Domes

There are multiple reports and photos of domes on the moon. I found a cluster of them from Clementine. These are, in a few cases, reminants of ancient volcanoes. But most are not. Their various shapes, lack of any evidence of a mouth, plus the fact that the dome is of the same material as the surrounding plain argues against the volcanic formation.  They appear to be a raised area of maria material. Because, I reasoned, that there were volatiles on the moon, what mechanism exists, if that were true, would cause domes? The obvious answer was frost heave on a very large scale. In order to have frost heave it is necessary to have an impermiable layer over the freezing area. Otherwise the ice breaks through the surface and sublimation occurs. If the breach is at the top then a mouth might be present appearing very similar to a volcano. In fact some breached frost domes may have been misidentified as ancient volcanoes for those that had the structural integrity to remain intact.  Sublimation would evacuate the dome, and in most cases, collapse. Very similar to a pothole on a blacktop highway. Thus leaving evidence of collapse craters that were not caused by an impact. It might also explain the mechanism for the various outgassings that have been observed and sensed.  I nearly invented the term "pothole crater" as a humorous label for these features but decided to contain myself. But what of the multiple examples of smooth topped domes? These domes had to have, because of their similarity, a common cause.

This lead me to believe that the lunar aquifer was below a caliche like or lava flow layer several to many meters below the surface. This idea was reinforced by Apollo and Luna series reports of a very tightly compacted breccia layer below the regolith. Some Apollo photographs show stratification of rille walls and large ejecta. This layer would also explain the absence of any indication of water by the various sensors due to the impermiability of the breccia or lava layers.  The formation of the breccia layer has been attributed to vibrational compacting. I lean toward a chemical bonding due to water vapor permeating the breccia. This layer does not allow the ice to migrate up toward the surface, except as mentioned, to be remotely sensed. I believe that the aquifer layer may not be found by remote sensing at all because of the depth. Some selected domes will have to be deep drilled to find the presence of the lifting agent.

Conclusion: The water has to migrate to collection points by gravity or by capillary action. This implies a possible liquid state or plasticity in the ice due to temperature and/or pressure exerted by the overburden and residual lunar heat. This migration would possibly leave surface indications in the form of collapsed walls in craters, secondary slumpage of interior crater sides, sinious rilles, and cobra head features.