Starship Asterisk*

The fastest martian winds recorded by Pathfinder were 12m/sec and they found that the light winds recorded could not raise the dust storms that are seen on Mars, so that some other mechanism was needed. But Pathfinder lasted less than three months, and martian dust storms are seasonal.
http://marsprogram.jpl.nasa.gov/MPF/sci ... 8/1901.pdf

Another group used the Hubble to image actual dust storms and measure their movement. At altitide, the storm cloud tops moved at least twice as fast as at ground level, and sometimes seven times faster.
http://www.planetary.brown.edu/m42/m42_29.pdf

At the site where Phoenix landed, wind speeds ranged from 11km to 58km per hour. The usual average speed was 36 km per hour.
http://an.rsl.wustl.edu/phx/solbrowser/ ... mmary.aspx

So while the dust storms demonstrate that it must get fast enough to raise dust, and it does, the mechanism is not clear. Some ideas:
http://www.sciencedirect.com/science?_o ... 798260f504

AND: If the 'pink' areas were formed geological (areaological?) ages ago, then either dust devils that mark it are excessively rare or they would have denuded the arae and it would all be black/blue. They are not, as that and the Rovers have shown, so the pink dust must be relaid from time to time, by fast enough winds!

John

kovil wrote:In relation to 'wind' forming or doing anything on Mars, it would have had to of been a very long time ago, as the Martian atmosphere is extremely thin.

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What little 'wind' that does occur on Mars today is not possible to move any appreciable amounts of material. It can only raise a little dust, or clear it from the Rover's solar panels !

So, what forces are available to do any 'work' on Mars today ?

As stated above, the Solar Wind and other energies from the Sun are available to do 'work' on Mars, and they interact directly with the ionosphere, which can translate those energies down to the surface, where some manifest as 'dust devils' !

I'm fairly certain that Solar Winds were not the cause of all those Martian sand dunes.

In relation to 'wind' forming or doing anything on Mars, it would have had to of been a very long time ago, as the Martian atmosphere is extremely thin.

Atmosphere of Mars (from Wikipedia)
Mars's thin atmosphere, visible on the horizon in this low-orbit photo. Mars lost its magnetosphere 4 billion years ago (well, I'm not so sure of that number as being correct, but it was a while ago), so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected these ionised atmospheric particles trailing off into space behind Mars.[59][60] The atmosphere of Mars is now relatively thin. Atmospheric pressure on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons to over 1,155 Pa (1.155 kPa) in the depths of Hellas Planitia, with a mean surface level pressure of 600 Pa (0.6 kPa). Mars's mean surface pressure equals the pressure found 35 km above the Earth's surface. This is less than 1% of the surface pressure on Earth (101.3 kPa). The scale height of the atmosphere, about 11 km, is higher than Earth's (6 km) due to the lower gravity. Mars' gravity is only about 38% of the surface gravity on Earth.

The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water.[5] The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a tawny color when seen from the surface.[61]

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What little 'wind' that does occur on Mars today is not possible to move any appreciable amounts of material. It can only raise a little dust, or clear it from the Rover's solar panels !

So, what forces are available to do any 'work' on Mars today ?

As stated above, the Solar Wind and other energies from the Sun are available to do 'work' on Mars, and they interact directly with the ionosphere, which can translate those energies down to the surface, where some manifest as 'dust devils' !

One above suggests that the trails go under an overhang. I don't think there is an overhang, just some sharp ridged dunes, and oblique sunlight, so the left side of the dune is shadowed.

PHN wrote: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.

The straight lines are down the slip face, the side of the dune that is advancing, driven by winds from the opposite side. They must be due to the sand at the top being blown up to the lip and over the edge, to be deposited on the slip face. Longitudinal dunes form where the wind is constant and unvarying in direction, which facilitates such regular deposition. But typically, as the wind on the upwind face lifts sand into the air, over the downwind, slipface it becomes turbulent, slows and drops its sand load. In the turbulence, one would expect the sandy air to deposit a mixture of sand from a wide are of the upwind side, so the regular stripes are unexpected. At the least, the blue and pink particles (colour exaggerated, of course) must be very, very similar in size, texture and mass to be deposited so regularly. So what are they?

APOD pics used to be accompanied by some interpretation. HiRise never do.
I would be most interested to read what Areologists thought about this.

John

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NoelC wrote:What's amazing to me is that the natrual processes quite clearly operating on Mars have not led to the emergence of life.

While it seems obvious that there is no life as we know it (including mammalian politicians, to take just one example of an extremophile) on Mars, it's way too soon to assume that there is no life at all. On earth there are bacteria that live inside rocks eating iron to power their metabolism. (Google "hyperthermophiles".) Why not on Mars?

Rob

Man, too many people must look at porn on their computers... Tats... Erotic... ???

What's amazing to me is that the natrual processes quite clearly operating on Mars have not led to the emergence of life. Am I the only one who believes life doesn't have to be "as we know it" (i.e., water-based)? Granted, there's no liquid flowing on the surface of Mars (today), but why not some kind of submartian sand worm?

-Noel

The pseudo bar code has me intrigued, having looked at it in a couple of different views I'm seeing some oscillatory traces including a series of dampened oscillations, rather than separate lines. Not possible it would seem.

Looked like tatoos on skin to me too. Amazing.

Mars is a giant Etch-o-Sketch. The dust devils and sand slides make the designs on the dust surface. Then a big dust storm comes along and erases all the designs.

mudman wrote: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?

I know that looks like an overhang, but if you just readjust your reality a bit, you'll suddenly refocus on them and see them as sharply peaked sand dunes with the black on one side.

Rob

Oneiromancer wrote: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.

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

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?

bystander wrote:

aunt maggie wrote:Does anyone see barcodes?

Star*Hopper wrote:...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

orin stepanek wrote:

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?"

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

aunt maggie wrote:Does anyone see barcodes?

Star*Hopper wrote:...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.

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

Does anyone see barcodes?

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.

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?

Czerno wrote: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.

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.

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