Live Dust Devil? Options

[wyogold]

I agree with Bob.  There may be some seasonality to their occurence, but I think we're seeing more of them now because (1) we're looking for them against a darker background, and (2) we're looking for them more frequently!  Wasn't there evidence that a DD had recently passed through one of the craters that Spirit visited between Bonneville and reaching West Spur?

yes spirit missed a huge dd.
http://www.unmannedspaceflight.com/index.php?showtopic=721

http://www.msss.com/mars_images/moc/2005/01/03/

http://www.msss.com/mars_images/moc/2004/01/05/

I also agree. I think the dust devils were there, but we were not in such a favorably position to see them. I think the most important ingredients for dd formation is wind. You need a good stiff breeze for dd formation. The stronger the wind, the more powerful they become. Is the wind going to get stronger as the year progresses? If so we should see more dust devils.

Scott

[edstrick]

When there's a major "dump" of dust into the atmosphere, such as from the Dec '03 regional dust storm before Beagle zip-crunched (or whatever), the injected dust rapidly goes global as it's distributed fairly homogeneously.

This increases direct solar heating of the atmosphere at all levels once the dust is well-mixed, and decreases heating of the surface. The result is that temperature contrasts between the surface boundary layer and the atmosphere above it are reduced, convection is reduced, and once enough dust has been injected, even global dust storms turn themselves off. They then go into an extended dust settling phase where atmosphere opacity exponentially decreases with a dust settling half-life time of something like 2 weeks.

They started realizing this with earthbased observations of the 1971 global storm, which was observed by Mariner 9 during the dust settling phase. (Note that the speculation that the Mars-3 lander was destroyed by high winds during the global dust storm are probably entirely bogus, as the storm was in the settling phase when the lander reached the planet)

So as dust injection, either from abundant local dust storms outside the rapidly retreating south polar cap edge or from any regional or global storm event, puts dust into the atmosphere over Gusev, it will tend to suppress dust devil activity, and probably cut it off alltogether if it reaches a certain fairly high level. At different times of the year, as with the dust devil at the crater southeast of Bonneville (formed after a global surveyor image but before the rover passed by), you may have sporadic bouts of devil activity as warm fronts or cold fronts or whatever local seasonal weather blows by happens, but not have nearly daily activity like the last few months.

[Phil Stooke]

There is a new 'month in review' PDF file at JPL... it includes a VERY interesting map of dust devil locations and motions... well worth checking out.

Phil

[Tman]

Daniel and/or Michael here we go!!! A dust devil exhibits itself quite close-by and it's a Pancam pic!

http://qt.exploratorium.edu/mars/spirit/pa...00P2629L4M1.JPG

20 seconds later in the left just again:
http://qt.exploratorium.edu/mars/spirit/pa...00P2629L5M1.JPG

[Decepticon]

Where is this PDF file?

[Bill Harris]

The "Month in Review" files are at the NASA/JPL MER site:

http://marsrovers.jpl.nasa.gov/home/index.html

Interesting map of DD locations and motions. I was wondering how closely they follow the tracks of the earlier DDs. Not well: evidently the current direction of the current DDs is different than prevailing direction of the DD tracks. The large, dark tracks in "DD Alley" were made by much larger events, or they are the result of repeated scouring by many small DDs. Note that many of the prominent streaks are downwind of craters, so these surface irregularities are prone to forming the DDs downwind.

--Bill

[jaredGalen]

It looks like it had quite a cleaning effect on the area around it.

A lot of features get somewhat brighter during it's passing

[MichaelT]

Daniel and/or Michael here we go!!! A dust devil exhibits itself quite close-by and it's a Pancam pic!

http://qt.exploratorium.edu/mars/spirit/pa...00P2629L4M1.JPG

20 seconds later in the left just again:
http://qt.exploratorium.edu/mars/spirit/pa...00P2629L5M1.JPG

Yes! That's an impressive one . It extends quite high into the atmosphere.


Michael

[Nix]

Nice one!

sol 527 dust-devil

Nico

[Tman]

It seems it's a pretty long tube-like DD at this moment of capture. I was hoping for more turbulence in the height. Anyway it is poster-like, with this background!!!

[alan]

Dust devil paths clipped from HUGE pdf file

[Nirgal]

Wow NIX: nice colors !!

this is definitely one of the best Mars dust devil images yet

How did you do the colors ?
doesn't the DD move between the individual color filters exposures ?

[Nix]

Thanks, color to wavelength conversion in PS, levels, hue-saturation-brightness.
There are other ways, you can assign pure R,G,B to L4,L5,L6 in this case and alter the levels differently. I tend to play a lot with the raw images and do things differently from time to time. There sure is no consistent process applicable to the stretching in the .jpegs.

Nico

[slinted]

I've been playing around with several different methods to visualize the full extent of the dust devils. I've come up with a false color view that helps to see both the bright component visible against the dark background of the floor of Gusev, but also the slight darkening that happens when sky is in the background.

This is a false color view, split into 2 components. The red component are pixels that are brighter than the background image, while blue pixels are darker than the background. The brighter the blue, the more darkening. The scaling factor is turned way up for this image, unfortuntely creating more 'bad' enhancement (jpg artifacts mostly) but also picks up the subtle darkening that occurs for this dust devil going all the way to the top of the frame.
Also, I use a linear scale based on the brightness of the background pixel to control the factor of enhancement. This means the enhancement factor is at its highest when the background pixel is very bright, and the factor is lower when the background pixel is darker.

I used http://nasa.exploratorium.edu/mars/spirit/...00P2629L4M1.JPGas a background image.

[CosmicRocker]

That's an interesting image. I can convince myself that the DD from sol 527 has a ribbed, spiral structure. Does anyone else see that?