"interesting Martian photos
Posted by Greg (203.45.205.153) on 2/4/2002 2:39:02 PM

Anyone know what these markings are? It is from the Martian south pole:

and this one:"
http://habitablezone.com/space/messages/17588.html

Perhaps they are examples of ice-wedge polygons, which occur in regions undergoing freeze-thaw cycles on Earth:

http://www.geo.wvu.edu/~kite/Geol221_2001Lect22Periglacial/sld034.htm

Ice-wedge polygons
http://www.science.uwaterloo.ca/earth/waton/polyfig5.html

See also the image on page 14 as it appears in the PDF file:

GUIDEBOOK TO PERMAFROST AND RELATED FEATURES
OF THE COLVILLE RIVER DELTA, ALASKA
http://wwwdggs.dnr.state.ak.us/scan1/gb/text/GB2.PDF

There was a rectangular grid seen by Mariner 9 in the south polar region of Mars dubbed the "Inca City" by the Mariner mission scientists that might be an example of these:

Mars Orbiter Camera (MOC) High Resolution Images:
Rectilinear Ridges In South Polar Layered Terrain ("Inca City")
http://www.msss.com/mars_images/moc/science_paper/f5/

However, as you can see these are usually rectangular or squarish shaped. I haven't seen examples with a squished parallelogram shape as in Greg's examples.
If these are ice-wedge polygons what might caused them to be compressed and only in one direction?
Perhaps it is glacier flow, but you would think the whole polygon would be carried along. Perhaps in flowing the ice is compressed in that direction?
Another possibility is perhaps the area under the wedges becomes lifted in some fashion as with pingoes. Then perhaps this could cause distortion of the shape. Some of the wedges appeared to be on a raised pedestal in the image Greg gives in the link:

. But again would this cause them to compressed in only one direction?
Since the wedges appear compressed perhaps this is an example of compressional tectonic activity in this region. Perhaps Nick can answer this. During compressional activity could features be compressed in one direction only?

Bob Clark