Starship Asterisk*

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

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.

Looked like tatoos on skin to me too. Amazing.

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.

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

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

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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

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' !

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.

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