on Mars can cut a swath in the martian soil, exposing what is under neat it......yet not move any blue berries around that were near it.

Originally posted by qmantoo

Many rocks in rover images are dust-free.

It is totally strange how everyone has been arguing for nothing being blown about, only the smallest of the small dust, and now suddenly you are so so happy that you have found an article to say that there is sand and grit blown about.

There is still the matter of NASA promoting both ideas in articles. Had you forgotten? Perhaps we should believe the one which suits us at the time. Just like NASA in fact.

Well, the science part of it is more important than what various people said on here. I don't see that there are two mutually-exluding ideas "promoted" by NASA. The only idea is that there is the fine dust carried freely by the wind (which is responsible for erosion too), and larger sand grains transported along the surface and perhaps lifted some distance into the air. There would be various-sized particles, so a particularly strong wind might carry particles large enough to scratch your spacesuit visor or unprotected instruments on a rover. Seasonal polar winds are strong enough to transport sand up the dune slope.

There might be more details and particulars to martian weather, and I'm certainly not an expert in that field, but I don't see any problem with what scientists tell us about Mars.

Thank you all for your (very patient) input. :-)

I am going to keep posting bits and pieces on this topic as I find them. More as a reference than anything else. I have already said that you all have not convinced me, and we just have to agree to disagree, so there is no need to answer any of these further posts. They are just my 'musings'.

Rover's decade on Mars surprises NASA

Sure, it has some wear and tear. One of its six wheels and two instruments stopped working long ago. It has an arthritic joint. Its flash memory occasionally suffers a senior moment. But these problems are considered minor for a journey that was supposed to be just a three-month adventure.
....
Meanwhile, Opportunity has logged 24 miles crater-hopping. The solar-powered NASA rover is now in a sunny spot on the rim of Endeavour Crater where it's spending its sixth winter poking into rocks and dirt.

Its power levels have unexpectedly improved. A recent "selfie" showed dust on its solar panels was later wiped away by blowing winds.

Early discoveries by the two rovers pointed to a planet that was once tropical and moist. However, the signs of water suggested an acidic environment that would have been too harsh for microbes.

More recently, Opportunity uncovered geologic evidence of water at Endeavour Crater that's more suited for drinking -- a boon for scientists searching for extraterrestrial places where primitive life could have thrived. The crater is the largest of five craters examined by Opportunity.