Mason is the remains of a lunar

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

that lies in the northeastern part of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

. It is nearly attached to the eastern rim of the flooded crater Plana, and southeast of Bürg. Along the northern rim of Mason is the southern edge of the Lacus Mortis, a small

lunar mare The lunar maria ( ; mare ) are large, dark, basaltic plains on Earth's Moon, formed by lava flowing into ancient impact basins. They are less reflective than the "highlands" as a result of their iron-rich composition, and hence appear dark to ...

. To the south is the larger Lacus Somniorum. This is a heavily eroded crater formation that is somewhat irregular in shape, being longer in the east–west direction. The rim is an uneven, disintegrated ring of ridges that have merged with the rough terrain to the south and east. There are clefts or valleys in the western rim that reach the eastern rim of Plana. The interior floor has been resurfaced by

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

, and forms a nearly level basin within the rim. The small crater Mason A lies in the northwest part of the floor. The crater is named after the English-American astronomer Charles Mason.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Mason. MACEDO

Satellite craters

References

Further reading