A Discussion on Dust on Opportunity's Solar Panels

I searched for "mars rover dust solar panel" and no results, so I guess it is OK to post this then.

I really cannot understand this piece of strangeness. In my common sense I feel that there should be a fair amount of dust on these solar panels. In the past, Spirit did not wake up from the Martian winter because there was just too much dust and not enough sunlight getting through to charge her batteries, yet Oppo is still going strong without much of a dusty covering. A dust covering would obscure the sharp, well-defined edges of the solar panels and make the shiny surfaces dull.

This image shows Opportunity's solar panels without any appreciable dust on them.
Another image taken with a different filter

Yet this is over 2100 sols into the mission. Thats over 5 and a half years after it landed.

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..

Maybe we should have a "hot potato" warning like we have smileys?

reply to post by qmantoo

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

Actually, it looks pretty dusty to me. It helps to combine images with different filters to create a false color image but try comparing it to an image from early in the mission.
But the dust comes and goes to a certain extent. It builds up then is cleared (somewhat) when stronger winds blow. It was pretty dusty last year.

Opportunity's panoramic camera collected images for the mosaic over three days from Dec. 21 to Dec. 24 of last year, according to NASA's Jet Propulsion Laboratory.

The dust reduces the efficiency of the rover's solar panels. Previous dust build-ups were cleared by wind storms.

spaceflightnow.com...

en.wikipedia.org...

Havent you heard about the mars janitor thats been talked about on here for a while now?
Hes a pretty efficient guy.

Actually, it looks pretty dusty to me.

Can you say that this is dust built up over 5 years? No. Can you say that Spirit was similarly not affected by dust? No. There is no evidence in the mars images for dust on the rovers. Basically, you cannot have a buildup of dust and then some 'strong wind' come along and sweep it clean again because that same strong wind would leave other evidence in other places.

Where is the buildup behind rocks of blueberries or where are the piles of blueberries? So far I see none of this kind of evidence which I would have expected.

You can point to the videos of 'dust storms' as evidence, but I also dont see evidence of dust storms ON THE GROUND. That kind of strength wind even in a thin atmosphere would definitely blow stuff about.

I will add some extra bits to the discussion to save you the bother. The Hirise page here and here both show a dust storm and the text along with those images is interesting to say the least.

The length of the shadow indicates that the dust plume reaches more than 800 meters, or half a mile, in height. The tail of the plume does not trace the path of the dust devil, which had been following a steady course towards the southeast and left a bright track behind it.

The delicate arc in the plume was produced by a westerly breeze at about a 250-meter height that blew the top of the plume towards the east. The westerly winds and the draw of warmth to the south combine to guide dust devils along southeast trending paths, as indicated by the tracks of many previous dust-devils. The dust plume itself is about 30 meters in diameter.

So in fact that although the white dust (more like smoke) is blowing one way, the dust devil itself is moving another direction.

It's also interesting that this image was taken during the time of year when Mars is farthest from the Sun. Just as on Earth, Martian winds are powered by solar heating. Exposure to the sun's rays should be at a minimum during this season, yet even now, dust devils act relentlessly to clean the surface of freshly deposited dust, a little at a time.

A way-out thought - Possibly it is a conscious being moving is a conscious way and the wind is blowing it's dust/tail in a different direction to its movement?

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. A dust "skirt" twice as wide as the plume itself is seen near the base of the dust devil, but the bright track is the size of the plume and not the skirt. Dozens of smaller dust devils were also spotted in the same Context Camera scene, steadily vacuuming the surface and pumping dust up into the Martian atmosphere.

From this it would seem that there is a signifcant amount of dust moved about in these dust storms. Why dont we see it in the images?

I guess it's possible on Mars that winds could clear the dust away.

Unlike here where moisture gets to it and makes it stick.

I would really love the rovers to be able to continue on their journey around Mars with fortuitous winds cleaning their instruments every so often. However, we get conflicting stories from NASA. On one hand the wind clears off the dust from the solar panels and there are huge wind storms and on the other hand there is no evidence of blown blueberries (which are only 5mm in diameter) being blown into piles behind rocks. Please explain that to me because I cannot.

Originally posted by qmantoo
I searched for "mars rover dust solar panel" and no results...

OK, you need to press the "ENTER" key after you type-in those search terms.
I did, and got ~244,000 results in 0.36 seconds, including this lovely comparison:


...that very clearly shows that this statement:

Originally posted by qmantoo
There is no evidence in the mars images for dust on the rovers.

...is completely wrong.

Actually, the very first result of the search was this illustrated article about cleaning events.

In answer to this question:

Originally posted by qmantoo
You can point to the videos of 'dust storms' as evidence, but I also dont see evidence of dust storms ON THE GROUND. Why dont we see it in the images?

We do. The same article includes this image:

Time-lapse composite of the Martian horizon during Sols 1205 (0.94), 1220 (2.9), 1225 (4.1), 1233 (3.8), 1235 (4.7) shows how much sunlight the dust storms blocked; Tau of 4.7 indicates 99% blocked. credit:NASA/JPL-Caltech/Cornell

Originally posted by qmantoo
On one hand the wind clears off the dust from the solar panels and there are huge wind storms and on the other hand there is no evidence of blown blueberries (which are only 5mm in diameter) being blown into piles behind rocks. Please explain that to me because I cannot.

Remember that Mars' atmosphere is only 1/50 to 1/100th the density of Earth's atmosphere. That means that an 80-knot wind on Mars would not be strong enough to knock-over a child. Now, according to this article...

Martian dust ... is less than 30 micrometres in diameter.

...which is ~1/167th the diameter of one of your 5mm blueberries. Volume goes up as the cube, so assuming similar density, the 5mm ball of hematite has over four-and-a-half MILLION times the mass of each dust grain.

It should be obvious that in such an environment, winds that can lift particles not much bigger than talc would not budge larger, pea-sized rocks, even in Mars' reduced (0.38%) gravity.

Originally posted by qmantoo
I see none of this kind of evidence which I would have expected.

This is the crux of the problem: It's a different planet. Your expectations may not be valid.

Originally posted by qmantoo
I would really love the rovers to be able to continue on their journey around Mars with fortuitous winds cleaning their instruments every so often.

On this, we can completely agree.

It might also be important to include that poor spirit was traveling in an area that didn't lend itself to easy travel.
Opportunity was able to overcome some of the dust issues by parking at an angle to receive more direct sunlight.
While Spirit got itself hung up in a sandtrap that didn't allow that better winter angle. So the batteries died, and the electronics went into a deep freeze.

reply to post by Saint Exupery

what took that picture?
and dont you need atmosphere for wind?

reply to post by Lil Drummerboy


Mars has an atmosphere. Very thin, but enough to lift tiny particles.

Originally posted by qmantoo
Can you say that this is dust built up over 5 years?

But dust doesn't build up over the years. It comes and goes with the wind, in a thin layer rather than in deep piles like snow or sand on Earth.

There is no evidence in the mars images for dust on the rovers.

Oh yes, there is, but it's a thin layer that doesn't stay there forever. You can see some dust on the Curiosity rover.

Where is the buildup behind rocks of blueberries or where are the piles of blueberries? So far I see none of this kind of evidence which I would have expected.

Well, perhaps the blueberries are too heavy to be blown about like the dust.

But I think Phage and St Exupery gave the best answers here, with great links and pictures. I guess I just reiterated what they said.

So basically, we have one person trying desperately to convince others that the existence of this machine on Mars is a hoax, using a very thin argument, no evidence and all while ignoring freely available evidence to the contrary, then we have others presenting the evidence to completely invalidate their argument

Reminds me of the no-plane theory, the actors theory, the "mind controlled shooter" theory...

Originally posted by Lil Drummerboy
reply to post by Saint Exupery

 

what took that picture?

according to NASA its the PAMCAM:::PAMCAM

The vertical projection used here produces the best view of the rover deck, though it distorts the ground and antennas somewhat. The eight-pointed star shape near the front of the rover (bottom of the image) marks the location of the camera mast, which is out of view of the Pancam atop the mast.

This mosaic view in approximate true color is a composite of frames taken through the Pancam's filters centered on wavelengths of 600 nanometers, 530 nanometers and 480 nanometers.

PAMCAM

Originally posted by Lil Drummerboy
reply to post by Saint Exupery

 

what took that picture?

I assume you mean the top images showing the dust accumulation on the top-mounted solar panels.

Both images are mosaics of a couple-dozen separate images that have been stitched together. The mast mounted camera rotated around to capture the whole vehicle. The only part the camera couldn't photograph was the camera itself (duh) and the mast it sits atop, right near the upper center of each image, near the apex of the solar panels. Note that you can see the shadow of the camera in each image.

To understand this process better, you can try it yourself. Take a camera down to a park and stand on top of a picnic table. Point the camera down and take pictures of the table. Rotate in place and take as many pix as it takes to capture the whole table-top (except for where your feet are). Once you have the pictures, you can rotate and stitch them together using photo-editing software (if you're using a computer) or scissors & tape (if you're using hard copies). When finished, you will have what appears to be an aerial view of the picnic table, except for the part you were standing on.

Does that make sense?

Originally posted by Lil Drummerboy
...and dont you need atmosphere for wind?

Mars has an atmosphere, but it's very thin. It's roughly the same density as ours is ~20 miles above sea level. Even if it weren't all carbon dioxide, it would still be too thin to breath. It is, however, thick enough to blow fine sand & dust. Do a Google Image Search for "martian sand dunes".

EDIT: Ninja'd. Serves me right for being long-winded.

I just found this uselful tidbit at marsrovers.jpl.nasa.gov...
Scroll down to "Solar-Panel Dust Accumulation and Cleanings"

Air-fall dust accumulates on the solar panels of NASA's Mars Exploration Rovers, reducing the amount of sunlight reaching the solar arrays. Pre-launch models predicted steady dust accumulation. However, the rovers have been blessed with occasional wind events that clear significant amounts of dust from the solar panels.

This graph shows the effects of those panel-cleaning events on the amount of electricity generated by Spirit's solar panels. The horizontal scale is the number of Martian days (sols) after Spirit's Jan. 4, 2005, (Universal Time) landing on Mars. The vertical scale indicates output from the rover's solar panels as a fraction of the amount produced when the clean panels first opened. Note that the gradual declines are interrupted by occasional sharp increases, such as a dust-cleaning event on sol 420.

Originally posted by qmantoo

So in fact that although the white dust (more like smoke) is blowing one way, the dust devil itself is moving another direction.

[

Now take a couple of minutes to actually THINK why that might happen

The amount of dust on the panels would have an effect on the amount of electricity generated.

However, the amount of dust in the atmosphere itself would also have an effect and also not have any bearing on how strong the wind was at ground level. We have days, sometimes 3-4 in a row when smog/fog/pollution is in the air and stops the sun coming through. If we were on Mars, that would lessen the amount of electricity generated.

What I am saying is that just because electricity generation went down does not mean that the dust levels went up and visa-versa it could have to do with the atmosphere not how much dust was distributed on the rovers panels.

Over millions of years, I would have expected to see more dust deposited in lee areas behind rocks etc. which are out of the wind.

reply to post by qmantoo


Judging by the graph, the sudden and sharp increases in electricity produced couldn't have been due to the atmosphere getting clearer, unless you're implying that the atmosphere had been getting more and more opaque over the course of 400 sols, then suddenly cleared up. The variations in the atmosphere transparency is more likely reflected in the small random differences in the distribution of data points.

Originally posted by qmantoo
Over millions of years, I would have expected to see more dust deposited in lee areas behind rocks etc. which are out of the wind.

Yeah, because everyone knows the wind never, ever, ever changes direction...

Your expectation is wrong (again).

Judging by the graph, the sudden and sharp increases in electricity produced couldn't have been due to the atmosphere getting clearer, unless you're implying that the atmosphere had been getting more and more opaque over the course of 400 sols, then suddenly cleared up. The variations in the atmosphere transparency is more likely reflected in the small random differences in the distribution of data points.

Maybe not, however, some planets like Mars have been known to have huge dust storms. The article has a comparison image of June and September showing the huge dust storm on Mars.



I still feel that we should be seeing these 5mm spherules blown about into piles since this article linked above from the UK Daily Mail says that NASA was concerned about the rovers possibly being adversely affected. Curiosity does not have solar panels for power generation like Opportunity does but uses nuclear power.

Now, if it may possibly affect something the size of a car, why not a 5mm spherule?