Starship Asterisk*

I have just been watching a David Attenborough TV program - perfect Planet - this episode being on volcanos. The solidifying outflow of the volcano has very similar patterning to those shown on Mars.

[quote=Ara post_id=309515 time=1609924923 user_id=145669]
To me it looks like perhaps being the other way round: dark solid rock (with cracks) surfaces in a sea of light colored sand. I wonder if this could be the case.
[/quote]

If you are wondering if the the dark amorphous shapes (that are themselves covered by darker stripes) are not really dunes but hard exposed rock, I'd say definitely no. The sharp crests on the thicker dark shapes strongly imply they are wind-formed dunes.

As for what this image looks like to me: a sea of latte, with floating milk chocolate dunes covered by a dusting of coffee bean powder stripes.

[quote=Ann post_id=309522 time=1609945898 user_id=129702]
[float=left]Martian sand dunes.png[/float] [float=right][youtube]https://www.youtube.com/watch?v=e2vj6ma-854[/youtube][/float]














Ann 🐇🥕
[/quote]

It *is* possible... Bugs has interacted with Martians!
Perhaps they sculpted his likeness on a grand scale?
[youtube]https://www.youtube.com/watch?v=YE95y62HjZk[/youtube]

To me, it looks very reminiscent of a dark, granular material being blown against the dunes from the upper right towards the lower left. Many of the ridges and valleys of the dune structures are more bare of the streaks on the right, in particular the end of the limb in the upper right of the photo. There are what may be "collections" of blown material collected at the bases of the dunes. The arcing nature of the lines could be caused be the result of airflow eddies.

Or, it may be that the darker material is an upper layer and has been eroded off to show the lighter material below.

I *think* that may be the gist of the post by grahamcunningham1089@gmail.com; lots of technical terms in there!

[float=left][attachment=0]Martian sand dunes.png[/attachment][/float] [float=right][youtube]https://www.youtube.com/watch?v=e2vj6ma-854[/youtube][/float]














Ann 🐇🥕

[attachment=0]StripedDunes_HiRISE_1080.jpg[/attachment]


To me; the Dunes look like abstract art! I kind of like it! :D

Just a thought. The dark spots are often arranged in curved rows, where the 'curves' cross-cut/overlap and generally have maxima to the top-right of the image. The joined chain of dunes to lower left seem to be joined en echelon, and the 'spot curves' are aligned with this orientation. Conclusion? Maybe the dark spots are in fact coeval with the dunes, reflecting (maybe) a compositional grading resulting from the dune-forming process. Speculative, sure, but a genuinely fun image!

The APOD kind of gives me the willies; it reminds me of the giant martian sand slugs 🐌 of my nightmares...

[img] http://res.cloudinary.com/growinginteractive/image/upload/q_80/v1446301722/growblog/brown-slug-2x.jpg[/img]

Er 🐌c

To me it looks like perhaps being the other way round: dark solid rock (with cracks) surfaces in a sea of light colored sand. I wonder if this could be the case.

It looks otherworldly. And, of course, it is.

Fascinatingly, though, it looks just a tiny little bit "worldly", too. This APOD is a reminder that Mars is the only other planetary body that is the least bit Earth-like, at least when it comes to conditions on the surface.

Ann

[url=https://apod.nasa.gov/apod/ap210106.html] [img]https://apod.nasa.gov/apod/calendar/S_210106.jpg[/img] [size=150]Striped Sand Dunes on Mars[/size][/url]

[b] Explanation: [/b] Why are these sand dunes on <a ref="https://solarsystem.nasa.gov/planets/mars/overview/">Mars</a> striped? No one is sure. The [url=https://www.uahirise.org/ESP_066476_2370]featured image[/url] shows striped dunes in [url=https://en.wikipedia.org/wiki/Kunowsky_(Martian_crater)]Kunowsky Crater[/url] on Mars, photographed recently with the [url=https://mars.nasa.gov/mro/]Mars Reconnaissance Orbiter’s[/url] HiRISE Camera. Many Martian dunes are known to be covered unevenly with carbon dioxide ([url=https://en.wikipedia.org/wiki/Dry_ice]dry ice[/url]) frost, creating patterns of light and dark areas. Carbon dioxide doesn’t melt, but [url=https://en.wikipedia.org/wiki/Sublimation_(phase_transition)]sublimates[/url], turning directly into a gas. Carbon dioxide is also a [url=https://en.wikipedia.org/wiki/Greenhouse_gas]greenhouse material[/url] even as a solid, so it can trap heat under the ice and [url=https://youtu.be/L_gnxWUuLm0]sublimate[/url] from the bottom up, causing [url=https://en.wikipedia.org/wiki/Geysers_on_Mars]geyser-like eruptions[/url]. During Martian spring, these eruptions can cause a pattern of dark [url=https://apod.nasa.gov/apod/ap070805.html]defrosting spots[/url], where the [url=https://apod.nasa.gov/apod/ap160119.html]darker sand[/url] is exposed. The [url=https://www.flickr.com/photos/186557130@N06/50642211592/in/pool-apods/]featured image[/url], though, was taken during Martian autumn, when the weather is getting colder – making these stripes particularly puzzling. One hypothesis is that they are caused by cracks in the ice that form from weaker eruptions or [url=https://en.wikipedia.org/wiki/Thermal_stress]thermal stress[/url] as part of the day-night cycle, but research continues. Watching these dunes and others through more [url=https://www.msss.com/http/ps/seasons/seasons.html]Martian seasons[/url] may give us more clues to solve this mystery.


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