Posidonius (crater)
Encyclopedia
Posidonius is a lunar impact crater
that is located on the western edge of Mare Serenitatis
, to the south of Lacus Somniorum
. The crater Chacornac
is attached to the southeast rim, and to the north is Daniell
.
The rim of Posidonius is shallow and obscured, especially on the western edge, and the interior has been overlain by a lava flow in the past. The crater ramparts can still be observed to the south and east of the crater rim, and to a lesser degree to the north.
There is a smaller, semi-circular rim of a concentric, flooded crater within the main rim, offset towards the eastern edge. There is no central peak, but the floor is hilly and laced with a rille
system named the Rimae Posidonius. The floor is also slightly bulged due to the past lava uplift, which also likely produced the complex of rilles. The northeast rim is interrupted by the smaller crater Posidonius B. Within the crater rim, offset just to the west of center is another smaller crater Posidonius A.
On the Mare Serenitatis surface near Posidonius is a notable system of wrinkle ridges that parallel the nearby shore. These are designated the Dorsa Smirnov. At the peak of these ridges is a small craterlet with a diameter of 2 km. This craterlet is surrounded by a patch of high-albedo
material, and is an example of a lunar bright spot. This peak was formerly designated Posidonius Gamma (γ).
Posidonius Gamma was first observed by the lunar cartographer Julius Schmidt
in 1857, who noted the similarity to the bright patch surrounding the crater Linné
.
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 is located on the western edge of Mare Serenitatis
Mare Serenitatis
Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.It is located within the Serenitatis basin, which is of the Nectarian epoch. The material surrounding the mare is of the Lower Imbrian epoch, while the mare material is of the Upper Imbrian epoch...
, to the south of Lacus Somniorum
Lacus Somniorum
Lacus Somniorum is a plain located in the northeastern part of the Moon's near side. It is located at selenographic coordinates 38.0° N, 29.2° E, and has a diameter of 384 kilometers...
. The crater Chacornac
Chacornac (crater)
Chacornac is an irregular lunar impact crater attached to the southeast rim of the crater Posidonius. It lies just to the east of the Mare Serenitatis, and north of the crater Le Monnier....
is attached to the southeast rim, and to the north is Daniell
Daniell (crater)
Daniell is a lunar impact crater located in the southern half of the Lacus Somniorum. To the south-southeast is the much larger crater Posidonius. Nearby can be found the Rimae Daniell rille system....
.
The rim of Posidonius is shallow and obscured, especially on the western edge, and the interior has been overlain by a lava flow in the past. The crater ramparts can still be observed to the south and east of the crater rim, and to a lesser degree to the north.
There is a smaller, semi-circular rim of a concentric, flooded crater within the main rim, offset towards the eastern edge. There is no central peak, but the floor is hilly and laced with a rille
Rille
Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...
system named the Rimae Posidonius. The floor is also slightly bulged due to the past lava uplift, which also likely produced the complex of rilles. The northeast rim is interrupted by the smaller crater Posidonius B. Within the crater rim, offset just to the west of center is another smaller crater Posidonius A.
On the Mare Serenitatis surface near Posidonius is a notable system of wrinkle ridges that parallel the nearby shore. These are designated the Dorsa Smirnov. At the peak of these ridges is a small craterlet with a diameter of 2 km. This craterlet is surrounded by a patch of high-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...
material, and is an example of a lunar bright spot. This peak was formerly designated Posidonius Gamma (γ).
Posidonius Gamma was first observed by the lunar cartographer Julius Schmidt
Johann Friedrich Julius Schmidt
Johann Friedrich Julius Schmidt was a German astronomer and geophysicist.-Biography:...
in 1857, who noted the similarity to the bright patch surrounding the crater Linné
Linné (crater)
Linné is a small lunar impact crater located in the western Mare Serenitatis. The mare around this feature is virtually devoid of other features of interest. The nearest named crater is Banting to the east-southeast....
.
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 Posidonius.| Posidonius | Latitude | Longitude | Diameter |
|---|---|---|---|
| A | 31.7° N | 29.5° E | 11 km |
| B | 33.1° N | 30.9° E | 14 km |
| C | 31.1° N | 29.6° E | 2 km |
| E | 30.5° N | 19.7° E | 3 km |
| F | 32.8° N | 27.1° E | 6 km |
| G | 34.8° N | 27.2° E | 5 km |
| J | 33.8° N | 30.7° E | 22 km |
| M | 34.3° N | 30.0° E | 10 km |
| N | 29.7° N | 21.0° E | 6 km |
| P | 33.6° N | 27.5° E | 15 km |
| W | 31.6° N | 20.1° E | 3 km |
| Y | 30.0° N | 24.9° E | 2 km |
| Z | 30.7° N | 22.9° E | 6 km |