Abstract:

As a common linear structure on the surface of the Moon, lunar ridges have certain distribution regularity. The maps of lunar ridges obtained from the DEM data of LRO(Lunar Reconnaissance Orbiter) were analyzed, and the result revealed that most lunar ridges are of compressional formation mechanism as a combination of drag folds on the surface and thrust faults underneath. The former study always explained the dynamic origin of lunar ridges by a combination of the basalt subsidence of the mare basin and the thermal shrink of the Moon, but it cannot explain the preferred NS orientation of these lunar ridges in the central area of the mare basin. This phenomenon is probably influenced by the regional compressional stress oriented to the eastwest, which is corresponding to the stress state of the tidal forces at low and middle latitudes of the Moon, and it can be inferred that tidal forces may be the main factor for the formation of these lunar ridges. According to the CCD images of Change I and panchromatic images of Lunar Orbiter and LRO，1,464 pieces of lunar ridges at low and middle latitudes of the Moon were identified, and the orientations of them were analyzed. It reveals that the overall trend of these lunar ridges is roughly consistent with the tectonic pattern predicted with tidal forces by Melosh. It can be concluded that there is a strong correlation between tidal forces and the distribution styles of lunar ridges. Furthermore, this study proves that the formation of lunar ridges is related to tidal forces.

Key words: tidal force, lunar ridge, linear structure, thermal evolution