Firmicus (crater)
Encyclopedia
Firmicus is a lunar
crater
that lies in the eastern part of the Moon
's near side, so that from Earth
it appears oval in shape due to foreshortening. It is, however, very nearly circular. The crater is located to the west of the Mare Undarum
, and northeast of the similar-sized crater Apollonius
. To the north of Firmicus are the craters van Albada
and Auzout
. Attached to its northwest rim is the Lacus Perseverantiae
, a miniature lunar mare
.
The most notable aspect of Firmicus is the dark, flat floor. It has a similar albedo
to the surface of Mare Crisium
to the north, making it stand out somewhat from its surroundings. The floor has suffered no significant impacts since it was created, although there are undoubtedly many minor impacts across its surface. The outer rim of Firmicus has undergone some erosion, particularly along the northern rim where it is overlain by a pair of small craterlets.
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
that lies in the eastern part of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's near side, so that from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
it appears oval in shape due to foreshortening. It is, however, very nearly circular. The crater is located to the west of the Mare Undarum
Mare Undarum
Mare Undarum is an uneven lunar mare located just north of Mare Spumans on the lunar near side, between the crater Firmicus and the eastern limb. It is one of the many elevated lakes contained in the Crisium basin, surrounding Mare Crisium. The selenographic coordinates of this mare are 6.8° N,...
, and northeast of the similar-sized crater Apollonius
Apollonius (crater)
Apollonius is a lunar crater located near the eastern limb of the Moon. It lies in the region of uplands to the west of Mare Undarum and northeast of the Sinus Successus on the Mare Fecunditatis...
. To the north of Firmicus are the craters van Albada
Van Albada (crater)
van Albada is a lunar crater that is attached to the south-southeastern rim of Auzout. It lies southeast of Mare Crisium, and north-northeast of the larger crater Firmicus. Directly to the east is Krogh....
and Auzout
Auzout (crater)
Auzout is a lunar impact crater that is located to the southeast of the Mare Crisium, near the eastern limb of the Moon. Due to foreshortening this crater appears quite oval, but is actually relatively circular in form. Attached to the southern rim is the smaller crater van Albada. To the...
. Attached to its northwest rim is the Lacus Perseverantiae
Lacus Perseverantiae
Lacus Perseverantiae is a small lunar mare extending westward from the northwestern exterior of the crater Firmicus, with smaller extensions to the northeast and northwest at the eastern terminus. Its name is Latin for Lake of Perseverance...
, a miniature lunar mare
Lunar mare
The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...
.
The most notable aspect of Firmicus is the dark, flat floor. It has a similar albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
to the surface of Mare Crisium
Mare Crisium
Mare Crisium is a lunar mare located in the Moon's Crisium basin, just northeast of Mare Tranquillitatis. This basin is of the Pre-Imbrian period, 4.55 to 3.85 billion years ago. This mare is in diameter, and 176,000 km2 in area. It has a very flat floor, with a ring of wrinkled ridges...
to the north, making it stand out somewhat from its surroundings. The floor has suffered no significant impacts since it was created, although there are undoubtedly many minor impacts across its surface. The outer rim of Firmicus has undergone some erosion, particularly along the northern rim where it is overlain by a pair of small craterlets.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Firmicus.| Firmicus | Latitude | Longitude | Diameter |
|---|---|---|---|
| A | 6.4° N | 65.1° E | 8 km |
| B | 7.3° N | 65.8° E | 14 km |
| C | 7.7° N | 66.5° E | 13 km |
| D | 5.9° N | 64.4° E | 11 km |
| E | 8.0° N | 63.6° E | 9 km |
| F | 6.5° N | 61.8° E | 9 km |
| G | 6.9° N | 61.9° E | 9 km |
| H | 7.5° N | 60.3° E | 7 km |
| M | 4.1° N | 67.2° E | 42 km |