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Eric Vaxxine
2006-Feb-21, 02:16 PM
Please, can someone explain how we get identical sand dunes?

Zoom in on this image, and look at the top three ...




http://www.msss.com/moc_gallery/e19_r02/images/E21/E2100192.html

NEOWatcher
2006-Feb-21, 02:19 PM
Please, can someone explain how we get identical sand dunes?


Mass production on an assembly line...:dance:

Seriously though, the same process to create one, creates the other, so odds are good that they will end up the same.

edit: Actually; it looks like they got the assembly equipment from hershey's.

twinstead
2006-Feb-21, 02:19 PM
Depends on your definition of identical.

R.A.F.
2006-Feb-21, 02:21 PM
...can someone explain how we get identical sand dunes?

Sure they "look" alike, but identical?? Why would you assume that they are identical??

Laguna
2006-Feb-21, 02:22 PM
They look similar, but they are not. Look closer.
They differ in form, orientation and size.

Swift
2006-Feb-21, 02:29 PM
I didn't quite see it in the linked image. But I recall images from Earth orbit that showed formations of repeating dunes on Earth (couldn't quickly google up an image). I think if you have a prevailing wind and relatively uniform sand, that the dunes would each have a similar formation mechanism and should therefore have basically identical shapes, whether on Earth or Mars.

R.A.F.
2006-Feb-21, 02:42 PM
They look similar, but they are not. Look closer.
They differ in form, orientation and size.

Precisely...they are not identical.

Halcyon Dayz
2006-Feb-21, 02:48 PM
The wide-angle photo has a nice 'face' though. :think:

BenderBendingRodriguez
2006-Feb-21, 02:53 PM
Heh, I noticed the 'face' too, now that you mentioned it. Must be the foreman of the dune-assembly-line.

Jeff Root
2006-Feb-21, 03:05 PM
Those rounded things are not dunes, although they have dunes
around their edges. Just what are they?

-- Jeff, in Minneapolis

phunk
2006-Feb-21, 03:20 PM
Sure look like dunes to me.

Eric Vaxxine
2006-Feb-21, 03:51 PM
OK, maybe identical was not the right word. But, I have seen sand dunes on earth, all in a row, looking similar, but not with such an odd shape.

Now I KNOW this is Mars and we can't expect 'earth-like' dunes, but .. well... I am hoping someone can really explain the extraordinary similarity between those three odd shaped Dunes. (unless prevailing winds is technically the most scientificly correct answer).

If only we had Google Mars, then we could get some images with detail.

(edited. Aiming for clarity and accurate vocabulary)

Huevos Grandes
2006-Feb-21, 04:02 PM
They look similar, but they are not. Look closer.
They differ in form, orientation and size.

They are not identical. Maybe the lackeys at the JPL photo-processing propaganda unit didn't add enough fake imperfections to convince viewers on the first pass. As others have said, the same local processes and environment will shape very similar shapes, if unchecked.

I imagine that once the taikonauts arrive on Mars in 2018, they'll note many of the rocks look identical too...

R.A.F.
2006-Feb-21, 04:12 PM
...I am hoping someone can really explain the extraordinary similarity between those three odd shaped Dunes.

WHY do you think that this "similiarity" is extraordinary??

You're "finding mysteries" where there are none.

Eric Vaxxine
2006-Feb-21, 04:13 PM
Ok.

NEOWatcher
2006-Feb-21, 04:18 PM
Looks like this to me. (http://emmott.com/portfolio/photography_food/15.php)
And if it were on Mars, wouldn't they look like M&Ms ? (sorry, couldn't resist)

01101001
2006-Feb-21, 05:01 PM
Other views, captions, and commentary:

NASA Gallery: Wirtz Crater Dune Field (http://mars.jpl.nasa.gov/gallery/sanddunes/moc_20030404f.html)
Space.com: Amazing Mars: Wind Plays Starring Role in 11,664 New Mars Images (http://www.space.com/scienceastronomy/amazing_mars_030422.html)
NASA Planetary Photojournal: Dunes and Dust Devil Tracks (http://photojournal.jpl.nasa.gov/catalog/PIA04507)

(It doesn't take a conspiracy to produce repetitive patterns. It doesn't take a conspiracy to produce repetitive patterns. It doesn't take a conspiracy to produce repetitive patterns.)

JayUtah
2006-Feb-21, 05:32 PM
Well, I live on the edge of a desert. Dunes and other fluid-affected formations are nothing new to me. I'm not a geologist or a soil mechanics specialist, but from observation alone I say that dunes are more likely to be nearly identical than not.

aurora
2006-Feb-21, 09:08 PM
I'm mildly curious to find out why the OP'er thought this was a conspiracy.

Kelfazin
2006-Feb-21, 10:36 PM
An example of dunes on Earth taken from space:

here (http://www.vias.org/spacetrip/earth_easternalgeria.html)
here (http://disc.gsfc.nasa.gov/geomorphology/GEO_8/GEO_PLATE_E-2.shtml)
here (http://ag.arizona.edu/~lmilich/dune.html)
and here (http://www.geo.utexas.edu/courses/371c/project/2002/Beveridge/PaleowindsGIS.htm)

and from the 3rd link, note this quote:


Replication of dunes is now believed to result from organized turbulence, but the evidence is weaker for mesoscale dunes than for megascale ones. Megascale dunes seem to organize in patterns both parallel and transverse to windflow. Mesoscale dune wavelength is sometimes strongly correlated with sand grain size. Topographic obstacles are also known to generate wavelike atmospheric motions in their lee, and the formation of these lee-wave dunes is well documented


*edit to fix link*

Eric Vaxxine
2006-Feb-22, 10:09 AM
I'm mildly curious to find out why the OP'er thought this was a conspiracy.

I have posted this incorrectly. Apologies. It will close soon I am sure, but perhaps a Mod will move it.

Jay Utah provided an answer I understand. Thanks.

I live as far from a desert as a person can and to see such similar, detached shapes... well it looked odd to me, but quite clearly is normal. Excellent. Answers sought and received.




Left 'I' out

Wolverine
2006-Feb-22, 10:28 AM
...perhaps a Mod will move it.

Thread moved from Conspiracy Theories to Space Exploration.

Eric Vaxxine
2006-Feb-22, 11:16 AM
Thanks Wolverine

Jens
2006-Feb-23, 03:53 AM
I'm mildly curious to find out why the OP'er thought this was a conspiracy.

The original post was this:


Please, can someone explain how we get identical sand dunes?

The OP may have been wrong about "identical" ("such similar" would have been a better choice of words), but I don't see anything about a conspiracy. Am I missing something?

01101001
2006-Feb-23, 04:31 AM
The OP may have been wrong about "identical" ("such similar" would have been a better choice of words), but I don't see anything about a conspiracy. Am I missing something?
Uh, yeah. It was originally posted in the Conspiracy Theories forum, then moved to Space Exploration.

Jens
2006-Feb-24, 03:23 AM
Oh, I'm sorry about that. I didn't realize where it had originally been posted. I guess there's probably a way to find out, but I don't know it yet...

01101001
2006-Feb-24, 03:38 AM
I guess there's probably a way to find out, but I don't know it yet...
I don't think there's anything explicit in the current thread material showing its original forum.

When a moderator moves something (as here (http://www.bautforum.com/showpost.php?p=687501&postcount=22)) it would be nice if there was always an article stating so and its previous home. "Moved from xxxx to yyyy."

If you are suspicious or curious, a laborious eyeball search might reveal the "Moved:" indicator in the original forum, if it's worth it. Probably best is just to be aware that threads do move, and to always regard comments with that possibility in mind.

Wolverine
2006-Feb-24, 07:41 AM
When a moderator moves something (as here (http://www.bautforum.com/showpost.php?p=687501&postcount=22)) it would be nice if there was always an article stating so and its previous home. "Moved from xxxx to yyyy."

Agreed. I usually make a specific effort to do so, and have amended my above post accordingly.

Eric Vaxxine
2006-Feb-24, 01:47 PM
Dust between dunes. I am 'asking' here, not suggesting this is odd/alien/unusual/anomalous/interesting.

Is it normal for dunes to have clear ground between them? This looks like there is ground rock between the dunes.
It might be perfectly Marsnormal. I don't know!

http://www.msss.com/moc_gallery/r22_s04/images/S04/S0400433.html


Thanks to P.S. for the info.

ryanmercer
2006-Feb-24, 04:44 PM
I can't find two in the lot that are even remotely close... they all have a good deal of size difference and some look "squashed" or "squezed"

01101001
2006-Feb-24, 05:35 PM
Is it normal for dunes to have clear ground between them?
Is White Sands National Monument in New Mexico normal?

Google Satellite Map of White Sands portion (http://maps.google.com/maps?f=q&ll=32.77111,-106.205521&spn=0.065675,0.170288&t=k)

Is the Sahara Desert normal?

Google Satellite Map of Sahara Desert portion (http://maps.google.com/maps?f=q&ll=25.324167,-2.15332&spn=2.259044,4.103394&t=h)

Is the Namib Desert normal?

Google Satellite Map of Namib Desert portion (http://maps.google.com/?t=k&ll=-26.917631,15.31271&spn=0.069644,0.128231&t=k)

Is the Gobi Desert normal?

Google Satellite Map of Gobi Desert portion (http://maps.google.com/?t=k&ll=40.621249,92.981586&spn=0.059285,0.128231&t=k)

Eric Vaxxine
2006-Feb-28, 11:48 AM
It's like there is no norm.
Thanks for your input 01101001

JonClarke
2006-Mar-01, 10:54 AM
Dust between dunes. I am 'asking' here, not suggesting this is odd/alien/unusual/anomalous/interesting.

Is it normal for dunes to have clear ground between them? This looks like there is ground rock between the dunes.
It might be perfectly Marsnormal. I don't know!

http://www.msss.com/moc_gallery/r22_s04/images/S04/S0400433.html


Thanks to P.S. for the info.

Well, these look a lot like dome dunes, except from the perculiar "spike" in front, which might be due to changing wind directions. Dome dunes are a sub-type of barchan dunes, which are characteristic of environments with sparse sand, so you get scattered dunes on a bedrock or gravel surface. The smaller dunes surrounding them are a later feature, they are a different tone and therefore compositionally different. It is quite possible that the larghe dome dunes are inactive, even cemented.

Jon

Eric Vaxxine
2006-Mar-02, 09:40 AM
..... It is quite possible that the larghe dome dunes are inactive, even cemented.

Jon


Ahhh thats something I have not heard of before. If dunes were to become cemented, wind action would sculpt them in a common fashion.