Borman, I found this abstract on a Mars conference site that might explain the round depressions you noted:<br /><br />Evidence for widespread and recent (very late Amazonian) ponding in Utopia and western Elysium Planitia, based on terrestrial polar analogues.<br />Osinski G. R. (1) and Soare R. J. (2,3)<br />(1) Canadian Space Agency, 6767 Route de l’Aeroport, Saint-Hubert, QC J3Y 8Y9, Canada (****@space.gc.ca), (2) Department of Geography, Planning and Environment, Concordia University, 1355 de Maisonneuve W., Montreal, H3A 1M8 QC, Canada, (3) Department of Geography, Dawson College, 3040 Sherbrooke St. W., Montreal, H3Z 1A4 QC, (****@dawsoncollege.qc.ca)<br />On Earth, thermokarst ponds occur in ice-rich regolith whose thermal equilibrium has been disturbed. Using Hi-Rise, MOC and THEMIS images, we have identified scalloped depressions in Utopia and western Elysium Planitia that are consistent in scale and morphology with drained thermokarst ponds (alases), present in the Canadian Arctic. Pingo-like mounds and thermal contraction (possibly ice-wedge) polygons also are widespread in the region. By analogy with terrestrial polar regions, this suggests that periglacial processes could have played an important role in the development of the regional landscape on Mars. We focus on the possible alases and show that two of their characteristics – internal terraces and small orthogonal polygons – are uniquely consistent with ponded water and then water loss by episodic evaporation or slow drainage. The characteristics are not consistent with water loss by sublimation. In terms of age, the alas-like features could be very young. In some instances, they cross-cut gullies and are superposed on them. As the gullies themselves are thought to be amongst the youngest geological features on Mars, this points to the depressions being younger still. We propose that the scalloped depressions are youthful features whose evolution is a product of very recent shifts in obliquity, w <div class="Discussion_UserSignature"> </div>