I don't have a ball-mill handy and I'm not sure what variables the weathering of the pyroxene and feldspar would introduce into the equation (although this mix ought to be more real-life). I'm looking for a neutral matrix and can sieve commercial sand through 50 to 100 screen.

--Bill

This is great stuff Bill. Such structures seem to require water evaporation, and are modified by water in the air. Ummm.. Too bad you can't reduce the pressure some.

Scott

Thanks for the image slinted. This really brings out the similarity to the "Magic Carpet" feature that jaywee and mhoward mentioned.
Like the "Magic Carpet" seen when the air bags were retracted, this arose from material been pressed down and dragged away.
On the MarkCarey.com/mars forum there is discussion that this material may be or may have been moist:

Dark subsurface, blue ripples, red sand....
http://www.markcarey.com/mars/discuss-3388...s-red-sand.html

If there were thin interstitial ice from atmospheric deposition this ice may have been melted by the squeezing and dragging of the wheel.

cf.

From: Robert Clark - view profile
Date: Wed, Jan 4 2006 1:02 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics
Subject: Could We Make A "Solar Still" On Mars?
http://groups.google.com/group/sci.astro/m...76e921c4b865f2e



Bob Clark

That is highly unlikely, at least with pure ice. Ice is capable of compression melting only over a very small temperature range at reasonable pressures (e.g. down to about -10C for an ice skate), and even this requires significantly higher pressure than the wheel could exert (* caveat: pure ice, that is). See, for example "Why Ice is Slippery" by Rosenberg, Dec 2005, Physics Today pp 50-55.

I am unaware of any data measuring the phase diagram of highly concentrated sulfate/sulfurous brine. I think it is likely that Martian ices, if they are present, would be sulfate/sulfurous brines. I think it is likely that the water/ice phase transitions of such a brine could occur at lower temperatures than pure ice, perhaps -40C; but I don't know if said frozen brines could be compressed to form a liquid at reasonable temperatures.

It's amazing how a malfunction has also caused a neat discovery.

Don't forget that the pressure is approx 1.5% that of earth's pressure. It is exceptionally unlikely that liquid water, even one highly rich in dissolved minerals, cound exist at that surface temperature and pressure. Ice, if present, would most probabyl sublime to the gas phase.

Nick Hoffman explained it best over at THZ when replying to Robet.

Subject: No




Doug

That's a fair point. But the dragging also would have provided frictional heat.


Bob Clark

It is now well known that salts can lower the freezing point of water. It's not as well known but also key that they can also lower the required pressure for liquid water. This is discussed here:

On the possibility of liquid water on present-day Mars.
Haberle, Mckay, Schaeffer, Cabrol, Grin, Zent, and Quinn.
Journal of Geophysical Research, no. E10, p. 23,317-23,326, Oct. 25, 2001
http://www.agu.org/pubs/crossref/2001/2000JE001360.shtml

"We now examine the effect of dissolved salts on the potential for melting. Pure water is unlikely on Mars since salts are believed to be a significant component of the Martian soil [Clark and Van Hart, 1981]. The presence of salts will lower the melting point and reduce the equilibrium vapor pressure of the solution. An example of the effect of a NaCl brine on the potential for melting is shown in Figure 7. In this example, the eutectic point is 251 K and the equilibrium vapor pressure of the solution at that temperature is 1.23 mbar. Clearly, the presence of salts greatly expands the regions where melting could occur and increases the total time such conditions might exist. In this particular example, virtually the entire planet (except the polar regions) experiences conditions favorable for melting at some point during the year, including the Tharsis plateau.
...
"For the NaCl brine mentioned above, boiling would not occur at its eutectic anywhere on Mars since the surface pressure never falls below 2.60 mbar anywhere on the planet during the year."
On the possibility of liquid water on present-day Mars, p. 23,321-23,322


There is also this:

37th DPS Meeting, 4-9 September 2005
Session 24 Mars III
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Music Concert Hall
--------------------------------------------------------------------------------
[24.09] New evidence for recent climate control as the source of the equatorial water equivalent hydrogen regions on Mars.
S.M. Nelli, J.R. Murphy (NMSU), W.C. Feldman (LANL)

The origin of the longitudinally confined equatorial water equivalent hydrogen (WEH) regions on Mars is disputed. Current arguments for their existence are: 1) recent ice age, 2) near-surface water table, 3) recent sublimation of the CO2 veneer of the south residual polar cap, and 4) in equilibrium with the current atmospheric conditions on Mars. The NASA Ames GCM is used to explore current Martian climate conditions as the source for the equatorial WEH-rich regions on Mars. There is a correlation between the simulated total annual deposition (but not accumulated) pattern of water ice and the equatorial WEH-rich regions on Mars. Model results indicate that local nighttime thermodynamics and thermal inertia/topography create bulk water ice precipitation regions over Arabia and Tharsis. Nighttime air in contact with the ground cools via radiation and conduction, precipitating water ice at locations where the local near-surface atmospheric temperature falls below the dew point. The highest topographic longitudes, coincident with the lowest surface thermal inertias, beget the lowest temperatures, resulting in a longitudinal wave two pattern of water ice deposition upon Arabia and Tharsis. These current longitudinally confined "wet" conditions provide water vapor that is readily available for adsorption by hydratable minerals during the night.

Support for this project comes from NASA Planetary Atmospheres Programs (NAG5-12123) and by the DOE through Laboratory Directed Research and Development funds.
--------------------------------------------------------------------------------
http://www.aas.org/publications/baas/v37n3/dps2005/766.htm


Bob Clark

I think the frictional heat is minimal, and not enough to melt briney ice. Drag a wheel across your hand, the warming is at most a few degrees.

Yeah. The frictional heat seems as if it would be hardly be worth mentioning. If there were significant water molecules this close to the surface and this close to the equator, they would have been detected by the orbiters, wouldn't they have?

Isn't this just really fine stuff agglomerating with the help of electrostatic forces, or other weak forces?

EXACTLY - and Odyssey hasn't done that.

Nick has it right.
[/color]

QUOTE

[color="black"]If more or less any random bit of Mars had saturated brines a few cm below the surface then there would be wetter areas with standing brine pools - lakes, streams, swamps and the like. The atmosphere of Mars is WAY too dry for that scenario - just the shallow brine would totally saturate the atmosphere through diffusion. Then you have to look at how the brine would be restored?

It may "look" like mud, but there's no way it can actually *be* mud. Focussing on your desires and hopes rather than scientific reality may be warm and cosy but it's totally incorrect and will lead you up a long and painful blind alley.

Mars is a very difficult planet to comprehend because [bold]it is not Earth-like[/bold]. All our human instincts and ideas are irrevocably shaped by our birth, education, and multi-million year Mammalian evolution on Earth. It is a hard buit profitable exercise to think yourself outside of that box. If you persist in believing only your eyes and your instincts, you will never understand Mars.

http://www.habitablezone.com/nexus/index.asp?svcpt=space

Personally - I see no evidence other that 'it looks a bit like mud' - and good scientific reasoning that it can't be. It's a no brainer.If it WERE such a material - where's the cohesion to the wheels?



Doug

Does Spirit not have enough energy for any direct to Earth communication sessions (sending images like Opportunity)? This Odyssey blackout couldn't have come at a worse time for Spirirt.

That's Murphy's Law.

I mentioned this before (probably on another thread), but back in my junior-high days for a science fair I built a Mars Jar (post-Viking) & mixed the soil in accordance with VL1 results. I assumed that the potassium and sulfur were oxides, so I purchased the pure stuff accordingly...and both of them were snow white.

To my horror at the time, the oxides refused to mix well with the red clays & iron oxide that constituted most of the soil; I ended up with distinct white layers in the final product (as viewed from the side of the transparent enclosure). Back then, I thought that this was my own sloppy procedure; after Spirit's repeated exposure of just such layers, I am beginning to believe that my model was pretty accurate after all!

This is a no-brainer: it ain't mud.

We have an exceedingly fine powder that compacts under pressure, just as we've seen at Oppy's Magic Carpet, many Mossbauer presses and countless wheel tracks.

It could be mud, though. There could also be lizard bones and @lien @rtifacts on the ground and windmills on the horizon, but that is less likely, too.

--Bill