Moon Storms?, Where the dust blows form + to - Options

[abalone]

Who said that old data cant be interesting?

http://www.spacedaily.com/news/lunar-05zzzc.html

[Guest_Richard Trigaux_*]

Strange indeed.

It is generaly accepted that dust cannot stay in the "air" on the Moon, it falls as quickly as a lead block, and cannot form curls like in Earth atmosphere.

But static electricity may indeed raise tiny particles of dust, and make them hover like in an atmosphere. After, the dust grains get discharger by solar UV and they fall. But why would they raise in the morning? Perhaps solar wind reverts charges on the surface. Perhaps solar wind creates these charges.

Strange electrostatic clouds.

[dilo]

This is truly amazing!

[abalone]

This is truly amazing!

Bit more detail here.

http://science.nasa.gov/headlines/y2005/30...onfountains.htm
This could have profound consequences for long term power generation from solar cells set up in islands of constant light as found near the poles and any missions that stays for more than a few days. A similar problem may be encoutered when trying to land on asteroids, possibly??? even Hayabusa in its recent landing attempt. It had problems before it attempted to land but this seemed to fall apart when its made those gentle touchdown.

[Guest_Richard Trigaux_*]

I think we can posit the following scenario:
1) solar wind creates the charges
2) charged particules hover above the surface, lke a gaz
3) solar UVs discharge the particules which fall again on the ground, sticking everywhere.


It would be interesting to know what happens when there is the full moon.
At this time the Moon enters the Earth's magneto-tail, a region of highly turbulent solar wind, which may even contain bubbles of plasmas (plasmoids). So there may be regions of higher density of solar wind, producing high dust storms, and eventually fluorescence.

Is not this what was sometimes observed as "Unidentified Lunar Events" (ULE) or "Lunar Transcient Phenomena" such as
-regions becoming blurred for some minutes (Plato tiny craters become invisible)
-lighs (often red) appearing over certain regions (some points are prone to this, like Aristarcus or Alphonsus)
-Even UFO-like lights moving fast against the Moon background.

All this could be produced by higher density strands of plasma hitting the Moon surface, giving dust storms and... auroras. Especially at the full moon.

Note that, in order to be visible against the sunny full Moon soil, these auroras must be much more luminous than ours.

[edstrick]

Note that the brightness of the post-sunset glow observed by Surveyors was low. I believe it required long exposures relative to daytime shots. The viewing is optimum for observing fine dust: near 180 degrees phase angle, where diffraction effects are strong (like cirrus clouds 5 or 10 degrees from the sun in the sky, or like Jupiter's normalloy nearly invisible dust rings in Voyager and later mission's images taken from the nightside looking up-sun) The total optical depth of the suspended dust is probably very small.

The existance of Lunar Transient Phenomena is still unresolved. Impact flashes have certainly been observed from Earth in recent years, especially during meteor showers like the Leonids. The transient phenomena have never clearly been observed except by visual observers. There was a program back in the ?mid 70's? to observe the moon with a digital imaging system on a telescope and use image processing techniques to look for short term variability, but I never heard any significant positive results from it.

You really need a small telescope in the Earth-Moon L-1 point or something as a stable platform to take high signal-to-noise observations with maybe 1/10 km resolution.

[abalone]

I think we can posit the following scenario:
1) solar wind creates the charges
2) charged particules hover above the surface, lke a gaz
3) solar UVs discharge the particules which fall again on the ground, sticking everywhere.

To quote from already cited article
"On the daylit side of the Moon, solar ultraviolet and X-ray radiation is so energetic that it knocks electrons out of atoms and molecules in the lunar soil. Positive charges build up.................................. the natural question then becomes, what happens on the night side? The dust there, Stubbs believes, is negatively charged. This charge comes from electrons in the solar wind, which flows around the Moon onto the night side. Indeed, the fountain model suggests that the night side would charge up to higher voltages than the day side, possibly launching dust particles to higher velocities and altitudes."

There seem to be two distinct processes, the first (daylight side) due to the photoelectric effect from ultraviolet and X-ray radiation and the second due to solar wind electrons being lighter than protons and thus more easily deflected onto the night side of the moon.

These two processes would work the same on any asteroid. Eros showed this dust mobility in having all small craters smothered in dust. In fact many of the small bodies that we have had recent photos of show a similar trend.

[Rob Pinnegar]

These two processes would work the same on any asteroid. Eros showed this dust mobility in having all small craters smothered in dust. In fact many of the small bodies that we have had recent photos of show a similar trend.

Right... and one would think that this effect would be much more noticeable on the smaller bodies because of their weaker gravity. If the Moon had experienced as much dust motion as Eros over the eons, the maria probably wouldn't be visible by now, because they'd be covered over with dust.

Of course, I'm probably missing about 20 important points here. This is pretty simplistic reasoning.

[Phil Stooke]

This lunar dust storm stuff is interesting, but it would be easy to misinterpret the media coverage of it. We're not talking about an effect that would be like a dust storm in Iraq or Manitoba... or even Mars. VERY small amounts of VERY tiny particles are on the move.

The fact that we can see albedo boundaries on the Moon shows very clearly that this effect is miniscule. I've just been looking at the Luna 24 landing site, where a bright patch south of Fahrenheit crater has an edge that is sharp to within a few tens of meters, probably only ten meters if my image was good enough. And it's probably been there for 3 billion years. So in all that time there isn't enough dust movement to obscure an albedo boundary with probably zero effective relief.

As for asteroids... Hmmm, not so sure. But the ponds on Eros and the plains on Itokawa, presumably the same things, don't suggest to me that dust is constantly on the move in large quantities. Fine debris is moving, certainly, but if it moves significantly every time the terminator sweeps by it would either show depositional characteristics or at least not be concentrated so much in low points. I mean... Itokawa... if dust is moving in such a low gravity environment will it really get concentrated in low areas like that? All small craters smothered in dust on Eros? I think they are smothered in ejecta, not the stuff this story is about.

Phil

[Guest_BruceMoomaw_*]

I clearly remember this phenomenon -- as detected by the LEAM instrument -- being mentioned in a document something like two decades ago (one of the documents listed in NASA's extensive "STAR" catalog, I believe). I also more dimly remember Tommy Gold crowing about it somewhere as partial vindication for his lunar-dust theories.

[Guest_BruceMoomaw_*]

Interesting footnote on dust from the AGU meeting: abstract http://www.agu.org/cgi-bin/SFgate/SFgate?&...P11A-0099" refers to the color and albedo differences seen by NEAR in Eros' soil. But the poster itself -- which I saw at the meeting -- goes into more detail:

(1) Not only is there a distinct albedo difference between most of Eros' soil and the much lighter material exposed by landslides on slopes, but there's a color difference: the freshly exposed material is less reddish. Clearly evidence of some kind of space weathering process. But, as an added puzzle, the "ponds" on Eros are intermediate in their coloring: somewhat more bluish than the surrounding soil.

(2) The poster also raises the possibility that the relatively mild space weathering effects on asteroids (unlike the lunar surface) just might be due entirely to mechanical effects, rather than actual mineralogical changes. It turns out that when you grind up dark mafic rocks, they get more reddish -- until the particle size drops below 20 microns, at which point the powder starts turning bluer again. So, if you have a phenomenon that tends to plant smaller grains on surface soil -- such as micrometeoroid impacts, or seismic shaking that launches the smaller grains farther so that they land back on the surface later -- this by itself might produce the color effects seen on Eros, especially if the grains in the ponds are particularly fine (as in fact they seem to be).

[edstrick]

In the case of small bodies that are or closely resemble chondritic meteorites, there is another thing to consider. Up to some tens of percent of the total material isn't rock, it's nickel-iron and iron-sulfide. Mechanical, optical and I presume electrostatic properties of this component will be very different from the silicate rock component of the regolith. Various mechanical and electrostatic, perhaps electromagnetic processes may play roles in separating and transporting these very different materials compared with the rock compoinent. And seemingly insignificant processes may emerge as the big role players in mini-gravity, mili-gravity and micro-gravity conditions.

[Guest_BruceMoomaw_*]

Maybe we'd better move this over to the Asteroids section, but...

http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1631.pdf :
"The findings of a chondritic composition for the GRS-derived Mg/Si and K values were in close agreement with compositions derived from the XRS
experiment. However, the GRS-derived Fe/O and Fe/Si values did not agree with most of the chondrite values; specifically the Fe abundance was low by about a factor of two. Three possible explanations for the apparent Fe depletion were considered in [5]. Among these, the most likely concerned physical processes within the asteroid regolith that might cause metal migration at the landing site and explain the discrepancy between the GRS and XRS results."

http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2031.pdf :
"The NEAR GRS (gamma-ray spectrometer) derived Fe/Si ratio of 0.8 ± 0.3 is considerably lower than the XRS derived Fe/Si. The GRS samples to depths of tens of centimeters, whereas the X-rays only sample to hundreds of microns. This
suggests that the elevated Fe/Si is a surface phenomenon. At present it is unclear whether the observed Fe/Si may have been inflated by phase-angle effects or whether the Fe in the surface layer may in fact have been enhanced by size sorting
in the regolith (the “Brazil-nut” effect)."

Also see http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1868.pdf for speculations on such effects.

[Guest_BruceMoomaw_*]

More on the subject:

http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1633.pdf
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1868.pdf

[Bob Shaw]

I clearly remember this phenomenon -- as detected by the LEAM instrument -- being mentioned in a document something like two decades ago (one of the documents listed in NASA's extensive "STAR" catalog, I believe).  I also more dimly remember Tommy Gold crowing about it somewhere as partial vindication for his lunar-dust theories.

Bruce:

It does, indeed, seem like a typical Gold/Hoyle 'edge-of-the-envelope' theory - interesting, stimulating, but, er, *wrong* in many cases...

Bob Shaw