Drygalski is a large lunar

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...

that lies along the southern limb of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

. It partly overlies the crater Ashbrook to the west on the far side of the

. Just to the north of Drygalski is the smaller

Boltzmann Ludwig Eduard Boltzmann (; 20 February 1844 – 5 September 1906) was an Austrian physicist and philosopher. His greatest achievements were the development of statistical mechanics, and the statistical explanation of the second law of thermodyn ...

. The location of this crater restricts its observation from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, and even under conditions of favorable libration it is viewed from the edge. It is only illuminated by the Sun at an oblique angle, and it lies close to the south polar craters that are permanently shielded from sunlight. The outer rim of this crater has been worn and eroded by subsequent impacts, leaving a rugged, mountainous ring that is overlaid in places by small craters. The most notable of these are Drygalski P across the southwest rim where it joins Ashbrook, and Drygalski V along the north-northwest inner wall. There is a small ''catena'', or crater chain, beginning tangentially the northern outer rim then arcing to the north towards Boltzmann. To the south is an odd formation of two or more small craters, forming a short valley. Portions of the interior floor within the inner walls is flat and level, having 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 moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

. The flattest parts are in the southern and eastern sections of the interior. The surface is more rugged in the west, and is marked by several small craterlets. At the midpoint of the interior is a rugged central peak formation with several smaller ridges along the flanks.

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 Drygalski. The following craters have been renamed by the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

. * Drygalski Q — ''See'' Ashbrook.

References

* * * * * * * * * * * * Impact craters on the Moon {{Craters on the Moon: C-F