Possible lunar ring dikes

A search for lunar features that showed characteristics of terrestrial ring dikes was conducted, using the Lunar Orbiter series of photographs. Features exhibiting one or more of the following four criteria were included as lunar analogs to terrestrial ring dikes: (1) inner ridges approximately concentric with the crater wall, (2) inner rills approximately concentric with the crater wall, (3) outer ridges and/or rills approximately concentric with the crater wall, and (4) interior and exterior slopes of the crater wall approximately equal. Features exhibiting each of the four criteria were found, and some had combinations of two or more including rills merging into ridges - e.g., in Taruntius and Posidonius. Gambart is an example of equal inner and outer slopes, while Hesiodus A and Marth are two of the best examples of complete inner rings concentric with the outer rings. Ten per cent of the candidates were probable impact craters but had subsequent volcanic activity of a ring dike nature. The initial search showed a distribution of the possible lunar ring dikes that was nonrandom and strongly associated with the margins of the maria, further implying that they are volcanic features.