Martian Dust Devil Trails (21 Oct 2009)

[CuDubh]

Mars flexes his biceps.

So cold results in forearm fracture.

Oh well, the tats look great...

[soupphysics]

Anyone else notice the eye on the left side of the picture?

I also thought it looked like bare skin with tatoos!

[Ozymandias]

The markings look beautiful, especially the one the right.

Do we know what exactly this light colored part of the surface is?

[kovil]

Fantastic photo !!!
Makes me want to go to Mars and marvel at the beauty of the fractal patterns in the sand dunes, and maybe live there !
Mars has so many beautiful and awesome landscapes, tho they probably look best from above, from the surface I couldn't see it nearly so well.
So curious that the dust devils 'burn' the surface of Mars like that.
Out here in Nevada the daily dust devils, at the times of the year when the conditions favor them, rotate counterclockwise, but once I saw clockwise rotators !
One day an arriving thru the brush counterclockwise one suddenly reversed to clockwise for 200 yards as it went past me, then back to counterclockwise when it got back into the brush !
As it went across the bare ground of the yard it went clockwise, I made special note of watching it carefully, as I thought I'd seen further off ones going clockwise, but at their distance it's tough to be 100% certain. Of this one I am 100% certain, as it was 50' away at its closest, and 150' away when I first noticed it.
On its slow arrival I could hear the wind in the brush making noise and looked up to see a bit of dirt being raised in a counterclockwise direction as it stayed in one place for a while, then it moved toward me more to where the new water line for the house had been installed and the dirt was bare of brush where it suddenly reversed direction and got much stronger and more focused down to about 2-3 feet in diameter at its base from about 6-10 feet at its base before, to my 'conservation of angular momentum' surprise ! , and picked up wind speed dramatically.
What would cause a dust devil to suddenly and forcefully reverse its direction of rotation ??? As it then moved to where the foundation of the new house was being excavated it suddenly again got much stronger and the base widened to 20' and the wind speed doubled into a real huge dust raiser ! I ran around the corner of the existing house to avoid being totally dusted but watched it move out of the foundation area and across the large amount of brush cleared yard for the trucks to turn around in, about a half acre was cleared, it lowered its intensity and wind speed greatly and weakened a lot as it moved across the brush cleared ground, and a little inner voice was wondering if it would go back to counterclockwise when it got back into the brush again, I made very special note to watch it very carefully, and it did !!! It went back to counterclockwise rotation. I could also see, both times it reversed its rotation, in the dust going up in the air. I could see the twisting spirals of dirt making a ropelike twist going up, and could see the opposite twist directions in the air, as well as the rotation direction at the ground's surface.
Makes a person wonder what kind of 'energy' is involved in this event.
Are the same forces present on Earth as Mars in for what and how dust devils form and is their 'prime mover' ?
Usually the dust devils go west to east and rotate counterclockwise. For 3 days the wind was from the east and I thought I'd seen them rotating clockwise, and they were !
Tho lately the wind is from the east and they are rotating counterclockwise as usual, so it's a bit of a mystery as to why the clockwise rotation, and especially the one that reversed its direction of rotation, twice !!, and right in front of me ! Wish I had a video of it !!!

[Oneiromancer]

I know there's another thread about this, but I just have a question, and that question is likely to be ignored by people who merely enter that thread to give their opinion about the APOD. If you think this should be in the other thread, go ahead and merge the two.

What's the blue thing on the photograph of 21 October 09? http://antwrp.gsfc.nasa.gov/apod/ap091021.html

Is that ice, an optical effect, or something else? And what are those transversal black stripes?

[mfortsm]

I also thought it looked like bare skin with tatoos!

bare skin was a polite way of stating it

[ricardelico]

What about gigantic dust devil marks as an explanation of the "canali" described by Secchi, Schiaparelli, Lowell?

[ricardelico]

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[ricardelico]

sand slides?

[bystander]

What's the blue thing on the photograph of 21 October 09?

Is that ice, an optical effect, or something else? And what are those transversal black stripes?

Good question, I was wondering the same. It looks like the same thing at the upper left (only it's not blue) and the two objects look to be connected by some image blurring. Atmospheric effects? Camera artifact?

[Oneiromancer]

Well, this is going to cause some clutter, but oh well.

sand slides?

Strangely,

What about gigantic dust devil marks as an explanation of the "canali" described by Secchi, Schiaparelli, Lowell?

I thought the canali had been proven to be optical effects? Are those blue marks optical effects? (But again, there's those strange black stripes which seem to contradict that.)

According to the explanation, the dark marks are darker sand which is revealed by the dust devils. So, in analogy, the bluish marks would be some other material uncovered from beneath the sand, which is blue? What material would be blue? Maybe large mineral deposits? If they are mineral deposits, they must have some solid form, perhaps ores, or it would have blown away long ago. Unless the material was deposited there because of the dust devils, and some physical or chemical process gathered it there because of its atomic/molecular properties, perhaps because it was denser than the dust? But how did they get there anyway? And again, why the black stripes?

My first impression was that they were glaciers, and the stripes were morene. Where was this photograph taken? Perhaps it's close to the poles, where there is CO2 in ice form?

[Czerno]

Fantastic, almost erotic (!) picture, but once again the APOD caption is missing basic information :
what scale is it ? are the colours genuine or false ?

[wpope1]

It appears to me that the dark areas are deposits of something onto the already rippled sand dunes and not an uncovering of the sand to reveal darker soil. Zoom in and see for yourself.

[bystander]

what scale is it ? are the colours genuine or false ?

Find your answers at the HiRise site: http://www.uahirise.org/ESP_014426_2070

See the full picture in RGB here and in grayscale here.

The APOD seems to be from the center of the strip with the image inverted.

[Oneiromancer]

Ah, yes, the black sand is merely the sand uncovered by the dust devils. The white thing seems to be a basin in the sand, which is why the black sand collected there: it blew in, and then didn't get out again because the basin offered shelter. Perhaps the basin was earlier hollowed out by the wind. But why? How did the wind form this basin?

It just occurred to me that the blue thing might be a cloud of ice particles. Ice has a low density and therefore blows away quickly once uncovered from the soil?

[bystander]

The artwork of the Martian landscape
Phil Plait - Bad Astronomy Blog
Discover Magazine - 2009 October 15

... What you’re seeing here are sand dunes on Mars. This region is in the center of a large crater at mid-north latitude on Mars, a couple of hours past local noon, and with a resolution of 50 cm (18 inches) per pixel. Sand dunes are common in crater beds, where the wind can blow steadily across the surface and sculpt the ever-present sand into those flowing sculptures. ...

The important thing to note here is that the sand in the craters of Mars is actually dark grey in color, since it’s made of basalt. The reason it looks red in pictures is because covering the sand is a thin layer of much finer dust, and the dust is what’s red. When a dust devil moves over the Martian surface, it can pick up the very light dust particles, but not the heavier sand grains. So those blue-grey swirls are tracks where the dust devil has vacuumed up the dust, revealing the darker sand underneath. If you look carefully in the tracks, you can see the sand dune ripples are undisturbed. Only the dust is gone.

There’s more to see in the picture as well. There is a sloping dune peak cutting across from top left to lower right (it’s more obvious in the larger context view of this region), and again more dark streaks, linear this time, probably caused by sand sliding down the dune face. When the sand moves, the dust covering it gets disturbed and once again you see the darker color of the sand itself. I also love the way the dune shapes change depending on where they are in the picture, caused by differences in the wind patterns across the floor of the crater.

[aunt maggie]

Does anyone see barcodes?

[Star*Hopper]

Late into the chat.....but 1st thought when I saw it earlier was:
"Well I'll bedammed.....Martians were tribal tattoo artists & spoke '2of5'!!!"

~S*H

[bystander]

Does anyone see barcodes?

...Martians were tribal tattoo artists & spoke '2of5'!!!"

I don't know how much speaking they could do, interleaved 2 of 5 (ITF) only codes for decimal numbers.

[orin stepanek]

Dust devils have been credited with unexpected cleanings of mars rover solar panels.

Isn't it neat these devils keep the solar panels clean. 8) Probably contributes to the longevity of the probes.

Orin

[bystander]

Dust devils have been credited with unexpected cleanings of mars rover solar panels.

Isn't it neat these devils keep the solar panels clean. 8) Probably contributes to the longevity of the probes.

What I want to know is, "Who (or what) is operating the Dust Devil?"

[Star*Hopper]

Does anyone see barcodes?

...Martians were tribal tattoo artists & spoke '2of5'!!!"

I don't know how much speaking they could do, interleaved 2 of 5 (ITF) only codes for decimal numbers.

Not very keen on ULoN, I take it.
*sigh*

~S*H

[mudman]

The picture in greyscale, magnified, middle left hand side at http://hirise-pds.lpl.arizona.edu/PDS/E ... browse.jpg raises another ton of questions. Just for one, how can there be an overhang with dust devil tracings apparenly going under it?

[DonAVP]

I am new to posting on this thread but have been looking at APOD for over three years. Not sure if you all know this trick. If you left click on the image a refresh of just the image will be loaded in without any text. If a plus sign if visible when your mouse is over the image you can left click the image to zoom out to a one to one image size. I did this on today's image and could see a lot more detail.

When I first saw the image it looked as though there was a flaw or data loss were the blue area is running from the upper left to the lower right. It still looks like a flaw to me. In some areas of the blue I can see sand duns other areas they are not seen. I am assuming that the dark feather like scrolls and the tracks of the dust devils. That leave the question what is the blue area with the darker blue steaks or scratches. Some have referred to these darker blue areas as land slides.

Don

[PHN]

I know there's another thread about this, but I just have a question, and that question is likely to be ignored by people who merely enter that thread to give their opinion about the APOD. If you think this should be in the other thread, go ahead and merge the two.

What's the blue thing on the photograph of 21 October 09? http://antwrp.gsfc.nasa.gov/apod/ap091021.html

Is that ice, an optical effect, or something else? And what are those transversal black stripes?

The straight parallel black lines are likely caused by sand slides. They seem to be located on the steep surfaces of large sand dunes. My theory says that the sand starts to slide at the top and clears the reddish dust all the way down.