I thought it would be better to have a separate thread to follow this season's DDs and use the old "First Dust Devil this season - any bets" thread only for the bet itself.

Mods, if you think that's not appropriate please just delete this post/thread.

I think 'this' season needed editing as 'this' season could be any season - so I've changed that bit

The sol 1120 DD seemed like a good time to 'dust' off my old scripts:

B/W enhanced (3.5 meg)

false color enhanced

It's a nice tall one too, all the way up to the top of the frame towards the beginning of the sequence. This one also shows a good view of some sizable 'blobs' of dust being lofted up as it travels. It is especially nice seeing a dust devil right at the start of the movie, when we get the shorter lag between frames of the movie.

Excellent work, Slinted... and beautiful DD! I do not undertstand why Spirit didn't decided to continue the 3sec temporal samplingin the last frames (when DD disappear), maybe we will receive more frames later...

Very nice... Does the image sequence with 3 second intervals mean that this DD was recognized and imaged by the new software routine? Imagine capturing a swarm of DDs, like the sol 568 swarm, with a frame every 3 seconds.

Dr. Lemmon just put up a great explanation of what limits the timing of one of these 'fast' movies on his site:


CosmicRocker: While this was great timing, to catch one right from the start of the fast sequence, I don't know if that is an indication of the new software being used yet. I think we'll know the software when we see it (I'm expecting something that looks significantly different than the traditional DD movie sequences).

There appears to be a DD captured in a rear hazcam from sol 1141. Look on the horizon a bit left of center, just right of the far hills.

Yes CosmicRocker, you're right .

A change in a big part of the sky, on the left side of these frames:
http://marsrovers.jpl.nasa.gov/gallery/all...6MP1561L0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...6MP1561L0M1.JPG
If that's a dust devil, it's either really close or really big.

I forgot to mention it, but several DDs were captured in three navcam EFFs on sol 1147.

There were some nice dust devils on Sol 1147:



http://qt.exploratorium.edu/mars/spirit/navcam/2007-03-26/

Edit: CR - timing is everything....

Considering the fact that the images came down several days ago, it's quite a coincidence that we both thought about them at the same time.

It sure would be nice to see these DDs in a HiRise image. I've been wondering...As the season heat up, would there be any value in doing coordinated imaging with both HiRise and Spirit observing at the same time?

17 frame 1/2 size sol 1149 dust devil animation here.

It looks like it came very close to Spirit. Notice the traveling "shadow"(?) and the darkening at the end.

The differences were stretched 32X

Thanks Horton!
That's very impressive!

Good catch Horton. Those features are very faint, much fainter than any of the major dust devils last season, but this may have just been bad timing. The shadows on the ground approaching the hills look legit, showing up in 5 separate frames. So it may well have been more active before we see it enter the frame, lofting and carrying a substantial dust cloud along with it.

I'm fairly sure the darkening of the last few frames is an artifact of stretching the 'fast' movie sequences. All the 3-sec-per-frame movies show that same darkening of the final few frames, probably because the noise along the borders of the image changes the stretching done to the raws.

Update on the sol 1149 DD and images here.

Couple of dust devils caught by the pancam on sol 1169

http://qt.exploratorium.edu/mars/spirit/pa...25P2446L7M1.JPG
http://qt.exploratorium.edu/mars/spirit/pa...25P2446L7M1.JPG

We're just not in the right topography for a cleaning event I think. Maybe down the far side of Home plate or up near pitchers mound we might get something.

Doug

how often must I say ....stop quoting a post in full in a reply. Doug

HOW OFTEN MUST I SAY THAT DUST DEVILS ARE NOT ASSOCIATED WITH CLEANING EVENTS!

I agree 100%. But they observed a strong gust kicking up dust. That is what I was making reference to.

There seemed to be a bit of activity over near El Dorado, even in the 'off season'. Too bad Spirit doesn't have fully functioning wheels, it would have been easier to drive somewhere windier and then back to the science targets...as it is now, they may be able to get somewhere where they can do science and pick up a gust. I doubt they'll get much on this side of Home Plate.

There were two single frames from recent dust devil movies that showed activity. They only showed up in one frame, so the links below are enhanced subframe versions of the individual images instead of the movies:

Sol 1166
Sol 1168

Since there was some confusion about what the new change-detection software would look like when used for dust devil movies, I thought I'd point out that these two (as well as the sol 1147 movie) look like they are products of the new software. The movies made with the new software have the sequence number 'P1562' (labeled on the pancam site as 'dust_devil_watch' for the first frame and 'Unexpected sequence!!!!' for any subsequent frames) and are full-frame navcams as opposed to the old sequence P1561 movies which were 256x1024 subframes. In time, we may see subframe 'watch' products, since it had been discussed that the new software could be used to reduce the size of the images returned by selecting only those parts of the images that had detectable change, but for now the full frames are being returned, probably for diagnostic purposes.

"In the past, dust devils and gusts have wiped the solar panels of dust, making it easier for the solar panels to absorb sunlight."


I'm confused. (Film at 11!)

I refer you to the first Squyres Q'n'A where Steve says it was unlikely to be DD's as one of the cleaning events was at night. I imagine that's just the writer assuming what most people do

Doug

Dust devil visible to the south in the sol 1187 front hazcams. It's only visible as a darkening against the sky - we can't see its base, which appears to be behind Low Ridge. It's visible in both L and R, so it's clearly not dust on the lens. I think this is the first we've seen this season to the south. Here's a difference image between sols 1187 and 1189:
Click to view attachment

The images that came down today showed dust devil activity on sols 1180 and 1191:

Sol 1180 showed a long and very distinctive track on the ground in the last frame, following the passage of a large somewhat disorganized DD visible in the previous frame

B/W enhanced (3.3 meg)

false color enhanced

Sol 1191, around 2:30 PM (a little later then we usually see movies being taken) has a nice tall tight cone coming in from the right (if it's the same one as seen in the previous frame). This one is only 5 frames so far, hopefully we will have more soon.


B/W enhanced

false color enhanced

Thanks for posting the DD movies, however when i was trying to locate the raw images for either, i cant find the most interesting ones on the NASA nor lyle.org sites..

i can see the first several DD images but the two images for 861 and 1076 seconds seem to be missing for SOL 1180.
wha happen?

atomoid, you might be looking at an older cached version of the JPL page. The last two frames are on that site now, although they were downlinked on a later date than the first ones. Here are the direct links :

http://marsrovers.jpl.nasa.gov/gallery/all...8F0006L0M1.HTML
http://marsrovers.jpl.nasa.gov/gallery/all...8F0006L0M1.HTML

A big one:

http://207.7.139.5/mars/spirit/navcam/2007...AZP1561L0M1.JPG

Come on, the dusty rover is over here.

"...it was unlikely to be DD's as one of the cleaning events was at night." - Doug

Well, while it is true that most whirlwinds form during warmer sun-lit afternoons, it is not true that this is the only time they form. We know that wind still blows at night (as implied) - and we know that craters of the right size, depth and formation create many whirlwinds that travel great distances before they collapse.

So statements that a whirlwind cleaning would be unlikely simply because an event took place at night - or statements saying that no whirlwind ever caused a cleaning event are both rather shortsighted and proof-less in my view.

a post script...

I've lived for many years in the American Southwest - in the desert areas of Texas, New Mexico and Arizona - where many times I have seen whirlwinds operative well after sunset, one specifically that I remember well, that nearly took me off of a telephone pole near Lordsburg, NM at just about midnight.

At other times, I've seen multiple twisters in the moonlight northwest of El Paso, TX and southwest of Globe, AZ.

None of this means DD's happen at night on Mars, but I've seen nothing that proves that they don't either.

I think the likelihood of whirlwinds forming on Mars at night is a lot less than them forming at night on Earth. There is a lot more energy in the terrestrial system than in the Martian system, held both in the ground and in the air. Mars gets significantly less insolation than Earth and the ground re-radiates stored heat much faster than on Earth, due to the far thinner atmosphere.

Dust devils have not been observed at Gusev during the daytime in winter months. It doesn't get warm enough for them to form until late morning, at that. One can conclude from that fact that there is not enough energy in the system, even during daily daily heating, during the winter months to form them. I'm certain that physics can describe the reasons in terms of the energy needed to energize updrafts sufficiently for creation of dust devils.

There is a lot more energy in the system during daylight hours in the winter than there ever is at night during the summer. If dust devils cannot form during the day in the winter, physics requires that they cannot form at night, even in the summer. It's not necessary to bring in the McGuffin of inability to observe them at night, especially since it's impossible to prove a negative. For example, if you want to try and go hang gliding at night, even though physics tells you that there won't be any thermals to ride, heck, you can't observe whether they're there at night or not, so, hey -- go for it. You first.

-the other Doug

Are you sure you're talking about small thermal driven DD's STP? It's the heat of the early afternoon that triggers them.

Maybe you're right - but until I hear differently, I'm going on the science teams words.

Doug

Among other things, the May 14th Spirit Update said, I hope that went well.

This DD isn't negligible! (Sol1195 - Already highlighted by Alan).
Look at the the pictures sequence (slightly enhanced), seems going straight toward Spirit! :
Click to view attachment

And about cleaning event (OT?), there is a net improvement in the appareance of last sundial pictures...
Click to view attachment
probably, is only an apparent change due to uncalibrated colors, but I would like is real

Certainly not enough difference in those sundial images to say if there was any sort of event. With the major cleaning events near Larrys Lookout it was obvious - streaks of blown dust behind objects and half the magnet blown clear.

Doug

Yeah. I can't say I can see much of a difference between the sundial images, Marco. I hope to see it soon, but Spirit may need to go to a new location to find a breeze. There are new DDs in the recent images and perhaps she'll get lucky. At least we see that Spirit saw DDs on sol 1191, when MRO was supposed to be looking down at Gusev.

Problem is, I don't think that the straight-line winds that actually cause cleaning events really get down into the bowl in which Spirit is currently sitting -- Home Plate lies generally in the topographic low of the Inner Basin, and straight-line winds are somewhat dissipated before they reach our current location.

If trying to engineer a cleaning event is ever a goal of the Spirit team, they'd probably try to analyze the prevailing winds and place Spirit at an angle into them, on top of the highest spot they can now reach with the bum wheel.

-the other Doug

Doth mine eyes deceive me, or is that a gust in the latest navcams heading our way?!
Gust Angel?
Come to Papa! Right now we can risk a shaking up, if it means a good cleaning.
Can somebody put together the 'animation'?

The brightness changes are 4x the base frame.

I've been playing around with some new software at home and thought others may be interested in seeing a little test movie I did of a 'dust devil'.

I used a background taken by Spirit, generated a panorama, added sky and sun and then put in several layers to produce the whirlwind effect. There are also a few little foreground dust movements as well.

Just for effect I've added some titles and music track.
As I say just a test, next thing to add would be a ground shadow and a tracking move across the panorama - but hey, it's my first try at this.

Movie File Here: 5.89mb

Enjoy
Astro0

I enjoyed that movie, Astro0, thank you.

One comment I would make relates to the effects of perspective on time and motion. Because in the distance horizontal distances are very foreshortened your dust devil appears (to me) to have a very fast groundspeed at first, getting slower and slower over the ground on approach. It might be useful to construct a perspective grid as follows:
Start with a horizontal line along the bottom of the image and another along the horizon, then add another half way between the two, then a whole series more, always halving the remaining distance from the previous line to the horizon. To a first approximation these should represent equal increments of distance which would presumably be traversed in (approximately) equal times by an approaching dust devil.

I don't know how much the NASA images constrained your movie - perhaps the DD actually did slow down - so if my comments are irrelevant please ignore . . .

Thanks ngunn.
I think I see what you're getting at.
Just my first attempt at this type of animation.

My take on it is that as the DD builds in height its sheer volume causes it to slow its movement across the ground. Looking at DDs here on Earth, smaller more defuse ones tend to move faster where as larger ones drag along. I think I was going for a more artistic representation while I learn the software.

As I said before, I want to work on creating a more realistic motion, shadows, dust movement etc for future versions.

Thanks for the input.
Astro0

Actually, my recipe for the perspective grid needs correcting - what I described in fact generates lines that progressively double in distance on the ground, whereas you need uniform ground intervals - at least as a starting point. Here's the correct version. Taking the vertical distance in the picture plane from horizon to bottom of frame as one unit, mark the following points, measuring downward from the horizon: one half, one third, one quarter, one fifth, one sixth, etc. These will represent equal distance increments on a horizontal ground surface. Hope that is useful, and sorry for getting it wrong yesterday!

I think it's very cool however I think Nigel has a very good point - the DD appears to slow down far too much when it hits the foreground. For realism you might be able to take timed points from the ground track of one of the real DD's and map the effect over that.

Now this is a really nit-picky point but, is the DD in the movie going the right direction? It's shown going north or east; I thought they usually went more or less the other way. I could be wrong - perhaps they can go whichever way they want to. Anyway, great movie, Astro0.

Beautiful (and big) DD on Sol 1215:

I just posted up an update to my dust devil page.

Sol 1204 was a lucky movie, catching a tall dust devil showing fine structure right from the start of the movie (when frames are the quickest).

Sol 1215 shows another tall dust devil, this one heading straight in towards Spirit (although it does appear to grow more diffuse as it comes...it might not have made it all the way to the hills).

Sol 1217 is a bit different. The fourth frame shows a diffuse 'ghost' of a dust devil passing by on the left side of the frame. It could just be one that was very nearby, or it could just be a disorganized shell of a dust devil blowing by. It reminded me of the close pass in front of the rover we saw back on Sol 568.

The sol 1215 and 1217 movies might still have more frames coming down.

Another great DD on Sol1230:

And the same, in anaglyph
Click to view attachment