Irregular mare patch

An irregular mare patch also known as an IMP, is a smooth, rounded, slightly mounded area, generally about 500 meters wide, occurring in the lunar maria.

[1] Due to their small size, and corresponding difficulty of observational astronomy from Earth, the first irregular mare patch discovered, Ina, was only found in 1971 after analysis of photographs taken by Apollo 15.

Even more important, the hypothesis of volcanic action is at odds with the current theory of the Moon's geology, which states that the Moon should have cooled and solidified by about 1 billion years ago, precluding further geological action.

[1] Understanding irregular mare patches may require new geological theories to be properly explained.

[3] According to the current scientific theories, the Moon's small size means that its mantle should have fully solidified by about 1 billion years ago, which is backed up by seismic data.

An irregular mare patch in the Mare Tranquillitatis . Note that the image may appear depth inverted; the large round object in the upper right corner is a crater and the large round object in the center is a dome.
Irregular mare patch crossing Rima Sosigenes in western Mare Tranquillitatis.