Giant Hummocks and Polygonal Faulting in Deep-Water Sediments: A New Terrestrial Analog for Martian Polygonal Terrain
2000 Spring American Geophysical Union Meeting
http://www.agu.org/cgi-bin/wais?n=P42A-07 [abstract]

The authors note that the kilometer scale polygons seen in the northern plains of Mars are analogous to the polygons seen at a similar scale on the ocean floor on Earth.

There have been aqueous and non-aqueous explanations of the kilometer scale polygons on Mars. Supporting an aqueous explanation is their correlation with fluid flow landforms on Mars:

Sedimentary deposits in the northern lowland plains, Mars
Lucchitta, B. K.; Ferguson, H. M.; Summers, C.
Lunar and Planetary Science Conference, 17th, Houston, TX, Mar. 17-21,
1986, Journal of Geophysical Research (ISSN 0148-0227), vol. 91, Nov. 30, 1986, p. E166-E174.
http://adsabs.harvard.edu/cgi-bin/bib_query?1986JGR....91..166L [abstract]

The spatial distribution of volatiles in the Martian hydrolithosphere
Costard, Francois M.
Earth, Moon, and Planets (ISSN 0167-9295), vol. 45, June 1989, p. 265-290.
http://adsabs.harvard.edu/cgi-bin/bib_query?1989EM%26P...45..265C [abstract]

Other aqueous models for the formation of the giant polygons suggest liquid water convection as the cause:

A Formational Model for the Martian Polygonal Terrains
Wenrich, M. L.; Christensen, P. R.
Lunar and Planetary Science, volume 27, page 1419
http://adsabs.harvard.edu/cgi-bin/bib_query?1996LPI....27.1419W [full
text]

Convection in a catastrophic flood deposit as the mechanism for the giant polygons on Mars
Jour. Geophys. Res., v. 105, E7, July 25, 2000, pp.17617-17628,
http://ethel.la.asu.edu/asu_tes/TES_Editor/PERSONNEL/LANE/polygonabstr.html
[abstract]

Bob Clark