To an extent we have been conditioned by Phoenix to equate polygon formation with ice. In the GSA paper excerpt they are identified as contraction features. These can be caused by dessication, thermal contraction or even chemical reactions and mineral phase changes (or combinations of the above) can have the same effect. I guess the point I am trying to make is that there are a lot of pieces of the jigsaw that have to be put together before we can even make a reasoned guess at what occurred in Gale.

Heading to Glenelg, Earth, tomorrow to mark Curiosity's arrival at Glenelg, Mars. Doug McCuistion, Director of the Mars Exploration Program, shuttle astronaut Bonnie Dunbar and John C Brown the Astronomer Royal for Scotland will be there.


Glenelg Event on Facebook

Shouldn't they really be heading to Glenelg in Canada?

This image from sol 67 shows an interesting rock. Perhaps its a "Hota" type rock lifted up onto the surface and seen in cross section. There so seem to be quite a few pebbles/rocks embedded in the lower section.

http://mars.jpl.nasa.gov/msl/multimedia/ra...1_DXXX&s=67

Two parts of the sol 67 mastcam 100 pan.



You can find bigger versions here and here.

The putative mud features were brought up at the recent telecon by Dr. Ken Kremer of Spaceflight magazine. Dr. Grotzinger only addressed it in the most general terms:

Heading there tomorrow

Sol 72 ChemCam Popcorn!





ADMIN NOTE: Post edited to remove inline image. Refer to Rules and Guidelines on Posting Etiquette 3.2

The Martian Glenelg was named with the Canadian one in mind, certainly, but that in turn was named after the original Scottish one. Scottish Glenelg is of considerable geologic interest, sitting on the Moine Thrust plane, and with three geologic units around it.

Martian Diaries - Glenelg

" The title “Glenelg” was chosen on the strength of two characteristics. Glenelg is the name of a geological unit near Yellowknife, Canada, and as science team member Dawn Sumner notes, “Yellowknife is the name we chose for this map quad, and the features in the quad are named after features associated with Yellowknife.”

The word’s palindromic nature – it’s the same spelled forward and backward – also played a key role, since Curiosity plans to visit the site and then retrace its treads on the way toward Mount Sharp. You know, just a little mission architecture humor.

But the full etymology of Glenelg goes back several centuries, to a remote, windswept peninsula in western Scotland. "

Is the black bell shaped "popcorn" a picture of the plasma generated by the laser or the hole left? And any idea why some pebbles at the bottom left quadrant appear to move?

Looks like the "bell" shape is the hole itself. And there sure seems to have been a vapor/plasma outflow towards the bottom of the image energetic enough to blow around a few 'pebbles' (though I'm not sure how large they are; probably too small for us to think of as pebbles, really).

Or maybe a shock wave through the crusty surface shook some of the looser bits.

I'd have to agree with that. While I think the fractures seen in the rock from sol 56 do bear a strong resemblance to terrestrial mud cracks, there's no way to know that with confidence from a single drive-by image. The voids could easily be from some other type of shrinkage crack, ice crystal casts, or some sort of fractures.

However, I find it intriguing to note that polygonal fractures/features at several scales have been observed in the sediments of Gale Crater. Large scale polygons (and boxwork) have been imaged from orbit, we have seen medium scale polygons on the distant foothills of Mt. Sharp in some long range mastcam images, and now we've seen several examples of small scale polygons in some near range mastcam images. It's tempting to speculate that this entire range of polygonal structure or fabric may be genetically related.

As far as that goes, mud cracks are a classic example of a fractal pattern with similarity on multiple levels.

I think this is the area referred to in the GSA paper, a few hundred meters north of the landing site:



Here's the location in relation to the landing site and Glenelg:



Never too soon for reasoned guesses...

Glenelg destination too ? We can take a close look, can't wait...