Mars rarely impresses me lately, though I have to admit, HiRISE has taken some pretty nice images. This one impressed me:

Caught in Action: Avalanches on North Polar Scarps

This image shows dust clouds resulting from avalanches along cliffs near the north polar cap. Very cool stuff. I wonder what the trigger mechanism is since there appear to be several avalanches going off at the same time.

That is an amazing shot! So is the earth-moon shot (although whoever brightened the moon to make it visible got a little carried away).

Interesting that these events were captured in color. Anyone know what the time separation is between color layers? It might be fun to pull apart the layers and examine them for particle movement.

The EDRs are available, BTW; they are from observations PSP_005558_9040 and PSP_005558_9045. We don't have automated processing for non-Mars images beyond the EDR stage.

Here are the 4 I can find - in my tweak-IGB-to-make-it-a-bit-more-marslike guestimation. THe whites are a bit blue, but other than that I like it. North is 77 degrees clockwise from straight up, or 13 degrees above 'right'. These are numbered 1-4 going from East to West. There's one more, a little more East, but I think it's 'over' - its a lot more feint, perhaps it happened a few mins before the image was taken

There is a slight delay, I think, between the channels - but it'll be very small. Look at the CCD layout, ( http://hirise.seti.org/epo/hirise_lesson1_files/image017.png ) the ir, r and gb filters are perhaps one ccd's width apart, in the direction of motion - so 2000 pixels, 500 metres. THey start and stop the channels so they line up - but there will be a tiny delay because of the orbital speed. I can't recall what that is ( 2.5km/sec rings a bell- may be WAY off ) - so if that's right, 500m will be a 1/5th of a second. So, every pixel difference, would be 1.25 m/sec - if that 2.5km figure is right. I don't think it is - and it'll vary with altitude anyway.

Doug

Good god!!!! I actually swore when I saw those images! Just stunning!

Serious question Guy... when images like these come in, why don't you make a bigger deal of them in the general media? These deserve to be seen by many, many more people. NOT a criticism, just wondering.

Yeah, that's pretty much what we did too!


A lot of it seems to depend on what NASA wants to do. We do work with our own press people at the university, and we do much of this in coordination with NASA. But the big media events are pretty much all done through NASA. So the big events really only happen when NASA decides it's a good media event. Otherwise we just put out press releases like this. Sometimes the press picks them up and runs with it, and sometimes they don't. So we never really know how much coverage we'll get until the news outlets start calling and asking questions.

Thanks DataMiner, really appreciate the feedback. I don't want you or anyone thinking I was criticising, I just really believe that images like this, showing dynamic processess, movement, all at a familiar scale, are real gifts to NASA and Mars exploration. People can identify with images like this - unlike the people here on UMSF, they might not know what a "sedimentary boundary" or an "eroded outcrop" is, or why they're exciting or important, but they know what a cliff is, and what a landslide is, and what a puff of dust at the base of a cliff means, so I think images like these are godsends, they really are.

This morning I was at a primary (that's ages 5-11ish) school here in Cumbria in the north of England, doing a couple of my astronomy Outreach talks. Talked to a total of a hundred or so kids during the 3 hours I was there (one little girl, Molly, is absolutely determined to go to Mars when she grows up. I let her hold my tiny piece of martian meteorite; her smile was brighter than Venus at closest approach, I swear!). How I'd have loved to have shared this image with them!! It really brings Mars to life...

Before - PSP_007140_2640 After - PSP_007338_2640
One is map projected, the other not so I had to fudge a bit for this animation, but you get the idea.
Click to view attachment
Avalanches in both!

Astro0

I figured out what caused them. It was the shock of Jason looking at a Mars image that resonated throughout the solar system and expressed itself as a seismic event on that ridge. If you hadn't have looked at it - there wouldn't be any landslides

Doug

Whoah -- you're right, Astro0, there's an avalanche in the "before" picture too! Totally awesome. I had hoped to get this posted earlier today -- but now I'm glad I didn't, I'll have to point those other avalanches out!!

Can anybody get their head around why the views of the IRB image using the IAS viewer, look so greenish, and why the HiRISE team's versions are such a deep red? I assume it has something to do with the white frost deposits messing up the auto-stretches, but I would have thought that the frost would have sort of provided a "white point" that should have forced the darks toward a more natural color.

--Emily

Stu,

I certainly don't interpret your post as criticism, and even if I did, I personally have almost zero input on the subject! I'm mostly an observer when it comes to our press coverage. I am willing to take complements/flames on how well maintained/buggy the HiRISE PDS Node is, since I do have direct oversight of that! About the closest that I get to any press release material is sending out announcements to a few NASA internal lists about our data releases, pieces of which sometimes find their way into the press releases, but more often than not they are only used internally.

Well - from an old HiBlog entry

"What is the difference between “RGB” and “IRB”? The RGB products are different than the IRB products in that the IR channel has been replaced by a “synthetic blue” layer that creates an image that is somewhat closer to natural color. In many of the images, the infrared band does not contribute a lot of information. The bands in this product have also been stretched to provide better contrast. In other words, the RGB images are more aesthetic. The IRB product is a science product. It contains the IR, RED and BG layers."

I'll bet they made that from R and GB.

My technique - roughly - http://www.unmannedspaceflight.com/index.p...t=0#entry110381

Meanwhile - there IS disparity between the channels. Between the IR and the GB, I think there's motion. What's the orbital speed of MRO - we can calculate the speed at the front of the big one. It's certainly several pixels worth - if my 2.5km/sec guess is right, we're looking at several m/sec.

OK - more maths - I've found figures of 3 to 3.25km/sec - Let's call it 3.14 (what a nice number)

Assuming that the IR and the GB CCD's are, measured in pixels of CCD width, something like 2100 pixels apart. Very roughly. Thus 525 metres apart. Thus, 0.167 seconds.

So - one pixel difference, is 25cm in .167 seconds, or just about 1.5m/sec

Attached - a flick between IR and GB - I can see maybe 10 pixels of motion at some points on that 'front' - so 15m/sec. Other places, more like half that Very very rough maths - please pick holes in it - but I think we're talking a true ballpark figure there.


Doug

So this is one of those quantum mechanics thingies? Ya know, changing the outcome by measuring it...

Think about it. Jason spends all his time look at Io images - and it's like a volcanic red-light district. He looks at ONE Mars picture...and bam. Only plausible explanation.

What can we say about Martian avalanches ?
On Earth, fresh snow avalanches are possible starting at a 30°slope, not before. I guess we're not talking of fresh snow here
If you look at the two main avalanches, you'll notice that on the "before" pictures, there is white material on what look like a terrasse down the main "polar cap" on the right of it. This white material is no longer visible on the "after" pictures on both two main avalanches. Best guess will be that it has been blown away by the avalanches.
It's also amazing to see the dust clouds going straight up. It realy remember what happen on Earth snow avalanches : the snow cloud goes up the same way.
I'm also wondering about noise. On Earth, you first heard a big BANG, then lot of noise, and by the time you're able to see where the avalanche come from (the noise seams to come from everywhere when you're in the mountains), the snow cloud has formed and you ear a kind of "tumbling". It's nice but frigthening if your close by.
Sometimes you can also ear stones avalanches or even stone falling. I've got a story about this. I was climbing on the CRW of the Everest, around 6200m when I heard a very strange noise, alike an animal cry. When you're in this area of the Himalayas, first thought is the YETI. And I can tell you, you could have convinced me it was an animal. After a while, I sew stones falling one by one from high above doing this animal like noise. I'm wondering what kind of animal inhabit this area of Mars!
What MRO will show us next ?!

One last thing : this will be the ultimate place to bring Spirit to for a solar panel cleaning

<CLINK!!!>

(I may have actually damaged my own hearing with that swear...)

Well...I just mentioned a day or so ago that taking movies of potentially active areas like the gullies would be quite a nice Discovery/New Frontiers mission...gotta add the north polar cap to the list!!!

I thought that some UMSF'ers doing Outreach might be able to use this enhanced version of the largest avalanche.
Sort of part way between the various versions out there already.
Click to view attachment

Astro0

Wow! That is totally amazing! Thanks for the images everyone.
This morning I saw the avalanche mentioned in CNN's news ticker. And it also made it into some of the German online newspapers and magazines (e.g. Spiegel).

Michael

Astounding That's all that I can say.

I just play with a crop/mosaic of the jp2/IAS to have "more natural" color (very very approximative)

I saw the story on CNN this morning. It was the first time I saw that group actually get excited about an astronomical image - they talked about how amazing it was for a while after the story. Stu, with regards to publicity, a team can only do so much - they can't force news agencies to give the story attention. What is really special about this image is that it is large, color, sharp, and super-easy to interpret (I don't mean scientifically - I mean to understand what it is a picture of without knowing anything about Mars).

Might as well post my version, join the avalanche party!

Click to view attachment

I hear what you're saying Ted, about the team not being able to force news agencies to do that, but I still think that there must be a way to get pictures like this more exposure, and to at least bring them to the attention of news editors and reporters as being special. Maybe there could be a a special unashamed "Wow! Look at this!!!" section on the HiRISE site, something like that, I don't know. I just know that this is one of those images that goes beyond science and beyond martian exploration and is immediately obvious to the man or woman in the street - who wouldn't normally care about space images - as being interesting, because it shows a phenomenon they're familiar with.

Not criticising, I just feel frustrated that the HiRISE guys work so hard to get these images, yet only a relatively small number of people see and appreciate them. Maybe it's just an Outreach/Media thing, same old question - how do we get the media to stop obsessing about the cuts on Amy Winehouse's arms or the cellulite on some starlet's bum and report how we're seeing incredible landscapes on incredible worlds across the whole solar system...

Some musings about how often these things happen:

The fact that an avalanche is also seen in action in the "before" picture seems to rule out the possibility that we caught some very rare event, e.g., multiple avalanches triggered by a meteorite impact or earthquake (unless, I suppose, we have a series of earthquakes and aftershocks). More likely, these avalanches are happening continually. If each one is visible for a couple of minutes (say) and there are on average two in progress at any one time, and they happen all day (which might not be true, if they are triggered by solar warming), that's one per minute or 1400 per day, or 23,000 in the 16 days between the two images! For this to be consistent with the lack of gross changes in the appearance of the cliff between the two images, each must involve a pretty small amount of material. I wonder how little material might be needed to kick up that much dust?

John.

Could they be mini dust storms caused by localised puffs of wind blowing downslope? Do they have to be gravity-driven avalanches at all? Is there any clinching evidence for the latter as opposed to the former?

Following that line of thought: could they be the result of Co2 venting from shallow buried pockets?

I agree with ngunn, where's the newly exposed faces? The fresher rock? It doesn't look like there is much, and with that much mass wasting, how come the cliff is so steep to begin with? In the HiRise release, it looks like there are a trio of dust devils right next to the cliffs, so there is definitely some wind action. Take some of those big non-dust devil gusts we saw with Spirit, plant it at the bottom of a cliff, and it'd look very much like these, wouldn't it? With the disparity in albedo between the white cap and dark rock at the bottom, there must be some pretty strange wind conditions.

Just for the pure fun of it and if these are avalanches as reported, here's a little animation I knocked out for use in my Outreach work. Feel free to use it. Remember it's not technically or visually accurate, it's just an aid.
Click to view attachment

Enjoy
Astro0

This MOC image seems to show the remains of similar events (maybe a few active ones...I want to say yes, but I am not sure at this resolution (this image is binned, so MOC was capable of more). Click to view attachment

I tried to find out pictures of avalanches on Earth taken by sattelites but was not successful.
As avalanches on Earth last less than a minute, I guess, what we're seing here is different. We're more seeing the effect of the avalanche on the dust around than the avalanche itself. I guess the dust can stay in the atmosphere for quite a while.
We'll have to look more closely to MOC images of yet "unseen" avalanches

To me it looks like there are some suspect areas nearer the top of the slope.

In this first image, the cloud seems to be coming from a dark area, maybe a cavern?
http://img127.imageshack.us/img127/1181/avalanche1qe1.jpg
Here is another of the other area that has already been shown.
http://img127.imageshack.us/img127/4097/avalanche2pc3.jpg
I did these with ISIS3 and projected them to polarstereographic at 0.3 meters per pixel.
This was a challenge since the BG13 ccd channel data was sent to Earth in Summing Mode 4. Which means the BG13 ccds were 4x smaller than the RED ccds and 2x smaller than BG12, IR10, and IR11. I also had to update my MRO data folder in ISIS manually by downloading a couple of Spice kernels and running makedb.
cartrite

Let's just all be glad we didn't land one of the rovers there

I was wondering more or less the same thing: are katabatic winds from the pole spilling downhill and blowing up dust? If the winds are katabatic, this phenomenon is still gravity driven even if it might not be appropriate to use the word "avalanche".

--Chris

Shouldn't there be some pretty powerful (well, as powerful as <10mb will allow) katabatic winds coming off that slope anyway?

P

I also have suspicions about the avalanche theory. I don't see any trail of material from upper layers to lower, and there are some pretty stark color differences between layers that should make transport of material down the slope pretty obvious. I like the wind theory - we've certainly seen dramatic evidence of what winds can do at Gusev.

Could be, but it must have been one hell of a wind, and the cloud must've been pure fine-grained material. Doug's estimate of velocity (15 m/s) translates into 54 km an hour relative to the surface, and I have no idea how fast the wind in Mars' thin atmosphere would have to be moving to transport a substantial amount of material at that rate, especially after apparently making a translational jog (and losing energy) after reaching the bottom of the cliff. Is this a rather dramatic (and obviously quite brief) seasonal phenomenon?

Also puzzled why the dust cloud's origins are so close to the base of the cliff. Probably displaying my ignorance yet again here, but I'm assuming that the winds would originate from the top of the cap itself due to springtime warmup. However, to do the dramatic vertical drop that we see, the winds would have to be much colder then the ambient temperature beyond the edge; could they descend that rapidly and powerfully?

Possible alternative explanation: There's a strong prevailing wind (in fact, a circulation pattern) around the edge of the polar cap. When this increases to sufficient strength, it dislodges dust deposits along the rim, and causes massive dustfalls after enough erosion has occurred. However, this does not seem to support the nearly vertical fall we saw, unless the mass of disturbed material was so large that observable drifting effects were negligible.

Excellent images cartrite, very detailed! As someone who can't see HiRISE images in full resolution I always appreciate it when people take the time to post crops from them here, so thank you.

These images are really frustrating me, because the more I look at them the stranger the material's behaviour seems to be if it's from avalanches. As others - with a lot more knowledge of this subject! - have already pointed out, the lack of "clean" areas at the top of the cliff is odd, as is the way there seems to be no sign of material bouncing or spattering off the slopes above the puffs of dust. But what really catches my eye are features like this at the base of the cliff...

Click to view attachment

What's happening there? If those streaks are frost how come it forms so locally? Or are little "jets" of gas or wind blowing out of the base of the wall and causing frost to form here? Or are they just areas cleared of dust by puffs of gas coming out of the cliff base? Or am I missing a totally simple geological explanation? They just look odd to me. Anyone else think so?

Just thinking aloud.

True... but on the other hand, the dust plumes seem to be localised and caused by discrete events. Winds would surely blow all the time, and (modulo effects from local relief) all the way around the polar cap, and therefore the dust clouds would extend much further along the cliff,.. no?

I suspect there are other processes than avalanches that cause features such as the streaks. Actually they may good candidates for wind-driven dust/ice coming off the pole.

Your Welcome as is all here.
I was thinking about what I was looking at here and thought that the clouds that were in the images I posted were just that, clouds forming. Since there is a near vertical cliff face catching sunlight, there must be some heat being generated relative to the surrounding atmosphere causing an updraft and co2 clouds to form. Near the surface there must be a lot of co2 evaporation. The light covered area at the bottom of this cliff may be frozen co2 (snow) that condense out of these clouds that form regularly in this area. The 2 clouds are separated by about 8100 meters. The images were 4000 lines cropped from line 92000 and 65000. 2 Avalanches at the same time? It would be nice if there was a spectrum taken of these clouds to see what they are really made of. Dust or co2/water vapor.
cartrite

Okay, I need a bit of help here guys. This might be interesting, it might not, I'm not sure. But this morning in the library, taking advantage of their high broadband download speeds, I did a bit of "avalanche hunting" on images taken around the pole, and HiRISE image PSP_002804_0930 caught my eye when I zoomed in on it because it shows this...

Click to view attachment

Now... this is a very weird area when you look at the whole image, so I'm not exactly sure what this crop shows, but I think it shows a steep scarp and I think it shows cloud or dust effects at the base of that scarp. Not avalanches, I don't think, but certainly something cloudy and dusty. So... if my guess is right, are we seeing localised dust storms at the base of a polar scarp? Maybe some of you with better machines, more geologicalm knowledge and better processing skills could take a look? It just caught my eye, that's all. I'm quite prepared to be totally, absolutely wrong!

This is really a fascinating example of science at work!
A newly observed phenomenon is seen in MRO images
and a hypothesis is presented as to its cause (avalanches).
Then closer examination and additional observations
bring up new possibilities -- new hypotheses. More
observations will be needed to sort it all out.

My own inexpert impression is that the clouds are the
result of the release of volatiles -- CO2, H2O or both --
from specific layers in the cliff face. I wonder if this
is related to the process by which gullies originating
from layers in crater walls are formed.

I wonder, could we be seeing something like ground water sapping but driven by CO2 rather than water? If that scarp consists of a mixture of dust and frozen CO2 the carbon dioxide in the lower part might sublime and the soil lose coherence and bring down part of the scarp above.
There might even be a link with catabatic winds. A martian Chinook might be a "CO2-eater" rather than a "Snow-eater".

Well spotted! I think you might have found a key part of the puzzle here, though I'm not sure what it means.

Another thought- this is a steep cliff that is losing its seasonal frost coating. The seasonal frost is full of dust, and the dust will get left behind as the frost evaporates. So maybe you get an accumulation of unstable fairy-castle dust bunnies clinging to the cliff, and these collapse periodically?

John.

Here's a bit of wild guesswork:

Wind blowing off the scarp occasionally wafts a little accumulation of CO2 'spindrift' over the edge. This affects the descending air in two ways as adiabatic warming starts to cause rapid sublimation of the fine CO2 grains. Firstly the warming is inhibited, meaning this air remains denser than neighbouring air which warms normally. Secondly a large volume of (cold) CO2 gas is produced directly from the sublimation. My back-of-envelope calculations are definitely unfit for posting but I reckon one litre of CO2 ice descending and subliming in this fashion would produce a volume of gas at Mars ambient pressure sufficient to cause significant local amplification of the downdraught. The strongest dust-raising effects of the amplified gust would occur on the lower slopes and at the foot of the scarp.

Hi Stu,

I think you might be seeing some jpeg2000 zooming effects. I just took a look at this area zoomed in to full resolution on the red nomap file, and the ground texture doesn't seem to be obscured very much, if at all. There are some brightness differences here, but (to me, at least) the brightness differences look like they are the result of topographic differences rather than an atmospheric effect (but I could be wrong).

Here's a full resolution cut-out of the same area:

Click to view attachment

The reduced version of this cut-ot does indeed look kind of hazy, but at full resolution, this effect disappears.

Thanks DataMiner... wow, that's amazing! It was worth being (hopelessly!!! haha!) wrong just to be shown that HiRISE is even more amazing than I thought! I had no idea that kind of fuzziness could be caused by an image having too MUCH detail!

Oh well, it was just an idea.

( On the bright side... pauses for drum-roll... I signed up for broadband today, at last, so within a week or so I should be able to enjoy all these images properly, without having to ask kind people on here for close-ups! )

By the way, new poem here if anyone wants to read it... "Look Out Below..."

Stu....

I love your poems.....

And to all, i have to say, and I know I have said this before........ being old enough to remember Mariner 4, and waiting for the release of those blurry images transmitted at something like 8.5 bits per second... and which, I must add, doomed Barsoom, but introduced reality... WELL, these HRISE images JUST BLOW ME AWAY.... bring me to tears sometimes....

wow.... what a beautiful world is Mars.....

Craig

I see whirlwinds dance, avalanches too
I see them bloom for me and you
And I think to myself what a wonderful world.

I see skies of rust, and clouds of white
The light dusty day, the dark frozen night
And I think to myself what a wonderful world.

Shades of orange, brown, and red, so pretty in the sky
Dust on the panels of rovers crawling by
I see an arm meeting rocks, saying how do you do
They're really saying tell me about you.

I hear lonely winds blow, I watch them grow
They've seen timeless ages, more than I'll never know
And I think to myself what a wonderful world
Yes I think to myself what a wonderful world.

with apologies to Louis Armstrong: