Irregular mare patch

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.

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]

  1. ^ Wood, Charles. "Strange Little IMPs." Sky and Telescope, February 2015 issue.