 Lunar Orbiter 4 image | |
| Coordinates | 33°42′N37°00′E / 33.7°N 37.0°E Coordinates: 33°42′N37°00′E / 33.7°N 37.0°E |
|---|---|
| Diameter | 35 km |
| Depth | 1.1 km |
| Colongitude | 323° at sunrise |
| Eponym | Asaph Hall |
Hall is a lunar impact crater in the southeast part of the Lacus Somniorum, a lunar mare in the northeast part of the Moon. It was named after American astronomer Asaph Hall. [1] This feature can be found to the east of the prominent walled plain Posidonius. Just to the south, and nearly attached to the southern rim of Hall is the smaller crater G. Bond.
Lunar craters are impact craters on Earth's Moon. The Moon's surface has many craters, almost all of which were formed by impacts.
An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
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 name is Latin for Lake of Dreams, a title given to this feature by Riccioli.
This crater formation has been significantly disintegrated by smaller impacts around the outer rim, leaving a wall that is deeply notched and incised. There is a gap in the western rim through which the interior has been flooded and resurfaced by layers of basaltic lava. Thus all that remains of the original crater is an irregular, crescent-shaped formation along the southern edge of the Lacus Somniorum. The southern rim is attached to the rough terrain to the south of the mare, and the irregular satellite crater G. Bond G is attached to the southeast rim.
Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows.
Lava is molten rock generated by geothermal energy and expelled through fractures in planetary crust or in an eruption, usually at temperatures from 700 to 1,200 °C. The structures resulting from subsequent solidification and cooling are also sometimes described as lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites, though such material located below the crust is referred to by other terms.
Passing across the open mouth of this crater is the rille named Rima G. Bond (after the nearby crater), a wide cleft in the surface of the mare. This feature begins to the north of Hall and travels to the south-southwest, gradually bending back to the south-southeast. It passes through a section of raised terrain along the southern edge of the mare, and this rise joins the southern rim of Hall and encloses G. Bond.
Rille is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is rima, plural rimae. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length. However, the term has also been used loosely to describe similar structures on a number of planets in the Solar System, including Mars, Venus, and on a number of moons. All bear a structural resemblance to each other.
