Singing Sand Dunes

Palomar · 2005-01-11 09:36:13

http://www.livescience.com/forcesofnatu … .html]Evil spirits, said Marco Polo

*I don't recall ever reading about this phenomenon before.

Study took place in Morroco, the Atlantic Sahara, which is 1 of only 35 known places where this phenomenon occurs.

They quote Marco Polo as saying "...at times fill the air with the sounds of all kinds of musical instruments, and also of drums and the clash of arms."

Study focused on a barchan, which apparently "sings" throughout the year, and sometimes two or three times in an afternoon if it's windy enough.

They couldn't wait for the phenomenon to spontaneously, naturally occur so they helped the process along by sliding down dunes to create an avalanche.

Cool.

--Cindy

P.S.: Some of these sounds can last for 15 minutes and be heard from 6 miles away.

Shaun Barrett · 2005-01-11 19:35:18

Hi Cindy.
I know the article says that smaller barchans have to have hot sand in order to 'sing', but I couldn't help but wonder about the dunes on Mars.
The planet has some spectacular dune fields, some of the dunes being very large, and it also has winds. Although the air is thin, I was wondering whether the 'Mars Microphone' (designed by The Planetary Society but sent to Mars aboard the ill-fated Mars Polar Lander) might have picked up the feint sound of similar phenomena on Mars. ???

I was so disappointed when that microphone died with the Polar Lander. The atmosphere of Mars may be filled with the soft sighing of the winds and the feint hiss and rumble of shifting sand .. a whole world of sound we know nothing about as yet.

The good news is that The Mars Society has secured a berth for a new Mars Microphone on board the 2007 NetLander mission, to be launched by the CNES (national space agency of France).
:up:

Palomar · 2005-01-12 07:17:50

*Hi Shaun:

Yeah, it's interesting to speculate about the sounds Mars dunes might create. Likely most folks interested in this sort of thing have also considered -- like me -- that sand might be heard swishing or spattering against a wall on Mars, etc.; perhaps the wall of a hab or against a rover's panels. I hadn't considered other sounds though, pertaining to dunes...because I wasn't aware some Earth dunes do this until yesterday.

Anyway, I recalled an article about sand avalanches on Mars and (thank goodness for a good memory), yep -- I'd posted it the old Devils & Dunes thread a year ago:

http://edition.cnn.com/2000/TECH/space/ … unes/]Sand avalanches on Mars

Includes a photo of an avalanched area. :up:

--Cindy

Shaun Barrett · 2005-01-12 07:46:15

In the picture with the recent avalanche, toward the right hand side and about 2/3rds of the way down, there's a small area at the base of a dune which is very dark.
On the dune which overlooks this almost black patch of 'sand'(?), there's what looks like a linear depression with a line of dark holes in it. The depression and the holes line up directly with the dark patch.

mars.sand.avalanch.large.jpg

I'm still very curious about those dark patches we see here and there on Mars and I wonder why people at NASA are so quick to dismiss them as just a different type of sand. I'm very suspicious there's more to it than that and I'm surprised at NASA's apparent lack of interest.
???

SpaceNut · 2005-01-12 07:46:33

Don't forgot snow avalanches here on Earth make a lot of simular noises as well.

Palomar · 2005-01-12 11:19:45

In the picture with the recent avalanche, toward the right hand side and about 2/3rds of the way down, there's a small area at the base of a dune which is very dark.
On the dune which overlooks this almost black patch of 'sand'(?), there's what looks like a linear depression with a line of dark holes in it. The depression and the holes line up directly with the dark patch.
I'm still very curious about those dark patches we see here and there on Mars and I wonder why people at NASA are so quick to dismiss them as just a different type of sand. I'm very suspicious there's more to it than that and I'm surprised at NASA's apparent lack of interest.
???

*Yes, I see what you mean Shaun. Frankly, it looks like an entrance to a definite depression -- or even a cave? There is a natural cave near to where I live (not in sand), and it looks remarkably similar. What we're seeing is dark -- and yes, it seems the sort of dark which indicates absence of light as opposed to a different type of material. And I also distinctly see the other effects you describe.

???

Good questions and observations. NASA, go figure. What a love/hate relationship I have with that agency!

--Cindy

Shaun Barrett · 2005-01-12 19:01:13

Thanks for the response, Cindy.
I guess this topic of 'dark sand' is of limited interest because I've raised it before at various times and with different images, only to find the thread tends to die fairly quickly. There could be a number of very good reasons for that, of course, including a paucity of further evidence to back any speculation. And maybe that's why NASA itself dismisses such curiosities with such a cavalier attitude - there's no prospect of investigating them in more detail until we get people on the surface, so "let's just call them patches of dark sand and move on". ( ??? )

I've noticed you are prepared to muse for a while on some of these anomalies, as are Rex, CM, Atomoid, and REB, for example. But most people here are much more likely to run with a political hypothesis than one about Martian life or geology.
You've expressed frustration about essentially this same point yourself and we're in agreement on it, I think.
Mars, to me, is an all-encompassing fascination. It's a very real place to my mind and I'd love to go there and fossick through its caves and dry river beds; feel its gravity, see its sky, and maybe hear its sounds. It's a strangely visceral attachment I have to the place, which I can't explain and which brings out the exploratory instinct of the small boy in me, and that's why I keep asking what some people must see as highly speculative and less-than-objective questions, I guess.

To those of you with a more literal frame of mind regarding Mars, I apologise for some of the stuff I write about. But that doesn't mean I'm going to stop!
:;):

SpaceNut · 2005-01-12 20:45:59

If the scale is even close to right one of those dark areas appears to be about 100m by maybe 20m and each appears at the lowest spot in each instance. I wonder if these where once green and are now dead areas of composting plant life?
It would be interesting to retake a few photos over a period of time to see if the dunes move and if the spots stay.

Palomar · 2005-01-13 08:33:06

SpaceNut:

If the scale is even close to right one of those dark areas appears to be about 100m by maybe 20m and each appears at the lowest spot in each instance. I wonder if these where once green and are now dead areas of composting plant life?
It would be interesting to retake a few photos over a period of time to see if the dunes move and if the spots stay.

*Yep, good thoughts. :up: Would indeed be interesting. I can't help wondering if that little trail of depressions on the dune above the dark patch might have been created by a falling rock from above (perspective is a bit tricky in that photo, at least to me). It seems like a chain of depressions, which we've seen on Callisto and Ganymede, in the form of crater chains. If created by a rock, perhaps it smashed down into that edge of the dune below (where the dark patch is), which may have been a mere -crust- of sand at that point; the rock crashed through, creating a gap. ::shrugs:: Who knows...just speculating. [::edit:: Or perhaps a chunk of ice; some dunes on Mars at least go through a freeze then thaw cycle]

-*-

Shaun:

There could be a number of very good reasons for that, of course, including a paucity of further evidence to back any speculation. And maybe that's why NASA itself dismisses such curiosities with such a cavalier attitude - there's no prospect of investigating them in more detail until we get people on the surface, so "let's just call them patches of dark sand and move on".

*I think that's likely. It'd be great if we could get a dozen landing parties on Mars, which of course would include 12 sites for exploration. Colonization could soon commence...(let me dream).

-*-

Shaun:

I've noticed you are prepared to muse for a while on some of these anomalies, as are Rex, CM, Atomoid, and REB, for example. But most people here are much more likely to run with a political hypothesis than one about Martian life or geology.
You've expressed frustration about essentially this same point yourself and we're in agreement on it, I think.

*Agreed.

-*-

Shaun:

Mars, to me, is an all-encompassing fascination. It's a very real place to my mind and I'd love to go there and fossick through its caves and dry river beds; feel its gravity, see its sky, and maybe hear its sounds. It's a strangely visceral attachment I have to the place, which I can't explain and which brings out the exploratory instinct of the small boy in me, and that's why I keep asking what some people must see as highly speculative and less-than-objective questions, I guess.

*I just wish more people were willing to chime in, particularly one scientist who used to post here, who apparently is long since gone. So what if some questions seem "less than objective" (yours didn't strike me that way, though)? Sincere questions are always good questions.

--Cindy

Shaun Barrett · 2005-01-13 08:37:20

:up:

GraemeSkinner · 2005-01-13 08:50:51

Never heard of singing sand dunes before, looks like I've got some catching up to do.

Graeme - off to google singing sand....

GraemeSkinner · 2005-01-13 09:10:43

Well, you learn something new every day so they say, and they're right http://www.schweich.com/sbdA.html#Para130]1st Result and very informative, though being a member of the IoP I'm more biased towards the following site http://physicsweb.org/articles/news/8/12/5/1]LINK for my info - its similar to one posted earlier.

*Shaun - The image you posted above to me does not show patterns created by differing types of sand, though I must confess until I saw this thread I'd not seen the image before, i'd almost think that the surface had been baked hard then cracked.

Graeme

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#1 2005-01-11 09:36:13

Re: Singing Sand Dunes

#2 2005-01-11 19:35:18

Re: Singing Sand Dunes

#3 2005-01-12 07:17:50

Re: Singing Sand Dunes

#4 2005-01-12 07:46:15

Re: Singing Sand Dunes

#5 2005-01-12 07:46:33

Re: Singing Sand Dunes

#6 2005-01-12 11:19:45

Re: Singing Sand Dunes

#7 2005-01-12 19:01:13

Re: Singing Sand Dunes

#8 2005-01-12 20:45:59

Re: Singing Sand Dunes

#9 2005-01-13 08:33:06

Re: Singing Sand Dunes

#10 2005-01-13 08:37:20

Re: Singing Sand Dunes

#11 2005-01-13 08:50:51

Re: Singing Sand Dunes

#12 2005-01-13 09:10:43

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