Has this Richat Structure / MRO Circular Layered Form Comparison Been Made Before ? Options

[MouseOnMars]

Hello,

Maybe this has been noticed before. I came across this structure in Africa, that I did'nt know about after looking at the MRO image. It's a well known landmark for Shuttle Astronauts, so I'd be surprised if the comparison has'nt been made (the feature was imaged by MGS MOC).



http://hirise.lpl.arizona.edu/PSP_001981_1825



Larger.

Open In Google Mars: http://homepage.ntlworld.com/barney.holmes...lar_Feature.kml

http://en.wikipedia.org/wiki/Richat_Structure

MouseOnMars

[djellison]

Great to see the layering of two craters on two different planets look so similar - how do they compare in size? Looks like it could be a couple of orders of magnitude!

Doug

[centsworth_II]

According to the Wiki article, the Earth crater is 'almost 50km'
in diameter, and according to the HiRise browse version with
scale bar, the Mars crater is about 3km (or 4) in diameter.

[ElkGroveDan]

Great to see the layering of two craters on two different planets look so similar

There is still some discussion on the nature of Richat, with many geologists leaning toward an eroded anticline and away from impact origins. I haven't heard the latest, but I suspect like all "controversies" there are adherents still on both sides.

EDIT: and I'm in the anticline camp

[edstrick]

This thing and the Reichat <sp?> structure are opposites. There has never been any confirmed evidence of impact there and the overall appearance is progressive stripping of up-domed layers on a modest rise, probably due to igneous intrusion.

The martian example results from an extensive series of layers deposited in a bowl shaped crater, thicker in the center, thinner when deposited on the sloping sides...and probably compacted overall, depressing the center relative to the sides... it's now being eroded mostly flat, exposing the deeper layers at the outer edge, the thicker but stratigraphically higher layers at the center.

[ngunn]

They may be opposites geologically, and different in scale, but from a purely geometrical perspective they are very much akin. Take a flat slice through any set of approximately spherical layers, whether domed upward or downward, and the result is the same. It's only a question of whether you slice your beetroot near the top or near the bottom. There are probably examples on other worlds too. Possible candidates include Venusian coronae and various circular features on Titan.

Incidentally, how certain is that version of events for the formation of the Martian feature?

[MouseOnMars]

Thanks for the replies

This thing and the Reichat <sp?> structure are opposites. There has never been any confirmed evidence of impact there and the overall appearance is progressive stripping of up-domed layers on a modest rise, probably due to igneous intrusion.

The martian example results from an extensive series of layers deposited in a bowl shaped crater, thicker in the center, thinner when deposited on the sloping sides...and probably compacted overall, depressing the center relative to the sides... it's now being eroded mostly flat, exposing the deeper layers at the outer edge, the thicker but stratigraphically higher layers at the center.

So the Martian feature is accepted to be a crater ?

Here it is from ESA. If I spin around the views then I can just see what you're talking about. Raised edges and a bowl with a raised center ? If I look carefully at the 3D terrain at the Google Mars location then the same basic structure seems to be there... a raised center area and raised perimeter "wall". That's just what I notice. I'm no crater expert !

I also notice the multiple layered fringes around the edge of the MRO image that suggest some kind of repeated event, although that could be the normal result of an asteroid hit.

MouseOnMars

[stevesliva]

Wow, good analogue! A google image search for "concentric crater" also provides a lot of food for thought.

[MouseOnMars]

Wow, good analogue! A google image search for "concentric crater" also provides a lot of food for thought.

That's what I thought. I got quite a shock when this loomed up into view in Google Mars
I'd just been looking at the MRO image and came across it randomly.

Here is a link to an Anaglyph of it from http://marsunearthed.com

http://marsunearthed.com/MRO/MRO_Anaglyphs..._015/MRO015.GIF

MouseOnMars

[edstrick]

"...but from a purely geometrical perspective they are very much akin..."

EXACTLY!

[jdub]

I've just finished another anaglyph of this unusual Meridiani crater, it's from a beautiful HiRise stereo pair and gives us our best 3D look yet. Enjoy!

http://marsunearthed.com/MRO/MRO_Anaglyphs...4/MRO054_3D.GIF

[algorimancer]

Wow, that's seriously 3D. Aside from the crater, much of this reminds me of the canyonlands of the american southwest. It'd be great hiking

[Gray]

jdub,

That's a terrific anaglyph. Thanks for preparing it. I'm fascinated by the smaller craters that interrupt the layering within the feature.

[jdub]

Glad you like it guys, hope you're using red/cyan glasses. Here's a bigger (4 meg) version - you should see the 100 meg!

http://marsunearthed.com/MRO/MRO_Anaglyphs.../MRO054c_3D.GIF

[Gray]

Wow!!

The "pinnacles" around the flanks are impressive - even considering the vertical exageration. I wonder what makes this feature so much more resistant to erosion than the surrounding terrain.