MOONWATCH

Unlike its neighbouring seas which frame it well, Mare Vaporum or the Sea of Vapors lacks a well-defined boundary. In this it is unlike Mare Imbrium to the northwest, Serenitatis to the northeast and Tranquillitatis to the east; instead 270km x 400km Vaporum appears as an irregular dark patch.

A dark volcanic region known as dominates the, a curious collection of 1-4km craterlets and rilles that form two lines at an angle to one another, either side of 10km . The appearance of the crater lines and Hyginus is reminiscent of a large bird flying directly towards you. The multitude of small craterlets and the rille, or narrow channel, that connects them is also thought to have volcanic origins.