Paleonet: *That* Martian photo...

[Joseph Botting]

  Hi All,  I'm sure you'veall seen the lurid headlines by now: “Alien crab on Mars!”;“Crab-like alien facehugger is seen crawling out of a cave onMars!” and so on. We've all seen it before, of course – fromhuman bones to statues, it's all a question of seeing patterns inrandom cloud formations.  This one, though,seems to be a bit more interesting. Obviously it's not a crab or a'facehugger,' but from a geological point of view, there's somethingthere. While some sources (including SETI) have said it's justanother case of pareidolia, there are enough differences from thesurrounding rock that this seems to me an insufficient explanation;it differs in colour and texture, and forms a shape that iscompletely distinct from everything else in the field of view and thewider panorama. With all the knowledge of rocks, fossils andpseudofossils on Paleonet, I thought it might be an entertainingsubject for some speculative discussion. 
So, here's the imagethat's made it into the tabloids, in a typical article:https://www.rt.com/news/311451-mars-nasa-image-monster/
Scroll down andyou'll find an enhanced close-up (I can duplicate a lot of thedetails of this with simple sharpening, so I don't think there's muchmore to the 'enhancement' than basic processing). 
The original is theone that matters, of course, and here it is:http://mars.jpl.nasa.gov/msl-raw-images/msss/00710/mcam/0710MR0030150070402501E01_DXXX.jpg
And here is theoutcrop (upper left) in the full panorama:http://gigapan.com/gigapans/160350
What I can make outof all this is that this is an object that clearly differs from theadjacent rock, which is either embedded in a fracture in the rock orattached to a vertical surface, and which appears to be superimposedonto the background; the projections, especially at the base, clearlyoverlie the sedimentary layering. The centre appears to be demarcatedby a subcircular furrow or ridge, and the outer part extended into atleast 10-12 radiating projections. There are no other remotelysimilar objects in the entire panorama, which is very large. 
So, withoutresorting to extremely lost sea creatures(!), has anyone seen asimilar structure on Earth that could provide an analogue? I've beenpondering things lik complex concretionary structures incross-section, but it is hard to envisage a way of creating theradial projections, and I've not personally seen anything similar. Afulgurite might possibly be another explanation (I'm not sure whatthe differences would have been for fulgurites on the early Mars –depends on conductivity of the sediment, amongst opther things), butthat also is not convincing. Can anyone come up with a morepersuasive sedimentological interpretation?
Of course, it's allspeculation (unless they can somehow get Curiosity around the craterrim to have a close look), but there's nothing wrong with some ofthat every now and then – and I'm looking forward to learning fromyour experiences of other strange sedimentary structures!
All the best, Joe
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