The Mare Orientale ( German: East of the sea ) is a Mare of the Moon. It is the lavagefüllte central area of a circular plain. The Mare is located opposite its name in the far west, on the back of the moon, on the border to the front. Therefore, it is seen from Earth only during extreme libration. Photos of Moon orbiters show a huge, surrounding 4-fold ring structure from 300 to 1000 km in diameter, the middle rings are formed by two circular, up to 5 km high mountain ranges. The large pool with the lavaüberfluteten middle part is after the South Pole - Aitken Basin and the Mare Imbrium impact basin is the third largest of the moon.
The center of the Mare Orientale selenographic the coordinates 19.4 ° S and 92.8 ° West. Its name dates back to the time before the space than had the East- West direction and transferred to an astronomical point of view from Earth to the Moon's surface.
Completion of the "Great bombardment "
The East Sea is selenologisch the youngest Mare of the Moon and date back 3.85 billion years, at the end of the great bombardments. Unlike other Mary, it has only been partially flooded by basalts after the impact of the asteroid, because the lunar crust is thicker there. Therefore, a relatively large amount of the original impact structures are still visible. The dark, smooth Mare - level in the middle part has a diameter of about 300 km and is surrounded by three concentric ring structures similar to those when you throw a stone into the water. The diameter of the outer ring wall is about 950 km. Its eastern part is formed by the Montes Cordillera and is still visible at the edge of the moon, sometimes the next inner ring mountains of the Montes Rook.
The ring structure is well preserved broken only by a few striking younger craters, of which the three largest - Lovell, Maunder and Shaler - measure 120 to 140 km. Directly on the outer northeast edge connects the 180 km wide crater Schlüter. Between the mountainous Cordillera rings and Rook, two narrow Lava " seen" have formed, which was given the name Lacus Veris and Lacus Autumni.
Mascon and gravity field
Under the Mare Orientale already the first lunar orbiter could see strong perturbations caused by a large Mascon under the lava bed. After the huge impact the lunar crust formed a new balance of in the but later - after solidification - heavier magma ascent. In contrast, the shock waves caused by concentric ring Mountains ( blue ring at the right edge ) have strong negative gravity anomalies because they protrude into the moon jacket obviously lower ( isostasy ).