Mare Fecunditatis

5.5°S, 53.0°E

Mare Fecunditatis, ‘Sea of Fertility’, is an irregularly shaped lava expanse, about 500 × 600 km with an area of 300 000 km2 that is thus somewhat smaller than the Caspian Sea on Earth. Because of limbshortening through perspective, from Earth it appears oval. Like all the maria, Fecunditatis is also the lava-flooded central region of a larger impact basin and the centre of a mascon. Under high solar illumination it may be seen that the lava surface is covered with bright rays of ejecta material, which cross one another and are of different origins.

Messier 1.9°S, 47.6°E

Messier A 2.0°S, 47.0°E

Messier and Messier A together form one of the most striking crater pairs on the nearside of the Moon. Messier is a markedly oval crater that measures about 9 × 11 km. Its oval shape is the true one, and is not caused by perspective through limb foreshortening.

Messier A is a double crater with overall measurements of about 11 × 13 km. The two craters overlap. Messier A is the origin of two bright rays of ejecta, each of which is c. 100 km long, and which look like the tail of a comet. The two craters were possibly created simultaneously through the grazing impact of one or two bodies, although there was possibly just one impactor, which broke into two parts through gravitational effects, shortly before impact.